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

2. Powder Metallurgy Machining Hot and Cold plastic deformation Casting
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

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 Atomization Chemical methods Electrolysis processes
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. Lower corrosion resistance Reduced plastic properties
Disadvantages of P/M
Lower corrosion resistance
Reduced plastic properties
Ductility
Impact strength

19. Unit 5 Powder Metallurgy Principles 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
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22. Parting on the Lathe
PL8D35020DEFB12A92

23. Turning – Horizontal Lathe

24. CNC Turret Lathe Videos

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
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:

51. Basic Machining Processes
Chip Formation/Chip Control:
Chips that are shaped like “9”s are preferred. This means the tool geometry, cutting speed, and depth are correct
Many cutting tool have “chip-breaking” geometries that help to produce the desired chip shape