Plastic Injection Mold Designing & Processing
PVC is a widely used industrial thermoplastic used in the manufacture of various plastic products, including pipes, siding, daily necessities, and more. Its excellent strength and good weather resistance make it suitable for many projects.
By choosing PVC injection molding, you will be able to reuse your molds for increased productivity. This is highly cost-effective and efficient compared to other manufacturing methods. PVC injection molding allows you to manufacture more detailed parts with the ability to combine multiple assembly steps into a single process.
Uses of PVC
PVC can be divided into rigid PVC and soft PVC, both of which have a wide range of uses. In fact, almost every industry uses PVC to make the following products:
1. Shower curtains, raincoats and rain boots are all available.
2. Packaging, including bottles, blister packs and shrink wrap.
3. Cable and wire insulation, various valves.
4. Floor and wall coverings.
3. Medical tubes and infusion bags, various electronic products, and more.
Process points of PVC injection molding
(1) Drying
Due to the presence of chloride ions, PVC materials have little hygroscopicity and need to be dried at a temperature of 75-90°C for about 1.5-2.5h before production to ensure the quality of PVC injection molding.
(2) Melting temperature
Melting temperature is one of the most important process parameters for PVC injection molding. If not set properly, it may lead to material decomposition. pvc is an amorphous polymer and does not have a definite melting point. It usually melts when heated to 120-145°C, but emits hydrogen chloride (HCl) fumes below 150°C and large amounts of HCl when heated to 180°C. Since it emits toxic gases during injection molding, a large amount of heat stabilizer is required before the process can begin. The adjustable range of injection temperature is very narrow. For injection molding, the commonly used temperature is between 140 and 160°C; sometimes the temperature can reach 190°C, but the injection time should be controlled within 20min, otherwise the material will be seriously decomposed.
Material temperature parameters – first stage: 160 – 170°C, second stage: 160 – 165°C, third stage: 140 – 150°C. Due to the poor thermal stability of PVC, excessive heating time in the barrel will release hydrogen chloride (HCl), causing the plastic to appear as yellow or black spots on the surface of the product. In addition, HCl will corrode the cavity, so the mold cavity and the dead corner of the head need to be cleaned frequently.
(3) Mold temperature
Try to reduce the mold temperature (generally keep the mold temperature between 30-45℃), shorten the injection cycle, reduce the product deformation after demolding for small size parts, use calibrator and shrinkage controller to correct and control the deformation when necessary.
(4) Gating
PVC flowability is poor, mold gates and sprue as large, short and thick as possible, product wall thickness 1.5mm or more, minimize pressure loss and fill the cavity as soon as possible. In a word, it is more suitable to apply high pressure and low temperature (injection pressure over 200MPa, back pressure between 0.5-1.5MPa, holding pressure is 20%~30% of injection pressure).
PVC melt has high viscosity and small flow length-thickness ratio, and underfilling may occur in thin-walled products. Therefore, the gate and runner size should be minimized. The shrinkage is 4‰; the overflow limit is 0.05mm. If you want to produce small size parts, it is better to choose needle point gate or split gate; for thicker parts, fan gate is a better choice. The minimum diameter of the point gate or split gate is 1mm; the thickness of the fan gate should not be less than 1mm.
(5) Other factors
Injection pressure up to 150MPa; holding pressure up to 100MPa. injection speed: proper injection speed must be used to avoid material decomposition.
Advantages of PVC Injection Molding
There are many advantages to using PVC for injection molding projects, the main ones include:
1. Inexpensive, abundant supply, high density
2. Constant hardness and excellent dimensional stability
3. Good weather resistance, chemical resistance, abrasion resistance
4. High productivity with minimal finishing
5. High material stability and high durability
6. Recyclable, lightweight, good color retention
About Fine Art
1. Fine Art provides customers with a full range of services in mold design, mold manufacturing, injection molding products, as well as cost accounting, technical support, export transportation, etc.
2. We use professional design software for mold development and design. For example, CATIA V5 is a high-end CAD/CAE software for personal computers developed by IBM/Dassault System. Its Core Cavity Design and Mold Design modules are designed for injection molds and are powerful and easy to use.
3. Mold production We use high-quality materials that meet international standards and customer requirements, advanced processing machinery and equipment, and high processing precision.
4. We have 1000 square meters of mold factory and injection molding production workshop, and convenient transportation, only 150 kilometers away from Beijing airport and only 50 kilometers away from Tianjin seaport. So we can guarantee our availability and delivery speed.
Whether you want to carry out the mold design and manufacture of PVC Injection Molding, or are looking for the processing and production of PVC Injection products, please feel free to consult us!
