How to Calculate Draft Angle for Die Casting

What is Draft Angle for Die Casting?

Draft angle, or the taper for the walls of a die cast part, is an important metric to consider for die cast design. Draft angle runs perpendicular to the parting line, or the line on the die cast object where two molds meet. Engineers know that a proper draft angle will make the ejection of the die cast metal part from the mold much easier. And good designers know that a smooth ejection from the die ensures a better surface on the finished product and requires less secondary machining.

What is the Proper Draft Angle for My Die Cast Part?

Double the draft angle is usually required for inside walls of a die casting vs. the outside surfaces. In general, draft decreases as depth increases. According to the NADCA, calculation for draft and draft angle are as specified below:

There are various draft angle calculators online that automatically calculate your needed draft angle. However, hiring a professional die casting company with experienced designers is the recommended way to calculate this metric. A proper draft angle calculation requires the surface type, depth of the surface and the metal alloy being used to be taken into account. 

Why Are Ribs Needed for Die Casting?

Some die cast parts are ornamental only. Others have serious jobs to do once they’re produced – specifically that they will serve as structural part of a greater design. That means that strength and hardness under extreme pressure are essential. Thus, it might be necessary to add design elements that increase the strength of a part that could otherwise only be for show. One way that the strength of die casting components is reinforced is through the use of ribs. Die casting ribs help to increase the strength and soundness of any die cast component, regardless of alloy.

Why ribs for your die casting design?

•          Increase the strength of the component without adding unnecessary thickness to walls of the die cast part
•         Help melted metals to flow more smoothly to parts of the mold that would be otherwise difficult to properly fill
•          Decrease overall product weight while maintaining needed physical properties

Ribs & Initial Die Casting Design Prototypes

Die casting rib design should be incorporated into your mold design at the earliest stages possible. The correct placement of die casting ribs is essential to ensure that your ribs create only advantages for your die cast part. Also consider the placement of fillet radii to avoid stress concentrations. 

If you’re using an engineering company to produce your prototype, make sure to ask about what design elements they are planning on using to ensure that the physical properties of your final product meet your needs. 

Magnesium in Die Cast Parts

Magnesium is one of the top three structural metals used in the die casting process.  It is an ideal metal for die casting due to its lightweight properties and having the lowest density of all structural metals.  It is almost as lightweight as plastic and is good for use in components where weight is an important factor.

There are several applications for magnesium; as a component of aluminum alloys, as a die casting material, removing sulfur in the production of iron and steel, and in the production of titanium in the Kroll Process.  In its purest form, magnesium is strong and very lightweight making it a choice metal for high volume part manufacturing.  One of the main applications is its use in automotive and truck components like engine parts and high-grade car wheels.  In fact, Volkswagen Group has used magnesium in its engine components for years as well as BMW and Porsche.

Another application of magnesium die cast parts is in electronic devices.  Its low weight and good mechanical and electrical properties make it ideal for mobile phones, computers, and cameras.  It has also been used as an aerospace construction metal for aircrafts.   

Lastly, magnesium has several unique uses because of its flammability.  It burns at approximately 3,100 ^oC and produces an intense, bright white light while burning.  Because of its high combustion temperature, it is used for starting emergency fires, used in flash photography, flares, pyrotechnics, and fireworks sparklers. 

Magnesium is the third most commonly used structural metal and has a variety of uses and applications.  Its light weight property makes it a useful metal for electronics applications and it also has full recyclability.  It is a leading metal choice for manufacturing die cast parts.