Ensinger TECAFIL POM-C natural is an unfilled polyoxymethylene copolymer filament produced in 1.75 mm nominal diameter for fused-filament fabrication and material-extrusion platforms. The grade carries the designation TECAFIL POM-C natural - 1,75 mm - Filament Polyacetal (Copolymer) and is supplied in natural color with a diameter tolerance held to ±0.05 mm by in-line optical gauging. Because the polyacetal is a copolymer rather than a homopolymer, occasional comonomer units interrupt the oxymethylene repeat along the chain; this molecular architecture reduces the unzipping tendency under hot-end residence and produces a melt endotherm near 166 °C when characterized by ISO 11357-3:2018. The filament is selected principally where low moisture uptake, high rigidity, and dry sliding wear resistance are required in printed functional components.

The filament is wound with controlled payoff tension to accommodate stiff monofilament behavior. Spool packages are sealed with desiccant after drying; a resealable barrier bag with an internal dew point below -20 °C prevents surface condensation before processing. A direct-drive or dual-drive extruder is preferable because the high modulus of POM-C can store hoop stress in long Bowden tubes. The filament should not be routed around a radius below 50 mm; tight bends produce stress whitening and out-of-round feedstock that shifts the effective extrusion multiplier.

An all-metal hot end with a hardened or brass nozzle is adequate for the unfilled grade. Nozzle orifice sizes from 0.25 mm to 0.60 mm are used; a 0.40 mm aperture provides a practical balance between melt throughput and layer resolution. A heater cartridge with closed-loop PID control and an independent thermocouple probe is recommended because the temperature window between sufficient interlayer diffusion and thermal decomposition is narrow. A silicone sock stabilizes the block temperature; draughts across the block produce surface blemishes and layer-to-layer delamination at the top of tall parts.

What Distinguishes TECAFIL POM-C Natural from Homopolymer Acetal and Other Filaments?

Homopolymer acetal typically has a higher melting peak, often 175 °C to 181 °C, and a higher crystalline fraction. The higher crystal content yields a small stiffness advantage, but it also makes the polymer more sensitive to alkaline hydrolysis and thermal unzipping. TECAFIL POM-C natural has a lower melting point but greater processing stability in the presence of oxygen. Under melt-processing conditions, the rate of formaldehyde generation is lower than for homopolymer at the same melt temperature. In hot-water or humid environments, the copolymer backbone is generally less prone to chain scission at elevated temperature, which is relevant for pump and valve components printed for use at 60 °C to 80 °C.

Compared with unreinforced PETG filament, the product has a higher tensile modulus; representative published values place PETG near 2000–2200 MPa and TECAFIL POM-C natural near 2700 MPa under ISO 527-1:2019. PETG bonds more easily to glass and offers lower warping, but it does not match the dry sliding behavior of polyacetal. Compared with PA6 filament, TECAFIL POM-C natural absorbs substantially less moisture. PA6 conditioned at 23 °C and 50 % RH can take up 2.5–3.0 % water by mass, which swells the polymer and reduces the effective modulus; POM-C moisture uptake under the same conditions is typically below 0.3 %. This dimensional stability is useful in printed gauges, gear carriers, and assembly fixtures exposed to changing plant humidity.

Although POM-C is not as hygroscopic as polyamide, condensation on cold spools can create pit marks at the nozzle. A desiccant dryer set to 80 ± 5 °C for 2–4 h is used before long production runs; if the spool has been exposed to open storage for more than 24 h, the same drying step is repeated. Drying air with a dew point below -20 °C prevents re-wetting. The filament should not be dried above 100 °C because the spool body may soften and the monofilament surface may oxidize.

When Bed Temperature Falls Below 90 °C and the Part Fan Is Left at Full Flow

The first layer of polyacetal copolymer is highly sensitive to the temperature of the build surface. A bed set to 90–110 °C is required for consistent adhesion when combined with polyimide tape, a POM-based adhesion film, or a dedicated primer. Below 85 °C, the extruded bead can lose contact at sharp corners within the first 5–10 s; the free edge then cools, shrinks, and acts as a lever for progressive lifting. A passive enclosure that maintains an air temperature of 40–60 °C reduces differential shrinkage across the part. The part cooling fan should remain off for the initial 5 mm of height and should then be limited to 10–20 % on small features; full cooling air freezes the surface before interlayer diffusion is complete, producing a weak plane at the layer boundary.

Nozzle setpoint should be held within 200–220 °C. At temperatures above 230 °C, the melt begins to generate formaldehyde at an increasing rate, and prolonged idle can leave a brown residue in the hot-end throat. A residence time greater than 10 min at print temperature without extrusion can produce voids and viscosity loss. If the machine is paused, the hot end should be cooled below 100 °C or purged with LDPE or PP. A purge sequence of a low-temperature commodity polymer at 200 °C is also used to remove degraded acetal before reloading the POM-C filament. The nozzle should then be primed onto a sacrificial bed until clear melt appears.

Support removal is more difficult than on PLA because POM-C fuses strongly to itself when printed at 200–220 °C. Breakaway supports with a sparse interface work better than dissolvable supports; common dissolvable support materials based on HIPS or PVA may not adhere reliably or may leave residues that affect sliding surfaces. Layer heights between 0.10 mm and 0.20 mm and extrusion widths of 0.35–0.50 mm are used for close-tolerance parts. The extrusion multiplier is kept between 1.00 and 1.03; overpacking causes ridge defects and increases contact pressure at the nozzle tip.

Mechanical, Thermal, and Tribological Reference Values

The following supplier-published or representative values apply to dry, unfilled POM-C feedstock and are not a guarantee for any particular printed raster orientation.

Mechanical testing of fused-filament parts introduces anisotropy because the melt bead freezes directionally. Tension specimens printed flat with a 0.15 mm layer height and tested perpendicular to the raster may show lower elongation than the baseline. Users should generate their own coupon data under ASTM D638-14 or ISO 527-2 at 23 ± 2 °C and 50 ± 5 % RH when part stiffness or safety is critical. Published data for this specific filament configuration are limited for z-direction tensile strength and compression after impact.

Where a selection matrix is required among unfilled engineering filaments, the following representative values are drawn from published supplier data and general unfilled feedstock documentation; they are not to be used for final part design.

Gears, cams, sliding guides, bushings, and snap-fit levers are common candidates for this filament. In unlubricated sliding contact against steel, unfilled POM-C typically produces a dry dynamic coefficient of friction in the 0.20–0.30 range when tested under ISO 7148-2:2012. This performance drops if contact pressure is high enough to raise the interface temperature toward the thermal deflection limit. The printed part should be characterized for wear rate at the expected speed, counterface roughness, and normal load; published data for this specific filament configuration are limited, so supplied bulk values cannot be substituted for end-use tribometric testing.

Chemical exposure is another selection criterion. POM-C copolymer tolerates aliphatic hydrocarbons, mineral oils, alcohols, glycols, and many dilute aqueous cleaning media at room temperature. It is not recommended for continuous immersion in strong acids, halogens, or phenolic disinfectants above 60 °C; users should test the specific chemical mixture against a printed coupon. Regulatory documentation for the unfilled natural grade is available under REACH and RoHS 2011/65/EU for the base resin; food-contact compliance must be verified on the finished printed article under EU 10/2011 or FDA 21 CFR because layer voids and surface roughness can affect migration behavior.

Long-term continuous-use temperature in air for unfilled POM-C is generally cited near 100 °C; short-term excursions may reach 140 °C at low load. Printed parts that operate above this range or under high mechanical load should not be placed into service without thermal aging tests under ISO 2578. The processing thermal history of the printed component may lower the practical ceiling relative to injection-molded stock because extrudate orientation, residual stress, and surface micro-voids are introduced by material extrusion. Printers with all-metal hot ends and actively heated build plates are mandatory; open-format machines without enclosures typically show higher scrap rates on parts exceeding 100 mm in length.