30-04-2012, 11:34 AM
HIGH SPEED MACHINING (HSM) – THE EFFECTIVE WAY OF MODERN CUTTING
HIGH SPEED MACHINING (HSM) – THE EFFECTIVE WAY.pdf (Size: 241.86 KB / Downloads: 225)
1 Introduction
Machining with high speeds (HSM) is one of the modern technologies, which in comparison
with conventional cutting enables to increase efficiency, accuracy and quality of workpieces and at
the some time to decrease costs and machining time [9].
Even though High Speed Machining is known for a long time (first tries were made in early
twenties of the past century) there are still a lot of questions and less or more complicated
definitions of HSM.
The first definition of HSM was proposed by Carl Salomon in 1931. He has assumed that at
a certain cutting speed which is 5 –10 times higher then in conventional machining, the chip tool
interface temperature will start to decrease (Fig. 1).
Fig 1. Temperature as a function of cutting speed [2, 9].
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It is not possible to verify this theory to its full extent based on recent experimental results.
There is a relative decrease of the temperature at the cutting edge that starts at certain cutting speeds
for different materials. Actually there are many different ways to define HSM, upon them HSM is
said to be [2]:
? high cutting speed machining (vc),
? high rotational speed machining (n),
? high feed machining (vf),
? high speed and feed machining,
? high productive machining.
Practically, it can be noted that 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 only machining with high spindle speed because many applications are
performed with conventional spindle speeds. HSM is often used in finishing in hardened steels with
both high speeds and feeds. HSM can be called rather the High Productive Machining when
machining components in roughing to finishing and also in finishing to super-finishing in
components of all sizes.
2 Applications of High Speed Machining
The use of HSM allow us to shorten the production time and to increase the accuracy of
machined parts. High Speed Machining is being mainly used in three industry sectors due to their
specific requirements [1].
Fig. 2. Improvement of production process when using HSM [2].
A) Traditional process. Non-hardened (soft) blank (1), roughing (2) and semifinishing
(3). Hardening to the final service condition (4). EDM process –
machining of electrodes and EDM of small radii and corners at big depths (5).
Finishing of parts of the cavity with good accessability (6). Manual finishing (7).
B) Some process as (A) where the EDM-process has been replaced by finish
machining of the entire cavity with HSM (5). Reduction of one process step.
C) The blank is hardened to the final service condition (1), roughing (2), semifinishing
(3) and finishing (4). HSM most often applied in all operations
(especially in small sized tools). Reduction of two process steps. Normal time
reduction compared with process (A) by approximately 30 – 50%.
= Manual
finishing
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The first category is industry which deals with machining aluminum to produce automotive
components, small computer parts or medical devices [1, 4, 10, 11]. This industry needs fast metal
removal, because the technological process involves many machining operations.
The second category which is aircraft industry involves machining of long aluminum parts,
often with thin walls [1, 4, 10, 11].
The third industry sector is the die mould industry which requires dealing with finishing of
hard materials [2]. In this category it is important to machine with high speed and to keep high
accuracy. In this industry HSM is used for machining such parts as [2]:
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 thir complex shape The surface is
very hard and often prone cracks.
Injection moulds and blow moulds are also suitable for HSM, because of their small sizes.
Which makes it economical to perform all operations in one set up.
Milling of electrodes in graphite and cooper. It is an excellent area for HSM. Graphite can be
machined in a productive way with Ti(C,N), or diamond coated solid carbide endmills.
Modelling and prototyping of dies and moulds. is one of the earliest area for HSM. Easy to
machine materials such as non-ferrous, for example aluminum are used. The cutting speeds are
often as high as 15 000 – 50 000 [rpm] and the feeds are also very high.
Using of the HSM in the above mentioned regions can cause the reduction of production
process when electrode milling ECM and EDM . HSM ensres a dimensional tolerance of 0,02 mm,
while the tolerance when using ECM is 0,1 – 0,2 [mm] and EDM 0,01 – 0,02. Replacing ECM with
machining causes the durability and tool life of the hardened die or mould is increased
considerably.