DT1410 - Materials and Processes in Design

1. DT1410 - Materials and Processes in Design Unit 5 - Powder Metallurgy - Principles of Machining Processes

2. Powder Metallurgy • Powder Metallurgy is one of the four major methods of shaping metals: • Machining • Hot and Cold plastic deformation • Casting • P/M

3. Powder Metallurgy • The Powder Metallurgy process is essentially the compression of finely divided metal powder into briquettes of desired shape that is then heated, but not melted to form a metallurgical bond between the particles.

4. Powder Metallurgy • The basic conventional process of making P/M parts consists of two basic steps: • Compacting (molding) • Sintering

5. Powder Metallurgy • Compacting: • Loose powder (or a blend of different powders) is placed in a die and is then compacted between punches. • Commonly done at room temperature • Compounded part is known as a briquette

6. Powder Metallurgy • Sintering: • The briquette is heated to a temperature high enough to cause the powder particles to bond together by solid-state diffusion. • The powder particles also homogenize any alloy constituents into the powder. • Melting does not normally occur.

7. Powder Metallurgy • After Sintering: • The P/M part is now ready for secondary operations: • Sizing • Machining • Heat treating • Tumble finishing • Impregnating with oils, plastics, or liquids

8. Powder Metallurgy http://www.youtube.com/watch?v=n_FW7Q2xO5o

9. Metal Powders • A number of different metals and their alloys are used in P/M: • Iron • Alloy steel • Stainless steel • Copper • Tin • Lead

10. Metal Powders • The three most important methods of producing metal powders are: • Atomization • Chemical methods • Electrolysis processes

11. Powder Compaction • Compacting or pressing gives powder products their shape. • Pressing and Sintering techniques can be separated into two types: • Conventional • Alternative

12. Powder Compaction • Conventional powder compaction: • The powder is press unidirectionally in a single- or double-acting press • Unlike liquids, which flow in all direction under pressure, powders tend to flow mainly in the direction of the applied pressure

13. Powder Compaction • Alternative powder compaction can be classified into: • Alternative compaction methods • Combined compaction and sintering • Alternative sintering methods

14. Powder Compaction • Advanced/Alternative Processes: • Cold Isostatic Pressing (CIP) • The process of compacting a powder by exerting a constant high pressure at room temperature. • Hot Isostatic Pressing (HIP) • The process of compacting a powder by exerting a constant high pressure at elevated temperatures.

15. Sintering • In solid-phase sintering the green compact part must be heated to 60 to 80% of the melting point of the constituent with the lowest melting point. • Time required 30 minutes to 2 hours in a sintering furnace to produce the metallurgic bonds

16. Characteristics of PM Parts • Superior engineered microstructures • Consistent properties and quality • Controlled porosity for filters/self-lubrication • Very low scrap loss • Wide variety of shape designs • Unlimited choice of alloys and composites • Low cost, high volume production • Good surface finishes • Close dimensional tolerances • Little or no machining required

17. Advantages of P/M • Almost as strong as wrought steels • Lighter weight parts • Ability to impregnate with oils, fillers, other materials with desirable properties

18. Disadvantages of P/M • Lower corrosion resistance • Reduced plastic properties • Ductility • Impact strength

19. Unit 5Powder MetallurgyPrinciples of Machining Processes Chapter 11 - Principles of Machining Processes

20. Principles of Machining Processes • Machining is essentially the process of removing unwanted material from wrought (rolled) stock, forgings, or casting to produce a desired shape, surface finish, and dimension.

21. Basic Machining Processes Turning • Characteristics • Work rotates, tool moves for feed • Type of Machine • Lathe & vertical boring mill • http://www.youtube.com/watch?v=OeN1etkFsbk

22. Parting on the Lathe http://www.youtube.com/watch?v=1mkg73G0Vho&playnext=1&list=PL8D35020DEFB12A92

23. Turning – Horizontal Lathe

24. CNC Turret Lathe Videos http://www.machinetools.net.tw/lathe/taiwan_cnc_turret_lathes.htm

25. Basic Machining Processes Milling • Characteristics • Cutter rotates and cuts on periphery • Work feeds into the cutter and can be moved in 3 axes. • Type of Machine • Horizontal milling machine

26. Basic Machining Processes Face Milling • Characteristics • Cutter rotates to cut on its end and periphery of vertical workpiece • Type of Machine • Horizontal mill, profile mill, machining center

27. Basic Machining Processes Vertical Milling • Characteristics • Cutter rotates to cut on its end and periphery • Work moves on 3 axes for feed or position • Spindle also moves up or down • Type of Machine • Vertical milling machine, machining center

28. Basic Machining Processes Vertical Milling • Characteristics • Cutter rotates to cut on its end and periphery • Work moves on 3 axes for feed or position • Spindle also moves up or down • Type of Machine • Vertical milling machine, machining center

29. Basic Machining Processes Shaping • Characteristics • Work is held stationary and tool reciprocates • Work can move in 2 axes while toolhead can move up or down • Type of Machine • Horizontal and vertical shapers

30. Basic Machining Processes Planing • Characteristics • Work reciprocates while tool is stationary • Tool is movable, worktable is not • Type of Machine • Planer

31. Basic Machining Processes Horizontal Sawing • Characteristics • Work is held stationary while saw either cuts in one direction (bandsawing) • Saw reciprocates while being fed downward • Type of Machine • Horizontal bandsaw, reciprocating cutoff saw

32. Basic Machining Processes Vertical Bandsawing • Characteristics • Endless band moves downward, cutting the workpiece • Workpiece moves • Type of Machine • Vertical bandsaw

33. Basic Machining Processes Vertical Bandsawing • Characteristics • Endless band moves downward, cutting the workpiece • Workpiece moves • Type of Machine • Vertical bandsaw

34. Basic Machining Processes Broaching • Characteristics • Workpiece is stationary while a multi-tooth cutter is moved across the surface • Each tooth cuts progressively deeper • Type of Machine • Vertical/horizontal broaching machine

35. Basic Machining Processes Horizontal Spindle Surface Grinding • Characteristics • Rotating grinding wheel moved up or down feeding into workpiece • Worktable holds piece and can move in 2 axes • Type of Machine • Surface grinders

36. Basic Machining Processes Vertical Spindle Surface Grinding • Characteristics • Rotating grinding wheel can be moved up or down feeding into workpiece • Circular table rotates • Type of Machine • Blanchard-type surface grinders

37. Basic Machining Processes Cylindrical Grinding • Characteristics • Rotating grinding wheel contacts turning workpiece that reciprocates from end to end • Workhead can be moved into and away from workpiece • Type of Machine • Cylindrical grinders

38. Basic Machining Processes Centerless Grinding • Characteristics • Work is supported by a work rest between a large grinding wheel and a smaller feed wheel • Type of Machine • Centerless grinder

39. Basic Machining Processes Drilling/Reaming • Characteristics • Drill or reamer rotates while work is stationary • Type of Machine • Drill presses • Vertical milling machine

40. Basic Machining Processes Drilling/Reaming • Characteristics • Drill or reamer rotates while work is stationary • Type of Machine • Drill presses

41. Basic Machining Processes Drilling/Reaming • Characteristics • Work turns while drill or reamer is stationary • Type of Machine • Engine lathes • Turret lathes • Automatic Screw Machines

42. Basic Machining Processes Boring • Characteristics • Work rotates, tool moves for feed on internal surfaces • Type of Machine • Engine lathes • Horizontal/vertical Turret lathes • Vertical boring mills

43. Motion and Parameters:Speed, Feed, and Depth of Cut • Cutting Speed: • The rate at which the workpiece moves past the tool or the rate at which the rotating surface of the cutting edge of the tool moves past the workpiece.

44. Motion and Parameters:Speed, Feed, and Depth of Cut • Feed Motion: • the advancement of the cutting tool along the workpiece (for lathes) or the advancement of the workpiece past the tool (for milling machines).

45. Motion and Parameters:Speed, Feed, and Depth of Cut • Feed Rate: • The distance that a cutting tool moves in either one revolution (feed per revolution) or in one minute (feed per minute) in a machining operation.

46. Motion and Parameters:Speed, Feed, and Depth of Cut • Depth of Cut: • The thickness of the layer of material sheared from a workpiece by a cutting tool in a machining operation. • The depth of cut determines the width of the chips produced in the machining operation.

47. Basic Machining Processes • Machinability: • the ease or relative ease with which a workpiece can be machined • compared by measuring the power required and cutting tool life for each workpiece material.

48. Basic Machining Processes • Cutting Tool Geometry: • Tool Geometry (shape) varies considerably depending on the machining application. • The shape and angle of cut of the tool are key to the proper removal of material

49. Basic Machining Processes • Cutting Tool Geometry:

50. Basic Machining Processes • Cutting Tool Geometry: