Cutting Tool Course Project

Contents

CONTENTS

INTRODUCTION

1 FLAT PATTERN DESIGN

1.1 General information

1.2 Determination of actuating dimensions

1.3 Overall dimensions

1.4 Geometry of the blade

1.5 Length of the intake part of the sweep

1.6 Number of teeth

1.7 Selection of angular steps

1.8 Material Selection

1.9 Technical requirements

2 ROUND PLATE DESIGN

2.1 General Information

2.2 Outer diameter of rams

2.3 Cutting Part

2.4 Sizing part of rams

2.5 Plate thickness

2.6 Chip holes

2.7 Number and width of ram feathers

2.8 Material Selection

3 DESIGN OF DISK MODULAR MILLING CUTTER

3.1 General Information

3.2 Determination of involute section profile

3.3 Selection of geometrical parameters of milling cutter teeth

3.4 Definition of milling cutter structural elements

3.5 Material selection and technical requirements

4 DESIGN OF WORM SPLINE CUTTER

4.1 Theoretical Information

4.2 Initial data

4.3 Calculation of worm spline cutter

4.4 Substantiation of material selection

5 TOOLBOX DESIGN

5.1 Basic Theoretical Information

5.2. Source Data

5.3. Calculating Instrumental Positioning Accuracy

block

6 END CUTTER DESIGN

6.1 General Information

6.2 Design Procedure

LIST OF SOURCES USED

Paper

DBE: from tables, sources.

The purpose of this work is to strengthen and expand the material studied in the cutting tool discipline, acquire skills in designing and calculating various types of tools, learn to work with reference literature and regulatory and technical documentation.

Design method - computational, using standard packages: COMPASS Autoproject, MicrosoftWord.

The objective of the course design is to select geometric parameters of the designed tool, select and substantiate materials for the cutting part, body and shank, determine dimensional relationships between individual surfaces and elements of the designed tools; selection and justification of tool parameters; execution of working drawings of all designed tools..

MILLING CUTTER, UNFOLDING, ROUND PLATE, TOOL BLOCK, OCCLUSION, TOLERANCE, QUOTA, DIAMETER, HOLE, TEETH, POLYHEDRAL NON-TRAVELLING PLATES, TOOL GEOMETRY, CUTTING PART MATERIAL, SHANK.

INTRODUCTION

In modern mechanical engineering, cutting is the main technological method that ensures high quality of machining of the surfaces of parts.

The cutting and auxiliary tools, tool presets outside the machine, and tooling systems play an important role in achieving high cost-effectiveness of expensive CNC equipment.

To fulfill this role, you need to use a tool that differs in the following qualities: high reliability during operation; fast shifting; high level of unification; readability; relatively low cost.

Thus, the general line for the development of mechanical engineering is compact automation of design and production.

Deployment is a process of processing holes to obtain high purity and accuracy. A flat pattern is a multi-toothed tool that, like a drill and a countersink, during processing rotates about its axis (the main movement) and translates along the axis, making a feed motion.

Round plate represents nut coupled with thread to be cut and turned into cutting tool by cutting chip grooves and napping teeth. It is used for cutting of external thread. The ram cannot cut threads of high precision, since after heat treatment in its threads it is impossible to eliminate distortions of the pitch, angle of the profile. However, due to the cheapness and easy operation of the rams, they became widespread. 

The worm cutter is an initial worm, with a point instantaneous touch to the surface of the workpiece, turned into a cutting tool. 

In order to transform the worm into a workable tool, it is necessary to cut the chip grooves, that is, to create a space for the chips formed during cutting and the front surface, to create a rear surface that ensures its smooth movement during cutting and positive rear angles on the cutting edges.

The units are an interchangeable assembly unit, which provides a quick change of it in the boring bar during operation or sharpening of cutting elements.

Tool blocks installed in the spindle shall provide static accuracy resulting in the outflow of cutting edges in accordance with the allowable cutting edge run-out for the tool. 

End cutters are widely used in the treatment of planes on vertical milling machines. Their axis is set perpendicular to the machined plane of the part. Unlike cylindrical cutters, where all points of cutting edges are profiling and form a treated surface, at end cutters only vertices of cutting edges of teeth are profiling. End cutting edges are auxiliary. Main work of cutting is performed by side cutting edges located on external surface.

Flat Pattern Design

1.1 General information

Deployment is a process of processing holes to obtain high purity and accuracy. A flat pattern is a multi-toothed tool that, like a drill and a countersink, during processing rotates about its axis (the main movement) and translates along the axis, making a feed motion.

Deployment allows you to obtain a hole of 2-3rd class of accuracy and 7-8th class of cleanliness of the treated surface.

According to the shape of the machined hole, the reamers can be divided into cylindrical ones used for machining circular cylindrical holes and conical ones used for machining conical holes (Figure 1.1). According to the method of application, machine and manual scans are distinguished. Manual deployments are used to deploy holes manually, and machine ones are used on various machines (drilling, turning, revolving, etc.). The drills can be tail and nozzle, solid and prefabricated, of constant diameter and adjustable. The relatively small diameter reamers are manufactured with a cylindrical or conical shank, which serves to fix it on the machine, or in a tap with a square hole when working manually.

The nozzle drills are mounted on special mandrels, which are installed in the spindle of the machine.

Solid flat patterns are the simplest in design, but cannot be adjusted in diameter. Therefore, expandable and prefabricated reamers with quick-cutting and hard-alloy insert teeth are used, which, after wear and reel, can be adjusted to the required size, which increases their service life. Expansion screens are used in the repair of all kinds of machines, they allow you to adjust the size of the diameter to certain limits. This makes it possible to apply the same sweep in the treatment of holes of different diameters.

Working part of expansion rolls is provided with hole whose axis coincides with tool axis and longitudinal slots. Adjustment of swing diameter is performed by means of ball, which is inserted into conical hole and pressed by adjusting screw. Such scans are manufactured with a diameter of 6 mm to 50 mm and allow changing the diameter within the range of 0.15-0.50 mm.

To ensure the possibility of restoring the diameter size as it wears, the designs of prefabricated reels are used, with the attachment of teeth in the body using corrugations, screws, etc.

Figure 1.1, b, shows a sweep in which the insertion teeth with corrugations are fixed using a wedge. This design allows adjustment in diameter by rearranging the teeth on the corrugations, followed by grinding in diameter and sharpening. Stop rings are provided to avoid axial shift.

For the treatment of conical holes, conical scans are used (Fig. 1.1, c). The pre-treated opening may be cylindrical or conical. Holes with a small allowance are deployed to the cone in one pass. When processing conical holes, when it is required to remove a significant allowance, a set of conical unfolds is used.

Rough sweep has steps on teeth arranged along helical line. With the end edges of each stage, the sweep cuts narrow chips freely placed in the grooves. This sweep turns the cylindrical hole into a stepped hole. The second flat pattern removes the allowance less than the draft flat pattern. Cutting edges of intermediate sweep are provided with chip-separating grooves formed by cutting rectangular thread. Finishing scanning is performed without chip separation grooves, and removes chips with the whole rectilinear cutting edge located on the cone generatrix.

The flat pattern has teeth with a flat front surface coinciding with the axial plane of the tool, that is, the leading angle of the finish pattern is taken equal to zero.

To deploy holes in metal sheets, boiler drills are used (Fig. 1.1, d). They have screw teeth, the direction of which is opposite to the direction of rotation. This prevents self-tightening and jamming of the flat pattern during operation.

Cylindrical unfolding features:

Cylindrical sweep consists of working part, neck and shank (Fig.1.2). The purpose of the neck and shank of the unfolds is the same as that of drills and zenkers.

Working part includes cutting and sizing parts and guide cone, which serves to protect against damage and facilitate penetration of sweep into hole.

The cutting (intake) part of the reamer is a cone, on the surface of which teeth are formed.

Sizing part consists of cylindrical section and section with reverse taper. Front and rear surfaces of reamer teeth on both cutting part and sizing part are flat.

The leading angle γ of the swing is generally assumed to be zero, since the sweep operates in a zone of small thicknesses of the shear layer, the nature of the cutting process depends mainly not on the leading angle, but on the radius of rounding of the cutting edge. On draft patterns and when processing viscous materials, the leading angle is 5-10 °. The rear angles of the turns fluctuate in the range of 4-8 °.

For finishing twists, angle α is selected less than for rough twists.

Sharpening of teeth on the cutting part is done by "dooster," and on the calibrating part - with leaving a cylindrical ribbon with a width of 0.05-0.3 mm. When treating viscous metals to avoid sticking of metal particles, the width of the ribbon decreases to 0.05-0.10 mm. The ribbon serves to guide the sweep in the hole, facilitates the sizing of the hole, and facilitates the control of the sweep in diameter.

A large influence on the work of the sweep is the angle in the plan β, between the sweep axis and the cutting edge, which, at a leading angle equal to zero, goes along the cone generatrix of the cutting part.

The ratio between the width and the thickness of the cut, which make up the cutting forces, the intensity and the wear pattern of the tool, changes with the change in the angle in the plan β. With an increase in the angle of the intake cone, the axial force increases, and the advance of the sweep becomes difficult. Therefore, the angle in the plan is taken to be small in the hand reels, which also contributes to the smooth entry and exit of the reamer from the hole. On the basis of experimental data for manual development when processing through openings φ = 1 - 2 °.

2 ROUND PLATE DESIGN

2.1 General Information

Round plate represents nut coupled with thread to be cut and turned into cutting tool by cutting chip grooves and napping teeth. It is used for cutting of external thread. The ram cannot cut threads of high precision, since after heat treatment in its threads it is impossible to eliminate distortions of the pitch, angle of the profile. However, due to the cheapness and easy operation of the rams, they became widespread. The number of chip holes in the rams ranges from 3 to 7 for threads with a diameter of 2 to 52 mm. The width of the tooth has a great influence on the work of the rat. As the width of the tooth increases, strength and rigidity increase, the ram is better centered and self-tightened during operation. However, the larger width of the tooth leads to increased friction, impairs chip withdrawal and its placement in the grooves, which can cause breakage of the ram.

2.2 Outer diameter of rams

The outer diameter of the dies Dp depends on the size of the thread to be cut, the diameter of the chip holes dc and other structural elements of the dies. As the diameter of the chip holes increases, the conditions for removing and placing the chip improve, and the risk of broken teeth decreases. At the same time, the outer diameter of the ram Dp increases and the width of the feathers decreases - m. This entails an increase in the warpage of the threaded surfaces of the ram during heat treatment, an increase in the consumption of materials both for the manufacture of rams and plastic holders, cartridges, etc. When assigning an outer diameter Dn, it is necessary to ensure that threads of several diameters can be cut with slabs with the same Dn. This helps to reduce the size of the plate holders and the process tooling for the manufacture of dies.

The recommended value of outer diameter and other parameters of round dies for thread diameter 20 mm is selected according to GOST 9740-71. The nominal outer diameter of the thread is equal to the nominal outer diameter of the bolt thread (D = d).

2.3 Cutting Part

Cutting part of dies forms thread profile according to single-generator cutting scheme. Each cutting tooth cuts chips of different width and the same thickness, as in the case of threaded cutting by the marks. The corner of an intaking cone φ at the accepted steps of a carving and quantity of feathers of Z determines shaving thickness. According to GOST 9740-71, the value of angle a = 45 ° for thread d > 20 mm is set.

To ensure the direction of the ram when entering the workpiece, the diameter of the cone at the end of the ram Dt must be greater than the outer diameter d of the thread being cut by 2Δt = 0.1... 0.5 mm, i.e.

Sizing part of rams

The formation of the threaded profile ends when the first teeth of the sizing part come into operation, which can be called "sizing" of the thread. The remaining calibrating teeth perform the functions of centering and feeding the tool. To perform these functions, it is enough to have a calibrating part of three to four threads. The increase in length l2 results in an increase in deformation of the wafer feathers during heat treatment, which reduces the accuracy of the thread; at the same time, chip removal conditions deteriorate.

Thickness of the plate

The thickness of the ram H, like the outer diameter Dp, is unified in order to reduce the number of sizes of blanks for the manufacture of rams, as well as cartridges and ram holders. The thickness of the ram is selected to accommodate a sufficient number of threads on the cutting and sizing portions. From this point of view, it is sufficient to take the thickness of the ram (6-9) P, which is usually held for threads with a large pitch.

2.7 Number and width of ram feathers

The width of the pen of the ram has a significant impact on its performance. With an increase in the width of the pen m (see Figure 2.2), the ram is better centered and guided, the conditions for self-supply are improved, and the margin for relays increases. On the other hand, the friction forces between the threads of the threaded thread and the sizing part of the rat increase, as well as the tooth profile errors, the lumen C decreases, and, as a result, the risk of chipping and breakage of the rat increases.

2.8 Material Selection

Due to the fact that it is impossible to lift the threaded profile of the rams after heat treatment, they are made of alloyed steels KhGSV and 9XS as per GOST 5950-2000. These steels have a lower tempering temperature than fast-cutting steels, so there is no melting of the tooth blades. When hardening these steels, warping is less than that of other tool steels. It is allowed to manufacture dies from fast-cutting steels. At the same time, it is necessary to adjust the threaded profile with special prongs.

Disk Modular Cutter Design

3.1 General Information

Finished shaped tooth cutters (disc, finger) are designed usually as milling cutters with naked teeth. For these tools, the leading angle is taken equal to zero and the leading plane passes through the axis of the cutter. In this case, the profile of the cutter tooth in axial section will coincide with the profile of the part when machining the spur wheels. Therefore, the profiling of the finishing shaped gear cutters for processing spur gears consists in determining the profile of the tooth cavity of the gear wheel.

As is known, the tooth profile of the involute gear consists of an involute portion and a spiral in the tooth cavity.

An involute circle is called a flat curve, which is described by any point of the producing line when rolling it without sliding along the main circle of radius r0 (Figure 3.1, a).

3.5 Material selection and technical requirements

According to GOST 1926587, we choose the brand of steel cutters - P6M5.

Roughness of machined surfaces as per GOST 278973 shall be: 

front surface - 7th class;

surface of support ends - 8th class;

 landing hole surface - 7th class;

the occipital surfaces of the tooth profile are 6th class.

Hardness of the cutting part is HRCe 63 ... 65

Limit deviations of outer diameter as per H16, thickness as per h12, mounting holes as per H7.

Allowable deviations:

deviation from radial front surface + - 45;

radial run-out along outer diameter, relative to hole axis, mcm:

for two adjacent teeth - 5 μm;

for one revolution of the mill - 100 microns.

End run-out at points farthest from cutter hole is 40 mcm. Beating of side cutting edges of teeth in direction of normal to profile of 10 mcm.

Difference of distances from end planes of cutter to points of profile lying on one diameter is 250 mcm .

Profile error, μm:

on the involvent site - 80;

at the apices of the tooth and at the roundings - 160.

Worm Spline Cutter Design

4.1 Theoretical Information

Worm splines are a tool that works by enveloping the profile of a workpiece. Worm cutters are worm on which grooves forming front surface of teeth and space for chip placement are cut. The turns are capped in order to obtain rear angles. Worm splined cutters are of two types - for cutting splined shafts with an involute profile of splines and splined shafts with a straight profile. These cutters are used for machining shafts with different types of centering - centering on the outer or inner diameter and side faces. Worm cutters with "antennae" are designed for cutting splined shafts with centering along inner diameter and side faces, which provide a rectilinear section along the entire height of the shaft tooth, and the grooves formed by them at the base of the teeth facilitate the grinding process. Worm cutters without antennae are used to cut splined shafts centered on outer diameter and side faces. Worm mills are designed depending on the series of shafts - light, medium or heavy and are made of the following accuracy classes:

Class A. Used for finishing splined shafts with tolerance fields for tooth thickness d9, h9, e9, f9 and inner diameter e9;

Class B. Used for finishing splined shafts with tolerance fields for tooth thickness d10 and inner diameter e8 (tolerance for outer shaft diameter is not limited);

Class C. Designed for rough treatment of splined shafts.

By design, worm mills are:

whole;

nozzle;

national teams.

By processing type:

draft (usually multi-start);

finished and pre-seasonal.

By the form the worm who is been the basis for a worm mill:

involute;

Archimedovs;

convolute.

4.2 Initial data

Design a worm spline cutter to cut the spline shaft D - 6x18x22h7x5e8 with chamfer. Shaft material Steel 35XM.

Calculation results are given in Appendix.

For worm spline cutter GOST 802787 sets the following tolerances:

tolerance for deviation of cutter axial pitch ± 0.015 mm;

tolerance for accumulated pitch deviation over the length of any three steps of 0.036 mm;

tolerance for deviation of front surface profile 0.05 mm;

tolerance for deviation of accumulated error of circumferential pitch of chip grooves 0.063 mm;

tolerance for deviation of chip groove direction over 100 mm length of mill working part ± 0.080 mm;

there should be no cracks, burrs and corrosion traces on the entire surface of the mill, there should be no nicks and crushed places on the ground surfaces;

radial run-out tolerance on both shoulders 0.006 mm;

tolerance for running out of support ends 0.005 mm;

tolerance for complete beating of mill teeth tops 0.032 mm;

tolerance for seating diameter mm.

4.4 Substantiation of material selection

This worm spline cutter is designed to cut the spline shaft D - 6x18x22h7x5e8. The designed cutter is made of fast-cutting steel P6M5. This steel is a cheaper substitute for P18 steel, and, like P18 steel, is intended for all types of cutting tool in the treatment of carbonaceous, alloyed, structural steels (preferably for the manufacture of a threaded tool, as well as a tool working with impact loads) [10]. After hardening and tempering, P6M5 steel has a hardness of 63... 65 HRC, which is enough to cut splines on a shaft of steel 35, the hardness of which after annealing 240 HV. Compared to the P6M5F3 steel, the P6M5 fast cutting steel has slightly lower mechanical properties, however, the P6M5 steel is not prone to overheating and decarburization, the P9M4K8 has higher mechanical properties than the P6M5, however, it is used to treat high-strength and heat-resistant steels and has a higher cost. The treatment is carried out by the rolling method - both the mill and the shaft rotate simultaneously. The method of producing a splined shaft is high-performance, but less accurate compared to the method of copying - obtaining a splined shaft with chisels, disk shaped cutters.

5 TOOLBOX DESIGN

5.1 Basic theoretical information.

Due to the fact that the life of the cutting parts of the tool is limited, it is economically feasible to separate the devices providing their functioning into separate units.

The NC and  GPS auxiliary tool design consists of two main elements: basic tools for installation on the machine and connecting surfaces for installation of the cutting tool. The device for automatic change of the tool and its attachment to the machine determines the structure of the shank, which should be the same for the whole tool to this machine. To obtain the specified dimensions of the part without test passes in accordance with the program, it is necessary to introduce devices into the construction of the auxiliary tool that provide for adjustment of the position of the cutting edge

In modern mechanical engineering, the system of auxiliary tools for CNC machines according to RTM2 P14-2-84 is widely used, in which, on the basis of unification, the nomenclature of typical structures necessary for practice is contained. 

The units are an interchangeable assembly unit, which provides a quick change of it in the boring bar during operation or sharpening of cutting elements.

Tool blocks installed in the spindle shall provide static accuracy resulting in the outflow of cutting edges in accordance with the allowable cutting edge run-out for the tool. 

The accuracy of processing depends on the error of the tool blocks. Accuracy of tool blocks is regulated by permissible radial run-out. For the thrower, the allowable run-out of cutting edges is 0.056 mm.

Static accuracy can be obtained by correctly selecting the construction and manufacturing accuracy of the auxiliary tool with appropriate manufacturing accuracy of the cutting tool. The beating of the cutting edges of the tool in the coordinate system of the machine is considered as a closing link in a complex dimensional chain formed by deviations in the linear and angular dimensions of the elements of the auxiliary tool.

The use of theoretical and probabilistic methods allows you to calculate the dependence of the beat of the tool on the accuracy of the production of the auxiliary tool. The angular errors of the links (axis misalignments) and vector errors (parallel axis misalignment) of the tool block elements can be summed up by bringing the axis misalignments to a vector view in the plane of the closing link (beating the cutting part) through the gear ratios.

5.2. Source Data

Design tool block for thread cutting M87K, length L = 12 mm with adjustment of cylindrical mandrel extension relative to adapter bushing with cone 7:24 within l1 = 230... l2 = 265 mm. Precision class NC machine H. Machining of the hole is performed when the spindle leaves to l3 = 250 mm. Tool - tick, cone 7:24 - No. 50, cone accuracy 7:24 - AT5, cylindrical joint accuracy 7:24 - IT5, part material Steel 35. Cutting modes: t0 = 0.65 mm; S0 = 1.25 mm/v For a given tool block with a mark, calculate the accuracy of the tool positioning. Dimensions and design of connecting surfaces of the block with cone 7:24 shall comply with GOST 2582783.

5.3. Calculating Tool Block Positioning Accuracy

GOST 2582783, which regulates the main dimensions of tool shanks with a conicity of 7:24 for CNC machines, has been developed for NC boring machines. The shank is used on machines with both automatic and manual tool change.

A tick holder is inserted into the shank, which is attached and adjusted using two bolts and a nut. It provides the so-called feed compensator, as well as a floating clutch (it smooths out not getting into the hole).

The run-out of the tapered hole of the spindle of the NC machine of accuracy class H at the end is 0.008 mm, at the departure 300 mm - 0.010 mm, that is, the permissible skew is 0.001 mm on the length 300 mm.

The degree of accuracy of the production of conical surfaces 7:24 - AT6. Run-out of cylindrical hole relative to cone 7:24 on cartridge housing 0.0012 mm.

6 END CUTTER DESIGN

6.1 General Information

End cutters are widely used in the treatment of planes on vertical milling machines. Their axis is set perpendicular to the machined plane of the part. Unlike cylindrical cutters, where all points of cutting edges are profiling and form a treated surface, at end cutters only vertices of cutting edges of teeth are profiling. End cutting edges are auxiliary. Main work of cutting is performed by side cutting edges located on external surface.

Since only the tip regions of the cutting edges are profiling on each tooth, the shapes of the cutting edges of the face cutter for the flat surface treatment can be varied widely. In practice, end cutters with cutting edges in the form of a broken line or a circle are used. Angles in plan F on end cutters can vary within wide limits. Most often, the angle in plan F on the end cutters is taken equal to 90 ° or 45-60 °. From the point of view of the resistance of the cutter, it is advisable to select it at the lowest value, providing sufficient vibration resistance of the cutting process and a given accuracy of processing the part.

End cutters provide smooth operation even with a small allowance, since the angle of contact with the workpiece at the end cutters does not depend on the allowance and is determined by the milling width and diameter of the cutter. The end cutter can be more massive and rigid than cylindrical cutters, which makes it possible to conveniently place and securely fix the cutting elements and equip them with hard alloys. End milling generally provides more performance than cylindrical milling. Therefore, most of the planar milling work is currently performed by end cutters.