July '20

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Page 74 of 102

CNC BASICS With the advent of COVID-19, many CNC machinists have found opportunities to fight the pandemic through the fabrication of Personal Protective Equipment (PPE). (Image courtesy AXYZ) The cold air gun is a simple device that uti- lizes filtered, com- pressed air and venturi effect ex- pansion chamber to produce cold air for spot cool- ing. (Image cour- tesy AXYZ) Using the right cutter for the job makes all the difference between getting a jagged, rough, frosty cut or a nice, smooth, clean cut. (Im- age courtesy AXYZ) cutting time, it creates better results than a single cut and has the effect of polishing the part during the cutting process. Upcut versus downcut spirals. The gen- eral recommendation for cutting plastics is to use single flute, upcut spiral cutters. Upcut spirals eject dust and chips upwards out of the cut, which reduces heat buildup, extends the life of the tool, and produces cleaner cuts. However, when cutting thin, flexible plastics, the recommended cutter is a single flute, downcut spiral, one that pushes the material down onto the bed and prevents movement and poor quality of the cut edge. Keeping things cool. When cutting soft- er materials, there can be issues with heat buildup and a tendency for the material to stick to the cutter. The solution is to use a cold air gun to direct a jet of cold air at the cutter, keeping it cool. Not only will this re- sult in better quality cutting results, but it also helps prolong the life of the cutter tool. Speed and sharpness. The speed used to cut through the material and the RPM at which the bit is run are critic- al to achieving a good finish. CNC router suppliers can provide advice as to the appro- priate settings for cutting specific materials. 7 0 G R A P H I C S P R O J U L Y 2 0 2 0 G R A P H I C S - P R O. C O M

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