A GUIDE TO MACHINING PTFE

Service Detail from Fluorocarbon Company Ltd

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PTFE is a thermoplastic, however, due to its high viscosity it cannot be processed using conventional polymer processing techniques. PTFE is processed by cold moulding followed by heat treatment (Sintering) during which polymer particles fuse to form a solid moulding.

When machining PTFE it is essential to design your application with PTFE’s inherent properties in mind, rather than trying to force the polymer to act against its nature. Although PTFE’s density and softness makes it surprisingly easy to machine, its high coefficient of expansion and stress creep properties can make PTFE difficult to achieve tight machining tolerances. A good rule for tolerances of plastic parts is +/- .001 per inch of dimension, tighter tolerances are possible with very stable, reinforced materials. Non-aromatic, water soluble coolants, such as pressurised air and spray mists, are recommended to use for optimum surface finishes and close tolerance.

PTFE benefits from the annealing process, reducing the likelihood of surface cracks and internal stresses occurring in the material. Along with reducing the internal stresses, annealing can reduce shrinkage, improve chemical and wear resistance and allow for tighter tolerances. Post machining annealing also helps to reduce stresses that could potentially contribute to premature failure.

PTFE is a versatile and cost-effective material with average tensile strength. It has very good thermal properties and excellent chemical inertness, especially to strong acids. PTFE is an outstanding electrical insulator over a wide range of temperature and frequency. Like many other high-performance plastics, its properties are often improved by adding fillers such as Carbon, Graphite or Glass.

At Fluorocarbon, we utilise our in-house compression moulding capabilities to create stock shapes for efficient machining of custom PTFE parts. Offering full traceability on all materials along with in-house tensile strength and elongation testing. Our materials are conditioned and stress relieved to ensure optimum quality for machining. Combining this with finished component design and machining facilities we provide the advantage of offering a cost-effective end-to-end service.

We ensure the highest standards of finished product by retaining complete control of the manufacturing process, whilst converting compounds into semi-finished stock. Compounds can be moulded or extruded and processed into machined components to suit specific requirements.