1. 3. Multipoint cutting tools  A multi-point cutting tool contains more than two main cutting edges that simultaneously engage in cutting action in a pass.  Sometimes, cutters with two cutting edges (more than one) are also considered multi-point cutting tools (instead of considering it as a double point cutter).  The number of cutting edges present in a multi-point cutter may vary from three to few hundreds.  Since cutting edge appears at the intersection of rake surface and flank surface, so a set of rake surface and flank surface also exists for each cutting edge.  Milling cutters are the common example for this category.  Except fly milling cutter (a single point cutter), others are usually multi-point cutter.  It can contain three cutting edges (say small end mills) to as high as 40 cutting edges for heavy duty large cutters. 1 TDM by G/giorgis B

2. Advantages of multi-point cutting tool  Since total feed rate or depth of cut is equally distributed among all cutting edges, so chip load on each cutting edge reduces greatly.  Thus higher feed rate or depth of cut can be utilized to improve material removal rate for enhancing productivity.  Because of the distribution of chip load, force acting on each cutting edge reduces significantly.  Sometime, one component of cutting force as a whole gets eliminated/reduced automatically (resultant of one cutting force component in a particular direction may become zero)  During machining, none of the cutting edge remains in continuous contact with the work piece; instead, engagement and disengagement occur repeatedly. This provides sufficient time to disperse heat from the tool body, which protects the cutter from excessive heating and plastic deformation.  Due to lesser period of heat accumulation within the tool body, tool wear rate also reduces. Consequently, life of the cutter increases. 2 TDM by G/giorgis B

3. Disadvantages of multi-point cutting tool  Due to intermittent cutting, cutting edges or teeth are subjected to fluctuating load.  This creates noise, vibration and endurance failure of the cutter.  Design and fabrication of the cutter is comparatively difficult. This makes such cutter costlier. 3 TDM by G/giorgis B

4. 3.1. Nomenclature of Drills  Drill bits are cutting tools used to remove material to create holes, almost always of circular cross-section.  Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials.  In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation.drill  The drill will grasp the upper end of a bit called the shank in the chuck. chuck 4 TDM by G/giorgis B

5. 3.1. Nomenclature of Drills/ cont… 5 TDM by G/giorgis B

6. 3.1. Nomenclature of Drills/ cont… Main Parts of Twist-Drill  Body: It is the part of the drill that is fluted and relieved.  Shank: It is the part that fits into the holding device.  Dead Centre: It is the sharp edge at the extreme tip end of the drill, formed by the intersection of the cone- shaped surfaces of the point. It should always be in the exact centre of the axis of the drill.  Point: It is the entire cone-shaped surface of the cutting end of the drill.  Cutting Edge: It is the part of the point which actually cuts away the material when drilling a hole. It is ordinarily as sharp as the edge of a knife. There is a cutting edge for each flute of the drill.  Lips: These are the main cutting edges of the drill and are formed by the intersection of the flank and flute surfaces. For efficient cutting, the lips should be straight, equal in length and symmetrical with the axis of the drill. 6 TDM by G/giorgis B

7. Main Parts of Twist-Drill/ cont…  Lip Clearance: It is the surface of the point that is ground away or relieved just back of the cutting edge of the thrill.  Margin: It is the narrow surface (between A and B in Fig.) along the groove that determines the size of the drill and keeps the drill aligned. It’s surface is part of a cylinder which is interrupted by the flutes and what is known as body clearance. The diameter of the margin at the shank end of the drill is 0.01 to 0.05 mm smaller than the diameter at the point. This allows the drill to revolve without binding when drilling deep holes.  Body Clearance: The portion of the drill from B to C in Fig. is smaller in diameter than the margin between A and B. This reduces the friction between the drill and walls of the hole being drilled, while the margin ensures the hole being of accurate size. 7 TDM by G/giorgis B

8. Main Parts of Twist-Drill/ cont…  Webs: It is the metal column in the drill which separates the flutes. It runs through the entire length of the drill between the flutes and the supporting section of the drill. It is in fact the ‘back bone’ of the drill. It gradually increases in thickness towards the shank. This thickness of the web gives additional rigidity to the drill.  Rake Angle of a Drill: It is the angle of the flute in relation to the work. For ordinary drilling, the rake angle established by the manufacturer of the drill is correct and should remain untouched.  If this angle was 90° or more, it would not give a good cutting edge. If the angle is ground too small, it makes the cutting edge so thin that it breaks down under the strain of the work.  The rake angle also partially governs the tightness with which the chips curl and hence the amount of space which the chips occupy. Other conditions being the same, a very large rake angle makes a tightly rolled chip, while a rather small rake angle makes a chip tend to curl into a more loosely rolled helix. 8 TDM by G/giorgis B

9. Main Parts of Twist-Drill/ cont…  Helix Angle: It determines the rake angle of the cutting edge of the drill. As it decreases, rake angle also decreases and makes the cutting edge stronger.  Usual helix angles for normal materials are 16°, 18°, 20°, 25°, 30° for diameter ranges 0 – 0.6 mm, 0.6 to 1, 1 to 3.2, 3.2 to 5, 5 to 10 and above 10 mm respectively.  For harder materials helix angles are smaller of the order of 10° to 13° and for softer materials helix angles of the order of 35° to 45° are used.  Twist drills are made in three tool types, viz. normal with helix angles from 16° for 0.6 mm hole to 30° for 10 mm hole; hard type with helix angles from 10° for 1 to 3 mm diameter holes; to 13° for 10 mm diameter holes; and soft type with helix angles from 35° for 1 to 3 mm hole to 40° for holes of 10 mm diameter. 9 TDM by G/giorgis B

10. Main Parts of Twist-Drill/ cont…  Point Angle: It is usually taken as 118° as it gives satisfactory results for a wide variety of materials.  Lesser point angle increases width of cut and is used for brittle materials.  Point angle of 80° is used for moulded, laminated plastics, hard rubber and marble.  Higher point angle reduces width of cut and produces thicker chips for same feed rate and is used for hard and tough materials. 140° point angle is used for celluloid, copper, aluminum alloys, stainless steel and austenitic steels.  Chisel-Edge Angle: It is the angle between the chisel edge and the cutting lip, as viewed from the end of the drill.  Larger it is, larger will be clearance on the cutting lip near the chisel edge. It varies from 130° to 145°. Large values are used for small diameter drills 10 TDM by G/giorgis B

11. 3.2. Nomenclature of milling cutters  Milling cutter is the cutting tool used in milling machines.  It has a cylindrical body, rotates on its own axis, and is provided with equally spaced teeth which engage the work-piece intermittently.  The cutter teeth are machined to give cutting edge on the periphery.  They may be gashed either axially or spirally.  The material from workpiece is removed by relative movement of workpiece and cutters.  There are a variety of cutters available depending upon the type and location of teeth, ways of holding the cutters etc.  The teeth of the milling cutters can be straight or parallel to the axis of rotation or at an angle known as helix angle.  They may be on the cylindrical surface or the flat surface (one side or both sides).  Further the helix may be right or left-handed. 11 TDM by G/giorgis B

12.  The cutter may be of the solid type with teeth and body on one piece or of the inserted type, the body being of low carbon steel and the teeth of any kind of tool steel.  In the integral tooth cutters, the teeth are formed by cutting away material from the body of the cutter; the body is cast or forged with integral projections to which blocks of some cutting material are attached by brazing or welding.  Inserted blade cutters have forged steel bodies with slots or grooves machined in the body periphery.  Cutting blades are inserted in the slots and fastened in place by some mechanical means. 3.2. Nomenclature of milling cutters/ cont… 12 TDM by G/giorgis B

13. Hand of Milling Cutter Rotation:  In order to determine the hand of rotation of any milling cutter, look at it from the front or cutter end of the spindle.  If the spindle rotates clockwise, the rotation is left hand rotation or left- hand cut, and if it rotates counter clockwise then it is right hand or a right-hand cut (Refer Fig. below)  The hand of helix can also be judged the same way. If from front or cutting end of a cutter the helix appears to have a clock-wise contour, it is right helix and if counter clockwise then it is left helix. 3.2. Nomenclature of milling cutters/ cont… 13 TDM by G/giorgis B

14. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter:  The teeth of fluted cutters are designed to cut on the periphery and in many cases on the side as well.  A typical milling cutter with various angles and cutter nomenclature is shown in Fig. below. 14 TDM by G/giorgis B

15. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter: i. Arbor: It is the shaft on which the milling cutter is mounted. ii. Shank: It is the parallel or tapered extension along the axis of the cutter employed for holding and driving. iii. Cutter Body: This is the main frame of the cutter on which the teeth are brazed or mechanically held or are integral with it. It has either a hole for mounting on an arbor or a solid shank for mounting in the spindle or collet. iv. Periphery: It is locus of the cutting edge of the cutter and is an imaginary cylindrical surface enveloping the tips of the cutting teeth. It determines the diameter of the cutter. v. Cutting Edge: is the only portion that touches the work. It is the intersection of the tooth face and the tooth flank of back surface. The cutting edge is generally a line which may be straight, helical or some complex profile. 15 TDM by G/giorgis B

16. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter: vi. Gash: It is the chip space or flute between the back of one tooth and the face of the next tooth. vii. Face: It is that portion of the gash adjacent to the cutting edge on which the chip impinges as it is cut from the work. viii. Fillet: It is the curved surface at the bottom of gash which joins the face of one tooth to the back of the tooth immediately ahead. ix. Land: This is the narrow surface back of the cutting edge resulting from providing a clearance angle. It never touches the work and is less than 1.5 mm in width. x. Tooth Face: This is the surface upon which the chip is formed when the cutter is cutting. It may be either flat or curved. xi. Back of Tooth: The back or flank of the tooth is created by the gullet and relief angle (secondary clearance). It may be flat or curved surface. 16 TDM by G/giorgis B

17. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter: xii. Lip Angle: It is the inclined angle between the land and the face of the tooth. It is also equal to the angle between the tangent to the back of the cutting edge and the face of the tooth. xiii. Clearance Angle (Primary Clearance): This is the angle between a line through the surface of the land and a tangent to the periphery at the cutting edge. It is necessary to prevent the back of the tooth from rubbing against the work. It is always positive and should not be small so as to weaken the cutting edge of the tooth. For most of the commercial cutters over 75 mm diameter, the clearance is 3 to 5°. Small diameter cutters have increased clearance angles to eliminate tendencies for the teeth to rub against the work. 17 TDM by G/giorgis B

18. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter: xii. Lip Angle: It is the inclined angle between the land and the face of the tooth. It is also equal to the angle between the tangent to the back of the cutting edge and the face of the tooth. xiii. Clearance Angle (Primary Clearance): This is the angle between a line through the surface of the land and a tangent to the periphery at the cutting edge. It is necessary to prevent the back of the tooth from rubbing against the work. It is always positive and should not be small so as to weaken the cutting edge of the tooth. For most of the commercial cutters over 75 mm diameter, the clearance is 3 to 5°. Small diameter cutters have increased clearance angles to eliminate tendencies for the teeth to rub against the work. Clearance values also depend on the various work materials e.g., for cast iron, 4° to 7° is required; whereas soft materials like magnesium, aluminium and brass are cut efficiently with clearance angles of 10° to 12°. 18 TDM by G/giorgis B

19. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter: xiv. Relief Angle (Secondary Clearance): A secondary clearance is generally ground at back of the land to keep the width of the land within the proper limits. It is necessary because after several sharpening of the cutter, the width of the land increases to a point where it begins to interfere with the work. It is usually 3° greater than the clearance angle (Primary clearance). Not all cutters have secondary clearance. 19 TDM by G/giorgis B

20. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter:  If this line lies on the same side of the radius as tooth, it is a positive rake. If it lies on the opposite side of the radius of tooth, it is a negative rake. For most of high speed cutters, positive radial rake angles of 10° to 15° are used.  These values are satisfactory for most materials and represent a compromise between good shearing or cutting ability and strength. xv. Rake: If the face of a milling cutter lies along a radius of the cutter, it is said to have zero rake. If the face of cutter lies along a line on either side of the radius, it has a positive or negative rake. 20 TDM by G/giorgis B

21. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter:  Milling cutters made for softer materials like aluminum and magnesium can be given much greater positive rake (20 to 25°) with improved cutting ability.  Usually only saw type and narrow plain milling cutters have straight teeth with zero axial rake.  As cutter increases in width a positive axial rake angle is used to increase cutting efficiency.  Positive rake is mostly used for high speed cutters, because it improves the flow of metal along the face, with resulting lower tooth temperature, lower horse power, longer tool life and a better finish.  For high-speed steel and carbide-tipped cutters, negative rake angles (both radial and axial) are generally used.  The primary object of the negative rake is to protect the cutting edge of the carbide tools which are relatively brittle compared to high speed steel. 21 TDM by G/giorgis B

22. 3.2. Nomenclature of milling cutters/ cont… Elements of Fluted Milling Cutter:  The negative rake causes the cutting forces to fall within the body of the cutter and particularly the portion supporting the inserted tooth and is thus ideal for carbide-tipped cutters.  With proper handling of tool, negative rake gives better finish on steel than positive rake.  Improved tool life is obtained by the use of increased tip angle and it can withstand shock loads better.  Plain milling cutters with teeth on the periphery are usually given a negative rake of 5° to 10° when steel is being cut.  Alloys and medium carbon steels require greater negative rake angles than soft steel.  Exceptions to the use of negative rake angles for carbide cutters are made when soft non-ferrous metals are being milled. 22 TDM by G/giorgis B

23. 3.2. Nomenclature of milling cutters/ cont… Number of Teeth on Milling Cutter:  Usually milling cutters and milling conditions vary so widely that it is difficult to set hard and fast rules for determining the number of teeth to be provided on a milling cutter.  For fluted and relieved cutters, a reasonably proportioned tooth can be obtained by the formula Z = 2.75 √D – 5.8 (where Z = No. of teeth, D = diameter of cutter in mm)  Fairly coarse teeth are obtained for cutters over 66 mm diameter by the formula Z = (D/12) + 8  For an inserted, blade-face mill it is better to assess the number of teeth on the assumption of their being spaced a suitable distance apart on the periphery of the cutter  Thus, Number of blades = circumference of cutter / desired blande spacing. 23 TDM by G/giorgis B

24. 3.2. Nomenclature of milling cutters/ cont… Elements of Face Milling Cutter:  Face milling cutters with multiple-tooth inserts are used for removing metal at high material removed rates.  It generally consists of a large-diameter cutter body with a number of mechanically fastened inserted tools.  Large volume material is removed by radially deep and axially narrows cuts.  The true rake angle of cutter depends on the axial rake, radial rake and corner angle, and it directly affects the shear angle in chip removal operation.  It also affects the cutting force, horse power and temperature generated during cutting.  Larger value of true rake angle lowers the cutting forces, horsepower and cutting temperatures, but leads to weakened cutting edge prone to breakage and chipping. 24 TDM by G/giorgis B

25. 3.2. Nomenclature of milling cutters/ cont… Elements of Face Milling Cutter:  The face milling cutter because of its large bulky body is relatively rigid.  Surface finish depends on feed rate and the number of teeth.  Cutter body diameter depends on the length of the workpiece and on the clearance available on either side of the workpiece.  More number of inserts are used for higher productivity consistent with available chip space to avoid chip crowding and better chip disposal.  Since a face mill with uniform spacing between teeth may result in vibration and chatter due to a regular tooth-impact frequency, a slight, uneven spacing is recommended.  Vibration and chatter can also be controlled by selecting cutting speed (lower value) appropriate for the axial depth of cut (high value). 25 TDM by G/giorgis B

26. End Mills:  These are capable of removing material with the periphery of the tool and with the end if it has bottom cutting features.  The dimensional accuracy of an end mill operation depends primarily on the rigidity of the set up, and on the radial and axial depth of cut, the thrust force produced.  Since end mill acts like a rotating cantilever, gripped by the machine tool spindle, the end deflection for a given cutter is directly proportional to the thrust and to the cube of the effective overhang.  Improved surface finish is achieved by using a large diameter cutter with many teeth and milling at a small feed rate.  The end mill geometry is a compromise of tooth edge strength, chip space, chip flow, rigidity and capability to withstand impacts as each tooth engages the workpiece.  The end mill geometry involves helix angle, core diameter, radial and axial rake angles, radial and axial clearance angles, corner radius, etc. 3.2. Nomenclature of milling cutters/ cont… 26 TDM by G/giorgis B

27. 3.2. Nomenclature of milling cutters/ cont…  The core diameter of the end mill determines its rigidity.  The number of teeth on the end mill also affects rigidity.  But chip space available decreases as core diameter of cutter increases.  Chip disposal also depends somewhat on the helix angle, being easier for high helix angle.  But as helix angle increases, cutting edge becomes weaker and thus its value is taken around 15 to 30 degrees.  As the radial rake face surface of an end mill tooth is subjected to the sliding action and pressures of chip curling and forming, it should be smooth and free of ridges to enhance chip flow and minimize heat and galling. End Mills: 27 TDM by G/giorgis B

28. 3.3. Nomenclature of broaching cutters BROACHING  a multiple tooth cutting tool  the forming tool moves linearly relative to the workpiece in the direction of the tool axis  Movement through or along the part 28 TDM by G/giorgis B

29. 3.3. Nomenclature of broaching cutters Broaching operations Good surface finish Close tolerances Variety of work shapes possible High material removal rate Cutting tool called a broach Owing to complicated and often custom ‑ shaped geometry, tooling is expensive Internal broaching operations Performed on internal surface of a hole A starting hole must be present in the part to insert broach at beginning of stroke 29 TDM by G/giorgis B

30. 3.3. Nomenclature of broaching cutters/ cont… Broaching tools 30 TDM by G/giorgis B

31. 3.4. Tools Manufacturing Tool manufacturing involves the production of cutting tools, including twist drills, milling cutters, and form tools. The manufacturing process can vary depending on the type of tool and the material being used. Here are some common steps involved in tool manufacturing: Material Selection: The appropriate tool material is chosen based on factors like the cutting application, desired tool properties (hardness, toughness, wear resistance), and cost considerations. Common materials include high-speed steel, carbide, cermet, and ceramic. Tool Design: The tool design is created based on the specific requirements and application. This includes determining the tool geometry, dimensions, cutting parameters, and any special features or coatings. TDM by G/giorgis B 31

32. 3.4. Tools Manufacturing/cont… Blank Preparation: The selected tool material is prepared in the form of blanks, which are typically cylindrical or rectangular in shape. This may involve processes such as forging, casting, or sintering, depending on the material. Machining Operations: The blanks are further machined to create the desired tool shape and features. This may include operations like turning, milling, grinding, drilling, or EDM (electrical discharge machining). Heat Treatment: Heat treatment processes such as hardening, tempering, or annealing are performed to enhance the mechanical properties of the tool. Coating Application: Many cutting tools are coated with special coatings to improve their performance and tool life. Coatings like titanium nitride (TiN), titanium carbonitride (TiCN), or diamond-like carbon (DLC) can provide increased hardness, lubricity, and heat resistance. TDM by G/giorgis B 32

33. 33 Finishing Operations: Tools undergo finishing operations such as grinding, lapping, or polishing to achieve the final dimensions, surface finish, and cutting edge sharpness. Inspection and Quality Control: The manufactured tools undergo inspection and quality control processes to ensure they meet the specified requirements and standards. This may include dimensional measurements, hardness testing, and performance evaluation. Packaging and Distribution: Once the tools pass the quality control checks, they are packaged and prepared for distribution to customers. Proper packaging ensures the protection of the tools during transportation and storage. It's important to note that the specific manufacturing processes and techniques may vary depending on the type of cutting tool, complexity, and the manufacturing capabilities of the tool manufacturer. 3.4. Tools Manufacturing/cont… TDM by G/giorgis B

34. Tool force dynamometers To estimate power required for machining operations, the force has to be measured by a suitable measuring instruments. Generally, cutting forces in cutting tool are measured in different ways such as: Dynamometer, Ammeter, Wattmeter, Calorimeter, Thermocouple, etc. Among these, dynamometers are generally used for measuring cutting forces. Especially, strain gauge dynamometers are used. In this case, spring deflection is measured which is proportional to the cutting forces. 3.5. Construction and principle of operation of tool dynamometers TDM by G/giorgis B 34

35. 35 The following requirements are considered during design and construction of any tool force dynamometer: Sensitivity: The dynamometer should be reasonably sensitive for precision measurement. Rigidity: to withstand the forces without causing much deflection which may affect the machining condition. Cross Sensitivity: The dynamometer should be free from cross sensitivity such that one force (say PZ) does not affect measurement of the other forces (say PX and PY). Stability against humidity and temperature. Quick time response. High frequency response such that the readings are not affected by vibration within a reasonably high range of frequency. Consistency: It should work desirably over a long period. Design requirements for Tool force Dynamometers TDM by G/giorgis B

36. The dynamometers being commonly used nowadays for measuring machining forces accurately and precisely (both static and dynamic characteristics) are either strain gauge type or piezoelectric type. Strain gauge type dynamometers are inexpensive but less accurate and consistent. Piezoelectric type are highly accurate, reliable and consistent but very expensive for high material cost and rigid construction. lower cost and ability to provide almost all the desired force values. 36 Construction and working principle of dynamometers TDM by G/giorgis B

37. 4. Jigs and Fixtures 4.1. Types and functions of jigs and fixtures The terms jig and fixture are often confused and used interchangeably, however, despite sharing similar functions, the two are functionally different.  Jigs are tools that hold a cutting tool in place or guide it as it performs a repetitive task like drilling or tapping holes.  Fixtures, on the other hand, do not guide a cutting tool, but hold a workpiece steady in a fixed position, orientation, or location. 37 TDM by G/giorgis B

38. 4.1. Types and functions of jigs and fixtures/ cont… Jigs are often used in drilling, reaming, counter-boring, tapping, and other one-dimensional machining operations or applied as guides for tools or templates. Special cramping jigs that ensure squareness are often used as well. Another common application for a jig is a drill bushing that helps guide a drill bit through the surface of the workpiece to ensure correct positioning and angle. 38 TDM by G/giorgis B

39. 4.1. Types and functions of jigs and fixtures/cont… Since the advent of automation and computer numerical controlled (CNC) machines, jigs are often not required because the tool path is digitally programmed and stored in the machine’s memory. However, jigs are still used in smaller machine shops to support manual machining of special or custom parts and one-offs. Fixtures are often used in milling, turning, planning, slotting, grinding, and other multidimensional machining processes, as well as automotive vehicle assembly and optical, laser scanning inspection systems. 39 TDM by G/giorgis B

40. 4.1. Types and functions of jigs and fixtures/cont… The material block clamped inside a CNC machine and a vise sitting on a workbench are also fixtures. Fixtures are also essential in an automobile assembly line to secure and guide cars through the welding and assembly process Differences aside, both jigs and fixtures are tools that make a significant difference. They increase productivity, improve the repeatability of parts, make part assembly and disassembly easier and help create a safer working environment Nearly all automated industrial manufacturing processes rely on jigs and fixtures to consistently build parts that function properly 40 TDM by G/giorgis B

41. 4.1. Types and functions of jigs and fixtures/cont… Engineers can make sure their jigs and fixtures are strong and well-designed by keeping these key considerations in mind. There’s an old saying among machinists – fixtures are where you make your money. If you’re good at making fixtures that save time, you’ll turn a bigger profit. Or so the saying goes. Our goal in this chapter is to learn the subtle differences between these manufacturing tools by examining how they are used to improve manufacturing quality, reduce production costs, and automate work. 41 TDM by G/giorgis B

42. 42 4.1. Types and functions of jigs and fixtures/cont… TDM by G/giorgis B

43. Type of Jigs Type of Fixtures Closed JigTrunnion JigPlate Fixture Plate JigPump JigVise Jaw Fixture Sandwich JigIndexing JigIndexing Fixture Angle Plate JigTemplate JigMulti-Station Fixture Box JigMulti-Section JigChucks Channel JigDrill JigCollets 43 4.1. Types and functions of jigs and fixtures/cont… Types of Jigs and Fixtures There are many different types of jigs and fixtures for machining operations that typically include: TDM by G/giorgis B

44. 4.1. Types and functions of jigs and fixtures/cont… There are two components to work holding with jigs and fixtures: The method of locating and securing the work holding device to your machine. This includes T-Slots but goes on to include modular fixture plates, 4 th -axis solutions, and much more. The actual work-holding device, such as a milling or drilling vise.vise We’ll go through the various methods of locating the work holding devices and then follow up with a description of various devices. 44 TDM by G/giorgis B

45. 4.1. Types and functions of jigs and fixtures/cont… 45 TDM by G/giorgis B

46. 4.1. Types and functions of jigs and fixtures/cont… T-Slot Plates Work-holding tools installed on the milling table are held in position with the help of the table T-slots. One of the biggest disadvantages of T-Slot Plates is that it’s hard to get your vise or other work-holding fixture back onto the table in exactly the same location and orientation. This can result in extra work every time a machine needs to be set up with new work holding for a new job. Figure:- T-slot plate and T-slot nuts TDM by G/giorgis B 46

47. 4.1. Types and functions of jigs and fixtures/cont… Fixture Plates Also called tooling plates, they are installed on top of a T-Slot table to provide a new way to position and secure your workholding devices.workholding devices They typically feature a grid of holes that alternate threaded holes for fasteners and precision dowel pins for positioning. With T-Slots, the T-Slot nuts slide. A fixture can thus be located anywhere. That sounds great except that the fixtures can be anywhere also. With a Fixture Plate, your fixtures can’t be located just anywhere. TDM by G/giorgis B 47

48. Fixture Plates/cont… They must go into the grid of available holes. In other words, with a Fixture Plate, fixtures are always at a well-defined location. The grid makes work holding positioning significantly easier and repeatable. Tooling Plates are typically made of either Cast Iron or Aluminum, though there are steel ones available too. They can be purchased or made from scratch. Figure:- a fixture plate TDM by G/giorgis B 48

49. Locating and Positioning Components The fixture plates are properly positioned and mounted on the T-Slot plates. Then the work holding devices, which include a variety of clamps including jig and fixture clamps are mounted on the fixture plate.work holding devices A diverse line of locating and positioning components for jobs that require precise alignment of the workpiece is available to design your work holding jigs and fixtures.locating and positioning components An extensive range of spring plungers is available and includes threaded spring plungers, hand-retractable spring plungers, press-fit spring plungers, push-fit spring plungers, pull-pin spring plungers, and index plungers.spring plungers TDM by G/giorgis B 49

50. Locating and … Components/cont… Also available are press-fit locating pins and spring locating pins, along with accessories such as pin liners, thread retainers, and lock screws. Tooling balls are used as reference points for inspection applications. Built to reduce design and detail time, CMM fixture blocks and plates provide a work base with a combination of standard-size mounting holes for positioning. Tooling balls Fixture keys are used to locate jigs and fixtures on slotted machine tool tables. Alignment pins and bushings are removable locating devices used to precisely align workpieces in jigs and fixtures. Fixture keysAlignment pins and bushings A full range of angle plates, gauge stops, locating screws, and stock crowders are also available.angle platesgauge stopslocating screwsstock crowders 50 TDM by G/giorgis B

51. Locating and … Components/cont… 51 TDM by G/giorgis B

52. 4.1. Types and functions of jigs and fixtures/cont… Advantages of Jigs and Fixtures  Productivity: They increase productivity by eliminating frequent repositioning and checking. Operation time is reduced due to an increase in speed, feed, and depth of cut because of high clamping rigidity.  Interchangeability and Quality: They enable the production of many workpieces repeatedly, accurately, and with uniform quality and interchangeability at a competitive cost.  Skill Reduction: There is no need for the skillful setup of workpieces on a machine. They allow unskilled or semi- skilled machine operators to set up the workpieces reducing labor cost.  Cost Reduction: Higher production, reduced scrap, easy assembly and savings in labor cost result in an ultimate reduction in unit cost. TDM by G/giorgis B 52

53. 53 The main elements of jigs and fixtures TDM by G/giorgis B

54. Body: It is a plate, box or frame type structure in which the components to be machined are located. It should be quite sturdy and rigid. Locating elements: These elements locate the workpiece in a proper position in relation to the cutting tool. Clamping elements: These elements firmly secure the workpiece in the located position. Grinding and setting elements: These elements guide the cutting tool in case of jig and help in proper tool acting in case of the fixture. 54 The main elements of jigs and fixtures TDM by G/giorgis B

55. Positioning elements: These elements include different types of fastening devices, which are used in securing the jig or fixture to the machine at the proper position.types of fastening devices, Indexing elements: They are not provided always. But, many workpieces may have to be indexed to different positions in order to perform machining operations on different surfaces or different locations. In such cases, these elements will have to be incorporated in the jig or fixture. 55 The main elements of jigs and fixtures TDM by G/giorgis B

56. Types of Jigs Following are the seven different types of jigs. 1. Template jig 2. Plate jig 3. channel jig 4. Diameter jig 5. Leaf jig 6. Ring jig 7. Box jig 56 TDM by G/giorgis B

57. 57 The template jig is the simplest of all the types. A plate having 2 holes guides the drill to make required holes on the workpiece at the same relative positions with each other as on the template. 1.Template Jig TDM by G/giorgis B

58. 58 A plate jig is an improvement of the template jig by incorporating drill bushes on the template. The plate jig is employed to drill holes in large parts maintaining accurate spacing with each other. 2. Plate Jig TDM by G/giorgis B

59. 59 The channel jig is a simple type of jig having a channel-like cross-section. The component 1 is fitted within the channel and is located and clamped by rotating the knurled knob. The tool is guided through the drill bush. 3. Channel Jig

60. 4. Diameter Jig The diameter jig is used to drill radial holes on a cylindrical or spherical workpiece. The work is placed on the fixed V-block and then clamped by the clamping plate which is also located the work. The tool is guided through the drill bush 8 which is set radially with the work TDM by G/giorgis B 60

61. The leaf jig is illustrated in the above figure. It has a leaf or a plate 13 hinged on the body at 11 and the leaf may be swung open or closed on the work for loading or loading purposes. The work 1 is located by the buttons 10 and is clamped by set screws 12. The drill bush 3 guides the tool. TDM by G/giorgis B 61 5. Leaf Jig

62. TDM by G/giorgis B 62 The ring jig is employed to drill holes on circular flanged parts. The work is securely clamped on the drill body and the holes are drilled by guiding the tool through drill bushes. 6. Ring Jig

63. 7. Box Jig The box jig is of box-like construction within which the component is located by the buttons and is clamped by rotating the cam handle which also locates it. The drill bush guides the tool. The box jigs are generally employed to drill a number of holes on a component from different angles. TDM by G/giorgis B 63

64. Types of Fixtures 1. Turning fixtures. 2. Milling fixtures. 3. Broaching fixtures. 4. Grinding fixtures. 5. Boring fixtures. 6. Indexing fixtures. 7. Tapping fixtures. 8. Duplex fixtures. 9. Welding fixtures. 10. Assembly fixtures. TDM by G/giorgis B 64 Fixtures are usually named after the type of machining operation for which they are designed and employed. Following are the 10 different types of fixtures:

65. 1.Turning fixtures It is quite easy-to-hold regular workpieces on lathes in standard job holding devices like chucks and collects, between the centre and on mandrels or faceplates. But irregularly shaped components offer a lot of difficulties in holding them correctly.like chucks and collects, TDM by G/giorgis B 65

66. 2. Milling fixtures These fixtures are used on milling for carrying out different milling operations on workpieces. The fixture is properly located on the table of the machine and secured in position by means of bolts and nuts.different milling operations on workpieces bolts and nuts. TDM by G/giorgis B 66

67. TDM by G/giorgis B 67 3. Broaching Fixtures These fixtures are used on different types of broaching machines to locate, hold, and support the workpieces during the operations, such as keyway broaching operations, such as keyway broaching, hole broaching, etc. The use of a clamping plate as a fixture for internal pull-type hole broaching.broaching machines

68. TDM by G/giorgis B 68 4. Grinding Fixtures These fixtures may be the standard work-holding devices, such as chucks, mandrels, chuck with shaped jaws, magnetic chucks, etc. For example; a vertical surface grinder with a rotary table will normally have a rotary fixture secured to its table. Similarly, a plain or string fixture may be provided on a surface grinder with the reciprocating table. A drill grinding attachment is a glaring example of a standard fixture used for grinding of drill geometry. Whatever be the types of fixture designed for grinding operation, it should have provisions for supply and exit of coolant, mounting of wheel dressers and should be properly balanced, if it is a rotating fixture.

69. TDM by G/giorgis B 69 5. Boring Fixture The operation can be performed in one of the following two ways: 1.By keeping the boring bar (tool) stationary and feeding the touting workpiece on to the bar. 2.By keeping the workpiece stationary and feeding the rotating boring bar into the work. Accordingly, therefore, the boring fixture is made in two common designs.One of these incorporates the principle of a drilling jig, and in this, the boring bar (tool) is guided through a pilot bush. Such fixture is also often referred to as boring jigs. the other design facilitates holding of the workpiece in correct position, relative to the boring bar.

70. TDM by G/giorgis B 70 5. Boring Fixture /cont…

71. TDM by G/giorgis B 71 6. Indexing Fixture Several components need machining on different surfaces such that their machined surface surfaces or forms are evenly spaced. Such components are required to be indexed equally as many as the number of surfaces to be machined. Obviously, the holding devices (jigs or fixtures) used are made to carry a suitable indexing mechanism. A fixture carrying such a device is known as an indexing fixture.

72. TDM by G/giorgis B 72 7. Tapping Fixture Tapping fixture is specially designed to position and firmly secure identical workpieces for cutting internal threads in drilled holes in them. Odd shaped and unbalanced components will always need the use of such fixtures, especially when the tapping operation is to be carried out repeatedly on a mass scale on such components. 8. Duplex Fixtures It is the name given to the fixture which holds two similar components simultaneously and facilitates simultaneously machining of these components at two separate stations. While one workpiece is machined at one station.

73. TDM by G/giorgis B 73 8. Duplex Fixtures Both the operations may be similar or different. Once machining at both the stations is over, the fixture is indexed through 180 degrees so that the first component is shifted to the second station for the second operation and the finished component to the first station. The finished component is then replaced by a fresh component and the first operation performed on it. The cycle goes on repeating,

74. TDM by G/giorgis B 74 9. Welding Fixtures Welding fixtures are carefully designed to hold and support the various components to be welded in proper locations and prevent distortions in welded structures. For this, clamping has to be light but firm, placement of clamping elements has to be clear of the welding area. The fixture has to be quite stable and rigid to withstand the welding stresses. In many cases, a preferred and commonly used practice is to first tack weld the structure by holding it in a welding jig and then transfer it to a holding fixture for full welding. This helps in reducing the chances of distortion considerably and the fixture is subjected to lesser stresses.

75. TDM by G/giorgis B 75 10. Assembly Fixture The function of these fixtures is to hold different components together in their proper relative position at the time of assembling them. For example, two or more steel plates can be held together in relative positions and riveted. These fixtures, which are used for holding the components for performing mechanical operations, are known as mechanical assembly fixtures. Against this, there are other types of fixtures which the components are held for joining, such as the welding fixtures are also assembly fixtures, but for hot joining.

76. 4.2. PRINCIPLES OF LOCATION Introduction In an interchangeable manufacturing process when a workpiece is placed on a machine table, spindle, jig, or fixture it must be properly positioned before it is clamped. The location refers to the establishment of a desired relationship between the workpiece and the jigs or fixture. Correctness of location directly influences the accuracy of the finished product. It is the duty of the location system to provide all necessary constraints so that the workpiece is correctly located and all possible movements of the workpiece are restricted. TDM by G/giorgis B 76

77. Introduction / cont… The jigs and fixtures are desired so that all undesirable movements of the workpiece can be restricted. Determination of the locating points and clamping of the workpiece serve to restrict movements of the component in any direction, while setting it in a particular pre-decided position relative to the jig. Before deciding the locating points it is advisable to find out the all possible degrees of freedom of the workpiece. Then some of the degrees of freedom or all of them are restrained by making suitable arrangements. These arrangements are called locators. TDM by G/giorgis B 77

78. TWELVE DEGREES OF FREEDOM A workpiece in space is free to move in any direction and can have twelve degrees of freedom Each direction of movement is considered one degree of freedom It can move in either of opposed directions along three mutually perpendicular axes and may rotate in either of two opposed directions around each axes i.e. Clockwise and counterclockwise. The Duty of The Location System The location system must, in conjunction with the clamping system completely constrain the workpiece or eliminate as many of the 12 degrees of freedom as is necessary for the operation to be completed with the required accuracy TDM by G/giorgis B 78

79. DEGREES OF FREEDOM IN SPACE TDM by G/giorgis B 79

80. THE CHOICE OF LOCATION SYSTEM The requirements of the location system depend upon the operation being performed and upon the workpiece before the operation. TDM by G/giorgis B 80

81. Primary Datum This establishes the orientation of the part (stabilize the part ) to the datum reference frame. The part contacts the datum plane with at least three points of contact. The primary datum restricts FIVE degrees of freedom ( four rotary and one linear) Secondary Datum This locates the part (restricts part movement) within the datum reference frame. Requires a minimum of two points of contact with the secondary datum. The Secondary datum restricts THREE additional degree of freedom ( Two rotary and One linear ) TDM by G/giorgis B Primary, Secondary and Tertiary Datum 81

82. Tertiary Datum This locates the part(restricts part movement) within the datum reference frame. Requires a minimum of one point of contact with the secondary datum. The tertiary datum restricts the ONE degree of freedom ( Linear ) Primary, Secondary and Tertiary Datum TDM by G/giorgis B 82

83. TDM by G/giorgis B Primary, Secondary and Tertiary Datum 83

84. THE 3-2-1 RULE The 3-2-1 rule defines the minimum number of points of contact required. The 3-2-1 rule only applies on a part with all planar datums. This rule ensures positioning of a part in a repeatable manner for measurement purpose. According to this rule, the minimum number of points of contacts for the primary datum is 3, the secondary datum is 2, and the tertiary datum is 1. TDM by G/giorgis B 84

85. Datum Reference Frame TDM by G/giorgis B 85

86. Constraining Remaining Degrees of Freedom The 10 th degree of freedom is arrested by first clamp against secondary datum The 11 th degree of freedom is arrested by second clamp against tertiary datum The 12 th degree of freedom is arrested by either downward clamp or by gravity ( if workpiece is heavy) TDM by G/giorgis B 86

87. The 12 degrees of freedom include linear movement along three axes and rotational movement around those axes. A method of external locating that involves placing three locators against the bottom surface of the workpiece, two against one side of the workpiece, and one against the side right next to the two locators The twelve degrees of freedom all relate to the central axes of the workpiece. Notice the six axial degrees of freedom and six radial degrees of freedom. TDM by G/giorgis B Constraining Remaining Degrees of Freedom/ cont… 87

88. The axial degrees of freedom permit straight-line movement in both directions along the three principal axes, shown as x, y, and z. The radial degrees of freedom permit rotational movement, in both clockwise and counterclockwise radial directions, around the same three axes. TDM by G/giorgis B Constraining … of Freedom 88

89. 89 One of the most important elements of the machining process. Work holder includes all devices that hold, grip or chuck a work piece to perform a manufacturing operation Applied mechanically, electrically, hydraulically or pneumatically Jigs and Fixtures are critical to repeated manufacturing with high degrees of accuracy and precision. They hold one or multiple parts in one or multiple machine centers to provide stability and repeatable alignment of the part. 4.3. Workpiece holding principles TDM by G/giorgis B

90. Principles TDM by G/giorgis B 90

91. Multiplication of holding force TDM by G/giorgis B 91

92. Purpose and function of WH Location: orienting and positioning the part relative to the cutting tool Clamping: holding the part in its proper orientation with enough force to resist the force of cutting but not deform the part. Work holding devices are used for 1. Supporting 2. Precision in locating 3. Withstanding cutting forces 4. Apply holding forces 5. Safety of operator and equipment TDM by G/giorgis B 92

93. Physical characteristics of the workpiece  Degree of precision  Strength and stiffness of workpiece  Production requirements  Safety requirements  Use standard workholders Work piece surfaces - Flat surfaces - Cylindrical surfaces -Irregular surfaces Types of Location - Plane - Concentric - Combined - Radial TDM by G/giorgis B 93

94. Placement rules When more than one locator is placed on a surface, they should be distributed as far as possible on the surface - This would help in placing the workpiece on locators without much skill - Also the clamping force would not be able to shift the workpiece from such locators - A blank with irregular surface (such as sand casting) would be better located on such distributed locators TDM by G/giorgis B 94

95. Machining forces would not be able to disturb the equilibrium of the work piece in the fixture with properly distributed locators Wear of any locator contributes less to the inaccuracy of location if the locators are placed far apart While selecting the surface for the largest locators, consideration should be given to the largest area of the work piece The two locators should be placed on the surface with the next largest area and the single locator on the surface with the least surface area Placement rules/ cont… TDM by G/giorgis B 95

96. Support surfaces Select a surface where there is maximum likelihood for the part to deflect under the action of clamping and cutting forces Support areas selected should not disturb the location of the work piece in any manner nor displace the locators while providing the support Support areas selected should not interfere with the loading and unloading of the component into the work holding fixture TDM by G/giorgis B 96

97. Adjustable supports Adjustable locators positioned below the work piece 1. Threaded 2. Spring 3. Equalizers Figure: Threaded-type adjustable supports TDM by G/giorgis B 97

98. Spring-type adjustable supports TDM by G/giorgis B 98

99. Design Steps The classical design of a work holder involves the following steps: 1. Understand the work piece and tolerances 2. Visualize Machining Steps 3. Determine orientation of work in relation to the cutting tools 4. Study standard devices available 5. Form a mental (or CAD) picture of the work piece in position 6. Locate Clamp, buttons, bushings TDM by G/giorgis B 99

100. 100 4.4. Jig and fixture design and assembling Jig and Fixture Design Basics Now that we know the advantages of using jigs and fixtures and how to properly position and mount them in a machine tool, the jig and fixture designer should implement the following principles to ensure easy installation, repeatable location, high quality of workpieces at a competitive cost. Locating Points: Provide good for locating points for the workpiece. The workpiece to be machined must be easily inserted and quickly removed from a jig so that no time is wasted in placing the workpiece in position to perform operations. The workpiece location should be accurate to assure the desired cutting tool path. TDM by G/giorgis B

101. 101 Jig and Fixture Design Basics/ cont… Error Proof: The design of jigs and fixtures should not permit the workpiece or the tool to be inserted in any position other than the correct one. Idle Time Reduction: Jigs and fixtures should be designed so that processing, loading, clamping and unloading time of the workpiece is minimized. Jig and Fixture Weight: Jigs and fixtures should be easy to handle, as light as possible and use minimum material without sacrificing rigidity and stiffness. Lift aids should be incorporated as necessary to prevent operator fatigue. Jigs Provided with Feet: Jigs are sometimes provided with feet so that they can be easily placed on the table of the machine. TDM by G/giorgis B

102. Jig and Fixture Design Basics/ cont… Materials for Jigs and Fixtures: Jigs and fixtures are usually made of hardened materials to avoid frequent damage and to resist wear. Examples are mild steel, cast iron, die steel, carbon steel or high-strength steel. Clamping Devices: When designing jigs and fixtures, clamping devices should be as simple as possible without sacrificing effectiveness. The strength of the clamp should hold the workpiece firmly in place, but also take the strain of the cutting tool without moving. Movement of clamps should be minimized and clamping pressure should be low enough to prevent workpiece distortion.clamping devices TDM by G/giorgis B 102

103. 103 Jig and Fixture Design Basics/ cont… Additional, Essential Features of Jigs and Fixtures In addition to basic jig and fixture design, there are several tool design features the tool designer should address. Among those features are: Cleanliness of the Machining Process – designs must minimize time wasted in the cleaning of scarfs, burrs, chips, etc. Replaceable Parts and Standardization – the locating and supporting surfaces should be replaceable where possible and should be standardized to allow interchangeable manufacture. Coolant Provisions – features should be added to the tool design to allow cooling of the cutting tool and washing away swarf and chips. TDM by G/giorgis B

104. Jig and Fixture Design Basics/ cont… Hardened Surfaces – all locating and supporting surfaces should be hardened materials if possible so that they are not quickly worn out and accuracy is retained for a long time. Inserts and Pads – should always be attached to the faces of the clamps which will come in contact with the finished surfaces of the workpiece so that they are not damaged. Initial Location – should ensure that the workpiece is not located on more than 3 points in any one plane. Testing should be conducted to verify that there is no rocking. Spring loading should be implemented where possible. Clamp Positioning – clamps should be placed directly above the workpiece supports to avoid part distortion and springing and resist cutting tool forces. TDM by G/giorgis B 104

105. Jig and Fixture Design Basics/ cont… Workpiece Handling and Clearance – sufficient clearance should be provided around the workpiece to allow an operator’s hands to easily enter the fixture body for placing the workpiece and to accommodate any part variation. Round all corners and provide handles wherever they will make handling easier. Ejecting Devices – proper ejecting devices should be incorporated in the fixture body to push the workpiece out after operation if required. Clamping and Binding Devices – should be as quick-acting as possible. Complicated clamping arrangements should be avoided and some locating points should be adjustable. Safety – the fixture design should ensure operator and machine safety. TDM by G/giorgis B 105

106. Chapter 5 Design of punches, bending dies and drawing dies. Main contents: Die classifications; Basic die components; Structure and design of critical parts; TDM by G/giorgis B 106

107. 5.1. Die Classifications 5.1.1 Manufacturing processes blanking dies, punching dies, bending dies, drawing dies, etc... 5.1.2 Number of operations single-operation dies----simple/plain dies multi-operation dies----combination/compound dies ----progressive dies TDM by G/giorgis B 107

108. 5.1.3 Number of stations Single station dies Multi-station dies----progressive dies Single station dies may be : Combination (a die in which both cutting and noncutting operations are accomplished at one press stroke) or Compound (a die in which two or more cutting operations are accomplished at every press stroke). TDM by G/giorgis B 108

109. Progressive dies:- are made with two or more stations. Each station performs an operation on the work piece or provides an idler station so that the work piece is completed when the last operation has been accomplished. After the first part has traveled through all the stations, each subsequent strokes of the press produces another finished part. TDM by G/giorgis B 109

110. 5.1.4 Die structure Guiding: plain, with guide plate, with guide posts ； stock guide, guide rails, guide pins (elastic and solid), pilots Stripper: movable elastic and solid Stop pin: solid and elastic, finger stops, adjustable and fixed TDM by G/giorgis B 110

111. 5.1.5 Die material carbide,rubber, polyester, polyurethane, zinc alloy, etc… 5.1.6 Production quantities of pieces Class A—high, best of materials Class B—medium, cheaper materials, die cost Class C—low-volume, cheapest Temporary dies—small, lowest cost TDM by G/giorgis B 111

112. 5.2.1 Technological components Directly participate in forming the work piece and have direct contact with a material. Punches, die block, form block, guide rails, stripper, drawing die, blank holder. 2.2 The structural components Securely fasten all components to the subset and die set. punch holder, die shoe, shank guideposts, guide post bushings, springs, screws, dowels. 5.2. Basic die components TDM by G/giorgis B 112

113. Die with guide plate 1 -shank 2 -shank holder 3 -backing plate 4 -punch holder 5 -punch 9 -guide rail 10-die block 11-die shoe 13-guide plate 5.2.Basic die components/ cont… TDM by G/giorgis B 113

114. Die with guide post and guide post bushing 1 -shank 2 -shank holder 3 -backing plate 4 -punch holder 5 -punch 6 -guide post bushing 7 -guide post 8 -stripper 9 -guide rail 10-die block 11-die shoe 5.2.Basic die components/ cont… TDM by G/giorgis B 114

115. 5.3. Structure and design of critical parts 1. Introduction 2. Die blocks 3. Punches 4. Stripper plates 5. Die components for guiding and stopping TDM by G/giorgis B 115

116. 1. Introduction A blanking die -cheaper to make and faster in operation Return-blank die: sheared blank returns upward drop-blank die A punching die- may be manually or automatically fed 5.3. Structure and design … parts/cont.. TDM by G/giorgis B 116

117. Die blocks Die opening profile Fastening to the die shoe Sectioned die Calculation of die block dimensions 5.3. Structure and design … parts/cont.. TDM by G/giorgis B 117

118. Die opening profile a) gives the highest quality work piece, the most expensive. blanking parts having complex contours with greater accuracy. b) making small parts with low accuracy. c) the simplest, making relatively large parts. d) to punch small-diameter (d < 5 mm) holes. 5.3. Structure and design … parts/cont.. TDM by G/giorgis B 118

119. a) Fastening to the die shoe a) socket head screws are inserted from the bottom of the die shoe into threaded holes in the die block. Dowels are used to prevent a shift in the position of the block. b) held in the retainer (has a shoulder) c) pressed into the retainer (has no shoulder) d) fastened into the retainer with a ball and screw e) a bushing is used at the bottom 5.3. Structure and design … parts/cont.. TDM by G/giorgis B 119

120. Sectioned die work piece- large, die opening - complicated, contours - difficult to machine 5.3. Structure and design … parts/cont.. TDM by G/giorgis B 120

121. Calculation of die block dimensions A=a+2e, B=b+2e. a) Rectangular: b) Circular: 5.3. Structure and design … parts/cont.. TDM by G/giorgis B 121

122. 5.3. Punches Main consideration when design: do not buckle; Should be strong enough to withstand the stripping force; not be able to rotate as a result of the cutting action. TDM by G/giorgis B 122

123. 5.3.1 Punch face geometry Flat punch-double bevel die Concave punch-flat die Bevel punch-flat die Flat punch-concave die a) flat, b) concave, c)bevel, d) double bevel TDM by G/giorgis B 123

124. 5.3.2. Stripper plates Solid stripper The force of the press is used for stripping operation. Elastic stripper Usage: very accurate, thin material, thin punches. How: hold the scrap strip in a flat position before the punch makes contact with the work piece. TDM by G/giorgis B 124

125. 5.4 Die components for guiding and stopping The group of die components known as guides and stops includes the following components: A. Stock guide and guide rails B. Die stops and French notch punch C. Positioning the individual blank D. Pilots TDM by G/giorgis B 125

126. A. Stock guide and guide rails Guide rails: Used to guide the work strip through the die. They are placed between the stock shelf of die block and the stripper plate or guide plate. Types: solid and elastic 5.4 Die components for guiding …. TDM by G/giorgis B 126

127. B. Die stops and French notch punch Die stops: Used to stop the material strip after each feed movement is completed. French notch punch: Used for trimming away a length of work strip that is equal to the progression of the die. Finger stops: Used to stop new strips in the proper location in a die. 5.4 Die components for guiding …. TDM by G/giorgis B 127

128. C. Positioning the individual blank a) Three dowels b) A ring c) A combination of dowels and guide-rails 5.4 Die components for guiding …. TDM by G/giorgis B 128

129. D. Pilots Used in progressive and compound dies to position the work strip so that the relationships between stations or previously punched holes and the outside blanked contours of work pieces may be maintained. 5.4 Die components for guiding …. TDM by G/giorgis B 129