REGISTER OVERVIEW PLASTICS

PUR (POLYURETHANE)
Machining characteristics for compact PUR elastomers
a) Longitudinal turning
The hard Vulkollan types are very good for machining, whilst in
softer grades the material has a hard time keeping away from the
tool steel. However, the required degree of rigidity can be achieved
by means of supercooling. The following optimum machining
conditions have been established:
Face turning/Parting
For parting wide components, the same conditions as specified
under a) apply.
When parting thin discs, it is recommended to use a tool steel
whose cutting edge is very pointed at an angle of under 15°, so
can be viewed as a knife, and which also possesses the cutting
angle stated above. Diluted soluble oil should be used to cool the
parts, due to the heat generated by the high level of friction.
Thread cutting
Only coarse threads are recommended, since Vulkollan is relatively
soft compared to steel.
Milling
With a circumferential speed of 200 to 400 m/min., and a milling
tool made from high-speed tool steel with a clearance angle of
10° and y = 25°, the surface finishes specified under a) can be
achieved.
To ensure good chip removal, the milling tool should not feature
multiple teeth (no milling head).
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PLASTICS 13/103
Vulk. type Cutting speed Feed rate Tool Steel mould Surface finish
m/min. mm/rev. Material a b γ centre- line average in µ
Approx. 95 Shore 100 – 150 0.1 – 0.2 HSS 12 53 25 10
Approx. 90 Shore D 100 – 150 0.1 – 0.2 HSS 12 53 25 20
Approx. 85 Shore D 300 – 500 0.1 – 0.2 HSS 12 53 25 50
Approx. 70 Shore D 300 – 500 0.1 – 0.2 HSS 12 53 25 100
Note: Observe the relevant storage
regulations
→ see the chapter 14/43
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Drilling
Drilling can be done using standard steel drills. Cutting speeds
of 40 to 50 m/min. are recommended, with a feed rate that is as
low as possible, i.e. 0.01 to 0.03 mm/rev. A higher feed rate can be
selected for the hard materials.
Bores up to 20 mm deep can be made without using diluted
soluble oil. Due to the softness of the material, the diameters of
the bores for Vulkollan 70° – 90° Shore types are up to 4 % smaller
than the drill diameters.
Grinding
Smooth surfaces are achieved using grinding wheels made from
standard corundum with a vitrified bond, a fine grain, medium
hardness and a coarse structure. Grinding speeds must be very
high, i.e. 30 to 50 m/sec., with the high speed applying to soft
materials. Diluted soluble oil should be used to cool the parts
down in order to avoid overheating.
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