|
A summary of Information provided by CYRO Industries and reprinted by permission.
Other cutting methods
Saber Saw Cutting
This method is useful for cutting involving a frequent change of direction. The blade should have a raker set design with approximately 10 teeth per inch (25 mm) and should only be used for plastic. Adequate support is necessary to minimize the vibration of the reciprocating blade which may chip or crack the sheet. A straight board clamped to the sheet near the cutting line may be used as a saw guide and will assist in reducing vibration. Blow compressed air onto the blade to remove chips and to cool the blade.
Jig Saw Cutting
Jig saws or scroll saws should be used only for inside cuts and for intricate letters. The blade should be fine toothed with 9 to 12 teeth per inch (25 rnm) and contain some set for clearance. Use a fast, steady feed rate. Because the stroke is short, the blade heats up quickly, and tends to soften and fuse the plastic. A stream of air will help to cool the blade and keep the plastic from gumming. You may also use a cooling fluid like oil or water.
Straight Line Cutting
A guide such as a board, clamped on top of the sheet will help reduce vibration and assure a straight cut.
Laser Cutting
Laser technology is being rapidly accepted by the industry for quickly and accurately cutting, welding, drilling, scribing and engraving plastics.
Annealing Crazing
Annealing Crazing (fine, visible cracks that appear in the sheet over time) will occur at joints, bends, cuts, drilled holes and other fabrication areas if sheet stresses caused by cutting are extremely high. To eliminate the possibility of crazing, the fabricated sheet can be annealed.
Annealing is a simple heating procedure which relieves stresses without changing the shape of the fabricated sheet and often increases sheet strength.
To anneal sheet after fabrication:
1 . Preheat oven to 1800F. (820C.);
2. Remove all masking from sheet.
3. Place fabricated sheet in oven and heat it 1 hour for each millimeter of sheet thickness. (Example: Heat 3 mm sheet for 3 hours.) Minimum heating time = 2 hours for sheet 2 mm and less.
4. Turn off oven and let sheet cool slowly. Cooling time should equal thickness in millimeters divided by 4. For thin sheet cool at least 2 hours.
|
