Avoiding Re Welded Plastics When Using Router Bits
Router bits, whether they are for wood, metal, plastic or composite materials, have many problems that can potentially occur that have become common in the machining industry. Wood carving drill bits, composite drill bits and metal cutting router bits do not experience the re-welding of materials during the cutting process the same way that plastic router bits do, though. The chips can often be welded back to the base material during the routing of plastics, which is irritating and costly to machine shops.
Luckily, it is possible to avoid this problem when working with router bits at high speeds with plastic materials. It is important to start by choosing the right tools. Trying to use metal cutting router bits for plastics, for example, will result in a very poor finish. It is also important to use router bits that are the right size and program the proper chip load. Since plastic is extremely sensitive to heat and routing at high feed and spindle speed rates creates a rather warm environment, the size of the chip load is very important. Unlike wood carving drill bits, the size of the chip can greatly affect the finished product because is the chip gets hot it can melt and re-weld to the material.
When using router bits for plastics, it is important to produce an adequate sized chip to remove heat, while accommodating finish requirements. The ideal chip load formula is chip load = feed rate/ (RPM x # of cutting edges), which indicates there are several ways to adjust chip load. Other considerations are also necessary when using router bits for plastics, though. Small tool diameter size, direction of cut and the way the chip is influenced can affect the router bits. Small diameter cutting tools can cause welding because of limited chip clearance capability, but electing the right geometry for the router bits will fail miserably if the chip is influenced incorrectly.
In order to use plastic router bits and composite drill bits correctly, it is important to use the right size cutting tools, use the right cutting direction, and program a chip load that is appropriate for the material being used.