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Seminar On High Speed Machining (HSM) Report Download

Seminar On High Speed Machining (HSM) Report Download

Over the past 60 years, high speed machining (HSM) has been applied to a wide range of metallic and non-metallic work piece materials including the production of components with specific topography requirements and machining of materials with hardness of 50 HRC and above.
With most steel components hardened to approximately 32-42 HRC, machining operations currently include:
  1. Rough machining and semi-finishing of the material
  2. Heat treatment to achieve the final required hardness
  3. Machining of electrodes and electrical discharge machining of specific parts of the dies or moulds
  4. Finishing and super finishing of surfaces 
DEFINITION OF HSM
The first definition of   HSM was proposed by Carl Salomon in 1931.He assumed 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”. 
The figure below illustrates his definition. There is a relative decrease of the temperature at the cutting edge that starts at certain cutting speeds for different materials.
chip removal temperature as a result of the cutting speed
chip removal temperature as a result of the cutting speed
Actually there are many different ways to define HSM, upon them HSM is said to be,
High cutting speed machining (Vc)
High rotational speed machining (n)
High feed machining (Vf)
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”.

ADVANTAGES 
  • Major advantages of HSM are high material removal rates, the reduction in lead times, low cutting forces, dissipation of heat with chip removal resulting in decrease in work piece distortion and increase part precision and surface finish.
  • Low cutting force gives a small and consistent tool deflection. This in combination with a constant stock for each operation and tool is one of the prerequisites for a highly productive and safe process.
  • Cutting tool and work piece temperature are kept low which gives a prolonged tool life in many cases.
APPLICATION AREAS OF HSM

In this industry HSM is used to machine such parts as
  • Die casting dies: This is an area where HSM can be utilized in a productive way as most castings dies are made of demanding tool steels and have a moderate or small size.
  • Forging dies:  Most forging dies are suitable for HSM due to their complex shape. The surface is very hard and often prone cracks.
  • Injection moulds and blow moulds: These are also suitable for HSM, because of their small sizes. This makes it economical to perform all operations in one step.
  • Milling of electrodes in graphite and copper: It is an excellent area for HSM. Graphite can be machined in a productive way with Ti(C,N) or diamond coated solid carbide end mills.
  • Modeling and prototyping of dies and moulds:  This is one of the earliest areas for HSM. Easy to machine materials such as aluminum are used. The cutting speeds are often as high as 15000-50000 rpm and the feeds are also very high.   
Comparison between conventional machining and HSM process:

CONVENTIONAL
HSM
The contact time between the cutting edge and work piece is large
Contact time between the cutting edge and work piece is short
Less accurate work piece
More accurate work piece
Cutting force is large
Low cutting force
Cutting fluid is required
Cutting fluid is not required
Low surface finish
High surface finish
Material removal rate is low
Material removal rate is high

DISADVANTAGES 
Need for expensive and special machine tools with advanced spindles and controllers
Excessive tool wear.
The higher acceleration and deceleration rates, spindle start and stop give a relatively faster wear of guide ways, ball screws and spindle bearings which leads to higher maintenance cost.
Emergency stop is practically unnecessary! Human mistakes, hard ware or software errors give big consequences.
Good work and process planning necessary.
It can be difficult to find and recruit advanced staff.

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