Round Rod in POM+PE 1000 mm blue

Round rod in POM+PE is built on an acetal matrix with dispersed polyethylene and gives a material that lubricates its own sliding surface. The density is about 1.35 g/cm³, continuous working temperature goes up to 100 degrees, and the material keeps its properties down to -40 degrees. Water absorption is low, around 0.8 percent, which is one of the POM family's big advantages over the nylons when dimensions have to hold in damp environments. The fire rating is HB per UL 94. For a designer this is a material that behaves like POM but with significantly lower friction, which opens up dry running solutions without having to change the whole material class.

The polyethylene works as a built-in lubricating film in the material. Microscopic PE domains sit spread through the POM matrix and are released gradually as the surface wears. The coefficient of friction ends up lower than for unfilled POM and stick-slip is avoided almost completely. For bushings and shaft slides that means start-up is smooth even after a long standstill. Wear resistance stays high, and since the matrix is still acetal the parts are stiff and dimensionally stable. That gives a different behavior curve than pure PE-1000, which does have low friction but deforms easily under point loading. The difference shows up above all in applications where the load is high but the speed moderate, and where neither metal bushings nor soft PE would last.

On the lathe the rod behaves like ordinary POM. The chip is short, the surface comes out shiny and tolerances can be held tight with sharp HSS or carbide inserts. Heat build-up in the cut is low, but on deep drilling you should retract often so the hole does not start to heat up. The PE phase is sometimes visible as microscopically duller areas in a finely turned surface, entirely normal and without any functional significance. Secondary threading and milling work fine, and the material holds its shape through the whole machining chain. For larger runs, carbide inserts with sharp geometry and a moderate feed are recommended so that a melt film is avoided. For finishing it pays to let the part rest a few hours between roughing and finishing, so that internal stresses are released before final dimensions are taken.

Typical applications are plain bushings, guide sleeves, cam rollers, dosing screws, conveyor rollers and shaft slides where lubrication is impractical or forbidden. POM+PE is common in packaging machines, the food industry and pharmaceutical manufacturing where clean surfaces and dry running are requirements. In heavier workshop applications the rod is used for feed wheels and drive pinions where metallic lubrication is hard to maintain. In bottling and filling lines the material often replaces bronze and steel bearings where hygiene is a factor, and at the same time it lowers the maintenance need since re-greasing falls away. Chemically the material handles oil, fuels, weak acids and bases as well as most solvents. Strong oxidizers and concentrated acids should be avoided. Against cleaning agents in the food industry the behavior is stable, which is part of why the material is so widespread there.

The rod is supplied in round dimensions from slender diameters up to heavy blanks. Cut length is stated in the order. For fits against a steel shaft the clearance should be about 0.3 percent of the diameter at 20 degrees, a little more in warm environments since the material expands more than metal. During assembly, press fits in thin sections are best avoided since the polyethylene phase can give rise to local stresses. Bonding is difficult because of the PE phase; mechanical fastening with a flange or a set screw is safer and easier to service at replacement. Heavy diameters are stored standing or flat so that the rod does not sag into a bend over time, which can otherwise cause trouble at clamping. It is also a good habit to rough machine blanks close to final dimension before finishing, so that any internal stresses are released before the dimensions are locked.

In warm environments the clearance should be increased a little extra, since POM expands considerably more than steel. A rule of thumb that works in practice is to count on twice the thermal expansion of the metal you are building against, so that the fit does not shrink when the temperature rises.

The blue 1000 mm rod has polyethylene blended in that lowers friction, good for rollers and bushings that need to run easily.

Would you like help choosing between POM+PE, POM C and PE-1000 for your sliding application? Get in touch with load case and environment, and we will go through the alternatives and give a concrete recommendation.