PVC Injection Molding | Overview of the Best Solution
PVC Injection Molding
Details
Details:
Model
Material
Brand
Origin
Application
Booling-Injection-14
P20, 718, S136, 2738 etc
Booling
China
Automotive parts, industrial parts, medical parts, household
PVC injection molding is a processing and forming technology for thermoplastic plastics, which involves melting the plastic at high temperatures and injecting it into a closed plastic mold. During this period, manufacturers should pay attention to controlling the molding time, pressure, and temperature to find the best manufacturing solution.
Advantages of PVC Injection Molding：
- Good Processing Performance
- Electrical Insulation Performance
- Low Cost
- Relatively Stable
- Corrosion Resistance
Related Hot Products
PVC injection molding involves heating and melting plastic particles or powders, injecting them into a mold under high pressure, and cooling and solidifying them to obtain the desired shape and size of plastic products. Due to the poor fluidity of PVC material, manufacturers need to strictly control its process and avoid its decomposition during injection molding. This guide introduces solutions for water ripples and weld marks during PVC plastic injection molding, providing a comprehensive guide to solving these issues.
Reduction of PVC Injection Molding Speed
The most effective way for manufacturers to solve the problems of water ripples and weld marks in PVC injection molding is to reduce the molding speed, which includes:
- Reduce the Injection Speed of the Melt
The most effective way for manufacturers to solve the problems of water ripples and weld marks in PVC injection molding products is to reduce the speed of melt injection into the mold cavity, that is, to reduce the injection speed of the melt. This method can effectively prevent the occurrence of folded wavy or spiral injection, and avoid unstable filling phenomena such as melt diversion.
- Add Buffer Packages
Sometimes, due to the excessively wide cavity design of injection molds, the injection speed has been reduced to its limit, and when the screw can hardly move forward, water ripples and weld marks still frequently occur without effective solutions. At this point, the manufacturer can add a flow stopper or buffer pack on the runner near the gate, which can reduce the speed of the melt entering the mold cavity and thus achieve the goal of reducing water ripples and weld marks in the injection molded parts.
In addition, when the water ripples and weld marks are not particularly severe, using the above method combined with machine adjustment techniques makes it easier to solve these defects. However, if the problems and defects during PVC injection molding are more serious, more solutions need to be combined to achieve defect resolution.
The Increase of PVC Injection Molding Temperature
In addition, when manufacturers solve the problems of water ripples and weld lines in PVC injection molding, raising a certain temperature or increasing back pressure is also a feasible solution
Manufacturers can solve the problem of water ripples and weld marks during PVC injection molding by using a very slow injection speed. However, this solution will result in a longer flow time of the melt, increased heat loss, faster temperature drop, poorer melt flowability, and possibly uneven temperature, making filling more difficult. When solving the problems of weld marks and water ripples, it also leads to other additional defects.
- Raise the Temperature of the Melt and Mold
Raising the mold temperature and melt temperature is an effective measure to improve the water ripple and weld line defects in PVC injection molding. Raising the melt temperature can maintain the fluidity of the melt while reducing the injection speed, without cooling too quickly, but the raised temperature should be based on the premise of not burning the PVC.
- Increase Back Pressure
In the process of increasing the melt and mold temperature, manufacturers can add a little back pressure on this basis, and the improvement effect will be ideal. In the actual PVC injection molding process, manufacturers generally do not need to set too high a melt temperature but can adjust the back pressure. Increasing back pressure not only makes the temperature of PVC melt more uniform and has better fluidity, but also promotes temperature rise. So the solution of increasing back pressure is far more effective in improving fluidity than simply increasing the melt temperature. But if both schemes are implemented simultaneously, it will cause PVC to burn or carbonize, resulting in significant waste of raw materials. So manufacturers need to consider comprehensively when choosing a solution.
- Reduce the Flow of Cooling Water
Manufacturers should raise the mold temperature as much as possible while ensuring that PVC injection molded products do not experience shrinkage issues. Reducing the flow rate of cooling water is a common measure to raise the mold temperature. In summary, measures that can improve the fluidity of the melt will be beneficial in solving the problems of PVC weld marks and water ripples.
- Other Options
In addition, in the actual production of PVC injection molding, manufacturers can improve or solve such problems by reducing the content of secondary recycled materials and adding a little diffusion oil. When the problem cannot be solved, manufacturers can consider using a fine screw injection molding machine specifically designed for injection molding PC materials to solve the problem. But this plan cannot be adopted for a long time, as long-term use will result in wear and tear of PC-specific screws, making it impossible to carry out injection molding production of PC materials.
The Enlargement of Gate And Runner Dimensions during PVC Injection Molding
The first solution that manufacturers consider to solve the problems of water ripples and weld marks during the injection molding of thick PVC is to adjust it to a very slow first-level injection speed. The prerequisite for solving the problem is to enable the melt to be filled in a fan-shaped manner. However, if the slow injection flow rate is too small and the screw is difficult to move, it will lead to a long filling time, a significant decrease in melt temperature, and an increase in viscosity, making the final filling very difficult or even impossible. Moreover, if the gate of the mold is set too small, it will make it difficult to change the folding or spiral filling phenomenon. Therefore, manufacturers believe that the most ideal filling method is to ensure that the speed of the melt during filling is slow, flat, and stable, while also ensuring a large flow rate, which is a contradiction.
-Increase the Size of the Sprue and Runner
Due to the resistance of the mold runner and gate, the actual filling speed of the melt is slower than the set speed of the process parameters. In actual PVC injection molding production, it is common to want to continue slowing down the injection speed but the screw can no longer move forward. Therefore, the primary task for manufacturers at present is to adjust the slower injection speed and ensure that the larger flow of molten material can smoothly fill this contradiction. The key to this solution is to add and reduce the filling resistance to continue slowing down the injection speed. At this point, manufacturers may choose to increase the size of the sprue and runner to solve such problems, which is also an effective and key solution to overcome folding or spiral injection.
In addition, manufacturers need to increase the size of gates and runners as much as possible under actual processing conditions. This method has gradually replaced slower injection speeds and becomes a common solution to the problems of water ripples and weld marks in PVC parts.
However, when manufacturers modify the size of the runner, an excessively large runner may not be beneficial for solving this problem and may increase injection time and the volume of secondary recycled materials. Therefore, after adjusting the most suitable gate size, it can be stopped and enter the processing stage.
In the process of PVC injection molding, the appearance of water ripples and weld marks is very common. As for the manufacturer’s choice of solution to solve such defects, it depends on the specific situation.
Related News
Applied’s expertise in modifying materials at atomic levels and on an ihdustrial scaleenables our customers to transform possibilities into reality.
