Select different thicknesses of silicone film based on the characteristics of the workpiece line shape, such as arc value, edges, width and depth of the line shape, etc.
Due to frequent heating and stretching, the sagging of silicone film will increase. It should be installed in a timely manner according to the degree of sagging of silicone film to reduce sagging.
In order to extend the service life of the silicone film and prevent quality issues with the workpiece, the direction of use of the silicone film should be regularly changed, such as changing from the front end to the back end and from the left end to the right end.
If there are holes or short cracks at the corners of the silicone film, it can be repaired using silicone and a film repair machine. When repairing, compact the top with a flat heavy object. After drying for 24 hours, use 240 # sandpaper to level the repaired area and it can be used normally.
4、 Setting of process parameters
Distance between membrane pressure workpieces: For narrow and long workpieces with a width less than 100mm, the distance between workpieces should not be less than 80mm; For workpieces with a width greater than 100mm, the spacing between workpieces shall not be less than 60mm; The distance between the workpiece and the workbench frame shall not be less than 80mm. The spacing between the horizontal and vertical directions should be in a straight line to reduce the resistance of air flow.
Workpiece cushion plate: The width and length of the cushion plate should be 6-10mm smaller than the width and length of the workpiece. The edges and corners around the upper surface of the cushion plate should be rounded or chamfered with a radius of 3mm to 5mm × 45 ℃ angle to ensure that the air between PVC and the workpiece is completely drained, achieving the effect of PVC firmly bonding to the edge of the workpiece. The thickness of the backing plate should be about 3/4 of the thickness of the workpiece, which is one of the important measures to ensure that PVC is not pulled white.
Set temperature: According to the different types of PVC, the set temperature should be between 130 ℃ and 160 ℃. The temperature of ordinary PVC (relative to high gloss PVC) should be higher, while high gloss PVC should be lower (to avoid loss of gloss due to high temperature).
Setting time: The preheating time should be between 30s-50s (depending on the color of PVC, the preheating time should also be different. Light colored PVC should be appropriately extended, dark colored PVC should be appropriately shortened; thick PVC should be appropriately extended, thin PVC should be appropriately shortened), the vacuum pumping time should be around 8s, and the pressurization time should be around 10-20s plus the preheating time. The time to reach the set pressure should not be too long, should be around 5 seconds, to ensure that the PVC on the workpiece surface quickly adheres to the substrate and does not excessively stretch the PVC on the workpiece when it reaches the activation temperature.
Set pressure: Set positive pressure to 3.8-4.2 bar and negative pressure to 0.7-0.8 bar, that is, positive pressure+negative pressure=about 4.5-5.0 bar.
For excessively thick workpieces, high gloss PVC, and thin PVC with a thickness less than 0.3mm, the set temperature should be appropriately reduced, the preheating time should be appropriately increased, and the height of the entire bottom plate of the workbench should be increased to shorten the distance between the workpiece and the heating plate, in order to reduce or avoid PVC discoloration problems.
When thinning wood (veneer), use milky white latex adhesive, and the temperature of the veneer should not be lower than 105 ℃; The greater the pressure, the better, but the time to reach the set pressure should be longer, that is, slowly pressurize.