Design Guide for Metal Injection Molding

Computer simulation of the injection molding process is advanced and allows the study of every detail of mold filling in 3D.
The design engineer can analyse the filling dynamics in thick and thin areas on screen, study the effects of gate position, thermal gradients in the mold and phenomena such as jetting and binder segregation.
Designers can also optimise the kinetics of mold filling and determine shrinkage and distortion of the green compact relative to the mold dimensions.
A careful analysis and optimisation of the mold cavities can reduce design time and cost while significantly improving yield and quality.
 

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"The Design Should Considerations"

1. --Metal Part must be so designed to allow for easy ejection from the die. Sidewalls should be perpendicular; hole axes should be parallel to the direction of opening and closing of the die.
2. --Holes, even complicated profiles, are permissible in the direction of compressing. The minimum hole diameter is 1.5 mm (0.060 in).
3. --The wall thickness should be compatible with the process typically 1.5 mm (0.060 in) minimum. Length to thickness ratio can be up to 18 maximum-this is to ensure that tooling is robust. However, wall thicknesses do not have to be uniform, unlike other processes, which offers the designer a great amount of flexibility in designing the parts.
4. --Undercuts are not acceptable, so designs have to be modified to work around this limitation. Threads for screws cannot be made and have to be machined later.
5. --Drafts are usually not desirable except for recesses formed by a punch making a blind hole. In such a case a 2-degree draft is recommended. Note that the requirement of no draft is more relaxed compared to other forming processes such as casting, molding etc.
6. --Tolerances are 0.3 % on dimensions. If repressing is done, the tolerances can be as good as 0.1 %. Repressing, however, increases the cost of the product.