Nylon: One of the most popular engineering plastics, Nylon possesses a good tensile strength at a relatively low cost. It won’t be damaged by oils, solvents or alcohols but can’t resist acidic chemicals. Quite often used as fasteners as well as within the electronics industry. Nylon is relatively easy to machine, like nay plastics it is best to control the temperature and moisture the part will be exposed to as well as ensuring all tools are sharp.
Acetal: Acetal (also called Delrin) is a hard, wear resistant plastic that is often used as a replacement for Aluminium. It’s often used to make parts that will encounter a high level of abrasive wear such as Bearings, Wheels and Pulleys. In terms of machining, Acetal is a little brittle. You’ll need sharp carbide tools and high speed machining. If you machine too slowly chips will sit in the cut, which can start melting around the endmill. Instead of using coolant you can just blast the part with compressed air.
PVC: No doubt a material you’re very familiar thanks to Double Glazing salesman, PVC is widely available for a low cost. It offers a high chemical and moisture resistance but is a relatively soft plastic. PVC is generally easy to machine with although can be a littlemore abrasive than some of the other engineering plastics. There is something of an urban myth that machining PVC will release fumes, indeed if you were to burn the plastic it would release chloride but the chances of doing this from the heat off the cutter are small if precautions are taken.
Polyethylene: Often used in injection molding, Polyethylene has a high resistance to abrasion wear but is a relatively flexible plastic. Polyethlene grades range depending on their density but are often used on applications including Wear strips and liners, conveyor belts and food processing equipment. Polyethylene is one of the more difficult plastics to machine. It is one of the most sensitive plastics to the temperature and humidity, at low temperatures it becomes dimensionally unstable but at high temperatures it is prone to melting. As such chip control and speed/feed rates need to be carefully monitored for the best results.
Polypropylene: Often used for pipes, valves and similar fittings Polypropylene is a hard, smooth and chemically resistant plastic. In terms of machining temperature is a key factor as it will heat up very quickly and will melt above 50 degrees Celsius. As such it’s important to avoid cutting tools or anything that will create excessive friction. You should use lower spindle speeds when machining Polypropylene.
Cast Acrylic: Used in a variety of commercial applications, for example in corporate gifts and awards. Cast Acrylic is semi-brittle in nature and so you want to avoid abrasive cutting tools or anything that creates excessive friction. When cutting Cast Acrylic there will be a moderate amount of fumes created and so a mask may be needed.
Extruded Acrylic: Often used as a replacement for glass, Extruded Acrylic has a smooth and clear surface. It is however difficult to machine and much like glass has a tendency to crack and split. It melts fasts than cast acrylic but is generally a stronger material.
The machining of plastic requires a different skill set and environmental control, Bronte Precision are a trusted ISO 9001 certified contract manufacturer based in Bradford, West Yorkshire with a wealth of knowledge about the machining of plastics.