key point of injection mold design (1/2)

Injection molded parts design point.

1, the product produced using the injection molding process , the plastic in the mold cavity uneven cooling and uneven shrinkage and the design is unreasonable , prone to various defects in the product: Sink mark , weld lines , bubble, deformation, ejector mark, flash.

 

2 , in order to obtain high-quality plastic products, we must fully consider its structure in the design process of products, combined with the following.Analysis method to avoid defects according to the main structural features of injection molding products.

 2.1 direction and mold parting line

     At the beginning of each products designed, must first to determine its direction and mold parting lines , in order to ensure as much as possible to reduce Pulling and eliminate the impact on the appearance of the parting line .

2.1.1 determine the direction of the mold , ribs, clips and other structured products should be designed as the mold the direction, in order to avoid reducing core pulling, extend tool life .

2.1.2 Example: bumper mold direction is generally the direction of the vehicle body coordinate χ , if designed to mold the direction of the axis χ  Inconsistent, you must specify the angle at which the product graph..

2.1.3 determine the direction  , you can select the appropriate parting lines to improve the appearance and performance.

2.2  draft angle.

2.2.1 appropriate draft angle to avoid product scratch . draft angle should be greater than 0.5 degrees for smooth surface, fine  Surface greater than 1 degree, coarse surface greater than 1.5 degrees.

2.2.2 appropriate draft angle can avoid parts’ injury .

2.2.3 for the deep cavity design, requires the outer surface slope angle less than the inner surface , to ensure that no deviation when injection , to obtain a uniform thickness of the product , and to ensure the opening portion of the product density of the material strength.

 

2.3Wall thickness of products

2.3.1 certain kinds of plastic wall thickness range , generally 0.5 ~ 4mm, when the wall thickness is more than 4mm, the cooling time is too long , resulting in sink mark and other issues, should consider improve and changing the product structure.

2.3.2 The wall thickness would cause surface and sink mark.

2.3.3 products with uneven thickness would cause bubble and sink marks.

 

2.4 reinforcing rib

2.4.1 strengthen the rational application of ribs , increase product rigidity and reduce distortion.

2.4.2 stiffener product wall thickness must be less than 1 / 3 , otherwise the surface would have sink mark

2.4.3 ribs should be greater than the slope of one side of 1.5 °, to prevent ejector mark .

 

 2.5 Chamfer

2.5.1 rounded product may cause stress concentration is too small , causing cracking products .

2.5.2 rounded mold cavity is too small,may cause stress concentration , leading to the cavity cracking.

2.5.3 Set reasonable chamfer , but also can improve mold processing technology, can be directly used as cavity milling cutter R , While avoiding inefficient power processing.

2.5.4 Different chamfer may cause moving parting line should be combined with the actual situation of choosing different fillets or clearance angle .

 

  2.6 Hole

2.6.1 shape of the hole should be as simple as possible , and generally rounded.

2.6.2 consistent axial and mold the direction of the hole , core pulling avoided .

2.6.3 When the hole when the aspect ratio is greater than 2 , should be set stripping slope . The diameter of the hole should be at this time trails size ( the largest real Body size ) is calculated .

2.6.4 blind hole aspect ratio is generally not more than four .

2.6.5 the distance from the hole to the edge of product is generally greater than the aperture size.

 

2.7 injection mold core-pullingmechanism and avoid

2.7.1 When the plastic parts can not be successfully mold press release direction , pulling mechanism should be designed . Pulling mechanism of complex products can be molded Structure, but can lead to product patchwork line , sink mark and other defects, and increase the cost of shortening the life of the die mold .

2.7.2 The design of injection molding products, such as no special requirements to avoid pumping core structure . If the direction of the axial hole and tendons change, then trying other methods.

 

 

 

professional tool shop in china,refer to

www.freetech-mould.com