Injection Molding Spark plug cover, Plastic injection mold

Injection Molding Spark plug cover, Plastic injection mold

Service Details:

  • Brand:Kayou
  • Serial Number: M-0026
  • Country of Origin:Shenzhen, China
  • Certificate:ISO9001

Payment & Shipping Terms:

  • Price Quote:Negotiable
  • Minimum Order: 1
  • Average Delivery Time:25days
  • Payment Method:T/T
  • Package Details:Wooden Case
  • Ability to Supply:5 Set/per month
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Injection Molding Spark plug cover, Plastic injection mold

Description

Thermal plastics and easily hydrolyzed plastics
Thermosensitive means that some plastics are sensitive to heat, when the heating time is long at high temperature or the cross section of the feed port is too small, and when the shearing effect is large, the temperature of the material is increased, and the tendency of discoloration, degradation and decomposition is easy to occur. Plastics are called heat sensitive plastics. Such as hard PVC, polyvinylidene chloride, vinyl acetate copolymer, POM, polychlorotrifluoroethylene and so on. Thermally sensitive plastics produce by-products such as monomers, gases, solids, etc. during decomposition, and in particular, some decomposition gases have irritating, corrosive or toxic effects on human bodies, equipment, and molds. Therefore, mold design, injection molding machine and molding should pay attention to the screw injection molding machine, the casting system should have a large section, the mold and barrel should be chrome-plated, there must be no * angle sliding material, the molding temperature must be strictly controlled, plastic Stabilizer is added to reduce its thermal performance.

Some plastics (such as PC), even if they contain a small amount of water, decompose under high temperature and high pressure. This property is called easy hydrolysis and must be preheated to dryness.

Stress cracking and melt fracture
Some plastics are sensitive to stress, and are prone to internal stress during molding and are brittle and fragile. The plastic parts are cracked under the action of external force or under the action of solvent. To this end, in addition to adding additives to the raw materials to improve the crack resistance, the raw materials should be dry, reasonable selection of molding conditions to reduce internal stress and increase crack resistance. And should choose a reasonable plastic shape, it is not appropriate to set inserts and other measures to minimize stress concentration. When designing the mold, the draft angle should be increased, and a reasonable feeding port and ejection mechanism should be selected. The material temperature, mold temperature, injection pressure and cooling time should be properly adjusted during molding to avoid mold release when the plastic parts are too cold and brittle. After molding, the plastic parts should also be post-treated to improve the crack resistance, eliminate the internal stress and prohibit contact with the solvent.

When the polymer melt of a certain melt flow rate exceeds a certain value when passing through the nozzle hole at a constant temperature, a significant lateral crack occurs on the surface of the melt, which is called melt fracture, which impairs the appearance and physical properties of the plastic part. Therefore, in the selection of polymers with a melt flow rate of 髙, the nozzle, runner, and feed port sections should be increased to reduce the injection speed and increase the material temperature.

Thermal performance and cooling rate
Various plastics have different thermal properties such as specific heat, thermal conductivity, and heat distortion temperature. When the plasticization is higher than the heat, it requires a large amount of heat, and an injection molding machine with a large plasticizing capacity should be used. The hot deformation temperature is high. The cooling time of the plastic can be short, and the mold release is early, but the cooling deformation is prevented after demolding. Plastics with low thermal conductivity have a slow cooling rate (such as ionic polymers and other cooling rates are extremely slow), so they must be sufficiently cooled to enhance the mold cooling effect. Hot runner molds are suitable for plastics with lower heat and high thermal conductivity. Plastics with higher specific heat, lower thermal conductivity, lower heat distortion temperature and slower cooling rate are not suitable for idling, and proper injection molding machines and mold cooling must be used.
Various plastics are required to maintain an appropriate cooling rate according to their type characteristics and shape of the plastic part. Therefore, the mold must be set to the heating and cooling system according to the molding requirements to maintain a certain mold temperature. When the temperature of the material increases the mold temperature, it should be cooled to prevent the deformation of the plastic parts after demolding, shorten the molding cycle and reduce the crystallinity. When the residual heat of the plastic is not enough to keep the mold at a certain temperature, the mold should be provided with a heating system to keep the mold at a constant temperature to control the cooling rate, ensure fluidity, improve filling conditions or control the plastic parts to cool slowly. Prevent uneven cooling inside and outside of thick-walled plastic parts and improve crystallinity. For good fluidity, large forming area and uneven material temperature, it may be heated or cooled alternately or partially heated and cooled according to the molding condition of the plastic parts. For this purpose, the mould should be equipped with a corresponding cooling or heating system.

Hygroscopicity

Plastics have various additives to make them have different degrees of moisture. Therefore, plastics can be roughly classified into two types: moisture absorption, adhesion moisture, non-absorbent water and non-stick moisture. The water content in the material must be controlled within the allowable range. In the case, the water becomes gas or hydrolyzes under high temperature and high pressure, causing foaming of the resin, deterioration of fluidity, and poor appearance and mechanical properties. Therefore, hygroscopic plastics must be preheated as required by appropriate heating methods and specifications to prevent re-absorption during use.

 

 

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Injection Molding Spark plug cover, Plastic injection mold

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FAX :
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