What advice do you have on machining procedures for milling and turning operations for ACRYLITE® acrylic sheet?

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What advice do you have on machining procedures for milling and turning operations for ACRYLITE® acrylic sheet?

Safety

When using machining equipment, wear a protective face shield or safety goggles. Wear hearing protection if you will be operating equipment for a long time.

Follow normal workshop safety practices when machining ACRYLITE® extruded (FF) acrylic sheet. Eye, ear, and respiratory protection may be appropriate, depending on the operation.

Be sure to follow manufacturers’ safety recommendations for equipment and materials used with ACRYLITE® extruded (FF) acrylic sheet.

Direction of Travel

To achieve a smooth cut, feed the sheet in the proper direction as required by the tool rotation. Feed material into the rotating edge of the cutter.

Dimensional Changes

Stresses inherent in ACRYLITE® extruded (FF) acrylic sheet, as well as stresses imparted to fabricated articles by machining, may cause dimensional changes when sheet is heated to the forming temperature (300°F) after machining.

Anneal the part to eliminate stresses.

Lathe Operation

To use a single-edged cutter, carefully balance the chuck with adjusting screws to eliminate chatter marks. Edge quality will depend on the machine’s stability.

Milling Tools

As most blades are designed for machining wood or metal, modifications may be necessary. The rake angle should be 0°, reducing chipping by providing a scraping, rather than cutting, action. The clearance angle should be at least 2° - usually more – to minimize frictional heat buildup. If you’re using a standard milling tool, provide cooling.

Cooling

Plastics, including ACRYLITE® extruded (FF) acrylic sheet, are much more susceptible to heat distortion than metals. Use coolants such as compressed air, water, emulsions, etc., to minimize heat distortion effects and produce a polished surface. If cooling is not provided, decomposition and irregularities at the cut edge may produce high-stress areas, leading to crazing (numerous tiny cracks in the material).

If you use emulsions, have them tested for compatibility with acrylic. Incompatible emulsions may cause crazing. The Roehm America LLC Technical Center in Sanford, ME can test emulsions. If you would like to contact the Technical Center, call (207) 490-4230.

Filing-Shaving

If necessary, use a scraper made of high-speed steel to smooth sawn edges, eliminating notching. Flat-ground triangular files with a maximum edge width of 8mm (3/10”) are also effective. The file surface must not be hollow ground, as this will produce chatter marks due to the rake angle. A flat-ground file should have a 0° rake angle. As with sanding, use water for a smooth finish and less stress buildup from frictional heat.

Engraving

Use hand-held tools for artistic applications and fixed-tracing engravers for precise work. Adjust the engraving tip’s travel speed to avoid melting (whitening of the surface) from slow travel and chipping from fast travel. If melting persists, use a liquid coolant or air-cooling.

Thread Cutting

Due to the notch sensitivity of acrylics, don’t machine threads with sharp edges. To reduce stresses, use rounded threads. Note, too, that threads should not be intended to bear loads. If threaded connections will often be unscrewed, reinforce the internal thread with a metal insert.

Use a cutting emulsion or oil to produce a polished surface. Regularly remove chips from internal holes, and don’t allow the tap to “bottom out”.

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