Technology II.

1. Finishing methods 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 Thesuperfinishing stone issliding on a layeroflubricant on thesurfaceandpushed by certainforce • Thesurfaceisrough – peakslookingoutofthelubracantlayer • The stone cutsthepeaks – thesurfaceforlubricantisbigger, more sliding • The stone cutsallpeaks, no more materialremoval

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

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 : offabric, leather, cotton • Solid : rubber, wood, cork, mild metal • Brushes • Madeoffibres : plastic, metal wire (0,1-1,2 mm) • Belts - Endlessbeltpushed to the part. Betterand more productivethandiscs.

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 !!!

48. Video links: • Fine turning http://www.youtube.com/watch?v=do6BJA7G3R0 • Honing http://www.youtube.com/watch?v=IuzBQlYFgXo • Superfinishing http://www.youtube.com/watch?v=WNkNgsnov7o http://www.youtube.com/watch?v=ePhAIJDjouE • Lapping http://www.youtube.com/watch?v=RfC5H4dA-ds http://www.youtube.com/watch?v=fnoVV-RWIWY • Blasting http://www.youtube.com/watch?v=zK258AM2Axo http://www.youtube.com/watch?v=Q8qN9QYlzvI

49. Video links: • Tumbling http://www.youtube.com/watch?v=QR1mBCFhlpMhttp://www.youtube.com/watch?v=iIdc2YhkG5o • Polishing http://www.youtube.com/watch?v=TnzEMkkCxpw http://www.youtube.com/watch?v=G4xC_GzYAKM • INOX polishing http://www.youtube.com/watch?v=l-Zf2AAgA5U