Causes of Deformation During Plastic Mold Casting

There are many reasons for deformation in the lastic mold casting, which need to be comprehensively considered and prevented from mold design, material selection, processing parameters, use and maintenance, and molding condition settings.

1. Mold design factors

Irrational structural design: The structural design of the mold has a decisive role in its deformation. If there are sharp corners or significant differences in wall thickness in the design, stress concentration may occur during processing and use, which will lead to mold deformation. Improper design of the water entry position of the mold may cause uneven pressure on the mold structure during plastic filling, causing deformation. Poor exhaust performance of the mold may cause gas compression of the plastic melt during the filling process, which in turn causes mold expansion deformation.

Irrational cooling system design: The cooling system of the mold is unreasonable, such as uneven cooling effect of the water channel, which will lead to uneven temperature at various positions of the mold, inconsistent shrinkage and deformation of the product. The cooling of the mold should pay attention to the temperature balance between the cavity and the core, and the temperature difference between the two should not be too large, otherwise it will cause product warping and deformation.

2. Mold material factors

Insufficient mold material strength: The selection of mold material is crucial to the stability and durability of the mold. If inferior quality steel is used instead of high-quality steel, the mold may gradually lose its demolding slope after repeated use, causing the core and cavity parts to slowly deform. The hardness, strength, and toughness of mold materials vary. Improper selection may not be able to cope with various stresses during processing and use.

Improper heat treatment of mold materials: During the heat treatment of mold steel, if the quenching temperature is too high or the heat treatment process is improper, it may cause the carbide to fully dissolve and the grain to increase, thereby reducing the resistance to plastic deformation, increasing internal stress, and aggravating mold deformation. If the residual stress after machining is not fully stress-relieved and tempered, it will also be superimposed on thermal stress and structural stress during the heat treatment process, causing mold deformation.

3. Mold processing factors

Improper clamping method: During the clamping of the workpiece, the selection of clamping points, the size and uniformity of the clamping force, and the consistency of the clamping point and the support point will affect the deformation of the workpiece. For example, for thin-walled parts, excessive clamping force may cause the part to bend.

Unreasonable selection of cutting parameters: During the cutting process, the selection of cutting speed, feed rate, back cutting amount and other parameters of the tool will affect the generation of cutting force and heat, thereby affecting the deformation of the workpiece. For example, too high a cutting speed may cause the temperature of the cutting area to rise rapidly, causing thermal deformation of the workpiece. Parameters such as the sharpness and angle of the tool have a significant impact on the cutting force and heat generation during the processing process. If the tool is not sharp enough, it will increase the cutting resistance and heat, which will cause the workpiece to deform.

4. Mold use factors

Mold wear and damage: As the mold continues to be used, the core and cavity parts of the mold may gradually wear due to long-term pressure, friction and other reasons, causing the mold to deform.

If some parts of the mold (such as ejector plate, slide, etc.) are worn and loose, it may also cause product deformation.

Unreasonable molding conditions: Unreasonable molding conditions such as too high injection pressure, too high melt temperature, too high holding pressure, and insufficient cooling time may cause internal stress in the plastic part during the molding process, which may cause warping deformation. Too fast ejection speed of the mold, poor ejection structure, unbalanced ejection force, etc. may also cause deformation of plastic parts during the ejection process.

5. Plastic material factors

Plastic material has a large shrinkage rate: Plastic material has a large shrinkage rate, which is easy to produce large shrinkage stress during the molding process, causing deformation of plastic parts.

Poor fluidity of plastic material: Poor fluidity of plastic material may cause uneven filling of the melt in the mold cavity, generate internal stress, and then cause warping deformation.

Qingdao Xueyu Molding Products Co., Ltd. is mainly engaged in the design and manufacturing of injection molds, injection molding and secondary processing (spraying, pad printing, ultrasonic welding, stamping), etc. For more information about plastic mold casting, please contact us.

Website: www.xyzmould.com

Address: No.18 Henan Head Road, Henan Head Community, Jihongtan Street, Qingdao Industrial Park, Shandong Province, China

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