Machinists often struggle with the first stage of the part making process, which is the saw cutting of a blank when working with engineering plastics. Although plastics are far softer than traditional metals (even the softer ones like aluminum), they can be far more challenging to cut into blanks without the right tooling and set-up. Whether you are using a band saw to cut a few dozen blanks or a CNC panel saw to cut hundreds of blanks, some basic considerations are required given the inherent differences between plastics and traditional metals.
Plastic’s insulative (non-conducting) nature slows the dissipation of heat built up at the cutting interface leading to localized melting, warping and wandering cuts if excessive frictional heat is developed. Care must be given to balance the feed rate with the cutting speed so localized melting is avoided. Blades courser than one would use with metals are required. Clearance in the cutting area is also helpful in reducing heat build-up. Carbide tipped blades always do better than high speed steel, which last longer and yield better cuts.
Residual stress in plastic sheet is the enemy during sawing, so starting with a fully stress relieved material is the best place to begin. Modern Plastics sells only the highest quality plastics from reputable manufacturers, which means you know you’re getting fully stress-relieved materials from us.
Avoid Common Mistakes When Using Band Saws and Table Saws to Cut Plastics
Band sawing is versatile for straight, continuous curves or irregular cuts. When cutting material greater than .375″ thick try using band saw blades with 3 teeth per inch (3 TPI). For thinner materials 5 to 6 TPI will yield cleaner edges. We generally suggest Lenox, classic-style band saw blades. Naturally, the feed rate must compensate for the blade speed to avoid over heating. If localized melting occurs, either feed faster or slow the blade speed (if possible). Watch for dulling of the blade teeth. Despite the relative softness of plastics, they will dull your blades.
Table saws are more convenient for straight cuts, especially when many are being made. Thinner gauges can be stacked up to a total height of almost 4 inches provided enough horsepower exists. 14-inch diameter blades should have between 40 and 60 teeth, with 60 being more versatile. A 16-inch blade generally should have 40 teeth. The maximum number of teeth for either a 14 or 16 inch blade is 72, which is be suitable for thinner gauge, easy-to-cut materials.
We generally suggest all circular blades be triple chip grind such that the width of the blade is greater than the body of the blade. Rip and combination blades with a 0 degree tooth rake and 3 to 10 degree tooth set are best for general cuts in order to reduce frictional heat. If using hollow ground circular saw blades without set one should expect smooth cuts up to .75” total thickness.
Tungsten carbide blades offer longer life and improved surface finishes and are recommended.