Engineers and buyers often reach out to metal machining companies to produce plastic machined parts. They assume that the metal machinists use the same processes as a plastic machining company, and therefore there is no significant difference. In reality, the two companies are worlds apart. This article reviews the three major reasons why a company that machines metal should not be used to make plastic machined components.
Cutting fluids for each material are crucial:
Equipment used to machine metal – even if only used for metal occasionally – can contaminate parts with oil-based cutting fluids. Many plastics are also very sensitive to petroleum based cutting fluids and will degrade if they come into contact with these fluids. Additionally, many plastics are hygroscopic and will absorb the cutting oils. If the parts are being manufactured for FDA-approved uses or medical applications, they will not meet standards.
Metal fragments contaminate plastic parts:
It is difficult to adequately clean a machine that has been working on metals, especially if it has been working on stainless steel. This can lead to another contamination problem. If the plastic material is soft, residual metal fragments can become embedded in the parts.
Metal shops are experts in metal, not plastic:
Metal machining companies rarely have any in-depth knowledge of plastic materials, or more specifically, which material to use in an application. Plastic machinists know what plastics are best for any function, and can produce the part you need without the “trial-and-error” processes a metal machinist would use. A good plastic machining firm will have the material knowledge and the right machining processes to consistently give you the highest quality parts.