The worm modular milling cutter works according to the method. Basic designs of worm mills

In modern machine.building production, all greater requirements are imposed on the accuracy of gears. At the same time, this type of transmission is used very widely, and the gear wheels work at more and more speeds. The noise level of gears depends on the speed of rotation of the wheels and the roughness of the surface of their teeth. It is also known that the resistance of the gears depends on the magnitude.

Of all the methods of cutting the wheels, the method of dentisting is the most universal, but at the same time, less accurate. Dolbyaki, broach, and many other tooth.cutting tools can cut the wheels with great accuracy. True, it should be noted that the magnitude of the roughness, or rather the height of the cut on the details, during the operation of all these tools, does not differ much, namely, this cut creates micronerings on the chopped wheel. That is, subsequent processing is necessary. As a result, it turns out that in finely and medium-sized production, the use of worm tooth cutting mills is most profitable and technologically justified.

There are a number of problems of using worm modular mills. Due to the complex geometry and manufacturing technology, the cost of manufacturing these mills is great. At the same time, their resistance is clearly insufficient.

The current state of the issue

According to the work method, tools for cutting cylindrical wheels are divided into the following types:

I. Tools working by copying method, in which the instrument tooth profile or the projection of this profile is a copy of the profile of the cavity between the teeth of the cut wheel.

II. Tools operating by the method of centrodenal envelope, in which the centrides of the tool and the chopped wheel roll on each other without slipping. The profile of chopped teeth is obtained as envelope in various provisions of the cutting edges of the tool.

III. Tools that operate with the method of free.focused envelope, in which the profile of the chopped teeth also turns out as envelope of various provisions of the cutting edges of the tool, but there are no centrides on the tool and the chopped wheel in the process of working.

With the envelope method, the profile of the tool does not coincide with the processed profile of the hollow of the cut wheel.

In modern production conditions, tools working by copying and non.centralic anti.ogibing work with high accuracy and performance. At the same time, these tools (on the example of the lengths and tooth.cutting heads) can cut only wheels with certain parameters for which they were designed. Tools such as worm mills and holbys, although they lose exactly and performance several times, are more universal, which makes them more attractive to the conditions of small.scale production, which can be found in many automotive plants. If we compare with each other a dentist hound and worm cutter, it is clear that the profile of the cut wheel during processing by the share is more precise. However, the profile of the Dolbyak himself is much more difficult, in its production there are a number of problems in shaping and grinding of curved areas of tooth. It is also worth noting that the duration and speed characteristics of the work of the gears are most influenced by the size of the roughness in the engagement areas. In both cases, cutting of wheels cannot be avoided, and inaccuracies obtained with dentisting can be corrected with further processing to reduce roughness on the teeth of the wheels (moving and grinding). Hence, it should be concluded that in conditions of small.scale production (for example, IP VAZ), the most economically beneficial is the use of dentist worm mills.

The wear diagram of an ordinary cylindrical cutter shows that the size of the wear ribbons is different for different teeth (rice.one.1), which is associated with the different duration of their engagement and load. Each tooth of a worm cutter cuts a well.defined layer. In the process of working, the teeth of normal worm are loaded unevenly. Only 1/5 of the length of the cutting edges of the milling cutter participate in the cutting. The length and thickness of the cut layer is different in all cutting edges. Their values ​​depend on the depth of the cutting and feed, module, external diameter, number and size of the teeth of the cut wheel, the number of grooves and the angle of rise of the turns of the cutter. Loading the teeth of the milling cutter and the thickness of the layer removed by each tooth of the cutter increases with an increase in the distance from the profiling pole. The extreme teeth, pre.cutting metal from the hollow, are loaded significantly more central profiling and therefore limits the possibility of increasing the longitudinal supply from the loading. The largest section of the removed layer is on the top cutting edge (about 50%). Side cutting edges are also loaded: large section removes the incoming edge. To re.use such a milling cutter at the same installation, it has to be sharpened by the largest wear ribbon, thereby reducing the life of the tool. Therefore, they are usually used when cutting small gear wheels with a periodic movement of the cutter in the axial direction. These movements allow you to introduce new teeth each time, so that at the end of the persistence period, all cutting edges have approximately the same wear. The same effect is achieved by diagonal dentition; In this case, the instrument is reported by continuous tangential feed (along the cutter axis) along with the supply along the axis of the chopped workpiece. However, these methods of d Zybofrezing can only be used for small gear wheels, when milling the wheels of large modules and with a large number of teeth, the use of these methods is limited or completely impossible. When cutting such wheels, worm mills of ordinary lengths either allow a very small movement, or it is not allowed at all. Therefore, in the practice of d Zybofrezing of these wheels, other methods of increasing process productivity are used and increasing the resistance of milling plants.

For example, in order not to spend expensive finish cutters without need, often cutting large gear wheels are previously less accurate with accurate black cutters. However, these cutters are not deprived of a lack of uneven wear of individual teeth. When using axial cutters of a cutter or diagonal milling, more or less uniform wear of the teeth can be achieved.

There is also the following method to avoid overloading individual cutters of the cutter, this is the creation of a frozen cone in the milling cone, such as on the BestCut cutter, the manufacturer Hermann Leimbach, Germany [6]. When constructing this cutter, they strive to give such a geometric shape along its entire length to achieve uniform wear of teeth. To do this, the various spatial position of the envelope of all the edges, as well as the difference in the duration of the gearing, thickness and width of the cut for individual teeth, must be taken into account. Thus, when constructing the fence parts of the cutter for each individual tooth, a certain section of the cut is determined so that in conditions of different duration of the engagement, various cutting speeds and the rear angles, to achieve equal wear on all teeth.

In Fig.one.2 shows the shape of the BestCut milling. The curve of the fence part of the cutter is made in such a way that already its first tooth at the wheel input chooses the hollow deep enough. When the BestCut worm cutter is already working, there is no longer the intersection of two cylindrical bodies, but the intersection of a cylindrical wheel with a globoid.shaped worm cutter. The intersection curve in this case is distorted and lengthens in the direction of the inlet side of the wheel. Thus, the BestCut milling is involved in the work, especially when pre.cutting, depressions are significantly more than teeth than a standard milling cutter. The best load distribution is facilitated by a significant reduction in the average duration of the engagement.

Worm modular mill

Familiarization with the designs of the most common dental tools, the preparation of working drawings, calculation and measurement of sizes.

Set of other dentist tools.

I.Worm modular mill

Worm modular mills are used to cut the teeth of cylindrical straight.toothed and scooters /screw /, mainly external, gears. Worm cutters of a special design can also be treated with teeth of internal gear crowns of large diameter. Worm mills can be single and multi-assembled, integral and prefabricated.

The mill is a worm, turned into a cutting tool by cutting the grooves /straight or screw /, forming the front surfaces and cutting edges, and the back of the rear surfaces to form the rear angles on the cutting edges /rice. I /. In the line of the turns of the cutter normal to the line of turns, it is approximately the initial circuit circuit circuit circuit linked. Normal step R Calculated by the formula P = πm,

The normal step is measured by a caliper directly on the cutter. To reduce errors, it is better to measure with a caliper the total step of several teeth /turns /, and then dividing by the number

Vitkov get a step between neighboring turns. The module is determined by step.

The number of mills of cutters is equal to the number of longitudinal chips. The outer diameter of the cutter DA It can be determined by summing the double distance from the hole to the top of the full tooth and the diameter of the hole. So you can determine DA With any number of teeth. even and odd. The dimensions of the profile of the turns of the cutter: a) the head of the cutter tooth cuts the leg of the wheel tooth, and its height can be accepted Ha = 1.25m;

b) the height of the tooth legs HF should be slightly larger than the height of the head of the tooth of the cut wheel to exclude cutting with the hollow between the teeth of the cutter of the outer surface of the processed part

Tooth profile height and groove depth N measured in the radial direction with a depthmer. The thickness of the tooth along the initial straight S equal to the width of the hollow between the teeth of the cut wheel along the initial circle.

where σ. coefficient adopted according to GOST 9324. 60 different 0.15,

to. The value of the back of the renounced rear angle α.version depends

The cutter with a polished profile has a second, unnecessary nape with the value of the occipital K1 /rice. 2 / to exclude the possibility of the formation of the saddle when the cutter of the cutter is plugged with a grinding circle. Usually K1 = (1.25. 1.5) K. The value of the back is measured using a dividing head and indicator. The indicator measures a decrease in the back of the head when turning the cutter to the angle ψ, which is measured on the scale of the dividing head, and then the drop in the back of the formula is calculated ,

K2. lowering the nape measured by the indicator when turning the cutter to the angle ψ.

The rear angle at the top of the α.version cutter when the archimed spiral is shaken by the size of the fall of the back of the back

The lateral rear angle αb in the cross section normal to the blade /rice.3/

where Du. diameter corresponding to the point at which the rear angle is measured,

To measure the front angle, the γ mill is set so that its axis and cross section of the front surface of the end plane are horizontal /then the front surface is combined with the sponge of the standard. rice. four /. Then the difference difference is determined

Rise lifting angle /rice.5/ determined by the calculation for the average/ calculated/ diameter dt

To obtain the same front angles on the side cutting edges, the angle of inclination of the chip grooves is usually made equal to the angle of lifting the turns of the cutter; In this case, the step of the chip groove is determined by the formula

Know the size TC It is necessary for setting up a universal milling machine when milling the chip grooves, as well as for setting up a special sharpening machine when sharpening the front surface of the cutter.

Dental hobbys are used to cut the teeth of cylindrical toothed wheels usually in cases where it is impossible to apply a more productive worm mill /block wheels, wheels with bacts, internal crowns /. Dolbyak is a corrected gear wheel with an increased height of the tooth head to obtain a radial gap in the transmission and having the front and rear angles that provide normal cutting conditions. For the braid of the wheel, a braid dial.up is used, the direction of the teeth of which, when cutting the outer wheel, is the opposite when cutting the inner wheel coincides with the direction of the teeth of the wheel. The disk holby is depicted in rice.6.

To obtain the rear angles at the top of the α.version and on the side sides of the αb profile, in various sections, the perpendicular axes of the hollow, there is a displacement of the profile along the radius to the size

The initial circuit of the dolbyak is at a distance a from the end of the new dial. When sharpening in this section / II. rice. 6 / Dolbyak is a wheel with the displacement factor of the original circuit x = 0. Therefore, the new Dolbyak.

When the hollow is renewed, the profile of the right and left cutting edges of the tooth occurs in opposite directions, since the side rear surfaces are screw, edh.profit surfaces;

The thickness of the tooth along the dividing circumference is reduced in accordance with the change in the displacement ratio. In order to get a change in the external diameter of the holby agreed with a change in the tooth thickness, it is necessary to withstand such a ratio between the rear angle at the top of the tooth of the α.versh and on the side cutting edges in the cross section, normal to their projection on the end of the αb endings

where the α and the angle of pressure on the dividing circle in the original and in any other cross.section of the dolbyan plane perpendicular to its axis. It is different from the standard pressure angle and for a straight.toothed hollow is located according to the formula

Such a change / adjustment / pressure angle is done to reduce the errors of the profile introduced by sharpening the front surface at an angle γ.

Tooth.cutting worm mills

Worm mills are used to process straight.toothed, braid and chevar cylindrical wheels, as well as for cutting teeth of worm wheels with various types of engagement. The worm cutter as a tool is obtained from the worm by cutting the grooves that form the front surface of the teeth and the space for placing chips and strapping the teeth to create the rear angles throughout the contour.

In terms of constructive implementation, worm mills are whole, nozzle and prefabricated. By type of processing, they are divided into Black (multi.storage), finish and precision. By the appearance of the original worm, the basis of the worm milling cutter, they are Eliventic, Archimedes, convoy for cutting wheels with an elementary cloth.

For cutting of gears about cycloidal hooks and with the hooking of Novikov, cutters are used, which are based on the corresponding worms.

Worm mills operate on special dentoring machines 5k301, 5k.320, 5k32 and others., as well as on heavy machines 5342, 5345, 5364, produced by the Kolomensky machine.building. In the process of cutting the cutter and the workpiece rotate relative to their axes. In one turn, the milling cutter will turn to one/zto with a single mill and on a/zto, if the milling cutter is multi.assembled; here zto. the number of teeth of the chopped wheel, a – The number of mills of cutters. In addition, the machine has a movement to cut the tool in the radial direction to the workpiece and movement of the caliper for feeding. The supply is carried out along the axis of the workpiece during the processing of cylindrical wheels; in the radial direction. When processing worm wheels or cylindrical wheels in a narrow rim and in a tangential direction to the workpiece. When cutting worm wheels.

The method of dialing worm cutters is highly-proof and universal, gained widespread in all types of production for processing cylindrical and worm wheels. Processing is carried out continuously, according to the method of running. Unlike disk and finger mills, one worm mill can process the wheels in any number of teeth of this module. The disadvantage of the dental method during axial and radial feeds is the limited number of incisors that envelope the profile of the teeth of the processed wheel; as a result, the roughness of the treated surface of the teeth in some cases is high.

Constructive mills of cutters. When designing tooth.cutting worm mills, some gear parameters should be set: module m, the angle of pressure on the dividing diameter, t. e. hook angle a, tooth height h and tooth head height ha Front corner Gin Take for the top cutting edges and the rear angle ain, In the outer diameter. For standard mills Gin = 0, ain = 10-12 °.

Type of worm modular milling.

We take a type 2-Frem cutter whole, module m = 2mm, accuracy class a.

The outer diameter of the worm cutter is taken according to (table 4) de = 63mm

The angle of profile of the chip groove (table. 5) ?= 18?

where: x = 7mm coefficient of stock for the axial rearrangement of the cutter.

The angle of the cross.country cross.length lift angle with the surface of the main cylinder

Determining the size of the profile of the teeth of the worm modular milling

Profile in a normal section.

at ? = 1?57 ‘The correction of the angle of the profile of the cutter in the normal section ??= 0 ? (Table.one)

Profile angle in a normal section ?and =? = 20?

Oss section profiling.

The corner of the profile on the left side of the tooth is equal to the corner of the profile on the right side of the tooth, t.to. There are no screw chips.

Modern methods and technological solutions for the effective processing of a gear wheels of a large module

Currently, gear gears (gearboxes, gearboxes) are presented with significant requirements. These requirements include:

• Decrease in cost;
• Decrease in noise;
• Weight loss;
• Decrease in overall dimensions;
• Increasing reliability;
• Increase in the transmitted torque and an increase in the drive power;
• Improvement of dynamic characteristics;
• Increasing the coefficient of useful action;
• Increase in service life;
• Increase in maintenance.

Tough wheels are the main element of any gearbox, so most of the requirements for gearboxes directly referring to the gear wheels. These requirements can be formulated as follows:

• Accuracy of gears (ensuring kinematic accuracy and smoothness);
• Durability of gear wheels;
• Reliability of gears;
• The possibility of transmitting large twisting moments (taking into account factors such as friction, high loads, changes in the direction of load);
• Minimum cost of gears;
• The possibility of implementing additional functions (for example, the presence of synchronizer crowns).

Some of these requirements should be implemented at the expense of the corresponding design of the gears, part. due to manufacturing technology. However, manufacturing technology in any case should provide the possibility of implementing structural parameters with a given design accuracy.

As a result, you can determine the basic requirements for the production of gears:

• Constant high quality;
• High performance;
• High flexibility;
• Small investments;
• Minimum production costs.

In recent decades, significant changes have occurred in the technology for processing cylindrical gears. As a result, it became possible several times (and in some cases several tens of times) to increase the performance of cylindrical wheels tooth processing. The above requirements for gearboxes and gear wheels form more and more stringent requirements for the accuracy of gears.

Trends in increasing accuracy and processing performance over the past 40 years are clearly presented in rice. one.

Within the framework of one work, it is impossible to consider all aspects of the modern technology of processing of gear wheels, so we will limit ourselves to considering the following issues:

the effectiveness of the use of various methods for milling tooth tooths of gear wheels of a large module;

The effectiveness of the use of various modern tools for dentoring.

The main methods of tooth milling are the method of profile milling (a copying method with a single division) and the method of rolling milling. In the first case, the instrument is disk modular mills (less often finger modular mills), in the second. worm mills.

Prior to the use of the method of milling by worming with worm mills, the treatment of teeth was carried out only by the method of profile milling. In this case, the tool. a disk or finger modular cutter. has a profile in the section that matches the profile of a given tooth hollow.

The tooth processing is carried out along the part of the part over the entire length of one hollow, after which the part is rotated at the angle corresponding to the angular step of the teeth and the next hollow is processed. This process is repeated as many times as the teeth must be treated. The need to turn (“divide”) the part on the corner step when processing the next tooth determines another name for this method. the method of single division

With run.in milling, a continuous kinematic connection is provided between the machine table, on which the processed part is fixed and the spindle on which the worm mill is fixed. The tooth of the cutter has a profile of a straightforward rail. As a result, the invasive profile of the tooth of the part is formed by the envelope of the straight lines, which are formed at various angular positions of the profile of the tooth of the cutter

At domestic enterprises, the classic designs of a dental instrument are used to date. These designs for disk modular mills include: whole high.speed milling cutters, attacking high.speed milling cutters, prefabricated fast.cutting mills, attacking (prefabricated) carbide cutters and prefabricated carbide cutters

It should be noted that the modern processing technology involves completely different cuts of milling. Almost everywhere in technologically developed countries, when implementing modern technology of specialized tooth milling, milling cutters with replaceable multifaceted plates are used.

The principle of applying modular milling implies that the cutter profile is fully consistent with the profile of the tooth of the processed part. However, if cuts are used separately for draft and finishing processing, then the profile of draft mills does not have to fully match the profile of the tooth of the part with the corresponding allowance. Black milling mills can cut out a preliminary straight.sized (non.enlightenment) profile, can form a chamfer on a tooth head, can closely form an invaluate profile and can form a tooth with cutting (milling cutter with a pro.Tubensa) to exclude the processing of the bottom of the hollow during subsequent finishing processing. For large modules, the side surface of the tooth of the cutter is formed by several cutting plates

The selection of technology for processing a large module.

Taking into account the accuracy of the accuracy of processing with modular cutters, the scope of their application in the general form is determined as follows:

• for preliminary milling of parts with a large step (module), which are then finally processed by the method of running in worm cutters;
• For processing parts with a very big step (module) in cases where the capabilities of the machine (according to the working area or power characteristics) do not allow the use of milling by the rest and if the tolerances on the processed part are not too narrow;
• for processing worms with a small number of teeth and a small angle of rise;
• for processing profiles that are not formed by the movement of rolled;
• to process wheels with wide tolerances, when you need to process a small number of parts and there is no suitable worm mill, and if you order it too expensive or long.

The advantages of worm mills should be attributed:

• The absence of the need for accurate positioning of the cutter relative to the part. the worm mill forms the Evolvent at any center distance (taking into account the displacement factor), the side displacement of the cutter does not affect the accuracy of processing
• One worm milling cutter of a certain module can be processed by the parts of this profile with almost any number of teeth (for disk milling cutters, the profile of the final milling cutter is determined for a specific part)
• The worm mill heats the workpiece along the entire periphery evenly, local heating and the associated deformations are absent
• When using cutters with interchangeable plates, the number of cutting edges is significantly larger than that of disk mills, which increases the resistance of the tool
• Since the use of a worm cutter in cutting is simultaneously more cutting edges, the dynamic load on the part is less than when using a disk milling cutter.

The disadvantages of the use of worm mills when processing gear wheels of a large module include:

• When processing parts with a small number of teeth, a worm milling time is greater than the processing time of a disk mill
• Worm mills can only be treated with such profiles that can be obtained by the method
• Worm mills are practically not used for processing internal teeth (exclusively special cutters, lack of the ability to move)
• Worm mills can practically not be used for processing a large.diameter toothed wheels (about 4 mm), since a worm cutter with a working length exceeding the ability to install on a machine (more than 600 mm) is required to ensure the necessary length of the contact

The main criterion for choosing a particular processing method is economic efficiency. In this case (as, by the way, almost always when assessing the effectiveness of cutting processing), it is determined by the processing time (and the value associated with it) and the cost of the tool. First, we compare the time of processing the same part by the methods of profile and rolling grinding.

As an example, take the part of the mountain combine UDC. A gear with an outer diameter of 225 mm has a straight.to.anchor crown with a 12 mm module with 16 teeth. Calculation of processing time by four different methods is presented in the rice. fourteen.

As can be seen from the calculation, the minimum processing time is provided when using a disk modular milling cutter with carbide plates. The method of catering milling in this case loses by performance. Of the three variants of the tool milling tools, the most “fast” is a high.speed cutter with a progressive cutting scheme. In this case, this is explained by the possibility of increasing the supply due to a larger number of chip grooves, which reduces the effect of the cutting speed when using worm mills with a hard alloy plates.

We calculate the cost of processing for this example. The component of the processing value determined by the processing time is defined as the processing time (see. Rice. 14), multiplied by the cost of the machine tool (for this case, 50 €/hour has been accepted).

For solid fast.speed cutting, the cost of the tool on the part is determined by the period of resistance of the milling cutter between the crossroads, the possible amount of lasting (determined by the design of the cutter and depends on the useful length of the tooth of the cutter) and the cost of restoration of the cutter after the end of each persistence period (recovery includes, as a rule, a re.trial and a renewal and applying a new wear.resistant coating). Knowing the period of resistance in the details and the number of periods of the resistance of the cutter, you can calculate the full period of the resistance of the cutter, expressed in the number of processed parts. To determine the total cost of recovery, we multiply the cost of one recovery (these data are provided by a specialized unit performing these works) by the number of restorations (the number of periods of persistence minus one). Separating the cost of the cutter with the restoration of the number of parts processed over the full period of resistance, we get the cost of the cutter per part.

The results obtained for under consideration are presented in the rice. fifteen.

Design description and the purpose of the worm modular milling cutter

The part can be attributed to details like nozzle worms, has a characteristic worm profile, dissected by chip grooves, having a characteristic profile of the rear surface in the form of an archimed spiral.

The seat has the shape of a long Ш50h5 hole with two belts long L = 54 mm. To transmit torque, the design uses a basting groove b = 12mm, h1 = 3.5 mm.

The main constructive elements of whole mills are: the working or cutting part and body with the fasteners. The working part removes the allowance for processing, the direction of streams of chips, forms the processed surface, provides the required quality of processing.

Single.shaped worm mills are used for the final processing of straight.toothed and braid cylindrical gear wheels with an emergency profile. The milling cutter presented in this work and designed for the final processing of gears, class A according to GOST 9324-80. Worm milling cutter is a perennial tool with structurally current movement.

Technological control of the drawing of the part

The design of the cutter corresponds to GOST 9324-80 “Worm mills, finishing, single-shot for cylindrical gear wheels with an elementary profile”.

The drawing is made in accordance with GOST 2.316-68 “Rules for applying inscriptions, technical requirements and tables”.

Dimensions, landing and maximum sizes are indicated in accordance with GOST 2.207-68 “Making sizes and maximum deviations”.

Deviations of the shape and mutual arrangement of the surfaces of the part are made in accordance with GOST 2.308-68 “Indication on the drawings of the maximum deviations of the shape and location of the surfaces”.

The design of the processing is applied in accordance with GOST 2.309-73 “Application on the drawings of designations of roughness of the surface”.

All sizes and dimensional lines are made in accordance with GOST 2.303-68.

The outer frame, the drawing field frame is made in accordance with GOST 2.301-68.

The image of the part is made in two types. The main look and side view. The main form is combined in the main form, which makes the most complete idea of ​​the details. These two types are made in a projection connection and there are enough of them to read the drawing.

In the upper right corner is a table of parameters in which all the data about the mill is entered. In technical conditions, additional information for technological design is given, not contained in the image of the part. This is information about the state of the material after heat treatment, the unprofitable marginal deviations, the marking of the product.

All structural elements are presented in accordance with the current standards.

Classification of worm mills

Depending on the nature of the processing, this type of equipment is divided into several types:

• Black mills. Used for preliminary processing of the workpiece. Has a front angle of 5-7 ° and a small thickness of the teeth.
• Finishing equipment. Necessary for the final processing of steel teeth.
• Precision mills. Mostly used for the manufacture of turbine gears.
• Pitch worm mills. Used for moving and cutting stars.

Also, cutters are divided into single and multi-assembled, left- and right-handed, whole and prefabricated. In the labeling of the instrument, the hooking angle, module, tooth height and angle of lifting of the screws of the screws are indicated.

Operation Rules

Some types of mills have their own specifics of application. So, a tool designed for the manufacture of straight.sided slot shafts is subjected to uneven loading of the cutting edge. The top of the edge has the greatest contact and, accordingly, the top of the edge, which means 50% of the cutting surfaces, while the teeth are necessary along the entire length and perimeter. To minimize sharpening costs, an enhanced tool with a modified profile and carbide combs is used. This can significantly increase the performance of work. Standard cut dimensions are given in the table below.

Another problem of worm dentition is intermittent contact of the tool with a part. The result is the cut and wavy of the wheel, unacceptable for high accuracy products. Therefore, at the end of the cut, it is necessary to carry out a toothpoint or cheving.

Testing

In the production of gear wheels, cutting teeth on dental machines with worm cutters method is the most common and time.consuming. With this method, you can cut cylindrical gear wheels of external gearing with straight and oblique teeth of standard, conical and barrel.shaped, block wheels, worm wheels, slotted shafts, chain gear stars, etc.

One worm milling cutter of the same normal module and corner of the profile can cut a large number of straight.toothed and scooters with a different number and angle of inclination of the teeth, but with the same module and corner of the profile. Different gear wheels with a different number of teeth in the crowns are cut into one installation of workpieces.

With d Zybofrezing by driving, the tool and workpiece, being engaged, rotate around their axes, like a worm and a worm wheel (the worm is a worm mill). The longitudinal caps of cutters form separate teeth with a rectilinear profile, which, as a result of the back of the back, receive the rear angles necessary for the treatment of cutting. According to the method of the method, the profile of the teeth of the cylindrical wheel is formed by the rectilinear cutting edges of the worm mill. The process of cutting the workpiece of a worm mill can be considered like a gear rod 2 (worm mill) and a toothass wheel 1 (blanks) on rice. one, a.

In Fig. one, b It is shown how the next one after another, the teeth of 3 worm cutters come into contact with the tooth 4 of the processed wheel and form an elementary profile. The invasive shape of the wheel tooth formed by rectilinear cutting edges with one worm milling cutter has such properties that allow gear wheels with any number of teeth to hook properly and with a gear rack.

Another important advantage of evolving engagement is that gear wheels with an elementary profile are less sensitive to installation inaccuracies. The rectilinear profile of the teeth of the worm milling cutter is simple in the manufacture and control.

In Fig. one, in The kinematic diagram of the dental machine is shown. The wormer cutter 2 and the processed wheel 1 are obtained from the main electric motor 6 through the pulleys and the gear wheels of rotational movements, which are treated to each other, as the number of teeth of the wheel in the number of worms of the worm cutter, t.e. The worm mill and the processed wheel are kinematically accurately interconnected.

Recommended materials

a. gearing of a worm cutter with a wheel; b. the formation of an elementary profile;

B. a circuit diagram of a dental machine.

The main mechanism in the kinematic chain for the transmission of rotational movement of the processed wheel is a dividing worm gear 8/9. This transfer is made with high accuracy and collected with a minimum lateral gap.

A similar role in the transmission of the rotational movement of the worm mill is played by a brass.bellied cylindrical pair of 5/4. In addition to rotation, the worm mill has the ability to move along its axis relative to the braid of the wheel 5 and the supply of the supply of the processed wheel 1 on the slot shaft 3 parallel. Tough wheels to change the speed of cutting, supply, division are in node 7.

2. Методы и способы нарезания зубьев

Cutting cylindrical gear wheels. Cylindrical straight.toothed and braid wheels are cut with two main methods: copying and rising.

The copy method in which the profile of the cutting part of the tool corresponds to the profile of the hollow of the tooth of the cut wheel (rice. 2, in), It has mainly small productivity and low accuracy, therefore it is used limited, usually in a single production for processing unreasonable gears (for example, disk modular cutters on universal milling machines using a dividing head). The method of copying with finger modular cutters is used to process coarse.like cylindrical and chevity wheels, as well as when manufacturing with worm mills is not economical.

The method of driving, which has higher performance and accuracy, is widely used in various industries. Currently, the following methods of d Zipotation method are most widely used.

Zubofrezing with axial supply is carried out when the worm cutter is supplied parallel to the axis of the processed wheel (rice. 2, a). This universal method has the greatest use in industry for cutting cylindrical wheels and slotted shafts on ordinary gateplain machines. The disadvantages of this method include a large cut length L, which increases with an increase in the diameter of the worm mill and the angle of inclination of the tooth line.

3.bofilophazing with a radial axial supply lies in the fact that the supply of the worm cutter at the beginning of the cutting and until the full height of the tooth is radically to the axis of the processed wheel, then it stops and the axial feed is turned on (rice (rice. 2, b). This method is carried out on special dentitions with ordinary worm mills. Productivity with radial-axis feed is higher than with axial, by reducing the time for cutting. Due to the increased wear of the teeth of the worm cutter, the radial feed is selected in the range of 0.7-0.9 mm/about. This method is recommended to be used where it is necessary according to the conditions of processing, for example, with dentistry of gear wheels with a large inclination line of the tooth and closed gear crowns, with dentoring with two work passages and the operation of large.diameter wormers. Under normal conditions, the way with axial supply is more economical.

Dissing with diagonal supply is carried out on special dentists, where axial supply is combined with tangential. The mill is moved diagonally by the parallelogram composed of two feeds. axial and tangential (rice. 2, G).

Diagonal supply with diagonal supply compared to axial improves the mating profiles of straight.tooth wheels during the resting due to crossing the envelope of cuts. This is especially important for gear wheels, which are not subsequently subjected to final processing (for example, gear wheels of pumps). The surface roughness on the profiles of the teeth is also reduced. The period of the resistance of worm mills increases significantly due to the more uniform wear of the teeth along the entire working length of the cutter.

This method is advisable to use for processing wheels with wide toothed crowns, a bag of wheels or wheels with increased hardness, when it is necessary to have a large period of instrument resistance during processing. With diagonal dentition, it is economically justified to use long and accurate worm mills.

Testing with a variable axial supply is based on an increase in the supply at the entrance and exit of the worm cutter from the workpiece. The milling of the toothed wheel begins at the maximum feed, then it gradually decreases to a constant value. At a constant supply, the machine continues to work until the cutter exit from the workpiece. At this moment, the supply again automatically increases to the set maximum value.

An increase in the feed causes an increase in surface roughness on the teeth, so this method is used for gear wheels to T = 5 mm for subsequent finishing operations. Cheving or grinding, as well as in the case of cutting the gears with a large angle of inclination of the tooth line, where the cutting path is large enough. Discipotherapy with a variable axial supply allows you to increase productivity by 20-35 %.

The essence of the d Zybofrezing method for two working moves is that the first and second work moves are carried out sequentially, for one setting (rice. 2, e), over, the second work move is made with a minimum allowance. cutting depth is 0.5-1.0 mm. The first working move, as a rule, is carried out on a passing feed, the second. On the counter. Due to the small allowance during the second work move, the cutting speed and the axial feed is higher than at the first.

During testering for two working moves, which is used for wheels with a module over 4 mm in addition to increasing productivity, high stable accuracy of the parameters of the teeth, especially in the direction of the tooth, creates favorable conditions for automation of the dentistry process, the instrument resistance and performance for the subsequent dental surgery are increased.

Worm cutting mills for cutting wheels

Worm wheels can be chopped by worm cutters, cutters-flyers and finally treated with worm Shevers. Worm mills work with a radial or tangential feed.

When working with radial feed, the cutter is installed so that the teeth touch the outer surface of the rim of the wheel. Then, when the cutter rotates and the workpiece rotates, their axes are brought closer to A0g values, which provides the necessary diesel dentitions of the cut wheel. In the future, the teeth are cut at a constant interceptor distance and with joint rotation of the cutter and the workpiece without moving the cutter along the axis (rice. fifteen.3, a).

With the tangential supply of the axis of the cutter and the workpieces, the required interceptor distance is installed A02, Then Tangenzi is carried out-

Рис. 153. Схемы нарезания червячного колеса червячной фрезой:

а — с радиальной подачей; б — с тангенциальной подачей альная подача вдоль оси, причем средняя леска для триммера зубьев фрезы перемещается касательно к начальной окружности нарезаемого колеса (рис. 15.3, б). У таких фрез угол заборного конуса ср = 11-НЗ° на длине, равной 2,5—3 шагам, выполняется для уменьшения нагрузки на первый зуб фрезы.

Тангенциальный метод нарезания колес менее производителен, чем радиальный, но обеспечивает повышение качества поверхности зубьев путем увеличения числа зубьев фрезы, находящихся в контакте с заготовкой. Стойкость тангенциальных фрез оказывается выше из-за того, что сила резания распределяется на большее число зубьев фрезы.

Чтобы обеспечить геометрически правильное зацепление нарезаемого колеса с червяком, фреза должна быть спрофилирована идентично профилю витков червяка. Собственно профилирование червячных фрез, обрабатывающих червячные колеса, не отличается от профилирования червячных фрез для цилиндрических зубчатых колес. Исходные данные для расчета фрезы задаются в осевом сечении червяка: модуль; угол зацепления; осевой шаг; осевая толщина зуба; наружный диаметр; делительный диаметр; угол наклона витка; число заходов червяка; число зубьев колеса; радиальный зазор в передаче; диаметр окружности выступов червячного колеса; направление витков червяка.

Габаритные размеры фрезы в поперечном сечении выбираются не произвольно, что допустимо у фрез для цилиндрических колес, а зависят от диаметра червяка. Средний (делительный) диаметр зубьев фрезы равен среднему диаметру червяка:

Рис. 15.4. Определение габаритного размера червячной фрезы:

ТТМЯМРТП Tin ‘Л Л MU UPniiClUIinn

шаги зубьев фрезы и колеса также равны между собой. Внутренний диаметр d фрезы обычно принимается равным внутреннему диаметру di червяка:

Углы подъема винтовой линии па делительном цилиндре, модули и число заходов фрезы и червяка должны совпадать.

Наружный диаметр фрезы d(h делается больше наружного диаметра червяка da на удвоенную величину радиального зазора с с учетом припуска на переточку (рис. 15.4):

где 0,1 т — припуск на переточку, компенсирующий уменьшение радиального зазора в передаче при сохранении межосевого расстояния в процессе нарезания независимо от степени переточки фрезы.

Так как заходность фрезы должна равняться заходности червяка, то часто фрезы приходится изготавливать многозаходными. Поэтому углы ф7езь7;”/Г‘-делиТеТьный подъема витков фрез для червячных колес полу- диаметр; V — наружный чаются больше, чем таковые для цилиндрических диаметр колес, иногда до 35—40°.

В зависимости от формы профиля червяка фрезы для обработки червячных колес могут быть эвольвентными, архимедовыми и конволютными. Выбор тина основного червяка зависит от типа фрезы (черновая или чистовая): архимедовы — для чистовых фрез, а эвольвентные и конволютные — для черновых.