Round Rod in POM W 3000 mm natural

Round rod in POM W is a mineral filled version of acetal where wollastonite has been worked into the matrix to raise stiffness and keep dimensions stable even under longer loading. The density is just above 1.41 g/cm³, slightly higher because of the filler, and the material handles continuous service up to about 105 degrees. In sub-zero conditions it stays functional down to -40 degrees without turning brittle. The fire rating is HB per UL 94, which is normal for engineering plastics in this family. Water absorption stops at around 0.8 percent, one of the big reasons the POM family gets picked over nylon in damp environments.

POM W sits close to POM C in chemical build-up but behaves stiffer. The tendency to creep drops, which makes the material suitable where a part has to hold its shape over time under constant load. The coefficient of friction is low, wear resistance is good, and the material gives the same clean surface structure as ordinary acetal. That means tolerances hold even in damp environments, which is not always the case with nylons. The thermal expansion that is otherwise acetal's weak spot is reduced noticeably by the mineral filling, which makes machined parts less sensitive to temperature swings. The difference shows up most clearly in applications where the temperature moves between room temperature and service at 60 to 100 degrees, since unfilled POM would then need more assembly clearance.

The rod is machined on a lathe and in a machining center. The chip is short and clean, and since POM has low thermal expansion and stable dimensions it is possible to hold tight tolerances if the tool is sharp and the cooling is even. On deep drilling it pays to retract often to avoid heat building up, which can otherwise damage the bore surface. Wollastonite is gentler on the insert than glass fiber, but tool wear is still somewhat higher than for unfilled POM. Carbide inserts are a sensible choice on larger runs, and the feed can be kept fairly high without the chip starting to burn. Threading works in both internal and external fits, as long as the insert is sharp and the cut does not build heat. For finishing, a light abrasive finishing pass is recommended to lift micro flakes from the filler off the surface.

Typical uses are plain bushings, shaft sleeves, guide strips, cams, valve bodies and feed mechanisms in conveyors. The raised stiffness makes the material suitable for gear drives where an unfilled POM would deform at the tooth. In the same way it works in pump housings and stuffing box parts where low water absorption is an advantage over nylon. In dosing equipment and packaging machines POM W often shows up as a block blank for brackets and holders, since the whole part can be freed from a single blank without post-processing. In heavy machine environments with continuous service the material gets chosen when creep is a problem for standard acetal, for example in loaded fasteners and bearing housings. Chemically the material handles weak acids, bases, solvents and oil. Strong acids and oxidizing media should be avoided.

The standard color is natural, white to slightly bone white depending on filler content. Lengths and diameters are cut as needed. State the cut length you want in the order and you get the rod ready to put in the spindle. In warm applications between 80 and 100 degrees it is recommended to allow a little extra clearance for thermal expansion, even though the mineral filling halves the expansion compared with pure POM. Against a steel shaft, count on a radial clearance of about 0.3 percent of the diameter at room temperature, a little more if the equipment runs warm. Bonding is possible after priming, but for load bearing fasteners a mechanical solution is safer and easier to maintain. For welding, hot air and rod joining work on heavy sections, even though POM is rarely welded in practice since gluing and mechanical fastening are more common. Store the rod flat and dry and you avoid bending stresses in heavy diameters.

When storing heavy diameters it is wise to let the blanks lie for a few days before machining, so that any transport stresses are released. For designs that will serve in a cool environment, for example out in warehouses and freezer rooms, POM W keeps its stiffness without becoming prone to brittleness, which is one of the reasons the material is often chosen over nylon in cold applications.

Are you unsure whether POM W or POM C suits your part best? Get in touch and we will go through load case, tolerance requirements and environment together, and recommend the right grade based on real operation.

In natural and 3000 mm long, the same material in full length for longer runs of turned parts.