The main types of laminating machines are hot glue machines and cold glue machines. The basic components include dust removal, substrate heating, affinity agent coating, glue coating system, drying channel (cold glue machine), unwinding system, correction mechanism, transmission wheel and other mechanisms.
1. Dust removal fan: Its main function is to remove floating dust and solidify affinity agents
2. Substrate heating: The main function is to solidify the affinity agent, heat the surface of the substrate, and the surface temperature of the substrate should be around 45 degrees Celsius
3. Affinity agent workstation: mainly for affinity agent coating
4. Glue application system: Apply glue on the back of the film by scraping, and there is a significant difference between the glue application systems of cold glue machines and hot glue machines
5. Upper drying duct (cold glue machine): The main function is to evaporate the solvent in the glue, soften the PVC film, and maintain a temperature of 45 degrees Celsius
6. Unwinding system: Place PVC film to maintain uniform tension of the film
7. Correction mechanism: Adjust the distance between the left and right sides of the PVC film
8. Transmission wheel: Conveying substrate with high precision requirements
Requirements for film covering environment:
1. Workshop: The length should not be less than 25 meters, the width should not be less than 5 meters, it should be dust-free, and the temperature should be 25 degrees Celsius
2. Electricity: 380 V 50HZ
3. Clean room
Principle of adjusting the pressure wheel of laminating machine:
1. Cover the middle first, then the sides, starting from the middle to expel the air
2. Firstly, adjust the profile to pass through the machine at a uniform speed and in a straight line
3. Generally, 3-4 pressure wheels are needed to wrap each corner
4. The temperature is proportional to the speed, and the heating temperature of each part is adjusted according to the specific speed, especially the temperature of the hot air rush
Common problems encountered in film coating processing:
1. Poor adhesion of edge film
① The edge temperature of the adhesive film is too low. During the film covering process, the edge temperature of the adhesive film will drop quickly, and it will not form a corrosive surface on the surface of the profile, resulting in no adhesive strength.
Solution: Increase the temperature of the vertical oven and place a gun type hot air blower in a reasonable location.
② If the deviation between the position of the unwinding device and the position of the rear guide wheel is too large, once an angle is formed between the two positions, it will cause the moving film to produce curved motion, resulting in edge film breakage.
Solution: Fine tune the three-dimensional spatial position of the unwinding device, rubber box, positioning wheel, and driving wheel on the same centerline.
③ The degree of tension of the tension device does not match the speed of the driving wheel. The change in tension of the tension device varies with the speed of the driving wheel, otherwise it will cause the surface tension of the coating film to be unbalanced, resulting in film deviation and edge breakage of the film.
Solution: Under the speed of the driving wheel, the tension of the tension device should be adjusted to ensure that the film can smoothly rotate out of the unwinding device.
④ The edge cutting accuracy is not high when cutting the film. Due to the low cutting accuracy, burrs and cracks appear, which cause the surface tension of the coated film to deviate under the tension of the tension device, resulting in the edge of the film breaking.
Solution:
a. Replace the slitting blades of the slitting machine;
b. Adjust the ambient temperature of the slitting machine and the temperature of the film itself. (Cutting machine ambient temperature, membrane self temperature: 18 ℃± 2, not operable below 15 ℃)
⑤ The temperature of the gun type hot air blower is too high, which causes the adhesive to denature and age, rendering it ineffective. Solution: Adjust the temperature of the gun type hot air blower according to the ambient temperature. In general, when the ambient temperature is 18 ℃, the temperature of the gun type hot air fan should be at 120 ℃ and the wind speed should be at level 3.
2. Bubbles are generated on the surface of laminated profiles
① When the drying channel temperature is too low during cold glue coating, the molecules of volatile substances inside the glue have the characteristic of rapid volatilization after being activated under specific conditions. On the contrary, it does not possess this characteristic, which means that there will still be excessive volatile substances inside the glue. Due to the corrosion of the film by the excessive volatile substances inside the glue, the body will become soft and lose elasticity. After being rolled by the laminating roller, it will become thinner, resulting in layering. When the glue encounters specific conditions again, the volatile substances will accumulate and develop at the weak points on the surface of the laminated profile, forming bubbles.
Solution: Keep the temperature of the drying channel at 45 degrees Celsius
② The incorrect spatial angle of the laminating roller will cause certain angle changes during the laminating process. If the spatial angle of the roller is incorrect, it will create blind spots during laminating, causing the film to stack and produce voids, leading to the formation of bubbles.
Solution: Adjust the pressure roller again, preferably using pressure testing paper for the experiment
③ Incomplete release of bubbles in the mixed adhesive (for cold adhesive) Due to the generation of a large number of bubbles during the mixing process, bubble voids will appear on the surface of the film during scraping. The amount of adhesive stored in the bubble voids is very small, resulting in low bonding strength and weak areas. When there is an excessive amount of volatile substances inside the gum, bubbles will form.
Solution: Leave it for a period of time and wait for the bubbles to disappear
④ Unclean glue coating or uneven sol in the sol system (mainly referring to hot glue), impurities in the glue coating or particles in the hot glue can disrupt the normal amount of glue coating, resulting in broken tape, voids, and bubbles.
Solution: Clean the adhesive port and replace the adhesive
3. Wrinkles and cracks appear on the coated surface
① Excessive coating amount is targeted at cold glue. Due to the presence of corrosive agents in the glue, when the coating amount is too large, the volatilization amount will be insufficient, resulting in softening of the coating film, loss of elasticity, wrinkles or cracks; For hot glue, a large amount of glue can easily cause the film to soften due to the glue temperature not dropping in a short period of time;
Solution: The amount of cold glue applied should be controlled at around 100 grams per square meter, and the amount of hot glue applied should be controlled at around 60 grams per square meter
② The surface of the laminated roller is not clean, and there are relatively hard objects hidden on the surface of the roller. The hardness of the profile surface is also relatively high, and the color film sandwiched in the middle is likely to be damaged and broken;
Solution: Keep the pressure wheel clean
③ Improper coordination between the speed of the driving wheel and the tightness of the tensioning device, resulting in excessive or insufficient tension, stretching or no tension on the adhesive film, causing wrinkles or cracks;
Solution: Adjust according to actual experience, based on the principle that the film can be smoothly exported from the film roll
④ Scratches on the surface of the positioning wheel can cause scratches on the edge of the film, leading to cracks;
Solution: Replace the positioning wheel
⑤ The precision of cutting film edges is not high; Due to the low cutting accuracy, there will be scratches on the edges. Under the action of the tensioning device, the scratched area will be torn and cracks will appear;
Solution: Replace the film roll or loosen the tensioning device as much as possible to avoid tearing the scratched area of the film
⑥ The uneven pressure of the laminating wheel causes an imbalance in the surface tension of the film, resulting in stacking and wrinkling;
Solution: Adjust the pressure balance of the pressure wheel
⑦ The position deviation of the positioning wheel is too large, causing the two profiles to not be on the same straight line of motion, resulting in overlapping and tearing, causing wrinkles, cracks, and peeling.
Solution: Adjust the positioning wheel
4. Bending of laminated profiles
① When the surface of the profile is heated too high during the laminating process, there should be a limit to the heating of the profile surface. The specific rated temperature should refer to the Vicat softening critical temperature of the laminated profile. In general, the instantaneous heating temperature of the profile surface is controlled at 70 ℃± 2. If it is greater than 70 ℃± 2, the secondary polymerization density inside the profile will gradually increase as the temperature decreases after laminating, and the difference in polymerization density value between the internal and non heated surfaces will be large, forming strong internal stress and causing bending of the laminated profile;
② The tensile strength of the film exceeds the required range during the lamination process. If the tensile strength of the film exceeds the required range, the film will be stretched. After lamination is completed, as the temperature decreases, the extended part of the film will retract, causing stress in the laminated profile and bending deformation;
③ If the position of the film roller does not meet the structural mechanical requirements of the profile section, it will cause plastic deformation of the internal reinforcement ribs during the profile movement, thereby disrupting the stress balance of the profile itself and forming bending;
④ The defect of the profile itself is that the stress balance of the profile itself is poor, and under the action of external forces (temperature, pressure), the imbalance of the stress system is exacerbated, resulting in deformation.
⑤ Unreasonable handling: During the handling process, the profile that has just been coated with film is not in a balanced state, resulting in uneven stress when the film is stretched and retracted, leading to bending of the profile.
Solution: Adjust the temperature, reduce the tension of the film, adjust the position of the pressure wheel, replace the profile, and handle it reasonably
5. Membrane detachment
① The quality guarantee period for the special coating adhesive for plastic profiles is 6-12 months, and the performance of the coating adhesive will decrease significantly if it exceeds the expiration date, resulting in ineffective bonding;
② The temperature in the drying channel is too high and the amount of glue applied is too low. The temperature in the drying channel is too high and the amount of glue applied is too low, causing the coating glue to age and deteriorate, resulting in loss of performance;
③ Under normal conditions, the pressure of the laminating wheel is around 2 kilograms. If the bonding pressure cannot be reached, it will cause large areas of voids and form point like connections;
④ The temperature of the adhesive film is too low, and the adhesive cannot be activated, resulting in no adhesion to the film and profile;
⑤ The chemical index mismatch between the adhesive and the film or substrate causes the adhesive and film or substrate to be unable to react and bond together.
⑥ Unreasonable handling: During the handling process, the profile that has just been coated with film is not in a balanced state, resulting in significant curvature and stretching of the film, detachment from the adhesive surface, and the formation of voids, leading to the formation of bubbles or detachment.
Solution: Replace the glue, adjust the temperature and amount of glue applied, adjust the pressure of the roller, choose the correct glue, and handle it reasonably
6. The temperature of the storage site for finished film brittleness is too low or too high for a long time, with too low referring to below+10 ℃ and too high referring to above+35 ℃; The storage site has a strong magnetic field; The quality of the membrane itself is problematic.
Solution: Adjust storage conditions and try not to use expired films as much as possible
