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How does shrinkage of injection molded products relate to plastic injection molds?

How does shrinkage of injection molded products relate to plastic injection molds?

2018-05-28

1. Injection plastic mold structure affects the shrinkage of injection molded products The form of injection plastic mold gate has influence on the shrinkage of injection molded products. When using small gates, the shrinkage of plastic parts increases because the gates are cured before the end of holding pressure. The cooling loop structure of injection plastic mold is the key of injection mold design. If the cooling loop is not designed properly, the shrinkage difference will occur due to the temperature imbalance around the plastic part, which will lead to oversize or deformation of the product. And in thin-walled parts, the influence of mold temperature on shrinkage rate is more significant. 2. Injection plastic mold parting surface and gate affect the shrinkage of injection molded products Plastic injection mold parting surface, gate pattern and size will directly affect the direction of plastic material flow, density distribution, holding pressure and shrinkage effect and molding time. The use of straight gates and large section gates can reduce shrinkage, but in the case of large anisotropy, straight gates and large section gates shrink along the direction of molten plastic flow and shrink more along the vertical flow direction; on the contrary, when the gate thickness is small, the gate part of the injection plastic mold will solidify in advance, and the plastic in the cavity cannot replenish the molten plastic in time after shrinking, which will make the shrinkage of the product bigger. Point gate cooling and curing speed is faster, when the conditions of injection molding parts allow, you can set multi-point gate on the injection plastic mold, this can effectively increase the holding time, increase the pressure of the mold cavity, reduce the shrinkage rate of the product.

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Plastic mold slant top mechanism processing precautions

Plastic mold slant top mechanism processing precautions

2018-05-28

(1) In general, the ejection distance of the plastic mold slant top will not be very long, and it is easy to break. Plastic molds that can realize fully automatic production, the ejection distance of the slant top can be farther than the semi-automatic pickup slant top ejection distance, in order to prevent uneven force when the robot picks up the parts, resulting in uneven force when picking up the parts. Fully automatic eject distance = product height (H) + safety value (K) 5.00 ~ 10.00mm; semi-automatic production eject distance = product height (H) X (2/3) (2) The angle range of the slanting top is 3°~15°, and the z-optimal range is 3°~8°. When the angle of the slanting top is more than 12°, in addition to considering the strength, it is also necessary to increase the auxiliary rod to prevent the plastic mold slanting top from deforming and breaking due to excessive torque during the production process. (3) the most likely to appear in the production of the product sticky slant top phenomenon, the common method is to make the product release angle increase, the design should avoid the plastic mold slant top appear too much tendon position. (4) slanting top bar should not be too thin, small workpiece slanting top z small for thickness 3.00mm, greater than 500.00mm workpiece, slanting top z small thickness shall not be less than 25.00mm, in order to prevent the production of plastic mold slanting top due to excessive torque and deformation fracture. (5) plastic mold slant top belongs to one of the ejector mechanism, used as an ejector product, in the same position with slant top area does not need to put the top, to avoid the slant top and ejector interference, slant top and ejector interference, need to do simulation verification. (6) in the injection production, very afraid of encountering the problem is the slant top twist deformation, root fracture, in the design, plastic mold slant top tilt angle and tilt distance, slant top material, slant top size, slant top design will have an impact on the slant top. Because of its own structure is relatively easy to damage, so in the injection production, it should be carefully repaired and replaced to avoid hidden problems such as the front mold slanting top does not retreat, slanting top running burrs.

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Composition of plastic injection mold slant top mechanism

Composition of plastic injection mold slant top mechanism

2018-05-28

(1) Slant top head: Its main function is for molding, the bottom of the inverted buckle bit will usually be made straight for easy processing and mold matching. The other three sides will be made inclined to facilitate with the sealing glue. The slant top surface is usually lower than the glue bit surface, which can be reduced by 0.05~0.1mm, preventing the shoveling of glue when the slant top surface is ejected. (2) Slant top rod: mainly as a link between the slant top seat and the slant top head, when the tilt occurs, it needs to bear the ejecting force. (3) guide block: in the plastic injection molding process, the dynamic template to reduce distortion and avoid hollow processing (to reduce friction), increase the guide block to facilitate positioning and precision adjustment. (4) guide bush: in the combination of inclined top will have two guide bush as a lubrication guide, inclined top rod in a long time after the movement of wear and tear, increase the guide bush to reduce the wear of the inclined top rod at the same time; when the accuracy of the problem is also more convenient for maintenance and replacement. (5) slanting top seat: the overall slanting top seat guidance method generally has a "T" shaped guide and pin top type guide, we z more use is pin type guide, it is easy to process, easy to install. T" type guide price is slightly higher, need to be equipped with a separate T base, processing with some complex than the pin.

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Injection molding process related process requirements

Injection molding process related process requirements

2018-05-28

Injection molding is a specific cycle. There are five elements that affect injection molding: temperature, speed, pressure, position, and time, and these five process elements determine the quality of the injection molding process. Most of the quality problems frequently encountered in injection molding process are caused by the abnormal quality caused by the failure to control the five points. Temperature is the primary factor in injection molding. Temperature can be divided into several key factors: drying temperature, material temperature, mold temperature, etc. Drying temperature for the plastic material pre-drying to ensure its molding quality, to ensure that the dry plastic wetness within a certain range; material temperature for the normal plasticization of plastic and smooth filling, molding; mold temperature for the injection molding process to take into account the important factors, injection mold temperature, the size of the temperature, appearance, molding cycle and other factors affect the cooling rate of the product in the mold cavity and the appearance of the product quality. The second element speed: speed is divided into injection mold speed, molten material temperature, rejection speed, mold opening and closing speed, ejector forward and rejection speed. The increase in injection speed affects the increase in mold pressure, improve the speed of injection molding process can improve the flow rate, product quality uniformity, to ensure product quality, high-speed injection is suitable for long process products, low speed to control the size of the product injection speed affects the plasticizing ability, is an important parameter of plasticization quality, the higher the speed, the higher the temperature of the melt, the stronger the plasticizing ability of the loosening speed in order to reduce the melt specific volume, reduce the internal pressure of the melt to prevent its outflow of the opening and closing speed is an important condition to ensure mechanical operation. The third element is pressure: pressure is divided into injection pressure, holding pressure, back pressure, clamping pressure, mold protection pressure, ejector pressure. Injection pressure is used to ensure the melt from the nozzle - runner - gate - pressure loss in the cavity to ensure that the cavity is full; pressure-holding method is used to reduce the parts due to excessive injection pressure and cause sticky mold rupture or bending; being pressure method is used to avoid the mold in the high-speed high-pressure state of foreign objects and make the mold rupture; ejector pressure method is used to prevent the products out of the mold surface and make the mold damage.

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