For plastics processors
Are you a processor of plastics yourself and need semi-finished products made from PTFE or from other high-performance plastics? No problem at all. We offer diverse sheets, solid rods, hollow rods, foils or tapes made from PTFE materials and other plastics!
Our semi-finished products
Good to know
Find important information and guidance below on the manufacture and processing of semi-finished products.
Tolerances in semi-finished production
- Specifically the diameters often have very tight tolerances.
- Plastic materials follow other physical principles than metals. In particular, no guarantee for ensuring narrow dimen-sion tolerances as for metals can be provided due to an 8 to 10 times larger thermal expansion, volume changes due to moisture absorption as well as subsequent dimensional variations owing to slow reduction of residual tensions in long-term behavior.
- This circumstance naturally is the cause of undesirable discussions and annoyance and results not least in goods being rejected. Such predestined “scrapped” parts are inevitable even with the most reliable machines and skilled personnel.
- We therefore recommend our customers to prudently determine the tolerance ranges for turned and milled plastic parts.
- Normally, the functionality of the plastic part is guaranteed even under such enlarged tolerances.
- Accordingly, for plastic parts used in mechanical engineering, specifications of the ISO tolerance series IT 6.7 and 8 have to be avoided.
- For turned PTFE parts, the ISO tolerance series IT11 / IT12 are recommended (see also the leaflet “Tolerances for the machining of plastics” by the Fluoropolymergroup, an expert group of the “pro-K Industrieverband Halbzeuge und Konsumprodukte aus Kunststoff”, Germany.
Machining tools made of HSS are sufficient for processing unfilled PTFE material. For filled materials (PTFE com-pounds), carbide cutting tools should be used to extend tool life, and also the rotational speed should be somewhat reduced. Cutting speeds of 1 to 2.5 m/s are best suited for precision turning and at these speeds the use of cooling liquids need is not required. The feed rate should be between 0.05 and 0.25 mm per revolution.
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