Car Mirrors 3D Printing Prototype Model / Rapid 3D Printing Service

Car Mirrors 3D Printing Prototype Model / Rapid 3D Printing Service

Machining plastic is another technology often regarded as a black art by those who don’t do it. Imagine trying to machine a part to print in a material that changes size and shape as you work it (and sometimes afterward), chips or melts as you cut it, and cracks when you squirt it with your usual degreaser. No wonder many shops accustomed to cutting metal don’t want to deal with the wide range of mechanical properties and the sometimes strange behavior of plastics.

Just about any material “grows” as it gets warmer. When you’re machining metals, this is not usually an issue. However, some plastic materials expand at five times the rate of metals, or more. Over the same temperature rise, a part made of UHMW (ultra high molecular weight polyethylene) will expand 10 times as much as a similar part made from aluminum.

crylic or polycarbonate plastics, widely used as transparent windows and covers, tend to have poor chemical resistance. Hechtel told of a “beautiful acrylic greeting card rack made for our biggest customer.” It was ready to ship when someone wiped it down with acetone to clean it, causing the acrylic to craze.

In one case, a bullet-resistant polycarbonate window had long cracks growing up from the bottom. It turned out that the person who had cleaned the window every night used Windex, and the cleaner pooled at the bottom in the uchannel that supported the window.

Be very careful what chemicals you use with plastics. Consider using clean compressed air as your coolant. “Some water-based coolants are pretty benign,” Hechtel said, but best to consult your plastic and coolant suppliers to determine whether the materials are compatible.

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