PA6 (Polyamide 6, Nylon): wear-resistant and mechanically strong

PA6 is a polyamide, commonly called nylon. It is strong, tough, and wear-resistant, with low friction against steel, making it widely used for moving and loaded parts. The tensile strength of 70 to 85 MPa is well above that of ABS or PP. However, the material does absorb moisture, which changes the dimensions and properties. QDP takes this into account in the tolerances.

Polyamide attracts water from the air, up to a few percent of its own weight. This makes the material tougher and less brittle, but it also causes it to swell: a part may be noticeably larger after weeks in a humid environment than right after molding. For tight fits this is a real concern, and the granulate should be dried beforehand or the product will get streaks and weak spots. QDP factors this effect into the mold size and the tolerances.

They are very similar. PA66 has a higher melting point and stays a bit stiffer at heat, PA6 is tougher, less likely to break, and easier to process because it has a broader processing range. PA66 absorbs a bit less moisture. In practice, the difference for most applications is small and availability or price is usually decisive. QDP chooses based on the operating temperature and loading of the part.

PA6 shrinks about 0.8 to 1.5 percent, more than ABS and less than POM or PP. What makes it trickier than those numbers suggest is that polyamide also has post-shrinkage and absorbs moisture, causing the dimension to still change during the first weeks after production. For that reason, you measure at a defined moment and not directly from the machine. QDP establishes that measurement timing for products with tight fits.

As soon as stiffness or heat resistance becomes the limiting factor. Unfilled PA6 becomes noticeably softer under load and the thermal shape stability is around 55 to 70 degrees. With 30 percent glass fiber that increases to well over 200 degrees and the tensile strength more than doubles. You lose toughness, the surface gets rougher, and the mold wears more quickly. QDP advises the reinforced variant only if the construction demands it.

For technical parts that move or bear loads: gears, bearing bushes, guides, chain parts, brackets, and clamps. It is also common in power tool housings and machine building because it resists oils and greases. Where a metal part is too heavy or too expensive, polyamide is often the substitute. Moisture absorption remains something to watch as soon as tight fits are involved. QDP injection molds PA6 parts among others for machine building and means of transport.