1. Glass fiber reinforcement:
The use of high-grade plastics can certainly increase the rigidity of plastic parts, but this will increase the cost, so the material is mainly not to increase the material cost, and the low-cost plastic reinforcement method is used to solve the problem. Adding glass fiber is a common and mature method. Adding glass fiber can also improve the creep properties of the material.
The glass fiber added in the plastic has a diameter of 0.05-0.01 mm, a length of 3-4 mm, a tensile strength of 700-2300 MPa, a hundred times of PP plastic, a melting point of 1000 ° C or higher, and a price of 6000-9000. yuan / tonne. Adding glass fiber (10-30%) to PP can greatly improve the rigidity of the material, improve the creep characteristics, and not increase the cost. 1. Disadvantages and solutions after adding glass fiber
The disadvantage of adding glass fiber is that the melt viscosity is large at the time of injection, the fluidity is deteriorated, and the surface of the part has floating fiber, which can be solved as follows:
1: increase the mold temperature and injection temperature;
2: increase the injection speed and pressure;
3: Increase the gate and shorten the runner.
2. Disadvantages that cannot be overcome after adding glass fiber:
After adding glass fiber, the surface gloss of the product will be somewhat reduced, so it is impossible to make high-gloss paint-free parts; after adding glass fiber, the screw wear of the injection molding machine is increased, and the screw life is shortened. If it is used continuously, the screw will be replaced in 1-2 years, so the cost of injection molding has increased.
3. Improve stiffness when designing parts:
1 equal wall thickness design to reduce internal stress to avoid deformation;
2 Avoid flat design and make three-dimensional parts;
3 Micro-arc design for large-area planes;
4 increase the reinforcement ribs - reasonable layout and choose the appropriate rib size;
5 Increasing wall thickness also increases stiffness, but it is a costly method that is far less reinforced.
4. Improve the injection molding process:
Increase the injection pressure, a 500g heavy PP plastic parts, due to the size of the injection pressure, the weight can be different 50g, when the parts are light, the density becomes smaller, the rigidity is worse, and the deformation is easy. The premise of high pressure injection is that the mold is highly precise, otherwise there will be "flash". In particular, parts that are priced by weight and counted, when commissioned for external processing, the processing plant will reduce the cost and produce low-density parts.
5, surface coating:
The surface of the plastic parts is plated with aluminum, Cu+Zn alloy, and chrome plated to improve the rigidity and surface hardness of the parts, and to achieve deformation.
6, scattered work load:
Increase the support point from the design point of view to achieve the purpose of dispersing the workload to reduce the deformation.
7. Deformation prevention caused by IMD injection molding:
Mobile phone IMD injection molding, the rear shell is to strengthen the rigidity, after the built-in stainless steel sheet, the deformation is caused by the inconsistent plastic and stainless steel CTE, that is, the plastic shrinks after injection, the stainless steel shrinks small, and the stainless steel is squeezed and bent, thereby deforming the entire part. Experienced engineers have proposed a method of overcoming: that is, when injection molding, the stainless steel sheet is first baked to 80-90 ° C and then placed into the mold for injection molding. Since the CTE is calculated after heating, the CTE of both will be very close when cooled. When the keypad is placed in the IMD mode, although the materials are close to each other, the temperature difference is very long and it needs to be preheated.
Ningbo RuiChang Commodity Packaging Co , Ltd . specializes in the production and supply of PP Bottle in China for daily necessities packaging, high-end leading production equipment and experienced technical personnel, strict production process operation, is the guarantee of "Ruichang" quality. For more information visit: https://www.ruichangpacking.com