Introduction to the pretreatment process of the motorcycle plastic parts coating production line
At present, the pretreatment of the motorcycle plastic parts coating production line still mainly adopts chemical treatment methods. The main processes include pre-degreasing-main degreasing-washing 1-washing 2-pure water washing 1-pure water washing 2-surface adjustment ——Blowing water——Moisture drying——Strong cooling——Electrostatic dust removal.
The surface of the plastic parts is stained with oil, hand sweat, and mold release agents. If directly sprayed, the adhesion of the paint film will deteriorate, and the coating will crack, bubble and fall off. Therefore, the motorcycle plastic parts must be treated before the coating production line, relying on the scouring, infiltration, dispersion and emulsification of the degreasing agent to achieve the effect of removing oil stains, removing interface resistance, and improving adhesion. The simple degreasing method is scrubbing with gauze potato organic solvent; the common degreasing method with high degree of automation is cleaning with alkaline aqueous solution containing surfactants. Because of the impurities and dirt in the bath, the dirt in the bath will be attached again The surface of plastic parts affects the quality of the coating. Therefore, it is necessary to strengthen the filtration and renewal management of the bath liquid. In view of the characteristics of motorcycle plastic parts, annular pressure spray cleaning is generally used. This process focuses on controlling the following process parameters:
a) Degreasing temperature of motorcycle plastic parts coating production line: Generally, the higher the temperature, the better and the more thorough the degreasing effect. However, ABS plastic parts generally have poor heat resistance. Excessive temperature will cause plastic parts to deform, which is determined by the active temperature of the degreasing agent. The activity is best around 60°C, so the general degreasing process temperature is controlled at (60 ± s) ·c.
b) Degreasing time and spray pressure of the motorcycle plastic parts coating production line: sufficient spray cleaning time must be ensured during the degreasing process. Too short cleaning time will cause unclean degreasing. The normal pre-degreasing time is about 1 min and the degreasing time is 2.5. Min is appropriate, the cleaning method adopts pressure spraying, and the spray pipeline adopts a bad shape arrangement to ensure that all surfaces of the workpiece can be thoroughly sprayed. The nozzle spray direction and condition need to be adjusted regularly, which has a greater impact on the spray effect.
The spraying pressure is generally controlled between 0.1-0.2 MPa. When the degreasing liquid is sprayed on the surface of the workpiece during the degreasing process, the degreasing liquid has good contact with the workpiece under strong action, which promotes the penetration of the degreasing agent and destroys the oil film, and can be washed away Emulsified oil on the surface of the workpiece.
c) The replacement cycle of the tank fluid for the plastic parts coating production line of motorcycles: from the degreasing of plastic parts to spray degreasing, the tank body is smaller, and the more emulsified and saponified oil stains accumulate after long-term recycling, which is beneficial to bacteria, For the reproduction and growth of algae substances, in order to ensure the degreasing effect and prevent the contamination of fungi and algae substances, the tank liquid should be discharged in time after a period of normal production. Generally, the degreasing tank liquid is discharged once a week. If the production interval is too long , It is best to re-allocate the slots before starting the shift again.
2. Water washing and surface activation
The pre-treatment of the motorcycle plastic parts coating production line usually goes through 4 water washes after degreasing, mainly to clean the residual degreasing liquid on the surface of the workpiece, the particle impurities and harmful ions on the surface, and to activate the surface. Generally, the first 2 washings are industrial water spray washing, and the last 2 washings are pure water washing. The process time is 0.5-1.0 min, and the spray pressure is 0.2-0.4 MPa. The conductivity of the third cycle of pure water washing is generally controlled below 30 µ s/cm. Surfactant needs to be added to the bath continuously, and the conductivity of fresh pure water is controlled below 10 µ s/cm.
3. Blow water
The water blowing process of the motorcycle plastic parts coating production line is after the pretreatment, through the air nozzle, the water in the surface of the workpiece and the corners of the corner is blown with compressed air. The general blowing time of the beads is 0.5min, and the compressed air pressure is 0.5- 0.6 MPa, the pressure of the compressed air and the direction of the nozzle are the key points of this process. If the adjustment is not good, it will affect the subsequent drying effect.
4. Moisture drying
After blowing water, after a period of draining, the workpiece enters the moisture drying room for drying. Considering the heat resistance of the plastic parts, the drying temperature is generally controlled at about 60"C, and the drying time is 30 minutes.
5. Dust and static electricity removal for motorcycle plastic parts coating production line
Plastic parts have an electrostatic effect, and the surface is easy to absorb dust. It is difficult to remove dust with a general blowing method. Washing with a surfactant solution can simultaneously remove dust and remove static electricity. At present, for mass-produced plastic parts, an electrostatic dust removal device is commonly used to ionize compressed air and spray the surface of the plastic part to achieve the purpose of dust removal and static electricity removal.