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.

Benefits of Utilizing the Die Casting Process

Die casting is quickly becoming one of the most widely used manufacturing methods due to the many advantages it provides.  The die casting process is one of the most cost-effective manufacturing options.  Die casting is so efficient because it is able to offer a wide range of part manufacturing options, unlike competing methods.  Also, components made during the die casting process last while remaining aesthetically appealing.  Additional advantages to using the die casting process include fast production, accuracy, durability, and strength.

The die casting process is able to provide a quick production time even while working with on complicated components, unlike other manufacturing techniques.  In die casting, countless duplicate castings can be made with minimal machining.  Additionally, die casting creates product components that are stable yet resistant to heat and other external factors.  Die casting manufacturers also pride themselves on developing components that are stronger than those created with other methods, such as plastic injection molding.  This process also allows manufacturers to rely on the metal itself instead of the welding, since there is no need to fasten the parts together.

With all of these advantages, it is no wonder that die casting is becoming a leading process in the manufacturing industry!

History of the Aluminum Die Casting Process

The die casting industry has come a long way in involving into the modern aluminum die casting process that we know today.  The die casting process first started in 1838 when the first die casting equipment was invented.  In 1849, the first die casting patent was granted for a machine that was small and hand operated.  This early die casting machine was used for mechanized printing production.  Another major breakthrough was made when Otto Mergenthaler designed the automatic type casting machine called the Linotype in 1885.  The Linotype grew to become the leading machine in publishing world until approximately 1970.

After this development, the die casting process experienced exponential growth.  The die casting industry began to specialize in creating a large volume of cost-effective yet complex parts.  The aluminum die casting process as well as the zinc die casting process really began to take off in the year 1914, and the use of magnesium and copper was not far behind.  The aluminum die casting process has evolved over the years, but the basic components remain the same.

Despite the stability of the aluminum die casting process, researchers see new developments on the horizon.  Those in the die casting industry are looking to create castings with more finished surfaces and at a faster rate.  For example, researches are working to develop a high-pressure die casting process that injects aluminum into the mold as a semi-solid.

Although this history of the aluminum die casting process can seem short, the amount of progress that has been made in the die casting industry is astonishing.  The aluminum die casting process is one of the most widely used manufacturing processes today.  For a process that was created specifically for the printing industry, it is amazing that the aluminum die casting process can now be found in many products that countless of people use on a daily basis.  From the automotive industry to mobile phone manufacturing, almost every manufacturing industry can take advantage of the enhanced aluminum die casting process.

Die Casting Industry Safety Standards

In 2012, the die casting industry averaged 4.4 lost workdays due to injury/illness per 1000 hours worked. Operating a die casting machine is a dangerous job for employees. In fact, the injury rates for the die casting industry are around two times as high as other private industries.

Die cast facility safety standards are set by the NADCA (North American Die Casting Association). Die casting facilities install and maintain safety equipment to protect machine operators from injury.

Die casting machine operation is very dangerous because of the risk of burns from spewing or erupting molten metal in the direction of the machine operator. Metal alloys are heated to extremely high temperatures during the die casting process. The die casting process also involves moving machinery which can lead to operators becoming pinned or cut by the moving parts. Movement danger includes, but is not limited to, movement of the die clamp, movement of the core puller and movement of the tool clamp.

There are a myriad of other safety risks involved with operating die casting machines, including damage to hearing due to noise, electrocution and inhalation of dangerous vapors or fumes.  Sprains, strains and abrasions can also occur from equipment placed at improper heights. Dust explosions and fires are also a danger to die casting industry workers.   

The safety inspection for a die casting facility is conducted on a machine by machine basis. Safety orders vary between cold-chamber and hot-chamber die casting machines. Additionally, die casting machine operators undergo extensive safety training in operating safe practices. Operators are required to wear a helmet, safety glasses and side shields. Full face shields are used during more dangerous parts of the die casting process.