Understanding Draft Angles In Die Casting

Understanding Draft Angles in Die Casting

Die casting is an industrial manufacturing process used in the mass manufacture of components, critical and end use parts that serve various purposes. The process basically involves the introduction of molten metal into a mold cavity at very high temperatures. The injected molten metal is then left to cool and take the shape of the mold, forming the part. 

Draft angles in die casting refers to the slope that is included on the walls of die-casted mold in order to facilitate the ejection of the cast from the die cavity. It is essential on surfaces that are parallel to the direction of the die to aid removal of the part from the tool. Die casting is a critical component that must be properly calculated. This is because improper die casting draft angle will result in the die casted parts adhering to the walls of the die cavity. Even worse, improper draft angles can result to both mold and part damage when the mold surfaces are positioned perpendicular to the ejection. 

Why Draft Angles are Important? 
Draft angles are important for a number of reasons. These reasons cut across functionality, cost, damage control, part and product quality. Here are a couple of reasons why you should calculate draft angles correctly and incorporate them into your die casting design process: 

1.    Part ejection 
The primary function of die casting angles is to ease part removal and ejection. When draft angles are omitted from the design, removing the part from the mold can become tasking. Dents, strips and even breakages may result from too much abrasive force or friction when trying to remove the part. The availability of draft angles therefore guarantees part quality, adherence to part specification, better aesthetics and minimizes the chances of part defect. 

2.    Mold health 
Die casting with draft angles will significantly reduce the wear and tear experienced with the molds and lower the chances of damaging the mold. Draft angles can also ensure that the part comes out with more uniformity and dimensional stability. 

3.    Cost reduction 
The ability to produce better quality die casted parts without any damage to the mold or part is a direct and indirect effort of cost reduction. Consider and monetize the times it would take to fix a defective die casted part or repair its cosmetic quality due to part ejection problems. 

4.    Cosmetic quality 
Because casting with accurate draft angles make part ejection easier, one can expect the surface of the casted part to come out smooth, cleaner and more presentable. Making parts with inaccurate draft angles often results in products that suffer from scratches and dents, using draft angles ensures a uniform, smooth finish when the job is done. 

Draft Angle Guidelines 
•    Use a draft angle of 1.5 – 2 degrees to facilitate easy ejection of parts 
•    Draft angle is a requirement for textured parts, always ensure that the draft angles here is another 2.5 3 degrees 
•    Draft all components of a part/piece
•    Use at least 0.5 degrees of draft when working with vertical surfaces 
•    Any draft is better than no draft, although it is possible to cast parts at zero draft angles 
•    Use at least 3 degrees of draft when dealing with metal on metal molding components to ensure that the mold part components separate 

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