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The cause of overflow in the process of injection mold processing

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The cause of overflow in the process of injection mold processing

Issue Time:2020-10-10
The cause of overflow in the process of injection mold processing
Wanda mould
Post time: 09-2717:30
Overflow, also known as flash and overflow, usually occurs at the parting and closing positions of molds.For example, the parting surface of the mold, the slot of the insert and the hole of the pin.If the overflow cannot be eliminated in time, it will lead to partial collapse of the injection mold, and in serious cases, permanent damage will be caused.In addition, overflows from insert gaps and ejecting rod pores can cause the finished product to get stuck on the mold, affecting the release process.Then why do injection molds overflow in the process of processing?How to solve the overflow phenomenon?The following small series will answer for you.
I. Equipment
1. Improper adjustment of the clamping device of the injection molding machine or uneven toggle mechanism will lead to the failure of the mold to reach the due parallelization, resulting in the phenomenon that one side of the mold is tightly closed and the other side is not tightly connected, which is easy to overflow during the injection process.
2. The parallelism of the injection molding machine itself is defective, and the uneven distribution of stress on the pull rod will also lead to the mold cannot be closed tightly and cause overflow.
3, the injection molding machine appears check ring wear, screw wear too much, the injection volume set by the barrel is insufficient, cushion is too small, etc., are likely to cause overflow, so the operator must be timely repair or replace parts.
2. Mold
1. Poor precision of mold parting surface
Deformation and warping of the movable formwork (for example, the middle plate), foreign body on the parting surface, and skid marks on the outer edge of the mold frame can all lead to an injection mold spill.
2. Unreasonable mold design
(1) If the opening position of the mold cavity is too deviated, excessive unilateral tension will occur in the mold during the injection process, resulting in overflow.
(2) Polyethylene, polypropylene and other plastic materials have good liquidity, and in the melting state of low viscosity, easy to enter the mold clearance, so in the manufacture of high-precision mold, operators should try to thick parts of the mold feeding, in order to prevent overflow, affecting the integrity of the mold products.
(3) The poor matching accuracy of sliding mold core or the deviation of fixed mold core and cavity installation position will also lead to the occurrence of overflow.
(4) For multi-cavity mold, designers should pay attention to the reasonable design of the shunt duct and gate, otherwise it will lead to uneven filling force and overflow.
Third, technology
1. Under the action of high pressure and high speed, the tension of the mold will increase and cause overflow, so the operator needs to adjust the injection speed and time according to the thickness of the mold product.For thin products, high speed and fast mold filling, and for thick products, low speed mold filling.
2, some operators in order to prevent the injection mold depression, often choose to inject more molten material, but this may not be able to solve the problem, but there will be overflow.So when we encounter this kind of situation, we should respond by extending the injection time or the pressure retention time.
Above is about injection mold overflow reason analysis, small make up mainly from equipment, mold and process three aspects to introduce, hope to help you.