Why Plastics? Well, let’s start with the rising costs of metal. This has designers seeking ways to replace machined metal parts with plastic ones. As a result, job shops are seeing an increase in requests for plastic parts by their customers. Many are scrambling to find the best tools for these materials. DATRON customers who bought our equipment primarily for machining aluminum and other metals have found that they machine plastics as well as metals. This provides them with a way to increase revenue without increasing their equipment costs. Commonly machined plastics and substrates:
ABS, Acetal, Acrylic, Cirlex, Delmat, Delrin, Durastone, Formex, G-9, G-10, G-11, GPO3, Kapton, Lexan, Nomex, Nylon, Phenolic, Polycarbonate, Polyester, Polypropylene, Polystyrene, Polysulfone, PVC, Ryton, Torlon, Ultem, Urethane, Valox, Vespel, Vinyl
- Machining plastic connectors (Delrin, Torlon)
- Milling plastic counter plates (Phenolic)
- Machining plastic wave solder frames (G10, Delmat, Durastone)
- Milling plastic control panels (Acrylic, Polycarbonate)
- Machining plastic prototypes (Ureol, Polystyrene)
Tips for Machining Plastic
While the switch from metal to plastic machining doesn’t require a new equipment purchase, it may require new ways of thinking and working. That’s because plastics machine differently than metal, differently from one plastic to another, differently from lot to lot and from section to section (due to material inconsistency). Temperature and humidity variance often needs to be addressed since plastics often have a high coefficient of thermal expansion and without air conditioning certain plastics will cut differently from season to season. Machinists who have been around the block a few times can adapt quickly to challenges and this is a necessity because many of these plastic parts are produced in small runs and problems must be worked out quickly. The more you work with machining plastics the faster you get at solving problems and picking up the tricks of the trade.
For example, a plastic with a low Durometer reading (an indication of softness) will machine easily … perhaps too easily as the material can be squeezed out rather than cut cleanly out of the cutting channel. So freeze the plastic prior to machining it. In general we avoid using coolants when machining plastics because plastics can expand from absorbing moisture and this can make it tough to hold a tight tolerance. If tight tolerance is required, the part could be rough machined, set up to stabilize and then finish machined to the required tolerance. The general rules of thumb for feeds and speeds detailed to the left are indeed “general” where plastics are concerned. For example, compared to machining steel, when machining plastics, the RPM can be lower and the feed faster. This way the spindle
speed isn’t causing too much friction and the high feeds don’t allow the tool to stay in one area long enough for any heat present to melt the plastic. Another consideration is that if the RPM is too high, heated chips of molten plastic can fling out and melt to the surface of a perfectly good part. With DATRON high-speed machining centers, you have the widest range of speeds and feeds to find the sweet spot that works for any given material … plastic or metal.