1. Technology II.

2. Finishing methods With material removal – generative methods
(fine machining, honing, superfinishing, lapping)
Without material removal – forming methods
(glazing, blasting, tumbling, polishing)

3. 1. Fine machining Machining process
Turning or milling with depth of cut close to minimum depth of cut
Fine cylindrical of flat surfaces

4. Fine mach.
Tools
Turning – high precision inserts (PCD - alluminium, coated SC)
Milling – special shaped inserts, large diameter facing milling heads

5. Fine mach. - examples

6. Fine mach. properites Low depth of cut Ap = 0,01 – 0,05 mm
High cutting speeds – up to 1000 m.min-1
High cutting forces, high spindle load
IT = 4 – 6
Ra = 0,1 – 0,4

7. 2. Honing Abrassive process
Small amout of material is removed by honing stones
Mainly internal holes (bored and ground holes)

8. Honing Tool: Honing head with honing stones Honing stones:
Made of abrasive material
Adjustable
Seated on pushing springs

9. Honing Material of stones Any abrasive material can
Be used for a honing stone
- Same materials like grinding stones (corundum, SiC, CBN, PCD)
- more precise shape, smaller grain (10-50 μm)
- Cutting fluids are used for lubrication

10. Honing – process mechanics
Honing head is
Rotating – reciprocitive
Oscilating – up and down
Honing stones are pushed to the surface

11. Honing – process mechanics
Two speeds combined together make unique movement and special form of tool path.

12. Honing – machine tools
Special horizontal or vertical honing machines

13. Honing - examples

14. Honing - properties Improving the geometrical accuracy (IT) mainly
Setting certain surface pattern (lubrication)
Expensive and time consuming
IT = 3 to 6
Ra = (0,025)0,1 – 0,4

15. 3. Superfinishing Abrassive process
Small amount of material is removed by moving superfinishing stone
Both cylindrical and planar surfaces

16. Superfinishing Tool: Superfinishing stone
Has the negative shape of the machined surface (or it can be flat for large
surfaces)
Abrasive material again – fine grained (to 20 μm)

17. Principle
The superfinishing stone is sliding on a layer of lubricant on the surface and pushed by certain force
The surface is rough – peaks looking out of the lubracant layer
The stone cuts the peaks – the surface for lubricant is bigger, more sliding
The stone cuts all peaks, no more material removal

18. Superfinishing - surface

19. Superfinishing - methods
Cylinders Cones Flat surface Shape surface

20. Superfinishing - properties
Not improving the geometry!!! (IT remains) Lower speeds and force than gringing or honing
Method
Cut. Speed (m.min-1)
Move
Presure (MPa)
Grinding
None (infeed)
14-140
Honing
50 cycles (length of hole – 150 mm)
3,5 – 7
superfinishing
6-14
cycles (1-5 mm)
0,02 – 0,07

21. Superfinishing - properties
Ra = 0,025 – 0,1 Lubricant is used to carry away chips and minimize heat (deformation) – kerosene is used

22. Superfinishing – machine tool
Superfinishing device
– mounted on lathe
Superfinishing
Machines – special,
Expensive type (multi-
ple parts, long travel
distance)

23. 4. Lapping Abrassive process Removing very small amount of material
Removing surface undulations, roughness, tool marks and surface fuzz from grinding
For all types of surfaces

24. Lapping
Tool:
A flat disc or plate made of cast iron, al-alloy, copper, brass (low strength material)
Abrasive particles are carried by an agent – grease, oil, water (higher viscosity means higher abrasion)

25. Lapping - methods
The lapping tool is rotated (oscilated) and moved irregularly across the machined surface
Equalising laping – removing previous surface shape, flatening (spur, helical gears)
Forming laping – lap is the negative shape of the surface

26. Lapping - methods For: Holes Flat surfaces cylinders Made: Manually
mechanically

27. Lapping - methods Flat surfaces
Lapping plate (different sizes, manual, machine operated
- Moved irregularly along the surface

28. Lapping - methods Machine lapping
Part are placed between a rotary and stationary lap. Part are carried by a workpiece holder. Part are placed excentrically so is the rotating lap.
This makes the parts rotate and move

30. Lapping - examples

31. Lapping - properties
Lapping removes all tool traces – improves durability, lowers friction
Gives best surface quality (glass, mirror lapping)
IT = 1 – 5
Ra = 0,01 – 0,16

32. 5. Glazing Forming method
Removing peaks on surface by rolling them into flat surface
Used on rotational or flat surfaces

33. 6. Blasting Two forms - Forming (angle 80°)
- machining method (for angle of impact bellow 45°)
Particles are thrown at surface
All kinds of shape

34. Blasting - tool
Blasting elements are transported by high presure air to the surface Hardened steel balls cast iron balls Steel wire pieces (rounded) Glass balls – aerospace industry

35. Blasting - examples

36. Blasting - Aerolap

37. 7. Tumbling Forming method, abrassive method
Part to be machined and tumbling particles are placed in rotating cylinders
Non defined surfaces

38. Tumbling - method Abbrasive particles and parts mixed together
Special rotary or vibrational mills
steel cylinders, inner rubber linning (to prevent abrasion)
Sometimes active cutting fluid (water, NaCl, NaNO3, H2SO4 ) helping to remove the surface layer

39. Tumbling – surface quality

40. Tumbling - tools
Abbrasive particles – non-uniform pieces of grinding stones, porcelain, ceramics (5-20 mm)
Hardened steel balls (4-10) little surface hardnes improvement
Soft particles for tumbling-polishing (dry corn peels, palm bark, wood chips)

42. Tumbling - machines

43. 8. Polishing Abrasive method
A friction between the polishing tool and part is caused by polishing media (paste) heat melts the peaks of surface
All surface mainly flat surface with no strength demands

44. Polishing Abbrasive material is bond
to a tool (disc, belt) or it is a media (paste) freely between tool (textile disc, belt) and
part
NO improve in shape or accuracy!!
Just improves the surface quality

45. Polishing - tools Discs – multi-plated : of fabric, leather, cotton
Solid : rubber, wood, cork, mild metal
Brushes
Made of fibres : plastic, metal wire (0,1-1,2 mm)
Belts
- Endless belt pushed to the part. Better and more productive than discs.

47. Polishing - properties
Cutting speed
25-40 m.sec-1
No IT improvement
Ra 0,2 - 0,4 (removes tool paths)
!!! Implicates residual stress due to high temperature !!!