Operating procedures
1. Requirements for the use of film pressure glue
The film pressure glue is a two-component glue, the activation temperature is about 60 ℃. The storage temperature must be between 5°C and 30°C, and flocculation may occur below 5°C. The plastic bucket should not be placed directly on the ground, but should be placed on a wooden bracket, especially in winter. The validity period of the film adhesive is 6 months from the date of leaving the factory without opening the original packaging.
Film pressure glue preparation ratio: main agent: curing agent=20:1. When mixing the main agent and curing agent, keep the main agent under agitation. The curing agent is slowly added and stirred for at least 3 minutes. The amount of glue prepared each time should be used up within 4 hours. The plastic bucket should be tightly closed after mixing.
2. Glue spray process requirements
The spraying sequence is end face→front line style→front face+line style→end face, and the plane part can be sprayed once; the end face and the plane line style need to be sprayed twice.
The active time after the main agent and the curing agent are mixed is 4-6 hours, and the parts that have been sprayed should be processed within 4 hours to obtain the best bonding effect. Otherwise, the activation temperature needs to be increased due to the cross-linking reaction of the glue. Although the bonding effect is good from the appearance, the temperature resistance has been significantly reduced. If the glue is sprayed twice, it will show glue marks on the surface of the PVC.
After the glue is sprayed, the surface is white and dry. It is not sticky to the hands or has obvious gloss after drying. The drying time is 30-50 minutes (depending on the temperature, humidity and spray quality of the environment).
Commonly used fans are 1.5-2.0 meters away from the workpiece and aim at the workpiece to blow away the moist air to avoid PVC bubbling due to high humidity of the workpiece.
In winter, in order to increase the temperature of the workpiece, a small insulation room can be used to heat the workpiece to 20-25°C (it is forbidden to exceed 35°C, otherwise the workpiece will be deformed). Glue spraying should be carried out on a water curtain machine at an environment not lower than 16°C.
The spraying operator should wear a mask to protect the health of the operator.
Third, the use of silicone membrane for membrane press
According to the characteristics of the workpiece line type (such as arc value, edge angle, line width and depth, etc.), choose different thickness of silicone film.
The sag of the silicone film will increase due to frequent heating and stretching. It should be installed in time according to the sag of the silicone film to reduce the sag.
In order to prolong the service life of the silicone film and prevent the quality problems of the workpiece, the direction of use of the silicone film should be changed regularly, such as changing the front end to the back end and the left end to the right end.
If the corners of the silicone membrane have holes or short cracks, they can be repaired with silicone and a patching machine. When repairing, the top is compacted with a flat heavy object. After drying for 24 hours, the repaired area can be used normally with 240# sandpaper.
Fourth, the setting of process parameters
Film pressure workpiece spacing: For narrow and long workpieces with a width less than 100mm, the workpiece spacing is not less than 80mm; for workpieces with a width greater than 100mm, the workpiece spacing is not less than 60mm; the spacing between the workpiece and the worktable frame is not less than 80mm. The horizontal and vertical spacing should be in a straight line to reduce air flow resistance.
Workpiece backing plate: The width and length of the backing plate should be 6-10mm smaller than the width and length of the workpiece. The edges and corners around the upper surface of the backing plate should be rounded with a radius of 3mm-5mm or 3×45°C corners to ensure The air between the PVC and the workpiece is completely exhausted to achieve the effect that the PVC is firmly glued 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 the PVC is not drawn white.
Set temperature: According to the difference of PVC, the set temperature should be between 130℃-160℃. The temperature of ordinary PVC (compared to high-gloss PVC) should be higher, and the temperature of high-gloss PVC should be lower (to avoid loss of gloss due to high temperature ).
Setting time: preheating time should be between 30s-50s (different PVC color, preheating time should also be different, light color should be appropriately lengthened, dark color should be appropriately shortened; thick PVC should be appropriately extended, thin PVC should be appropriate Shorten), the vacuuming time should be about 8s, and the pressurizing time should be the preheating time plus 10-20s. The time to reach the set pressure should not be too long, it should be about 5s, to ensure that the PVC and the substrate are quickly bonded when the end surface of the workpiece reaches above the activation temperature and the PVC on the workpiece is not excessively stretched.
Set pressure: Set the positive pressure to 3.8bar-4.2bar, and the negative pressure to 0.7bar-0.8bar, that is, positive pressure + negative pressure = about 4.5bar-5.0bar.
For over-thick workpieces, high-gloss PVC and thin PVC with a thickness of 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 worktable should be increased to shorten the distance between the workpiece and the heating plate to reduce or avoid Discoloration of PVC.
When pressing thin wood (wood veneer), use milky white latex adhesive. The temperature of veneer should not be lower than 105℃; the higher the pressure, the better, but it takes longer to reach the set pressure, that is, slow pressurization.
