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

Where are they used?

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:

1. Mechanical engineering industry.
2. Aviation and automotive industries.
3. Instrument making.

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.

Typical structural layouts

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:

1. Vertical orientation of the workpiece axis. The layout of gear hobbing machines determines the processing features; they have a movable table. The layout is used in the production of universal models, which are most widespread.
2. Vertical orientation of the workpiece axis, the tool is movable horizontally. The device of this gear hobbing machine has a tool support through which axial feed is transmitted. This arrangement is most suitable for models equipped with an automation system for loading/unloading workpieces. It is precisely these CNC gear hobbing machines, the operating principle of which provides for automatic feeding of the workpiece, that have become widespread in the production of large batches of products.
3. Gear hobbing machines when placing the workpiece in the vertical direction. Considering the main components, we note the table, which is often movable in the vertical direction. Radial feed is carried out by a tool stand. These gear hobbing machines, the models of which can differ significantly depending on the purpose, have a design that allows them to be easily integrated into various automatic processing lines. Processing on modern gear hobbing machines comes down to reducing the number of operations requiring operator intervention.
4. Horizontal with the placement of the workpiece axis in this plane. The table is also movable in this direction and transmits axial rotation. The tool is mounted on a tool stand. This type of gear hobbing machine is widely used in the field of cutting small-module gears. The design has horizontal guides to ensure movement of the tool rack.
5. Horizontal machines have a fixture for placing the workpiece in this plane. The key feature is the immobility of the table. The tool rack is movable, designed to transmit axial and radial feed. These types of equipment make it possible to process gears that are made in the form of a single structure with a shaft.

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.

Computer numerical control

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:

1. Can be used for cutting bevel gears, as well as bevel wheels. Numerical control allows you to set the main processing modes.
2. When drawing up a processing program, all parameters are calculated. However, the division of the crown is somewhat different; tuning of the guitar is not required. This is due to the fact that a vertical gear hobbing machine or a horizontal type with CNC has movable units, the position of which and the main performance indicators are adjusted by the created program.

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.

Classification by drive type

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:

1. A group of gear hobbing machines with a dividing worm gear table. The equipment has variable coil thickness. The gap can be adjusted in the range of 0.03-0.05 mm with a significant displacement of the worm.
2. When considering the description, attention should be paid to the location of the systems. The features of this scheme include the installation of a separate housing for the dividing gear. In this case, the crowns are divided by adjusting the gap. The worm moves with the worm in a radial direction relative to the wheel.
3. It is also possible to run in a workpiece by gear hobbing when installing two worm gears with different directions of turns. This adjustment method is universal and is represented by an axial displacement of one of the worms. The center can shift a certain distance depending on the characteristics of the model.
4. There are models on which a gear unit is installed. The gear wheel is driven by a hydraulic pump.
5. The cylindrical type of gear can be mounted on a cutter spindle, which is represented by two halves. The gap is set by moving the wheel halves relative to each other.
6. Considering the drawing of various machines, we note a design option when both gears of the spindle cutter have a small taper of the teeth. In this case, gear-processing equipment can be controlled by moving one wheel in the axial direction.
7. The cutter spindle can accommodate a gear with a very large number of teeth. When carrying out the calculation, we note that the adjustment is carried out by slowing down the rotation relative to the main wheel.

In addition, other options for transmitting rotation have appeared. Some are suitable for single-unit production.

Classification by purpose

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:

1. Threaded.
2. Gear hobbing machines for bevel gears.
3. For cutting teeth of cylindrical wheels.
4. For machining cylindrical wheels and splined shafts.
5. For releasing worm wheels.
6. Thread milling.
7. For processing the end surfaces of wheels.
8. Gear finishing, rolling and testing.
9. Grinding.

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.

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7 Gear processing machines (ready 100%).doc

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Machines for processing bevel gears.

Methods for cutting bevel gears.

Machines for processing bevel gears operate using the copying method or the rolling method.

Using the copying method, the teeth of bevel wheels can be cut on machines operating with a pointed cutter according to a template, a disk or finger modular cutter, a circular broach 1 (Fig. 23) and a face cutting head (Fig. 24). Of these, the most productive is circular broaching.

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Cutting bevel gears on machines using the rolling method.

When considering the processing of bevel gears using the rolling method, the interaction of the cut wheel with an imaginary producing wheel in the form of a flat (or flat-topped) wheel is studied.

Flat wheel is called a limiting conical wheel, with an angle at the apex of the initial cone of 2180.

The tooth profile of the flat wheel is straight-sided. The engagement of a flat wheel with a conical one is shown in Fig. 25.

Fig. 25. Scheme of engagement of a flat wheel with a conical one.

Figure 26 shows a schematic diagram of cutting the cavity of a bevel wheel with one cutter with a single division.

Rice. 26. Scheme for cutting a wheel with one cutter.

If we imagine a flat wheel 1, in which only one of the Z teeth 2 is left in position A, this tooth is sharpened like a planing cutter and has the ability to perform a reciprocating movement P 1, you can understand the essence of the process of shaping the cavity of the bevel wheel 3. The flat wheel is given slow rotation B 2, and the workpiece receives the associated movement B 3, as if there were a conical pair in engagement
. When moving from position A, the cutter performing planing P 1 will gradually cut into the rotating workpiece and, having reached position B, will cut through one cavity of the involute profile. Having ensured the division movement B 4, the workpiece is rotated turn - and repeating the cycle, you can cut the second cavity, etc.

You can imagine a flat wheel with an arc tooth formed by section a-c of cutting head 3 (Fig. 27). The cutting head receives independent rotation B 1 - the main movement necessary to form a cavity along its length. When rotation B 2 of the imaginary flat wheel 1 from position A to position B and the associated rotation B of the workpiece 4, a depression will be formed on the latter, having an involute profile and an arc shape in length.

Rice. 27. Cutting head.

The largest number of machines for processing bevel wheels produced by the domestic industry operate either with a cutting head, providing an arc tooth, or with two cutters 2 (Fig. 27), forming not a cavity, as in Fig. 26, but a wheel tooth and providing a straight or tangential tooth by lenght.
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Operating principle of a gear planing machine

The operating principle of a gear planing machine operating using the rolling method can be represented according to the block diagram shown in Fig. 28. To process a bevel wheel with Z teeth, the following movements are required: Ф V (П 1) to form a tooth along the length, Ф S (В 2 В 3) - two interconnected rotational movements to form a tooth along the profile and a division movement Д (В 4) for alternately cutting all the cavities (teeth). When combining one continuous (B 3) and one periodic (B 4) movements on a workpiece, a summing mechanism is required in the structure of the machine.

The structure of the machine has two kinematic shaping groups and one dividing group.

Tooth shaping group along the length provides the executive movement F V (P 1) - the reciprocating movement of the cutters 3, which is created by the crank 2 placed on the cradle 1. The movement on the crank comes from the engine M 1 through the chain a b i v with d l.

Fig. 28. Structural diagram of a gear planing machine.

Group of tooth shaping according to profile provides complex executive movement Ф S (В 2 В 3), it has internal and external connections. The internal connection provides the trajectory of movement and connects the rotation B 2 of the imaginary producing wheel with Z pr, one tooth of which is realized by the cutters 3, and the rotation B 3 of the workpiece.

This connection is carried out through a chain qi x l m n CM r i y t .

Guitar tuning i x a connection is provided between B 2 and B 3 so that in one revolution of the producing wheel the workpiece makes
rpm

Purpose of the guitar i y will be explained in the following discussion.

The thickness of the cut layer of metal for each double stroke of the cutter will depend on how quickly the movements B 2 and B 3 occur.

The formation of one cavity (one tooth) occurs in a certain sequence:

The cycle is then repeated in each cavity until all the teeth are cut.

The cycle is controlled by a distribution drum (r.b. ), which makes one revolution per cycle and at the right time turns on the mechanism for supplying and removing the workpiece P 5, reverses the movements B 2 and B 3, turns on the dividing mechanism .

Thus, the time required for one revolution of the distribution drum determines the thickness of the cut metal layer. The cycle time tc in these machines determines the forming speed or feed. One revolution of the camshaft drum is associated with the number of revolutions of the M1 engine during the cycle.

External connection in the tooth shaping group along the profile is carried out along a chain M 1a f i s g r.b. h i x P p q .. Guitar i s provides tuning to a given pitch, and the guitar i k entered to obtain a given swing angle of the cradle   .

Division group D(B 4 ).

From the M1 engine along the chain a w x y z the movement is constantly supplied to the single-turn clutch of the dividing mechanism (dd). At the right moment in the cycle, the distribution drum turns on this clutch, it makes 1 revolution and automatically turns off. This is a movement through the right side of the indexing mechanism along the chain v and SM s i y t transmitted to the rotating (IN 3 ) workpiece

Guitar i at ensures rotation of the workpiece in a dividing motion per revolution.

If in the diagram (Fig. 28) crank 2 is replaced with cutting head 2 in Fig. 29, then you will get a block diagram of a gear-cutting machine for processing bevel wheels with an arc tooth, working according to the rolling method with a single division.

Fig.29. Scheme for cutting bevel wheels with an arc tooth.

Book table of contents Next page>>

10.3. Main parts and setup of machines for cutting bevel wheels with circular teeth. Setting up the kinematic chains of the 527B gear cutting machine.

The machine (Fig. 10.1) is designed for cutting the teeth of bevel and hypoid wheels with circular teeth using a gear cutting head using the rolling method, plunge-in or a combined method - cutting and rolling. The dividing rotation of the product is carried out periodically one step after the profiling of the cavity of one tooth is completed.

Rice. 10.1. Gear cutting machine 527B

In table 10.3 provides a list of the main parts and controls of this machine.

10.3. Main parts and controls of the 527B gear cutting machine

Position in Fig. 10.1	Purpose of parts and controls
1
2	Cover of the feed drive box, feed guitar and control guitar
3	Niche cover with hydraulic equipment and control dial
4	Remote Control
5	Niche cover with guitar modification
6	Tool rack
7	Mechanism with guitar roll-in
8
9	Cutting head
10
11	Traverse with rolling and dividing mechanisms
12	Product head
13	Divide guitar box cover
14	Product headstock axial installation shaft
15	Product headstock fixation roller
16	Table installation shaft in longitudinal direction
17
18	Coolant valve handle
19	Hydropanel
20	Table and hydraulic clamp control handle

Kinematic diagram of the 527V machine(Fig. 10.2) consists of the following main kinematic chains: tool rotation (main movement), division, rolling, feed, control and modifier.

Increase

Rice. 10.2.

Note. z - number of cut teeth; δ is the angle of the pitch cone of the wheel being cut, ω l is the angular velocity of the cradle swing, α d.u is the swing angle of the control disk; θ l - swing angle of the cradle;

K m - modification coefficient, α m.d - modifier swing angle, v - cutting speed, d 0 - cutting head diameter.

The modification chain connects the additional rotation of the cradle and the axial movement of the 1/240 transmission worm from the MD modifier.

In table 10.4 shows the formulas for setting the kinematic chains of the machine.