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compression molding time

Join Date: 2022-07-23

Compression molding time is the period of time from the start of heating and pressurization in the mold until the material is completely cured. Compression molding time is related to plastic type (resin type, volatile content, etc.), product geometry, thickness, compression mold design and structure, compression molding process conditions (pressure, temperature) and operation steps (whether to exhaust, pre-press, preheat).

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The influence of compression molding time on the product

Compression molding time has a great impact on the performance of the product, too short a time, resin curing is not complete, the physical and mechanical properties of the product is poor, the appearance of no luster, easy to warp and deformation after demolding and other phenomena. Increase the compression molding time, generally can make the shrinkage rate of products reduced. However, if the compression molding time is extended too much, it will not only prolong the molding cycle, reduce the productivity and increase the cost, but also make the plastic overheat, increase the shrinkage of the product, produce internal stress between resin and filler, cause the product surface to darken and blister, thus causing the product performance to decline, and in serious cases, cause the product to break.

How to reduce the compression molding cycle time?

Usually the compression molding time increases with the thickness of the product. The wall thickness of the part will directly affect the cycle time; thicker walls produce longer cycle times, while thinner walls produce shorter cycles, which is why the cycle time for compression molding of thin-walled products is less than three minutes.  MDC Mould's part designers will help refine your product to make the wall thickness as thin and uniform as possible, while still maintaining sufficient strength consistent with the application. In addition, the height of the part will also affect cycle time. The taller the part, the greater the displacement distance of the upper mold during release, and the longer the time required. Therefore a part with a flat and simple geometry will require less time when molding.

The cooling system inside the compression mold is a heat exchange system. There must be a sufficient number of cooling channels and a sufficient flow of coolant (usually water) to be able to reduce the cooling time of the product. The cooling time directly affects the overall cycle time. Different compression mold designers will design cooling systems with different features. This means that MDC's experienced mold designers can help you produce quickly.

Another aspect of the compression molding process that directly affects cycle time is the ejector system. The ejector system should quickly remove the part from the core. Manual release or poor mold design will only increase unnecessary cycle times. In addition, in many applications MDC Mould uses compressed air to meet the requirements for rapid mold removal. This is because the ejector (or release plate) is ejected slowly due to atmospheric pressure. If you do not reduce the speed, it may lead to distortion or damage of the part.

You can also shorten compression molding time by using pre-molding techniques. The charge is usually preheated before it is placed in the mold. Preheated polymers become softer, which shortens the time it takes to fill the mold and warm up the plastic, so compression molding times are shorter than without preheating.

In addition, compression molding process conditions can also have an impact on cycle time. Higher compression molding temperature accelerates the curing rate and reduces the required compression molding time, thus shortening the compression molding cycle time as the mold temperature increases.

Compression molding cycle times are long, ranging from a few minutes to an hour. For example, the cycle time for injection molding is usually only a few seconds. With 25 years of experience in compression molding processes and mold design, MDC mould understands the importance of compression molding time to your business costs and is capable of providing a one-stop solution for compression molding to ensure that you can produce your products quickly and well.

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