Previously, in most enterprises, the differential guitar was considered by technologists (at least as far as I know). At the moment, at some enterprises, the differential is calculated by technologists, and at some, this “concern” has passed on to gear cutters, to say nothing of when it is necessary to “secretly” make a job! I think this is due to the fact that from mass production of gears there is a transition to production in small enterprises, where this task falls on the shoulders of the gear cutter... My personal opinion, and I have already said this more than once, is that technologists should count the differential, although this skill will not hinder the gear cutter . Of course it’s not difficult, but why the extra responsibility? I think you will agree with me. Mostly no one just wants to take responsibility!
What do you need to know and have to calculate the differential for a gear hobbing machine?
- Constant guitar differential machine.
- Angle of inclination along the pitch diameter.
- Module.
- There should be a book for selecting replacement gears (an excellent and more acceptable option in electronic form. For example, “Petrik M.I., Shishkov V.A. (1973). Tables for selecting gears.” or “Sandakov M.V. - Tables for selecting gears.
- Calculator. I use a calculator on my smartphone.
Formula for calculating guitar differential:
c (machine differential) × sinβ/Mk
That is, the differential constant of the machine is multiplied by the sine of the angle being cut and divided by the module/value k - this is the number of cuts of the cutter. Usually the cutters are single-threaded, if not, then divide the module by multiplying it by 2, for example, if the cutter is double-threaded.
Guitar differential on worm wheels when cutting with a tangential feed, it is calculated using a different formula!
It’s simple, the main thing is not to make mistakes and get confused in the numbers!
Let's calculate the angle differential 10 degrees, 33 minutes, 23 seconds. Constant 15, module 8. Single-start cutter.
We find the sine of the angle 10 33 23. To do this, we convert this angle to decimal. How to do it? 23/3600+33/60+10=0.0063888888888880+0.55+10=10.5563888888889 We determine the sine of 10.5563888888889, it is equal to 0.183203128805159.
Next, open the table for selecting replacement gears (I use Petrik M.I., Shishkov V.A.) and look for the number (gear ratio) 0.343505866509673. In this case, you need to find the closest possible value. 0.3435045 is most suitable. Guitar differential: 43 61 83 92 - the first value is up, the second is down.
Setting up the differential guitar. 43 master, 92 slave. We put 43, connect it with 83, 83 on the same shaft with 61, connect 61 with 92. Like this:
Information about the manufacturer of the semi-automatic gear cutting machine 5S280P
Manufacturer of semi-automatic gear cutting machine 5S280P Saratov plant of heavy gear cutting machines, TZS, founded in 1947.
5S280P Gear cutting machine for bevel gears with circular teeth, semi-automatic. Purpose and scope
The machine is designed for finishing and roughing of bevel gears with a circular line of teeth, with a diameter of up to 800 mm and a module of up to 16 mm. In addition, it can machine hypoid gears.
Gear cutting is carried out using the rolling or plunge method. Face gear cutting heads are used as cutting tools.
On a semi-automatic machine, you can cut by rolling and plunging. When cutting gears, 7-6 degrees of accuracy are achieved according to GOST 1768-56 and the roughness of the machined tooth surface is not lower than class V6 according to GOST 2789-59.
The semi-automatic machine can be used in all branches of mechanical engineering in small-scale, large-scale and mass production.
The use of semi-automatic machines in mass production is ensured by the possibility of multi-machine servicing by low-skilled workers.
Design features and operating principle of gear cutting machine 5S280P
Unlike other machines of this type, it has:
- a new layout of units (reduced number of links in the kinematic chain of running and main movement), which made it possible to significantly increase the rigidity and accuracy of the “tool-product” system;
- independent stepless drive of the running-in and control chain, independent of the main movement drive;
- original division mechanism, not included in the running circuit;
- a special control mechanism that provides the work cycle, the required swing angle of the cradle and the depth of feed for cutting and controls the variable feed rate when working with the rolling and cutting methods.
On the 5S280P gear cutting machine, a convenient arrangement of controls, the possibility of flexible adjustment, the presence of a chip removal conveyor, hydraulic clamping and pressing of the workpiece, supply and removal of the product headstock ensure high productivity of the semi-automatic machine.
The operating principle of this machine is similar to that shown in Fig. 64, a, in which the cutters of the gear-cutting head reproduce in their rotation the tooth of the flat-top producing wheel, and the profile of the teeth of the cut bevel wheel is obtained during the rolling process as enveloping the side surfaces of the teeth of this wheel.
Machining of bevel gears with circular tooth line
according to the scheme of the generating wheel: a - flat-topped, b - conical
The machine can operate using three methods: rolling, plunging and combined.
Running method used for finishing of conventional bevel gears.
Plunge method
Plunge method(without running) are used for rough cutting of wheels of conventional bevel gears, as well as for finishing of semi-running gears, when the pair gear in the transmission is processed by rolling with modification along the profile.
Combined method wheels with an initial cone angle of 70...80° are processed. The method consists in the fact that at the beginning the tool is simply plunged into the workpiece (at a very low rolling speed), and after the tooth has been machined to its full depth, the cutting feed stops, and final processing of the tooth by rolling occurs.
Division in these machines (by 1 tooth) is carried out periodically after the workpiece is removed from the tool.
The machine is semi-automatic, hydraulically equipped and can be used in small-scale, large-scale and mass production.
Circular Bevel Gear Cutting Machines
The group of machines for cutting bevel wheels with a circular line of teeth is the largest and is divided into three subgroups:
- machines operating using the rolling method;
- machines designed for rough cutting;
- machines for finishing cutting using the circular broaching method.
A special place among these subgroups is occupied by machines operating using the rolling method. The machines of this subgroup are universal, and therefore the most complex. Some of them work according to the flat-top producing wheel scheme, others - according to the cone scheme.
The design differences of these machines depend on the forming method, as well as on the structure of kinematic diagrams, internal mechanical connections and the maximum dimensions of the workpieces and determine the features of their adjustments. It is not possible to study the settings of all machines. You can become familiar with the setup features of each machine directly from the manuals supplied with the machine. This chapter will discuss setting up the 5S280P gear cutting machine, which is common in industry. Familiarity with this machine will help you master any other gear cutting machines.
Working space of gear cutting machine 5s280p
The end of the spindle of the gear cutting machine 5s280p
The end of the spindle of the gear cutting head of the machine 5s280p
General view and general structure of the gear cutting machine 5S280P
Photo of gear cutting machine 5s280p
Photo of gear cutting machine 5s280p
Photo of gear cutting machine 5s280p
Semi-automatic gear cutting machine 5S280P precision class P is designed for rough and finishing cutting of bevel and hypoid wheels with circular teeth. The machine has the following design features: the number of links in the kinematic chain of running and main movement is reduced; the cradle is reversed using a conventional friction clutch; the table is brought into the cutting zone and retracted to division is carried out hydraulically using a servo system; the independent drive of the running-in and control chain is independent of the gear-cutting head drive; The division mechanism is hydraulically driven.
The machine operates using cutting and rolling methods. Plunging is used for rough cutting of gears, as well as for finishing cutting of wheels of semi-rolling gears; running is used for finishing cutting of all gears, except for semi-running driven ones. The running rotation of the producing wheel is carried out by a cradle carrying a gear-cutting head. The cutting edges of the head reproduce the movement of the side surface of the tooth of the producing wheel.
Division is carried out periodically. Upon completion of profiling of one cavity (when cutting with a double-sided method) or one side of the cavity (when cutting with a one-sided method), the dividing mechanism is turned on, turning the workpiece one step.
Working cycle of the machine. When working using the plunge method, the cradle worm 66 is disconnected from the feed drive, and the drive rotates only the control circuit. A special clamp is put on shafts X VII and X VIII (Fig. 132), which keeps them from turning during division. The feed copier 63 begins to move the table through the servo system. The control dial 61 rotates synchronously with the plunge tracer. The variable feed control copier 64 also rotates synchronously. At the end of the feed, the stop on the control dial gives the command to retract the table with the headstock of the product. At the end of the table retraction, commands are sent to the reverse clutch 70 from power stroke to idle, to the cylinder for changing the running speed, to the cycle counter cylinder, to the clutch 71 of the division mechanism. Division occurs during reverse rotation of the control circuit and ends before the stop on the control dial commands the working stroke.
The running-in method differs from the plunge-in method in that the cradle worm is connected to the running-in drive. The clamp is removed from the shafts XVII and XVIII and instead of it, replacement wheels of the rolling guitar are installed on these shafts, and the plunge copier is replaced with a finishing copier. Otherwise, the work cycle is the same as for cutting.
Location of the main components of the gear cutting machine 5s280p
Kinematic diagram of gear cutting machine 5s280p
Let's consider the main kinematic chains of the 5S280P machine
Main movement- rotation of the gear-cutting head is transmitted from the electric motor 1 through cylindrical wheels 2, 3, 4 to replaceable wheels a - b, and from them through cylindrical wheels 5, 6, 7, 8 - to the gear shaft 9 connected to the internal gear wheel 10, which is mounted on the spindle of the gear cutting head.
Break-in chain driven by electric motor 11 through V-belt transmission 12 - 13 to input shaft I of the feed box.
During the working stroke, rotation from shaft II is transmitted through replaceable gears a 1 - b 1 to shaft III and then through wheels 20-21, coupling 70 to shaft IV, through cylindrical wheels 22, 24, 25, 26, bevel wheels 27, 28, worm a pair of 66-67 cradle. From the worm through conical wheels 29-30, replacement guitar running wheels a 3, b 3, c 3, d 3, shaft XVIII, clutch 71, conical wheels 42, 43, 44, 45, replacement guitar wheels a 4, b 4, c 4, d 4 - to worm 46 and worm wheel 47.
At slow idle, rotation from shaft II is transmitted to shaft IV through wheels 16 - 18, and at fast idle - through wheels 17-19. Further movement from shaft IV to shaft X VIII is carried out in the same way as during the working stroke.
Division occurs during idle speed. From the hydraulic cylinder with the rack, rotation is transmitted to wheel 38, then through wheels 37 - 36 and the differential housing to wheels 35, 34 and shaft XXIV. The return of the hydraulic cylinder and differential housing to their original position occurs during the power stroke, when the single-tooth clutch engages with shaft XXIV.
From wheel 22 mounted on shaft IV of the feed box, rotation is transmitted from wheel 23 to shaft XXX, then through interchangeable guitar wheels a 5 - b 5, worm gear 52, 53 - to copier shaft XXXII through wheels 54, 55, shaft XXXIII and chain transmission 56, 57-control disk 61.
From shaft VII through replaceable guitar wheels a 2 - b 2, c 2 - d 2, bevel wheels 48 - 49, worm gear 50-51, the modifier disk 69 with an adjustable eccentric rotates. The eccentric of the disk moves the sleeve 68 in the axial direction, in which the cradle worm supports are mounted. The movement of the cradle worm carried out in this way provides a modification of the running-in.
Setting up a semi-automatic machine. The initial data for setting up the machine are the number of teeth of the wheel being cut, the material of the workpiece, the diameter of the milling head, the module of the gear being cut and all the geometric parameters of the gear.
- Main movement circuit guitar tuning. This chain connects the rotation of the motor shaft 1 and the milling head
- Setting up the fission circuit. The division circuit is switched on at the end of the table tap.
- Break-in guitar tuning. This chain connects the rotation of the cradle and the workpiece.
- Feed chain. The beginning of this circuit is electric motor 11
- Setting up the control circuit. Replaceable guitar wheels of the control circuit a 5 -b 5 provide the necessary rolling angles of the cradle, change the angular speed of rotation of the copiers
- Modifier guitar tuning. Modifier 69 has a special device for setting the required eccentricity along the vernier
Required table rotation speeds at different cutter speeds and numbers of teeth of the wheels being cut
- - If you have cutters made of high-speed steel with a coating and dimensions in accordance with GOST 9324-80, you can cut gears m = 4 with a number of teeth more than 20
- cutting speed 120–150 m/min- If you have cutters made of high-speed steel coated with TiN with a diameter of 190–200 mm, you can cut gears of any module with a number of teeth more than 8
- cutting speed 250–300 m/min- If you have cutters with carbide inserts with a diameter of 190–225 mm, you can cut gears of any module with a number of teeth more than 16
From the above it follows that when using modern tools on modernized gear hobbing machines, the productivity of the equipment can be significantly increased. This is especially noticeable in the manufacture of gears with a large number of teeth. This effect is achieved at significantly lower costs for technical re-equipment of the enterprise than when purchasing new equipment, the operation of which will inevitably require a transition to modern high-performance tools.
The cutting head (Fig. 131, a) is made in the form of a disk with grooves into which the cutters are inserted and secured perpendicular to the end plane of the disk. The incisors are external (Fig. 131.6) and internal (Fig. 131.c). In addition, incisors are divided into right-handed and left-handed, differing only in the location of the cutting edges.
Profiles of semi-rolled pair teeth
Cutting bevel wheels with circular teeth using the rolling method is characterized by a long processing cycle. To avoid tooth edges and reduce surface roughness, it is necessary to increase the bending time. A lot of time is also spent on machine idling, tool withdrawal, dividing process, etc. In mass production, gears of spiral bevel and hypoid gears are cut using a high-performance semi-rolling method. In a semi-rolling pair, only a wheel with a small number of teeth is cut by rolling, and a large wheel is cut by a face cutting head or a circular broach using the copying method. The teeth of a semi-rolling pair wheel therefore have not helical, but conical working surfaces, which are exact copies of the producing surfaces described by the cutting edges of the cutters of the end head or broach.
In Fig. 133 thick lines outline the profiles of the semi-rolling pair teeth. For comparison, thin lines show the profiles of the teeth of a regular pair, which are cut by rolling. Such teeth are cut on conventional gear cutting machines with a conical or flat producing wheel. In the latter case, a modification of the run-in is applied. Since only the drive gear is cut using this method, and the driven gear is cut using the copying method, these gears are called semi-rolling, and the cutting method is called semi-rolling.
Working on a gear cutting machine 5S280P
Technical characteristics of gear cutting machine 5S280P
| Parameter name | 5S280P | |
|---|---|---|
| Basic machine parameters | ||
| The largest diameter of the cut wheels being processed | 800 | |
| Largest module of the cut wheel, mm | 16 | |
| The greatest length of the generatrix of the initial cone of the cut wheels at β = 30°, mm | 400 | |
| The smallest and largest angles of the pitch cone of the bevel wheel, degrees | 5°42"..84°18" | |
| Number of teeth of cut wheels | 5..150 | |
| Maximum height of cut teeth, mm | 35 | |
| Maximum width of the crown of cut wheels, mm | 125 | |
| Processing time for one tooth, sec | 12..200 | |
| The highest gear ratio of cut gears at an angle between the axes of 90° | 10 | |
| Cradle installation angle, degrees | 0..360° | |
| Reading division price on the cradle rotation scale, min | 1 | |
| Distance from the end of the tool spindle to the center of rotation of the workpiece headstock at the zero position of the sliding base, mm | 93 | |
| Diameters of gear cutting heads, mm | 160, 200, 250, 315, 400, 500 | |
| Gear cutting head rotation speed, rpm | 20..125 | |
| The smallest and largest distance from the end of the spindle of the product headstock to the center of the stack, mm | 135..600 | |
| Reading accuracy on the scale of the axial position of the headstock, mm | 0,02 | |
| Installing the headstock at the angle of the internal cone, deg | +5..+90 | |
| Reading accuracy on the scale of setting the headstock to the angle of the internal cone, min | 1 | |
| Retraction of the table to the extreme non-working position, mm | 130 | |
| Vertical installation of the headstock of the product for cutting hypoid wheels up and down, mm | 125 | |
| Accuracy of reference along the hypoid displacement dial of the headstock, mm | 0,02 | |
| The largest displacement of the calculated base from the center of the machine to the cradle/from the cradle, mm | 30/ 65 | |
| Drive and electrical equipment of the machine | ||
| Number of electric motors on the machine | ||
| Main drive electric motor, kW | 7,5 | |
| Hydraulic pump electric motor, kW | 2,2 | |
| Magnetic amplifier of the feed mechanism drive, kW | 2,0 | |
| Feed mechanism drive electric motor, kW | 2,2 | |
| Cooling pump electric motor, kW | 0,6 | |
| Total power of electric motors, kW | ||
| Overall dimensions and weight of the machine | ||
| Overall dimensions of the machine (length x width x height), mm | 3170 x 2180 x 2200 | |
| Weight of the machine with electrical equipment and cooling, kg | 15189 |
Gear cutting machines are designed for cutting and finishing gear teeth of various gears. Based on the type of processing and tools, the following gear processing machines are distinguished: gear hobbing, gear planing, gear broaching, gear grinding, etc. According to the purpose of the machines, there are: for processing cylindrical wheels with straight and oblique teeth, worm wheels, chevron wheels, gear racks, bevel spur wheels, with curved teeth. Based on the degree of roughness of the processed surface, machines are distinguished: for preliminary cutting of teeth, for finishing, for finishing the surface of teeth.
There are two methods for cutting gears, the rolling method and the mark (copying) method. The copying method uses a tool whose cutting edge coincides in shape with the profile of the toothed rim cavity. The modular cutter 7 (disk cutter, see Fig. 174, a, or finger cutter, see Fig. 174, b) moves along the cavity of the cylindrical wheel 2, leaving an imprint of its shape at each moment of time. After processing one cavity, the workpiece is rotated in a circumferential step (division movement) and the next cavity is processed.
This method has its drawbacks: the tooth profile depends on the module and number of gear teeth. For precise machining, each wheel needs its own cutter. Therefore, a large set of complex cutters is required. In practice, they are limited to a set of 8 or 15 cutters for each module. In this case, wheels with different numbers of teeth (in a certain interval) are cut with one cutter. The smallest of the spacing wheels is obtained with the correct profile, the others are not accurate. The advantage of the copying method is the simplicity of the equipment. Processing can be done
Sti on horizontal and vertical milling using a dividing head. The copying method is not very productive.
The copying method is used in single production, more often during repair work. Special gear shaping machines with a cutting head provide very high productivity and are used in mass production.
The most common method is rolling. In this case, the cutting tool and the workpiece are rolled like gear links.
In a gear shaping machine, shaper 1 (Fig. 175, a) and workpiece 2 reproduce the engagement of cylindrical wheels. If the workpiece was sufficiently plastic, depressions could be squeezed out in it by rolling a solid wheel (tool) around the circumference. In a machine tool, the rolling movement (coordinated movement of the cutter and the workpiece) is a complex shaping movement. It serves to create the shape of the tooth in the cross section of the involute. To remove material from the cavity of the wheel being processed, cutting edges are created at the end of the cutter along the entire contour, and the cutter is given a reciprocating movement, which is also a shaping movement and serves to obtain the shape of the tooth along its length. You can cut a gear rack with a chisel. To do this, the movement that forms the tooth profile must consist of rotation of the cutter and the rectilinear movement of the rack coordinated with it. You can use cutting rail 2 (comb) to cut cylindrical wheel 1 (Fig. 175, b).
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In a gear hobbing machine, the tool and workpiece form a pair, like a worm gear. If you draw a secant plane through the worm axis perpendicular to the worm wheel axis, then the profile of a gear rack is obtained in the section of the worm. When the worm rotates 280
Rice. 175. Scheme for cutting gears using the rolling method:
A - chisel, b - comb, c - hob cutter, d - profiling of the ring gear with the tooth of a hob cutter
This rack moves along its axis, rolling with the teeth of the wheel. The same rolling takes place in a gear hobbing machine, where the hob cutter 7 (Fig. 175, c) rotates with the workpiece 2 (complex shaping movement).
The profiling of one cavity of the ring gear is shown in Fig. 175, g.
When processing a worm wheel, it is enough to go deep with a cutter to the full height of the tooth to get its shape along the length. When cutting a cylindrical wheel, a forming movement along the tooth is also necessary. If the tooth of the gear is straight, then this movement is simple. A helical wheel has a helical tooth, so its formation requires a complex movement consisting of moving a hob cutter along the axis of the wheel and turning the wheel itself. When cutting bevel wheels, the workpiece is rolled against an imaginary flat producing wheel. The rolling method is characterized by high productivity and accuracy. The advantage of the rolling method is the versatility of the cutting tool: with one module, one
The tool can theoretically cut wheels with different numbers of teeth.
Automatic gear hobbing machine 5M32. The machine is designed for milling teeth of cylindrical, spur and helical gears, as well as worm wheels in single and serial production. Worm wheels can be cut using radial and tangential feeds.
Technical characteristics of the machine. The largest diameter of cut cylindrical wheels is 800 mm; the largest cutable module is 10 mm; cutter rotation speed limits 50-315 min"1; feed limits: vertical 0.8-5.0 mm/rev; radial 0.15-1 mm/rev; axial 0.17-3.1 mm/rev.
The operating cycle of the machine is automated: quick approach of the tool to the workpiece, gear cutting, quick withdrawal of the tool to its original position and stopping of the machine. Cylindrical wheels can be processed using the method of down milling (vertical feed from bottom to top) and counter milling (vertical feed from top to bottom). When down milling, higher cutting speeds can be used.
The machine consists of the following main components: a support stand B is fixed to the frame A (Fig. 176), along which the milling support G moves. The JF table moves along the horizontal guides of the frame. Counter support D supports the upper end of the mandrel with the workpieces installed on it.
In the frame there is a gearbox G, and in the support stand there is a feedbox B.
Processing of workpieces on a machine is carried out in the presence of the following movements in the machine: the main movement is the rotation of the cutter; feed movements: a) vertical - caliper G; b) radial - table E c) axial movement of the slide slide G, rolling and dividing movement - coordinated rotation of the cutter and the part; auxiliary movement; accelerated movement of the support and table, movement of the cutter for more complete use of its turns.
1. Setting up the machine for cutting spur gears. The cutter is installed obliquely at an angle y to the horizontal equal to the angle of elevation of the turns of the hob cutter a (Fig. 177, a), i.e. y = a. The kinematic chains of the main movement, rolling and dividing, and vertical feed must be configured in the machine.
The main movement of the machine (see Fig. 176) is carried out from the electric motor Ml (N = 7.5 kW, n = 1460 min*1) through a gear pair (26/63), a gearbox with electromagnetic clutches, shaft IV, conical pairs ( 29/29), (29/29), (29/29), spur gear (20/80). By switching the Mi couplings M2, L/3, MA, M5, M6, nine values of cutter rotation speed are provided within the range of 50-315 min"1 282
Kinematic balance equations for minimum rotation speed Lf = 1460 x (26/63) x (45/57) x (32/81) x (29/29) x (29/29) x (29/29)1 x x( 20/80) = 50 min"1.
The rolling and dividing motion links the rotation of the cutter and the workpiece. This kinematic chain has the following form: hob cutter, gear pairs Z- (80/20), (29/29), (27/27), differential, gears, Z- (58/58), e - /, guitar replacement wheels a - c - d, gear pairs Z- (33/33), (35/35), dividing worm pair Z- (1/96). When a right-hand cutter operates, movement from shaft XIII is transmitted to shaft LU, bypassing the Z-gear drive (58/58).
The dividing and running chain is adjusted based on the condition: for one revolution of the K-entering cutter, the workpiece must make K/Z revolutions, where Z is the number of teeth of the wheel being cut: 1 x (80/20) x (29/29) x (29/29 )x x (27/27) x (/d„f) x (58/58) x (e/f) x (a/b) x (c/d) x (33/33) x (35/35 ) x (1/96) = =(K/Z), from where (a/b) x (c/d) = (24Kf)/(Zim^). When cutting spur gears, the differential operates like a regular gear, so the gear ratio is = 1. The gears are used to expand the range of adjustment of the replacement wheels of the division guitar. They are selected as follows: at Z< 161 (e/f) - (54/54), при Z>161 (e/f) - (36/72).
Formula for guitar tuning division at Z< 161 (a/b) х (c/d) = =24A/Z, при Z>161 (a/b) x (c/d) = 48A/Z
The machine is supplied with the following set of replacement wheels for the division and differential guitar: 23, 24, 25 (2 pcs.), 30, 33, 34, 35, 37, 40, 40, 41, 43, 45, 47, 48, 50, 53, 55, 58, 59, 60, 61, 62, 65, 67, 70, 71, 73, 75, 79, 80, 83, 85, 87, 89, 90, 92, 98, 100.
Vertical feed is carried out along the following kinematic chain: table, worm pair (96/1), gears (35/35), (33/33), shaft XVII, worm pair (2/26), feed box with electromagnetic gear clutches ( 45/45), shaft XXIII, with the transmission clutch Mb engaged (50/45), (45/45), worm pair (1/24), lead screw XXV with a pitch P = 10 mm. Switching electromagnetic clutches Mp - Mp provides nine feed values within the range of 0.8-5.0 table rpm. Feed reverse is carried out for the vertical feed chain: for one revolution of the table with the workpiece, the cutter must move by the amount of vertical feed SB. Kinematic chain equation 1 x (96/1) x x(35/35) x (33/33) x (2/26) x (40/56) x (/kp.) x (45/55) x (50 /45) x (45/45) x x (1/24) x 10 = SB, whence SB = 2/kp>, where /kp. - gear ratio of the feed box.
Accelerated vertical movements of the cutter are carried out from the M2 electric motor (N = 3 kW, n = 1430 min "1), through a chain drive - 284
Dacha (20/24) according to the following kinematic chain: 1430 x (20/24) x x (45/55) x (50/45) x (45/45) x (1/24) x 10 = 450 mm/min .
2. Setting up the machine for cutting a cylindrical wheel with a screw tooth. The cutter is installed at an angle y = p ± a0, where p° is the angle of inclination of the teeth of the cut wheel to the axis, and a0 is the angle of elevation of the helix of the cutter. The plus sign is placed for opposite directions.
The kinematic chains of the main movement, rolling and dividing, and vertical feed are adjusted in the same way as when cutting spur gears, but the workpiece, in addition to the rotational movement of the rolling, is also given additional rotation due to the inclination of the tooth. The kinematic chain that ensures the trajectory of the screw motion is called a differential chain. It goes (Fig. 176) from the screw XXV through the differential guitar ah - bu cx - du bevel gear (27/27), shaft XXIX, worm gear (1/45), differential, shaft XIII, gear (58/58), wheels e - /, dividing guitar, gear pairs (33/33) x (35/35), dividing worm pair (1/96). The equation of the kinematic chain of the differential is composed from the condition that when the cutter moves by the pitch of the helix Pl l. the workpiece makes one revolution: (P^/10) x (24/1) x (3/22) x (ax/bx) x (cx/dx) x x (1/45) x (/d„f) x (58/58) x (e/f) x (a/b) x (c/d) x (33/33) x (35/35) x (1/96) = == 1 vol. blanks.
For this case /daf = 2, the worm wheel Z-45 rotates the carrier, the gear ratio of the wheels is e/f = 1, the gear ratio of the division guitar is (axb)x(cxd) = (24k//), the pitch of the helix is Ръл. = (t x nnZ)/(sinp).
As a result, we obtain the gear ratio of the differential guitar wheels (c/b) x (cx/dx) = (7.95775 x sinp)/w„&.
The differential chain can also be adjusted when cutting spur gears with a simple number of teeth, for which there are no replacement wheels in the set supplied with the machine. To do this, special wheels are installed on the input and output shafts of the feed box, and the electromagnetic clutches of the feed box are turned off.
3. Settings for cutting worm wheels using the radial feed method. The cutter axis is installed horizontally (Fig. 177, c). The hob cutter must have parameters corresponding to the worm with which the worm wheel being cut will work in tandem. To cut a worm wheel, the following movements are required: rotation of the cutter, rolling and dividing movement, radial feed movement. The adjustment of the main movement and running-in chains is similar to the adjustment for cutting cylindrical wheels.
The radial feed chain connects the rotation of the workpiece with the lead screw XXXIV. For one revolution of the workpiece, the table must move by the radial feed amount Sp.
Equation of kinematic balance of the radial feed chain: 1 x x (96/1) x (35/35) x (33/33) h (2/26) x (40/56) x (/k p.) x (45/ 55) x (45/50) x x (34/61) x (1/36) x 10 = Sp, whence Sp = 0.6/kp.
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Rice. 177. Scheme for cutting teeth with a hob cutter |
The Mis clutch includes radial feed. Switching clutches M-) - M2 provides nine values of radial feeds in the range of 0.15-1.5 mm/rev. MX1 brake clutch. When plunging, the table is brought to a rigid stop, which ensures a stable part size. Accelerated movement of the table occurs from the M2 electric motor through feeds (20/24), (45/45), shaft XXIII, gears (45/45), (34/61), (1/36).
4. Setting up the machine for cutting worm wheels using the axial feed method. This method is mainly used to cut worm wheels for multi-start worms; the profile of the cut teeth has a higher accuracy than with the radial feed method. When cutting wheels using the axial feed method in the machine, the following movements are required (Fig. 177, d); rotation of a special hob cutter, rolling movement of the cutter and workpiece, axial feed of the cutter S0, additional rotation of the workpiece caused by the axial feed of the cutter. The adjustment of the main movement, running and dividing chains with this method is similar to the adjustment when cutting cylindrical wheels. This feed of the cutter is ensured by the movement of the slide and the milling spindle built into it. Feed chain (Fig. 176) from the workpiece to the AT7Kodinakov shaft with a vertical feed chain. From shaft XXIV, rotation is transmitted through a gear pair (33 x 22), three-stage block B1, reversible block B2, gears (40/70) (70/40), (2/36), (68/40) (4/25) on lead screw XI axial feed with pitch P = 8 mm. Let's create an equation for the kinematic balance of the axial feed chain, taking into account that during one revolution of the workpiece the cutter will move in the axial direction by the amount of axial feed: 1 x (9/1) x (25/25) x (22/22) x (2/28) x x(40/56) x(/kp)x (45/53) x (23/22) x (/0 x (32/40) x (40/70) x (70/40) x x(2 /26) x (68/40) x (4/25) x 8 =
Hence, S0 = 0.89/k. p. x/b where ix is the gear ratio of block B1, which together with the gearbox provides 27 axial feed values within the range of 0.7-2.1 mm/rev. Rapid movements of the cutter spindle along the axis are carried out by the Ml 286 electric motor
Rice. 178. Cutting gears on a gear planing machine:
A - working area of the gear planing machine, b - diagram of running in the workpiece of a bevel wheel with a flat producing wheel
Fast movements. Differential chain (or additional rotation of the workpiece). The hob receives axial movement. Since the cutter can be considered as a rack, when moving the cutter - rack by one axial step P0, the workpiece engaged with it, acting as a rack wheel, must turn 1/2 a turn. However, the workpiece already has a running motion, so a differential is used to sum up these two movements. Considering that the chain under consideration connects the axial feed screw XI with the workpiece, we write the kinematic balance equation (Po/8) x (25/4) x (40/68) x x (38/2) x (40/70) x (70 /40) x (40/32) x (ітф/іх) x (22/33) x (33/22) x (ax/bx) x x (cx/dx) x (27/27) x (1/ 45) x (/kp) x (58/58) x (e/f) x (a/b) x (c/d) x (33/33) x x (35/35) x (1/96) = 1/2 rev. zag.
Bearing in mind that Po = mx, where mx -■ module of the hob cutter in the axial section; i-x - gear ratio of block 2?1; itf = 2; (e/f)- = (54/54); (a/b) x (c/d) = 24k/Z, we get (ax/bx) x (cx/dx) = (2.77056 x x /,)/(mxk).
In the absence of a special hob cutter, you can use the running-in method by using a “flying” cutter, i.e., a mandrel with a cutter that represents one cutter tooth.
Gear planing machines are designed for cutting straight teeth of bevel wheels.
The principle of tooth formation when cutting bevel gears on gear-planing machines is as follows: the rectilinear forming teeth of wheel 1 (Fig. 178, a) are obtained due to the main movement - the reciprocating movement of the gears.
Cutter teeth 2. The cross-sectional shape of a tooth is formed on some machines by the method of copying the shape of templates, on others by the rolling method.
Using the rolling method, you can mentally imagine that workpiece 1 (Fig. 178, b) interacts with a flat producing wheel 2. This theoretical wheel has an initial cone angle of 90°. It is the ultimate form of a bevel wheel, just as the rack shape is the ultimate form of a spur gear with a radius R<®. Плоское колесо - это кольцевая рейка.
When rotating, the workpiece can roll over a stationary flat wheel, then its axis must rotate in space around the axis of the flat wheel. When analyzing the design of a machine tool, it is more convenient to imagine that when the workpiece rotates, a flat wheel rotates in concert with it, and the axes are stationary.
There is no flat wheel on the machine, but there is a unit - a cradle, the rotation axis of which is the axis of the flat wheel. On the cradle there are calipers with cutters. The straight cutting edges of the cutters are the lines of the tooth profile of the flat wheel. During translational motion, the edges describe a plane in space, the lateral surfaces of the teeth of a flat wheel. The rotation of the workpiece and the rotation of the cradle constitute a complex form-building movement of the rolling.
Gear planing machine 5A250. Spur bevel gears are cut using copying and rolling methods. The copying method is used for rough cutting of teeth on universal milling machines with special disk cutters. Modern machines use the rolling method. The 5A250 gear planing machine operates using the rolling method and is designed for rough and finishing cutting of spur and bevel gears in serial and mass production. With the help of a special overhead head, arc teeth can also be cut.
Technical characteristics of the machine. The largest diameter of cut gears is 500 mm; number of teeth of cut wheels - 10-100; the limits of the end modules of the cut wheels are 1.5-8 mm; number of double strokes of sliders-cutters - 73-470; The duration of cutting one tooth is 8-123 s.
The principle of operation of the machine is as follows: on the frame A (Fig. 179, a) a rolling cradle B is mounted with sliders/cutters 2 attached to it (Fig. 179, b). A table /" (Fig. 179, a) having circular guides 4 can move along the guides of the frame J. On them, together with the plate 2, the headstock of the product 1 is rotated to set the workpiece at an angle ft. The machine simulates the engagement of the bevel wheel (workpiece) being cut with an imaginary conical wheel. In this case, a cradle with straight cutters - 288
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Rice. 179. Schemes of operation of a gear-planing machine operating by the rolling-in method
A linear profile can be considered as a producing wheel. To shape the lateral surfaces of the tooth, the following movements are needed: the main movement is the reciprocating movement of the incisors; the back-and-forth motion of the cradle around the Ox axis and the associated conical rotation of the workpiece around the 02 axis. After completing the tooth profiling, the workpiece rotates to the next tooth (division). On the 5A250 machine it is possible to process teeth using the rolling method and the plunge method. In the rolling method, the cradle and the workpiece are rotated simultaneously until the groove is cut. Then the workpiece is moved away from the cutters and continues to rotate in the same direction, the cradle with the cutters moves in the opposite direction to its original position. Moreover, during one rocking movement, the workpiece will rotate by an integer number of teeth D. Processing of the next cavity begins, and after processing all the cavities, the machine automatically turns off.
With the plunge method used for rough cutting of teeth, the rolling movement slows down significantly, so the tooth profile in this case is close to straight-line. All teeth are processed sequentially, i.e. division occurs by 1/Z.
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The main movement (Fig. 180) is carried out from an electric motor (N = 2.8 kW, n = 1420 min "1) through gear pairs (15/48), (34/34), replaceable wheels a - b, gear pair (30 /72) and a shaft with a crank disk 2. From disk 2, through a system of levers, the sliders with cutters receive reciprocating motion. For each revolution of the disk, 2 sliders make one double stroke. The kinematic balance equation for the main movement chain has the form: 1420 x (16). /48) x (34/34) x
X (a/b) x (30/72) = Ldv. h/min, from where (a/b) = (n^JUS). From the machine passport it is known that a + b = 106. The main movement chain has the following replaceable wheels: 30, 35, 41.47, 53, 59, 65, 71, 76.
Feeding movement. The time /ts spent processing one depression is called a cycle. The machine is semi-automatic and is controlled by drum 7 located on the camshaft. During the cycle, drum 1 makes one revolution, and the working stroke corresponds to a rotation of 160°, and the idle stroke - to 200°.
Consequently, the camshaft makes 160°/360° revolutions during its stroke. The feed chain kinematically connects the rotation of the electric motor and drum 1 through gears 15/48, replaceable 290
Wheels ah - bu cx - dx, gear pair (34/68), friction clutch A/, gears (24/56), (44/96), (96/64) and worm pair (2/6). Equation of kinematic balance of the feed chain 1420 x (4>/60) x x (15/48) x (ax/bx) x (cx/dx) x (34/68) x (42/56) x (44/96) x (96/64) x (2/66) = = (1600/60°), hence the pitch guitar tuning formula
Accelerated motion occurs when the friction clutch M is included in a double block with numbers of teeth 88 and 84. Then the movement is transmitted either through a gear (52/88) (with the number of teeth of the wheel being cut Z = 16), or Z = (76/64) ( at Z> 17), and then along the chain, similar to the working feed.
During idling time txx the drum will rotate 200°, hence 1420 x (4.x/60) x (15/48) x (52/88) or (7/64) x (42/56) x (44/98 ) x (2/66) = = 200/360°, txx « 3 s/tooth (with 76/64 pair running) or /xx « 6 s/tooth (52/88 wheels included).
Distribution drum 1 supplies and withdraws the table and switches clutch M through a hydraulic distributor. One drum curve is used to work using the cutting method, the other - using the rolling method.
Rotation of the workpiece (division) by an integer number of teeth Z occurs in one revolution of the drum. The Z number should not have common factors with the number of teeth of the Z wheel being cut. This is necessary so that the tool falls into a different cavity each time. The workpiece rotates from the camshaft through gears (66/2), (64/60), (60/44), a bevel pair (23/23), through a gear pair (75/64) (with the running-in method) or (27 /108) (with the plunge method), through bevel gears (26/26), (26/26), (26/26), division guitar a2 - bъ c2 - d2, bevel pairs (30/30), (30/ 30), worm gear (1-120). The design equation is made from the condition that for one revolution of the drum 1 workpiece will rotate by ZJZ revolution: 1 revolution. r.bar. x (66/2) x (64/60) x x (60/44) x (23/23) x (75/80) x (26/26) x (26/26) x (26/26) x (d2/^) x (M) x x (30/30) x (30/30) x (1/120) = ZJZ.
From the equation we derive the division guitar tuning formula (a2/b2)(c2/d2) = 2 ZJZ
When working with the cutting-in method, instead of the number (75/80), put the number (27/108) into the equation, then (a2/b2) x (c2/d2) = IQZJZ.
The rolling chain connects the rotation of the cradle, which acts as a producing wheel, with the workpiece. The movement from the cradle is transmitted through a worm gear (125/2), bevel wheels (28/30), rolling gear (s3/^з)(6з/лз), wheel Z = 21, compound wheel Z = 14, conical pairs (32 /18), (23/23) and further along the fission chain discussed above.
The compound wheel allows, with a constant direction of rotation of the wheel Z = 14, to obtain a reciprocating rotational movement of the cradle.
The compound wheel consists of an internal gear ring with 196 teeth (in a full circle Z = 224), an external gear ring with 98 teeth (in a full circle Z = 112 teeth) and two internal half wheels (Z = 28). During the engagement of the Z= 14 wheel with the internal engagement section, the machine runs, and when engaged with the rest, the machine runs idle. When the Z= 14 wheel engages with the Z= 28 half-wheels, it moves together with the pair (16/32).
The kinematic balance equation is made from the condition that when the cradle is rotated by (1/2^) turn, the cut wheel will turn by (1/2) turn (Dsh is the number of teeth of an imaginary flat producing wheel) (1/ZJ x (126/2) x (28/30) x (c3/d3)(b3/a3) x (21/252) x x (224/14) x (22/16) x (23/23) x (75/80) x (26 /26) x (26/26) x (26/26) x (26/26) x x(a2/b2) x (c2/d2) x (30/30) x (1/20) = Z.
Substituting into the kinematic balance equation the value (d2/b2)x x (c2/d2) = 2ZyZ for the rolling method and the value Z^ = Z/sinyi, where is half the angle of the initial cone of the wheel being cut, we obtain (c2/kg)x x( 6zM) = 3.5^/sinyi. With the plunge method (s3D/3) x (6zM) = = 17.523/siny.
To determine Z, we create a kinematic balance equation on the condition that during the rotation of drum 1 by 160°, the cradle rotates through an angle of 160°: (66/2) x (64/60) x (16/31) x (14/224) x (252/21) x x(сзМ) x (b3/a3) x (30/28) x (2/135) = 0°.
Substitute the value (c3/d3) x (bъ/аъ) = 3.522ysin The 0° swing angle of the cradle depends on the parameters of the gear being cut; it is chosen to ensure complete running-in of the tooth. The cradle should swing in both directions at the same angle. When processing using the plunge-in method, Z, = 1. Headstock installation angle Installation angle of the product headstock during roughing The angle of installation of the rotary segments (min) is determined by the formula coP1 = 3428/Јg[(5t/2) + Ao)ttga] min, where L% is the length of the cone generatrix, mm; St - tooth thickness along the arc of the initial circle, mm; Acot - height of the wheel tooth leg, mm; and a is the engagement angle in degrees (usually a = 20°). Cutting bevel wheels with curved teeth. Bevel wheels with curved teeth are compact, silent, can withstand heavy loads and have a smoother ride than Bevel wheels with curved teeth are cut on a 5280 machine. A face cutting head is used as a tool. The machine can operate using the rolling method (for finishing) and the plunge method (for roughing). With the rolling method, the cutting head rotates, the cradle carrying the tool spindle receives a rotation coordinated with the rotation of the workpiece (rolling movement). After processing one cavity, the wheel being cut is moved away from the tool, but continues to rotate in the same direction as before, turning on the Z teeth. The cradle with the incisors quickly turns in the opposite direction to its original position. The cradle is reversed using a compound wheel. With the plunge-in method, there is almost no rolling movement (rolling is only needed for the division process to occur). Teeth are formed as the workpiece gradually approaches the tool. The method is productive, but less accurate compared to the rolling method. Dental finishing operations. To obtain the exact shape and size of the teeth, as well as to reduce the roughness of their working surfaces, gear wheels, after cutting on appropriate gear cutting machines, are subjected to finishing on gear finishing machines. Running in is the process of forming a smooth* surface of the tooth profile of non-hardened gears. The processing is carried out due to the pressure generated during the rotation of the wheel being processed and the hardened ground wheel (running reference wheel). Lapping -■ finishing process - Fig. 182. Scheme for grinding the teeth of wheels into a clean and smooth surface by artificially wearing the teeth of the wheel being processed using lapping and abrasive powder. The lap is a carefully crafted cast iron gear. Lapping is used for pre-heat-treated gears. The lapping process can increase the contact surface in length and height and reduce the roughness parameters of the teeth. Lapping is carried out according to two schemes: the axes of the lap and the gear are crossed, forming a helical gear. In the first case, lapping is carried out with one lap, to which, along with the rotational movement, a reciprocating movement is imparted. In the second case, lapping is carried out with two or three laps; In this case, the wheel being ground receives reciprocating motion. When processing with three laps, the axes of two of them are crossed with the axis of the wheel being lapped, and the axis of the third is parallel to it (Fig. 182). Grinding in can be carried out by pushing and braking. If lapping is carried out in a spacer, then the teeth of the tool (lapping) are placed in contact with both sides of the tooth of the wheel being processed and during the lapping process the axes of the wheel lapping are gradually brought closer together. When working using the braking method, contact occurs only along one side profile of the tooth of the wheel being processed. The necessary contact pressure is created by braking the wheel being processed. After processing the teeth on one side, the rotation of the lap is reversed and the teeth are processed on the other side. Shewing is used to reduce waviness on the surface of the teeth of cylindrical gears using a special shaver tool that scrapes chips 0.005-0.1 mm thick from the surface of the tooth profile. During shaving, the main movement is received by the shaver, from which the wheel being processed is driven, freely rotating with a mandrel in the centers of the worktable headstocks; in addition, the shaving wheel has a reciprocating motion. After every double table move Rice. 183. Schemes for grinding gears using the rolling method The gear wheel is given vertical feed. In some machine models, longitudinal movement is imparted to the tool. Grinding is performed to improve the precision of gear manufacturing and eliminate deviations caused by heat treatment. Grinding can be carried out by two methods: copying and rolling. When grinding teeth using the copying method, the grinding wheel has a profile corresponding to the profile of the gear cavity. The grinding wheel is profiled on one or both sides. Grinding the teeth of cylindrical gears using the rolling method is based on copying the gearing of the wheel with a rack, the role of one tooth of which is played by a profiled disk wheel or a pair of disc wheels. In Fig. 183 shows schemes for grinding gears using the rolling method with a disk wheel and two disc wheels. According to the diagram shown in Fig. 183, and the main movement is received by the disk circle. It rotates around an axis and receives a reciprocating motion (longitudinal feed motion) in the direction of the arrow. The wheel being ground rotates around its axis at speed Vx and moves linearly at speed V2. These two movements are interconnected and form a complex rolling movement. At this time, one side of the tooth is processed. After reversing the movement, the opposite side of the adjacent tooth is treated. Then the grinding wheel comes out of the cavity and division is performed - turning the wheel by one tooth. Depending on the type of machine, one or two sides can be processed at the same time (Fig. 183, b). Grinding with two disc wheels is shown in Fig. 183, v. Gear honing is used to process gears after gear shaving and heat treatment. The processing is carried out with a gear hone, which is a gear made of plastic with an abrasive mixture, grain size (40, 60, 80), which is selected depending on the steel grade, hardness and required parameters of the tooth surface roughness. The relative movement during gear honing is the same as during shearing. Gear honing machines are similar to shearing machines. Gear honing occurs at a peripheral speed approximately 2 times higher than the peripheral speed of the shaver. Among all metalworking equipment, gear hobbing machines should be highlighted. In the accepted classification system they were placed in a separate group. Horizontal, vertical or other types of gear hobbing machines are used to produce an involute gear profile. Obtaining a complex surface is carried out by the rolling method. Gear hobbing machine Models of gear hobbing machines may differ in a fairly large number of characteristics; they are not as widespread as equipment of the turning or milling group. Therefore they are used in: A universal gear hobbing machine is installed with other metalworking equipment, since processing on gear hobbing machines does not allow changing the diametrical size of the cylindrical shape. On sale you can find models suitable for use in serial, small-scale and large-scale production. The division pattern of a gear hobbing machine can also vary significantly depending on the features of a particular model. This must be taken into account when calculating the division guitar of a gear hobbing machine. When considering a gear hobbing machine and its operating principle, you should pay attention to its layout. Based on this indicator, the following groups can be distinguished: Note that the calculation of the differential of a gear hobbing machine is carried out depending on the features of the circuit. The differential method is extremely common. Setting up the division guitar of a gear hobbing machine is carried out to change the parameters of the cut teeth. CNC gear hobbing machines have main components that can be adjusted to the cutting conditions; they have high movement accuracy. CNC machines can be characterized as follows: Modern equipment does not require significant operator intervention, since the division guitar is often absent. Such gear cutting models are expensive and difficult to maintain. Therefore, in most cases, it is advisable to install and use a processing machine that has a differential guitar design. Gear hobbing machines have a rather complex design. The drive type determines how the disk division can be calculated. Let's consider the features and parameters of the following common drive circuits: In addition, other options for transmitting rotation have appeared. Some are suitable for single-unit production. Another important indicator is the purpose of the equipment. The design of machines is created for the production of certain products. According to this indicator, the following groups of equipment are distinguished: In addition, there is equipment created for certain processing conditions. He is taken to a separate group. In conclusion, we note that gear cutting equipment is produced by a variety of companies. For a long period, models produced in USSR factories were installed on production lines in the mechanical engineering industry. Today, foreign technology is far superior to domestic technology and allows us to produce products with high-precision dimensions and roughness indicators. Chapter 2
Cutting teeth with a hob cutter is carried out on gear hobbing machines using the rolling method. The profile of the cutting part of a hob cutter in its axial section is close to the profile of the rack, so cutting teeth with a hob cutter can be represented as the engagement of the rack with a gear wheel. The working stroke (cutting movement) is carried out by rotating cutter 4 (Fig. 1). To ensure running-in, the rotation of the cutter and workpiece 3 must be coordinated in the same way as when the worm 1 and wheel 2 are engaged, i.e. the rotation speed of the table with the workpiece must be less than the rotation speed of the cutter as many times as the number of teeth being cut is greater than the number of passes cutters (with a single-pass cutter, the table with the workpiece rotates 1/2 times slower than the cutter). The feed movement is carried out by moving the caliper with the cutter relative to the wheel being cut (parallel to its axis). New machine designs also have radial feed (plunging). When cutting helical wheels, additional 1. Main kinematic chains of gear hobbing machines Rice. 1. Operating principle of gear hobbing machines: 1 - worm; 2 - dividing worm wheel; 3 - workpiece; 4 - cutter; 5 - division guitar rotation of the table with the workpiece associated with the feed movement. Therefore, the gear hobbing machine has kinematic chains and their adjustment organs (guitars) indicated in Table. 1. Depending on the position of the workpiece axis, gear hobbing machines (Table 2-4) are divided into vertical and horizontal. Vertical gear hobbing machines (Fig. 2) are made of two types: with a feed table and with a feed column (stand). Rice. 2. General view of a vertical gear hobbing machine: 1 - table; 2 - bed; 3 - control panel; 4 - column; 5 - milling support; 6 - bracket; 7 - support stand A machine with a feed table on which the workpiece is fixed has a fixed column with a milling support and a rear support column with or without a cross member. The approach of the cutter and the workpiece is carried out by horizontal movement of the table (along the guides). A machine with a feed column that moves to approach the workpiece mounted on a stationary table can be made with or without a rear stand. Large machines usually do this. Notes: 1. Machines with the letter “P” in the designation, as well as models 5363, 5365, 5371, 5373, 531OA, are machines of increased and high precision and are intended, in particular, for cutting turbine gears. 2. Large machines (mod. 5342, etc.) have a single division mechanism for working with disk and finger cutters using optional overhead heads: for cutting wheels with external teeth with a finger cutter (see Table 5), wheels with internal teeth with a disk or finger cutter or a special hob cutter (see Table 1). On request, a broaching support for cutting worm wheels with tangential feed and a mechanism for cutting wheels with a cone angle of the tooth tips up to 10°, a reverse mechanism for cutting chevron wheels without a groove with a finger cutter are supplied. 3. Machines mod. 542, 543, 544, 546 and machines created on their basis are designed for cutting large high-precision worm wheels, for example index wheels of gear cutting machines. 4. Horizontal machines mod. 5370, 5373, 5375 and machines created on their basis are designed to work with a hob, finger and disk cutters; other domestically produced machines are used only for working with a hob cutter. 5. The letters indicated in brackets after the model name indicate variants of this model: for example, 5K324 (A, P) means that there are models 5K324, 5K324A and 5K324P. 3. Main table dimensions (in mm) of gear hobbing machines, number of index wheel teeth z k Rice. 3. Horizontal gear hobbing machine: 1 - bed; 2 - tailstock; 3 - milling support; 4 - faceplate; 5 - front headstock Horizontal hobbing machines(Fig. 3), intended primarily for cutting teeth of gear shafts (gears made integral with the shaft) and small gears with hobs, are made with a feed spindle headstock carrying the workpiece, or with a feed milling support. On a feedstock machine, one end of the workpiece is secured in the spindlestock and the other is supported by the rear center. The hob cutter is located under the workpiece on the spindle of the milling support, the carriage of which moves horizontally along the guides of the machine bed parallel to the axis of the workpiece. Radial cutting of the cutter is carried out by vertical movement of the spindle head together with the rear center and the workpiece being processed. On a machine with a feed support, the workpiece is secured in the spindle head and in rests. The hob cutter is located behind the workpiece, on the spindle of the milling support, the carriage of which, during working feed, moves horizontally along the guides of the bed, parallel to the axis of the workpiece.” Radial cutting of the cutter is carried out by horizontal movement of the milling support perpendicular to the axis of the workpiece. The drive of the gear hobbing machine table is a worm gear - a worm with a worm wheel. The kinematic accuracy of the machine mainly depends on the accuracy of this transmission. Therefore, the table rotation speed should not be allowed to be too high to avoid heating and jamming of the teeth of the indexing worm gear. In the case of cutting wheels with a small number of teeth, as well as when using multi-start cutters, the actual sliding speed of the worm gear pair should be determined, which for cast iron wheels should not exceed 1-1.5 m/s, and for a worm wheel with a bronze rim 2-3 m/s. Sliding speed Uс(approximately equal to the peripheral speed of the worm) and rotational speed nch can be determined by formulas where dch is the diameter of the initial circle of the dividing worm, mm; nh; n - rotation speed of the worm and cutter, rpm; zk; z - number of teeth of the dividing and cutting wheels; k is the number of passes of the hob cutter. The designs of the machines provide the ability to adjust the dividing pair, table and spindle bearings, wedges and worm pair of the support. The main adjustment operations are setting up the kinematic chains of the machine (speeds, feeds, division, differential); installation, alignment, securing the workpiece and cutter; setting the cutter relative to the workpiece to the required milling depth; installation of stops for automatic shutdown of the machine. It is convenient to consider the transmission of motion to various machine mechanisms on its kinematic diagram (Fig. 4), which greatly facilitates the derivation of formulas for setting up machine circuits. The diagram shows the number of teeth of cylindrical, bevel and worm wheels and the number of worm starts in a worm gear. Electric motors for the main drive, accelerated movements, and axial movement of the cutter (along the axis of the milling mandrel) are also shown, which in some cases makes it possible to increase the durability of the cutter. The diagram shows electromagnetic clutches, the inclusion of which in various combinations provides the required movements: MF1 or MF2 - rapid movement of the table or support; MF1 and MF4 - radial table feed; MF2 and MF4; MF2 and MFZ - vertical feed of the caliper up and down. Worm wheels are cut using radial feed of the cutter. Gear hobbing machines have a differential mechanism designed for additional rotation of the workpiece when cutting helical wheels. When working with the differential turned on, the wheel z = 58 receives and transmits the main and additional rotations to the table. The main rotation is transmitted through bevel wheels z = 27, additional rotation is from the differential gear through a 27/27 bevel gear, 1/45 worm gear, carrier, differential wheels z = 27. In this case, the driven wheel rotates twice as fast as the worm wheel z = 45 and carrier (see below for setting up the differential chain). The main and additional rotations are added (the rotation of the workpiece is accelerated) if the inclination of the wheel teeth and the direction of the cutter turn are the same (for example, the right wheel is cut by the right cutter), and subtracted if they are different (for example, the right wheel is cut by the left cutter). The required direction of additional rotation relative to the main one is provided by the intermediate wheel in the differential gear. When cutting spur wheels, the differential is turned off, the carrier is stationary, and only the main movement is transmitted (except for the setup of a machine for cutting a spur wheel with a simple number of teeth, discussed below). Guitar tuning machines mod. 5K32A and 5K324A (see Fig. 4). Guitar speeds (rotation of cutter). The high-speed chain connects the specified rotation speed of the cutter nf with the rotational speed of the main drive electric motor ne = 1440 rpm, therefore the equation of the high-speed chain has the following form: Where does the gear ratio of the guitar come from? where a and b are the numbers of teeth of the replacement guitar speed wheels. The machine is equipped with five pairs of replaceable wheels (23/64, 27/60; 31/56; 36/51; 41/46). The wheels of each pair can be installed in the specified and reverse order (for example, 64/23), which allows you to obtain, respectively, ten different cutter speeds (40, 50, 63, 80, 100, 125, 160, 200, 250, 315 rpm) min). Guitar division. To cut wheels with a given number of teeth r during one revolution of the hob cutter with the number of passes k, the workpiece must make k/z, revolution, which is ensured by the selection of replacement wheels of the division guitar with a gear ratio i business The dividing circuit equation has the following form: In general, the calculation formula for tuning a division guitar can be presented as follows: The Transaction values for a number of machines are given in table. 5. The machine is supplied with 45 replaceable wheels with a 2.5 mm module. guitars of division, feed and differential with the following numbers of teeth: 20 (2 pcs.), 23, 24 (2 pcs.), 30, 33, 34, 35, 37, 40 (2 pcs.), 41, 43, 45, 47, 50, 53, 55, 58, 59. 60, 61, 62, 67, 70 (2 pcs.), 71, 72, 75 (2 pcs.), 79, 80, 83, 85, 89, 90, 92, 95, 97 98, 100. Other options for selecting replacement wheels are also possible, for example 30/55 35/70, etc. To place two pairs of interchangeable wheels in any guitar, the following conditions must be met: a1 + b1 > c1; c1 + d1 > b1. We check: 30 + 55 > 40; 40 + 80 > 55; 0b conditions are met. Example 2. According to the table supplied with the machine, select replacement wheels for cutting a wheel z = 88 with a two-flute cutter on the machine specified in example 1. Solution z = 88/2 = 44. Using the table we find i div = 30 / 55 = a1 / b1 As you can see, one pair of replacement wheels is enough here. If the design of the guitar requires two pairs of replacement wheels, then the second pair is added with a gear ratio equal to one; For example: idel = 30 / 55 40 / 40. Feed guitar. For one revolution of the workpiece installed on the table, the support with the cutter must receive vertical movement by the amount of the axial (vertical) feed So (selected when assigning cutting modes), which is ensured by setting the feed rate. The equation of the vertical feed chain, if we consider this machine chain from the table to the milling support, has the following form (in-gear ratio of the feed guitar, 10 mm - pitch of the vertical feed screw): Accordingly, the values of vertical and horizontal (radial) feeds for this machine were obtained: where Disp. is a coefficient depending on the kinematic chain of a given machine. To simplify the selection of replacement guitar feed wheels, also use the table included with the machine. Guitar differential. When moving the caliper by the amount of the axial pitch Px of the helical wheel, the table with the workpiece, in addition to turning in the dividing chain, must make an additional turn by the magnitude of the circumferential pitch of the wheel being cut, i.e. by 1/z of a turn, which is ensured by adjusting the differential gear. Number of revolutions of the vertical feed screw in increments t=10 mm, corresponding to the movement of the nut with the caliper by the amount of the axial pitch of the wheel, nв = ta/t. Considering the kinematic diagram of the machine from the milling support to the table through the differential guitar with a gear ratio i differential, we compose the equation of the differential circuit: where mn and B are the normal module and the angle of inclination of the teeth of the cut wheel; k is the number of cuts of the cutter; Sdif is a coefficient that is constant for a given machine (see Table 5). Attached to the machine are tables for selecting replacement differential wheels depending on the module and tooth angle B. But since the number of B values in the tables is limited, replacement wheels have to be selected by calculation. The calculation formula includes the values Pi = 3.14159 ... and sin B, so an absolutely accurate selection of replacement differential guitar wheels is impossible. The calculation is usually carried out accurate to the fifth or sixth decimal place. Then, using specially published tables for selecting replacement wheels, the decimal fraction obtained from the formula is converted with high accuracy into a simple fraction or into the product of two simple fractions, the numerator and denominator of which correspond to the numbers of teeth of the replacement wheels of the differential guitar. Example 1. Select replacement differential gear wheels for cutting a helical gear mn = 3 mm with a single-thread worm cutter; B = 20° 15" on a machine model 5K32A or 5K324A. 1st solution option. Using the work tables, we find the closest value i differential and corresponding numbers of teeth of replacement wheels 2nd solution. Using work tables, we will convert the decimal fraction into a simple fraction and factor it into factors: 0,91811 = 370/403 = 2*5*37/(13*31).
By multiplying the numerator and denominator of the fraction by 10 = 5*2 we get The results of selecting replacement wheels from different tables are the same, but the first solution is obtained faster, so it is more convenient to use the tables given in the work. Example 2. Select replacement wheels for the conditions given in example 1, but at B = 28° 37". Since the tables show values of fractions less than one, we determine the reciprocal i
differential, and the values of the numbers of teeth according to the tables given in the work: I/1.27045 = 0.7871122 = 40*55/(43*65), i
diff = 65*43/(40*55) = a3/b3 * c3/d3. Accelerated movement of the caliper: Smin = 1420*25/25*36/60*50/45*1/24*10 = 390 mm/min; for the table Smin = 1420*25/25*36/60*45/50*34/61*1/36 = 118 mm/min. Cutting spur gears with prime numbers of teeth *1. In the absence of replacement guitar wheels, division wheels with prime tooth numbers above 100 can be cut with additional adjustment and inclusion of a differential chain. The essence of this machine setting is as follows: the division guitar is set not to z teeth, but to z + a, where a is a small arbitrarily chosen value, which is recommended to be less than one. To compensate for the influence of this value, the differential guitar is additionally adjusted. When drawing up the adjustment equation, one should proceed from the relationship: one revolution of the cutter corresponds to k/z revolutions of the workpiece along the dividing and differential circuits. It looks like this (see Fig. 4): k/z*96/1*1/idiv+k/z*96/1*2/26*ipod*39/65*50/45*48/32*idif*1/45X2*27/27*29/ 29*29/29*16/64 = 1 rev. cutters. Substituting isub = 0.5s0, we obtain the following tuning formulas: Tuning guitar division for machine tools mod. 5K32A; 5327 and others, where Sdel = 24 (see Table 5), tuning the guitar differential for machine tools mod. 5K32A and 5K324A If in the formula idel is taken with a plus sign, then idiff should be taken with a minus sign, i.e. the differential should slow down the rotation of the table, and vice versa. The pitch guitar must be tuned precisely to ensure S0 pitch. Example. On the machine mod. 5K324A cut a spur gear z = 139. Right cutter; k = l; S0 = 1 mm/rev. Solution. Guitar division *1 - Prime numbers cannot be factorized, for example 83, 91, 101, 107, ... 139, etc. Helical teeth can be cut without adjusting the differential by appropriately selecting replacement pitch and pitch guitar wheels. In this case where the signs (+) or (-) can be determined from the table. 6. 6. Conditions that determine the sign in the calculation formula i affairs Due to the fact that the formula includes Pi and sin B, an accurate selection of replacement guitar division wheels is impossible. Therefore, they are selected approximately, with the smallest error (almost accurate to the fifth digit). Using the above formula, the nearest number of teeth of the division guitar wheels at a given feed is selected and the actual gear ratio of the division guitar is determined from them (the index “f” denotes the actual value). Then, using this ratio, we determine i
replaceable guitar feed wheels are selected under and with the smallest error. Calculation i
under (accurate to the fifth digit) can be produced by the formula Where i
d.f - actual division guitar tuning. Example. On the machine mod. 5K32A, with a non-differential setting, cut a helical gear; m = 10 mm; z = 60; B = 30° right tooth inclination. Hob cutter - right-handed single-thread, milling is carried out against the feed direction. Solution. We take s0 = 1 mm/rev; Then Then (see work) If it is not possible to use the replacement wheel z = 37 occupied in the division guitar, we accept another set that gives a value close to the calculated value i
sub.f = 45/73*65/100 = 0.505385. Actual Feed Sof = 80/39*0.5054 = 1.03 mm/rev.
straight bevel gears. The shape of the cut tooth depends on the tooth shape of the mating flat production wheel. It is a flat conical wheel with teeth at the end and an angle at the apex of the initial cone of 2f = 180°. On the production wheel, the lines that determine the shape of the tooth depend on the selected tool and can be in the form of a straight line, a circular arc, an elongated or shortened involute, etc. The tools used are face cutting heads, finger modular and conical hobs. For example, an end cutting head (Fig. 181) with cutters having straight cutting edges cuts circular teeth of bevel wheels with a spiral angle of 0-60° using the rolling method with periodic division. With such processing, the main movement will be the rotation of the cutting head 2, the rotation of the cradle /, the coordinated rotation of the workpiece 3, and the rolling movement. The division is made by turning the workpiece after processing each tooth.
including running in, lapping, shaving, grinding and gear honing.
Where are they used?
Typical structural layouts
Computer numerical control
Classification by drive type
Classification by purpose
CUTTING CYLINDRICAL WHEELS WITH WORM CUTTERS
BASIC INFORMATION ABOUT THE PROCESS
Chain
What is provided
The extreme elements of the chain
Movements to be connected
Setting organ
Express
Cutting speed u, m/min (cutter rotation speed n, rpm)
Electric motor - milling spindle
Rotation of the electric motor shaft ( ne, rpm) and cutters ( n, rpm)
Guitar speeds
Axial (vertical) feed chain
Innings Soi mm/rev
Table - caliper feed screw
One revolution of the workpiece - axial movement of the caliper by the amount Eo
Guitar feed
Fission circuit
Number of teeth cut z
Table - milling spindle
One revolution of the cutter k/z table revolutions
Guitar division
Differential chain
The angle of inclination of the cut teeth in
Table - caliper feed screw
Moving the caliper by an axial step ta- additional rotation of the workpiece
Guitar differential
GEAR MILLING MACHINES
Design and technical characteristics of machines
Setting up gear hobbing machines
