Porosity in Die Cast Parts and What it Means to You

Porosity in Die Cast Parts and What it Means to You

What is porosity in die casting?
Porosity refers to small voids, holes, or pockets of air that are found within a finished part. These holes typically occur when air is trapped in the material being worked with. Porosity is a big concern in die casting, though it is typically acceptable in non-critical areas.

Porosity can happen in a variety of ways. Air can become trapped by the die cast machinery leaving gaps at the top of the die, it can occur when filling a mold too slowly, or when some of the material being used solidifies too soon. It can also occur when the air used to force molten metal into the mold isn’t completely forced out or able to escape through vents and overflows.

Causes of porosity in die casting:
• The design of the mold and cast parts
• The purity of the metal or alloy being used
• Pressure and shot speed of the machines
• Shrinkage of the material wall thickness
• Too much lubricant in the die
• Sharp corners in the mold
• Low metal temperatures
• Air trapped in the metal

How do you check for porosity?
• X-ray the finished material
• Using computerized tomography
• Cutting and polishing a section and then analyzing it under a microscope

Can it be prevented?
Porosity varies in severity and can occasionally be acceptable in the final product, but generally it is best to limit it as much as possible. There are so many areas that need to be closely monitored in order to avoid porosity – the die casting process (such as the design of the mold), purity of the metal, low metal temperatures, pressure and speed of the machines, and more.

The best way to minimize porosity is to make sure the engineers and the die caster are working closely together to provide strategic guidance from the very beginning of the project. In addition, making sure the die caster is experienced and is using only top quality materials also greatly reduces any possible issues with your die cast part.

Need a hand?
Early involvement with a seasoned die caster is essential in avoiding issues with your cast and any possible expensive corrective steps needed down the line. With over 74 years of experience in die casting, A&B Die Casting understands your materials, designs, and parts as well as the casting process factors that are most likely to cause different types of defects. This wealth of experience enables us to prevent many defects before they even occur. We can also assist with redesigning elements to address porosity-prone areas and shift them to locations that will not impact structural integrity.

If you are developing your own tolerance limits, the American Society for Testing and Materials (ASTM) lists the standards for porosity in castings on their website (https://www.astm.org/). They are an excellent resource for standards, books, journals, and articles for a variety of industries, materials, and products.

If you are concerned about the porosity of your casting, we recommend you contact us directly and chat about your specific project.

-A&B Die Casting
(877) 708-0009
www.abdiecasting.com

How Important is Temperature when you are Die Casting?

How Important is Temperature when you are Die Casting?

Die casting temperature control is a serious issue. When it comes to die casting, as temperatures increase the tensile and yield strengths of the alloy decrease. Ductility also increases as the temperature increases but differs based on the type of alloy being cast. The proper temperature is crucial for both the die and the metal to be cast. The metal being cast needs to be heated correctly to ensure proper flow and fill of the mold. If the temperature of the molten metal is too hot for the mold, it could damage the mold. If the temperature of the mold is too cold, the metal will cool too quickly as it flows into the mold and will cause defects.


Metal flowing into a die

What temperatures need to be closely monitored?
• The temperature of the die itself
• The temperature of the die casting machine or casting chamber
• The temperature of the alloy used for casting

All three of these temperatures must be kept within their individual optimum range in order to produce the highest quality die cast parts.

What is the proper die temperature?
The die temperature will depend on what alloy you intend to cast. You want to avoid putting excess strain on your die, stressing the die will lower the life expectancy of the die itself. It is best to pour your alloy into your die when it is approximately 50° to 70° degrees higher than the crystallization temperature of the alloy. The die needs to be maintained at approximately a third of the alloy’s temperature.

What is the proper die casting chamber/machine temperature?
The temperature required for the die casting machine is a complex calculation that includes things such as the alloy type, die type, size of the part to cast, and more. The chamber temperature needs to be determined by an experienced die caster.

What is the proper alloy temperature?
Alloy temperatures vary greatly depending on the material. Here are two examples of the most common die cast alloys – aluminum and zinc.

Aluminum
Aluminum 360, 380 and 413 are by far the most popular metal choices for die casting. Aluminum is resistant to corrosion, lightweight, and extremely durable. When casting aluminum 380, for example, you will get a tensile strength of 48 at 75° with yield strength of 24 KSI (Kips per Square Inch). If you increase the temperature to 212°, you will get a tensile strength of 45 KSI, while the yield strength stays constant at 24.

Zinc
Zinc 3, 5, and 7 are also incredibly popular die casting alloys. For these zinc alloys, a temperature of 75° produces an average of 40 KSI. If you increase the temperature to 275° you will produce an average KSI around 10.

Optimal temperature ranges for surface finish:

What happens if the temperature is incorrect?
If the temperature of the metal being cast is too hot for the mold it can damage the mold, which dramatically shortens the effective usage life of the mold. If the temperature is too cold the metal will cool too quickly as it is flowing into the mold which can cause defects (such as porosity problems or misruns).

How can A&B Die Casting help?
Here at A&B Die Casting we take the issue of temperature control very seriously. We are highly experienced at keeping our materials and casting equipment at the optimal temperature. We utilize 3D flow analysis software to ensure optimal die filling for superior casting quality. The software allows us to simulate how the specified material will flow into the a mold so that we can more accurately gauge the overall effectiveness of the mold as well as identify any potential issues with the material temperature fluctuations while it flows into the mold.

For over 70 years A&B Die Casting has been serving world-wide manufacturers with low-to-medium volume aluminum and zinc die castings. Our experienced team creates solutions for your production needs from the formative stages of engineering and prototyping to machining, finishing, assembly, packaging and shipping with adherence to your exact specifications.

Need assistance or want to get started on your next die cast project? Contact A&B Die Casting today!

Design Geometry Considerations for Die Casting

Design Geometry Considerations for Die Casting

Producing a top quality die cast component part starts with a solid and well thought out design. The goal of any die cast design is to create a casting that will maximize the function of the part, while being one that can be produced fairly quickly, efficiently, with few defects, and little to no secondary operations necessary.

There are many factors that need to be taken into consideration when designing a die, such as:
• Wall thickness
• Wall thickness uniformity
• Draft
• Pockets
• Fillets and corners
• Ribs and bosses
• And more

Wall thickness
Wall thickness is the distance between two parallel (or nearly parallel) surfaces and will vary depending on the thickness to length ratio of the entire part. If your part is very long it is difficult to maintain a very thin wall. You want your wall thickness to be as thin as possible while maintaining the strength and overall functional requirements necessary for your specific application.

Typical minimum wall thickness:

Wall thickness uniformity
Ideally, you want a design that creates uniform wall thickness all around the casting. This doesn’t mean that it needs to be 100% the same on all sides, only that you should strive to minimize drastic wall thickness variations. Dramatic variations in wall thickness can result in different rates of cooling along the cast wall which can alter the dimensions of the finished part. Uniform thickness also allows you to better control the flow of the metal into the die in order to ensure a complete fill.

Draft
When it comes to die casting a draft refers to the slope or taper that run in the direction of the die’s opening. The taper should be greater on the interior of the die walls than it is on the exterior walls so that when the alloy cools and solidifies it will shrink and fit more tightly on the inside of the casting. The greater the interior draft, the easier the finished part will be to remove from the die and the more precise the finished product will be.

Pockets
If your part needs to be light, pockets are excellent inclusions in die cast designs. Basically these pockets, also referred to as metal savers, are open spaces or holes placed in the design of the die. Strategically placed pockets make your final part lighter without compromising any of the structural integrity.

Fillets and corners
Fillets are the curved parts of the casting where two surfaces would normally have come together at a sharp angle. They are added to a die casting to eliminate hard edges and corners that are not desired in the final part. It is best to utilize large inner and outer corner radii for the cast part. The larger the radii the stronger the final part will be.

Ribs and bosses
Bosses generally serve as stand-offs and mounting points, while ribs are added to provide support without increasing wall thickness. If it is possible, design any necessary ribs and bosses directly into the die cast. These features help eliminate sharp corners and help increase the overall strength of the finished part.

Consulting with an experienced die caster during the design phase will help eliminate any potential problems affecting tooling and production of your new part.

How can A&B help?
A&B Die Casting leads the industry with a trusted worldwide reputation for unique economical approaches and value-added services for all of your die casting solutions. We pride ourselves on doing the hard work upfront so that we can generate the most value to our customers for years to come.

Need assistance or want to get started on your next die cast project? Contact A&B Die Casting today!

Die Castings vs. Hog-Outs

Die Castings vs. Hog-Outs

Die casting is an extremely popular manufacturing process for creating metal products. Die cast parts produce high quality, uniform pieces that can be created in just about any size, part geometry, surface texture, or finish. They can require minimal secondary processes since many features can be integrated into the design such as studs, hinges, drill holes, and bosses, to name a few.

What are the advantages of die casting?
• High quality: Die cast parts deliver a long service life.
• High reliability: Exceptional uniformity of mass-produced parts.
• Quick production: Die cast tooling requires minimal maintenance.
• Versatile: Die casting can create virtually any size, part geometry, surface texture, or luster.
• Minimal assembly: Assembly features such as studs, drill holes, and bosses can be integrated into the mold design.

What is a hog-out?
A hog-out is a part that has been fully machined from a bar or blank rather than formed, net shape, by a casting or forging process.

What are the primary advantages of hog-outs versus die castings?
• Flexibility: Changes can be made on a part-by-part basis, as the design is being developed. Design changes can be made, without the need for capex tooling changes.
• Lead time: A hog-out can be produced very quickly, usually measured in days.

What are the primary advantages of die castings versus hog-outs?
• In many cases, once tooling has been built, the die casting can be produced for a cost that is near the material cost for the hog-out alone.
• Features and design details that are very costly to produce in a hog-out can be readily incorporated into the die cast tooling and will carry through to every part made from that tooling.

Why choose die castings over hog-outs?
Die casting allows you to create sharply defined metal parts from a durable range of non-ferrous metals. Die casting enables the production of components with fine details and features without the need for additional processing. Additionally, die castings can be made lighter than can be done economically with hog-outs since the additional machining time for removing extra material in a hog-out can be costly.

Though hog-out parts are perfect for quick prototyping of 1 or 2 components, short production runs, smaller-sized items, or to test the fit of a component in something else; die casting becomes the clear choice once part design has been finalizes and production is anticipated. Hog-out parts also become incredibly expensive as part size increases due to the material needed as well as the machinist’s time machining the component.

Need a hand?
With over 75 years of die casting expertise, our team of experienced engineers will evaluate your requirements to help you decide which would be the best option to achieve the desired result for your part. Our in-depth knowledge and experience allows us to control the entire pre- and post-operative processing, as well as provide turn key part solutions with a variety of options, to meet our customer’s individual needs. Contact A&B Die Casting today to get started on your next project!

UPDATE! A&B Die Casting is open.

UPDATE! A&B Die Casting is open.

UPDATE: As of 03/23/2020 A&B Die Casting is open again for business.

Why are we open again so quickly? Manufacturers Have Been Deemed “Essential” Businesses. The Department of Homeland Security’s Cybersecurity and Infrastructure Security Agency issued new guidance last week deeming many types of manufacturers to be “essential business,” and the NAM is now calling on all states and localities to adopt their new guidelines so that manufacturers and supply chains can maintain their normal work schedules to help respond to the COVID-19 crisis. At the end of last week, the NAM urged governors and mayors to follow the federal guidance so manufacturers can continue to provide lifesaving goods and services. California has been the first state to quickly adopt these updated federal guidelines.

We are committed to employee safety and are taking all necessary precautions to keep our workforce and community safe while they work through this pandemic.

Thank you for your patience and understanding during this difficult time. Please contact us directly with any questions, concerns, or to place an order.

We look forward to continuing to work with you.
-Steve Dathe, President