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Warpage problem of automotive plastic parts       2014-03-06 16:48      visitor 



With the increase in the compact , miniature vehicles, it is appropriate to use plastic products towards lightweight volume , complex development. In this case , a growing number of thin-wall injection crate moulding products appear on some models.


Warpage is a common defect in the car shell plastic crate moulding , because it involves the accurate prediction of the amount of warpage , and warpage laws of different materials , different shapes of injection crate moulded parts varies greatly. Warpage problems exist that affect the shape accuracy and surface quality of crate moulded parts , when the amount exceeds the allowable error warpage after crate moulding defects become , thereby affecting product assembly .


Warpage is the shape of the injection crate moulded parts deviates from the shape of the crate mould cavity . Because not only affect warpage product assembly and performance , but also affect the appearance of the product quality. Warping deformation has become an important indicator of product quality assessment .


Plastic parts and elements of the mechanism causing warpage warping main structure with plastic parts , crate mould design and crate moulding process in three areas related. Plastic crate moulding shrinkage due to the flow direction is greater than the vertical direction , so that the shrinkage of the different parts and warpage.


A crate mould design


Improperly ( 1 ) gate location or insufficient quantity .


Not only the location and number of gates affect the balance of the flow will also affect the volume contraction at the end of filling . The purpose is to analyze the position of the gate in the part structure to find the best balance the flow gate location to minimize product defects , to obtain a good quality product .


( 2 ) the top of the improper position or products discontinuity .


Two aspects of the crate moulding process


( A ) die , cylinder temperature is too high .


Temperature will increase only warpage increases , while increasing the injection speed , the amount of warpage can be reduced .


( 2 ) injection holding pressure is too high or too fast .


Injection speed can improve the injection time is greatly shortened , but the clamping force to increase ; increase the injection rate can play a role in reducing the warpage . But the increase injection crate moulding products will increase the speed of the process of surface shear stress .


( 3 ) cooling the injection time is too long or too short .


Three structural plastic parts , plastic parts is to determine the structure of its own degree of warpage key .


Uneven wall thickness of plastic parts , wall thickness change suddenly or too small .


Different plastic parts , in different regions of temperature, pressure and flow rate thick uneven , causing differences in shrinkage , thereby causing warpage and stress the participation of the plastic parts .