Machining PLEXIGLAS®

Flame polishing is one option for polishing PLEXIGLAS^® edges. The best results are obtained if the cut edge is deburred with a scraper beforehand and then polished to a matte finish with a fine abrasive, grit size 400 to 600. The high surface stresses generated by flame polishing make subsequent annealing essential to avoid stress cracking during subsequent use, especially if the material enters into contact with adhesives and paint thinners or cleaning agents.

Flame polishing of intensely colored sheets may be difficult and can lead to a matte finish or discoloration. Unless work is skillfully performed, it involves the risk of “flashover,” i.e. the flames may lick over the cut edge onto the sheet surface, generating thermal stress and optical distortion.

Twist drills cannot be used for PLEXIGLAS^® unless the point angle is reduced from normally 120 degrees (°) to 60 to 90°. The rake angle must be ground down to between 0 and 4°. If the drill is to work correctly, the principle is to scrape rather than cut, so that chipping at the exit side of the hole is avoided. The clearance angle should be at least 3°.

Thin sheets should be clamped onto a flat, solid support to prevent chipping at their bottom surface.

From a material thickness of 5 millimeters (mm) onwards, use a cooling lubricant or a drilling (oil in water) emulsion compatible with acrylic. The drill should be lifted several times to avoid overheating.

Step drills and conical drills can be recommended as special drills. Step drills leave no chatter marks and guarantee clean cylindrical bores. With each subsequent drilling step, the hole is simultaneously chamfered, thereby increasing the economy of the work process. Conical drills with a triple-edge design produce slightly conical drill holes but there is no chipping on the exit side of the hole.

Owing to its very good insulation properties, PLEXIGLAS^® has high surface and volume resistivity. That is why PLEXIGLAS^® may become statically charged. Negative side effects are dust attraction and (rarely), sparkover. Static charges may be due to:

- mechanical friction in contact with solid objects, dry cloths or polishing agents
- friction produced by dry air currents
- removal of the masking film from the sheet

Static charging is most easily prevented by wiping the material with water or an antistatic cleaning agent.

How long the antistatic effect lasts depends on the volatility of the active substances in the chosen treatment agent. The lower the friction, the higher the atmospheric humidity, the lower the room temperature, the less dust there is around and so on, the longer the antistatic effect will last.

Another very economical method is blowing the sheet or parts of it down with ionized air. The effect, however, is of fairly short duration.

Static charging can also be durably prevented by applying thin metallic surface layers.

PLEXIGLAS^® RADIANT can be machined using the same parameters and appliances as standard acrylic sheets. The correct alignment of the coated surface with the machining equipment is crucial for correct and satisfactory machining of PLEXIGLAS^® RADIANT:

- For linear heating/line bending, the coated sheet surface must be on the vacuum side.
- For surface heating too, the coated sheet surface must be on the vacuum side.
- For sawing, drilling and routing, the tool should always exit through the uncoated sheet 
  surface.
- To obtain greater bond strength, the coated surface should be removed from the area to 
  be bonded.

Annealing involves the storage of plastic components with inherent stresses in a drying oven with subsequent slow cooling to room temperature.

The following conditions apply for annealing PLEXIGLAS^® to remove inherent stresses:

- temperatures: PLEXIGLAS^® GS approx. 80 degrees Celsius (°C) PLEXIGLAS^® XT approx. 
  70°C
- annealing time for PLEXIGLAS^® GS and XT: The material thickness in millimeters (mm) 
  divided by 3 corresponds to the annealing time in hours. This should not be less than two 
  hours in any case.

Cooling: For PLEXIGLAS^®, the cooling time in the drying oven in hours corresponds to the material thickness in mm divided by 4. The cooling speed should never exceed 15°C per hour. The temperature upon removal from the oven should be less than 60°C.

- The saw blade should protrude only slightly beyond the sheet. 
- Never work without a stop. • Switch on the saw before carefully starting to cut.
- Make sure the blade is guided accurately.
- Do not tilt the material.
- Secure the sheet against fluttering.
- Work at an average feed rate.
- From 3 millimeter (mm) sheet thickness onwards, cool the material with water, cooling 
  lubricant or compressed air.

Only unset circular saw blades are suitable for cutting PLEXIGLAS^®. This is the only way to ensure smooth, clean cut edges. We recommend using only carbide-tipped saw blades with the largest possible number of teeth. Blunt and incorrectly ground blades cause chipping on the underside of the sheet. The teeth of the saw blades should be alternately beveled, i.e. have alternating angles of 15 degrees (°) and 45°. We also recommend

- a clearance angle of 10° to 15°
- a rake angle of 0° to 5°
- cutting speeds of up to 4,500 meters/minute (m/min)
- a tooth pitch of approx. 13 millimeters (mm)

Circular saw blades with specially shaped tooth flanks like Bombastic and Spacecut provide clean and smooth cut edges when used in a sophisticated sawing machine that operates with frequency and feed control, among other innovations.