1. SEMINAR ON HIGH SPEED MACHINING (HSM)

2. CONTENTS Introduction Definition of HSM Advantages Application areas
Machining system
Some recommended parameters
Comparison
Disadvantages
Conclusion

3. DEFINITION OF HSM Carl Salomon assumes that
“At a certain cutting speed which is 5-10 times higher than in conventional machining the chip removal temperature at the cutting edge will start to decrease”

4. DEFINITIONS High cutting speed machining
High rotational speed machining
High feed machining
High speed and feed machining
High productive machining
Finally,
“HSM is a powerful machining method that combines high feed rates with high spindle speeds, specific tools and specific tool motion.”

6. ADVANTAGES High material removal rate High surface finish
Increased productivity
Possibility of machining of very thin walls
Reduction in lead times
Low cutting force
Cutting tool and work piece temperature are kept low
Connection time between the cutting edge and work piece is short
It eliminates the need of coolant
Reduction of production process

8. FEATURES
EFFECTS
Reduced heat transfer in to the work piece
Part accuracy
Reduction of cutting forces
Surface quality
Increased cutting speed
Stability of rotating cutting tool feed rate
Increased material removal

10. APPLICATION AREAS
Industry which deals with the machining of Al to produce automotive components, small computer parts or medical devices
Aircraft industry involves machining of Al often with thin walls
Die mould industry which requires dealing with finishing of hard materials .
Used to machine such parts as die casting dies, forging dies, injection moulds and blow moulds, milling of electrodes in graphite and copper, modeling and prototyping of dies and moulds.

11. MACHINING SYSTEM MACHINE TOOLS
3-axis horizontal and vertical milling machines
CNC 4-axis milling machine offers the option of tilting the milling cutters to improve the cutting conditions
5-axis machine with inter changeable spindle units allow to rough, semi finish and finish with a single set up.

12. DEMANDS ON THE MACHINE Spindle speed range <=40000 rpm
Spindle power >22 KW
Programmable feed rate m/min
Rapid travels <90 m/min
Block processing speed 1-20 ms
High thermal stability and rigidity in spindle
Air blast/coolant through spindle
Advanced look ahead function in the CNC

15. CUTTING TOOLS
TiN and TiCN coated Carbide for materials with hardness less than 42 HRC
TiALN coated Carbide for materials with hardness 42 HRC and above
For special applications like hard turning (HRC 60-65) PCBN is used
Cubic boron nitrite (CBN) and ceramic for cast iron
Poly crystalline diamonds (PCD) and Cermets are used for aluminum

16. RECOMMENDED PARAMETERS
1.True cutting speed
As the speed is dependent on both spindle speed and diameter of tools HSM should be defined as “true cutting speed” above a certain level

17. 2.Material removal rate
Material removal rate,
Q = (ap* ae * vf)/1000 cm3/min
where ap = vertical dist from tool tip to the reference point mm
ae = step over distance mm
vf = feed speed mm/min

18. 3. Surface finish
Surface finish is depends upon cutting tool geometry, coating of the cutting tool, wear status of the cutting tool etc.

19. COMPARISONS Conventional machine High speed machine
Max speed 600 m/min
Speed starts at 600 m/min
Max feed ~40 ipm
Feed starts at 100 ipm
Require high levels coolant
With coolant ,feed rate can go more than 2000 ipm
No need for coolant for low feed rate
Between conventional and high speed machines

20. Comparison between speeds used in conventional and high speed machining

21. The contact time between tool and work is large Contact time is short
Conventional
HSM
The contact time between tool and work is large
Contact time is short
Less accurate work piece
More accurate work piece
Cutting force is large
Cutting force is low
Low surface finish
High surface finish
Material removal rate is low
Material removal rate is high
Cutting fluid is required
Cutting fluid is not required
Comparison between convl and HSM process

22. Material removal rate high Material removal rate is low
HSM
EDM
Material removal rate high
Material removal rate is low
Dimensional tolerance 0.02 mm
Dim tolerance mm
There is no need of making cutting tool according to the contour to be machined
Cutting tool has to be made according to the contour to be machined
Comparison between HSM and EDM

23. DISADVANTAGES
Need for expensive and special machine tools with advanced spindle and controllers
Excessive tool wear
Good work and process planning necessary
It can be difficult to find and recruit advanced staff

24. CONCLUSIONS
HSM is not simply high cutting speed .It should be regarded as a process where the operations are performed with very specific methods and precision equipment
HSM is not necessarily high spindle speed machining. Many HSM applications are performed with moderate spindle speeds and large sized cutters
HSM is performed in finishing in hardened steel with high speeds and high feeds often with 4-6 times conventional cutting speeds

25. HSM is high productive machining in small sized components in roughing to finishing and in finishing to super finishing in components of all sizes.
Even though HSM is known for a long time, the research are still being developed for further improvement of quality and optimization of cost.

26. THANK YOU