Round Rod in POM+PTFE 1000 mm natural

Round rod in POM+PTFE is one of the more specialized products in the POM family. The acetal matrix gives stiffness and dimensional stability while the blended-in fluoropolymer lowers friction to a level no unfilled acetal reaches. The density is about 1.52 g/cm³, continuous working temperature up to 105 degrees and a lower limit around -20 degrees. Water absorption stops at around 0.65 percent, which is low enough for damp and warm environments. The fire rating is HB per UL 94. The higher density comes from the weight of the fluoropolymer, which makes heavy rods noticeably heavier than a corresponding POM C blank.

The material is designed for sliding components working under high PV load. The PTFE domains in the matrix give a self filming sliding surface where the coefficient of friction against steel is lower than for POM+PE and considerably lower than for pure POM. In dry running the wear stays low and stick-slip is practically engineered out. That makes the rod suitable for bushings in press tools, shaft sleeves in pumps and stuffing box bodies where leakage and vibration are problems. The material is also suitable where the load direction changes, since the restart friction is low. For designers who previously chose bronze bearings with grease lubrication, POM+PTFE is often a direct replacement, with a clearly reduced maintenance burden since lubrication falls away.

Machining is done on a lathe or in a machining center with the same methods as for unfilled POM. The chip is short, the surface comes out shiny with sharp inserts, and tolerances can be held tight. The PTFE phase makes the cut somewhat softer than in pure acetal, so the feed may need adjusting for the best surface. Threading works well. On deeper holes and internal threads, frequent retraction is recommended to keep the material from heating up. For larger runs, carbide inserts with sharp geometry are the natural choice, and cooling only needs to be moderate since heat build-up in the cut is low. When finishing slender diameters it pays to give the blank a few hours of rest between roughing and final dimension, so that internal stresses are released before the finish dimensions are locked.

Typical applications are plain bushings against steel and stainless, shaft sleeves in food machinery, stuffing boxes in valves, cam rollers with dry running and guide sleeves in optical units where friction has to be predictable. The material also works where the load direction changes, since stick-slip is negligible. In the tooling industry the rod is used for stops and center pins where positional accuracy is decisive, and in pump and compressor building as sealing parts against moving shafts. In heavier moving mechanics the material often replaces bronze and steel bearings where grease contamination is not allowed, for example in breweries and filling lines. Chemically the rod handles oil, weak acids, bases, fuels and most solvents. Strong oxidizers and concentrated acids should be avoided. The material is also stable against common cleaning agents, which is part of why it has spread so far in hygiene critical production.

The rod comes in round dimensions from slender to heavy diameters and is cut to the length you want. Fits against a steel shaft are calculated with about 0.3 percent of the diameter as radial clearance at room temperature. Bonding is difficult because of the fluoropolymer phase, so mechanical fastening is safer. During assembly you should avoid tight press fits in thin sections, since the solid material is somewhat more sensitive to stresses than an unfilled POM. For heavy blanks, slow cooling after turning is recommended so that internal stresses have time to release before precision measurement. Store the rod flat and dry and you avoid bending stresses, which can otherwise cause trouble when clamping long pieces. For assembly in heat the clearance should be increased a little to compensate for the material's thermal expansion against the steel shaft.

For fits against heavy shafts it pays to check the surface finish of the mating part, since a steel surface that is too rough wears the softer matrix unnecessarily. A polished or hard chrome plated shaft gives the longest service life, and combined with clean dry running the wear stays very low across the whole period between service intervals.

The 1000 mm long natural rod has PTFE blended in for lower friction, made for bearing bushings and sliding surfaces.

Would you like help deciding whether POM+PTFE or another sliding plastic suits your application? Send us the load case, mating surface and environment, and we will come back with a concrete proposal based on real operation.