Fortron PPS Product Brochure (B240) - Hi Polymers

Fortron ®
Polyphenylene sulphide (PPS)
Fig. 46 · Tolerance classes for the injection moulded
dimensions of components (IT 8 to IT 13 = in
accordance to DIN 16901 basic tolerances)
Tolerance T F
0.6
mm
0.5
0.4
0.3
0.2
0.1
general-purpose
injection moulding
IT 8
0
0 50 100 mm 150
Nominal dimension
injection moulding
of engineering
components
T F = 0.6 %
IT 13
IT 12
IT 11
injection moulding of
precision components
T F 0.3 %
IT 10
IT 9
Fig. 47 · Production tolerance for injection
moulded precision components with small nominal
dimensions
Tolerance T F
Tolerance T F
mm
0.03
0.02
0.01
0
3.5
%
3.0
2.5
2.0
1.5
1.0
T F
0.3% line
0.5
0
0 2 4 6 8 mm 10
In addition to dimensional tolerances, shape and positional
tolerances are generally also important in component
specifications. These tolerances restrict the
permissible deviation of the shape elements of a component
from the geometrically ideal shape and position.
Since shape and dimensional tolerances are
additionally dependent on warpage, they can only be
approximately predicted. For this reason, possibilities
for correction should be provided in the mould.
5.1.5 Changing from another thermoplastic
to Fortron
Since many other plastics are thermally unstable at
the processing temperatures of Fortron, they must be
completely removed from the machine. For purging,
materials such as polyamide (PA) or cross-linked
polymethyl methacrylate (PMMA) are suitable. These
materials are ejected at the appropriate melt temperatures
in rapid shot sequence with the cylinder disconnected
from the mould. As soon as the previous
material has been completely expelled, the cylinder
temperatures are brought up to the settings recommended
for Fortron. Then the purging material (i. e.
PA or PMMA) can be ejected.
When the cylinder temperatures required for Fortron
are reached, Fortron is fed into the injection moulding
machine and the purging material is thus expelled.
Injection moulding of parts cannot begin until the
purging material has been fully removed.
5.1.6 Changing from Fortron to another
thermoplastic
Fortron is expelled from the cylinder with the injection
unit disconnected using one of the purging materials
mentioned (e. g. PA or PMMA). As soon as the
melt is free of all traces of Fortron, the cylinder temperatures
are reduced to a level suitable for the purging
material, while the melt continues to be injected into
the open. When the required temperatures are reached,
the purging operation is completed.
Nominal dimension
36