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FREQUENTLY ASKED QUESTIONS

Die Castings FAQ

"Die casting is the process of forcing molten metal under high pressure into mold cavities (which are machined into dies). Most die castings are made from non-ferrous metals." (source: Wikipedia). It's known as "pressure die casting" in Europe.

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"Gravity casting" (a.k.a. "permanent mold casting" in USA and Canada) uses gravity to fill the mold.

Here are some basic design guidelines for die casting parts:

1. Even wall thickness.
2. Roudning of all edges and corners.
3. Smooth blending and continuity of all the features.

We will provide additional design modifcation suggestions to make sure your parts are casted successfully.

Yes, we can put PEM studs, nuts, Southco fasteners, or hardware like McMaster-Carr components or inserts to the casted parts.

You can start by providing the part's 2D and 3D drawings to us. We can provide Design For Manufacture (DFM) service for you—plese see our Design for Manufacture Tips for Die Cast Parts article.

Please provide us with the part's 3D CAD drawings (such as IGES, STEP, or X_T). We can also quote based on 2D drawings (in DWG, DXF, or even PDF format [but with weight information]). We can also import CAD files directly from popular CAD software, such as Pro/ENGINEER, UGS, Catia, and Solid Edge. In addition, we need the production information listed in our request for quote form. Quoting turnaorund is typically within a week, and can be even sooner if there is special timing constraint.

Magnesium has a density of 1.74 g/cm³, and is the lightest structural metal in common use. Aluminium has a density of about 2.71 g/cm³, and is the most widely used alloy for castings worldwide. Zinc offers a wide range of excellent physical and mechanical properties, and can be used to achieve thinner sections in the parts. Please see the page on material properties .

You can specify your color by using RAL or Pantone color codes. If you don’t have the color code, you can send us a color chip or a color sample for us to come up with a matching color chip.

Due to our specialty in short run orders, we are very flexible in order quantities. Our quotes always break down pricing by MOQ's: e.g., there might be a price premium if orders are below 3,000 pcs., and another one if orders are below 1,500 pcs. (these numbers vary and are just for examples).

Magnesium is: among 1) the lightest of all metals (63% of aluminum, 38% of titanium); 2) stronger than engineering plastics; 3) 100 times better in heat dissipation than plastics; 4) electromagnetic-shielding; 5) best in vibration absorption of all metals; 6) environmentally safe (non-hazardous and recyclable); 7) easy to machine; 8) abundant in supply (sixth most abundant on earth).

We support NADCA standard tolerance for die castings.

Die casting process produces smoother surface than other casting processes:

• the surface roughness value of die cast part is 0.5 Ra, whereas
• the surface roughness value of machined parts is 0.43 Ra.

Note that the general buffing sander has a roughness value of 1.6 Ra, therefore general sanding does not provide smoother surface than die casting itself already produces.

Magnesium alloys are the lightest of the three: magnesium alloy will be 2/3 the weight of aluminum alloy, and 1/4 the weight of iron.

The following methods can improve the shrinkage issue on the front side:

1. Face milling
2. Rough polishing
3. Sandblasting or vibration polishing
4. Sandblasting with paint

Yes, aluminum and magnesium alloy die-casting can share the same mold, but, no, aluminum and zinc alloy die-casting cannot share the same mold.

Aluminum (ADC12) density: 2.70 g/cm3; Magnesium (AZ91D) density: 1.74 g/cm3; Zinc (Zamak #3) density: 6.7 g/cm3

Rib height: 4mm, width: 2.5mm. Draft angle: 5° on one side, with a root chamfer of R1 to R2.

Height of the heat dissipation fins: 15mm, width at the small end: 2.5mm. Draft angle: 3°, with a root chamfer of R1 to R3.

The small end of the rib is 3mm with a draft angle of 1.5°, the large end is approximately 7mm or more, and the thickness design is 4 to 5mm for optimal average thickness.

In general, die-cast parts contain silicon, and after anodizing, they will appear in an uneven grayish black color. If anodizing is required, we recommend to use A356 alloy and sandblast before anodizing to achieve a more uniform surface. For surface treatment of die-cast parts in general, we recommend to primarily use powder coating ("baked paint"). Die-cast parts can be transparent-anodized, and will retain their original color afterwards.

No, magnesium die-casting cannot be anodized.

Corner designs with small molds are prone to cracking, so we recommend to add a fillet radius (R). For irregular weight reduction, one can fill in the surrounding shapes, modify the spacing, and connect with ribs.

For die-cast parts with a thickness of less than 1.5 mm, ribs can be added on non-visible surfaces of the product to help support and prevent deformation. These ribs can be retained or removed through post-processing (milling).

The minimum thickness for aluminum alloy die cast parts is 1.5 mm; for magnesium alloy die cast parts, the best production thickness is between 1.0 to 2.0 mm; and for zinc alloy die cast parts, the minimum thickness is 1.2 mm.

Depending on the tolerance requirements, precision waterproofing is recommended to undergo CNC post-processing. For general purpose dust-proofing, it can be die cast directly.

Aluminum and magnesium alloy die-casting molds are guaranteed for 80,000 cycles; zinc alloy molds are guaranteed for 200,000 cycles; plastic injection molds are about 300,000 to 500,000 cycles. Stamping molds are approximately 100,000 cycles (the samping molds themselves do not break; it's the stamping pins that wear out or break, and they can be removed for grinding repair or replaced).

The available shipping methods are: Land Freight, Mail, Express delivery, Sea freight, and Air freight.

Depending on the budget, common packaging options are: plastic bag, bubble wrap, non-woven fabric, bubble cloth, foam, polyethylene, honeycomb paper, packing peanuts (foam chips), EPE (expanded polyethylene foam), and custom cardboard/inner/honeycomb/wooden box.

CNC machining is needed when flatness requirement is less than 0.25mm.

The available surface treatment process for die casting are:

• Grinding
• Deburring
• Sandblasting
• Vibrating (or Vibration finishing)
• Cleaning
• Ultrasonic
• Liquid baking paint
• Powder baking paint
• Anodizing
• Hard anodizing
• Electrophoretic deposition
• Electroplating
• Brushing
• Passivation and electro-polishing
• Micro-arc oxidation
• Coating
• Non-chromate treatment
• Printing

Yes, we routinely sign mutually-agreed-upon NDAs with prospective customers since !

Typically multi-cavity tooling can be appropriate for parts that are relatively small and simple in shape, and will be produced in large quantities.

Yes, magnesium alloy be used to make fully machined CNC prototypes.

We recommend to reduce the threading depth by 0.5 to 1 mm to avoid protrusions from machining holes on the back side. If the threading depth cannot be reduced due to product requirements, it will be necessary to use a flat-bottom milling cutter to process the hole and then use a thread milling cutter to cut the threads, adding to the cost of production.

The edges should be chamfered by 0.2 to 0.5 C to avoid sharp edges.

We can design the mold to modify the 3D undercuts. Alternatively, we can use a T-shaped cutter for post-processing machining.

Yuhui are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

A sloped design at one direction of the column should be at 2/3 of its height for easy casting material entry and filling. The other three directions need ribs for support, with the rib height at about 1/2 of the column height. If the column requires threaded holes, micro-forming techniques should be used to prevent sand hole formations.

One common miss in design drawings is not specifying key dimensions or tolerances for the assembly areas prior to the tooling being made. These key dimensions or tolerances are added only after customers assemble with the first samples, resulting in issues during subsequent volume production.

During volume production, we can overcome the above miss by (in order of priority/preference, and in collaboration with the customers):

• relaxing tolerances where possible to align with actual production needs, or
• modifying the mold (without adding inserts), or
• adding inserts if absolutely needed, which will shorten the mold's lifespan.

The tolerances for investment casting are inherently slightly larger than those for die casting, and with a greater shrinkage rate. If there are tolerance requirements for hole spacing, it is recommended to modify with machining.

The baking temperature for coating is 60 to 80 degrees C.

Use an air gun to blow over before baking. Additionally, individually blow through the threaded holes with an air gun to avoid these issues.

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Die casting is a metal casting process, which characteristic is to apply high pressure to molten metal by using a mold cavity. And molds are usually machined from stronger alloys. The process is similar to injection molding. To let people have a comprehensive understanding of die casting, JTR company has organized and summarized what die casting is? What is the process of die casting? What are the materials of die casting? And other questions, I hope you can have a full understanding of “die casting“.

Definition of “Die Casting”

Die casting is an accuracy casting technique that makes use of high stress to require molten metal into a metal mold and mildew with intricate shapes. Spreadings made by die-casting are called die castings.

Most die castings are iron-free, such as zinc, copper, aluminum, magnesium, lead, tin, and lead-tin alloys and also their alloys. Relying on the sort of die casting, a cool chamber die casting device or a warm chamber die casting device is required.

The tensile strength of these materials is nearly double that of ordinary cast alloys, which has more positive significance for aluminum alloy automobile wheels, frames, and other parts that are expected to be produced with higher strength and impact-resistant materials.

Die Casting Process

The typical die casting process mainly consists of 4 steps, or high pressure die casting. These four steps, including mold prep work, material filling, injection, and shakeout, are also the basis for various customized die casting processes.

Lubricant is sprayed into the mold cavity throughout the preparation procedure. Along with helping to manage the temperature level of the mold, the lube can likewise assist the casting release. The mold can then be shut, and also the molten metal infused into the mold at high pressure, which varies from concerning 10 to 175 MPa.

After the molten metal is filled up, the pressure is maintained till the casting solidifies. The press pole after that pushes out all the castings, and also, because there may be several cavities in a mold,  there may be multiple castings per casting.

The falling sand’s process needs the separation of residues, including mold openings, runners, gates, and flash. The process is usually done by squeezing the casting through a special trim die. Other ways of falling sand include sawing and sanding. If the gate is fragile, you can beat the casting directly, which can save human resources. Excess casting die can be reused after melting.

High-pressure injection results in very fast filling of the mold so that the entire mold can be filled with molten metal before any part solidifies. In this way, even thin-walled parts that are difficult to fill can be filled sufficiently, and surface discontinuities of the die-cast part can be avoided.

However, this additionally causes air entrapment, as it is hard for air to run away when filling the mold quickly. Placing vents on the parting line can lower this trouble, but really exact processes can also leave porosity in the casting center. After most parts are die-cast, they can be processed by Surface Finishing Service to complete some structures that cannot be completed by casting, such as drilling and polishing.

Defects can be inspected after the shakeout is complete. The most common defects include stagnation (insufficient filling of the solution). These flaws can be brought on by inadequate mold or molten metal temperature level, metal contamination, as well few vents, excessive lubricant, etc. Other problems consist of porosity, shrinking, thermal splitting, and also flow marks. Flow marks are marks left on the casting surface by gate defects, sharp corners, or excess lubricating substance.

Metal for Die Casting

Metals made use of in die casting mostly include zinc, copper, aluminum, magnesium, lead, tin, and lead-tin alloys, although die casting is rare but viable. A lot more unique die-casting steels consist of ZAMAK, aluminum-zinc alloys, as well as American Aluminum Association standards: AA380, AA384, AA386, AA390, as well as AZ91D magnesium. The characteristics of die casting of numerous metals are as complies with:

Zinc: The easiest metal to die-cast, cost-effective to make small components, easy to coat, high compressive strength, plasticity, and durable life.

Aluminum: Lightweight, high dimensional stability while making complex and thin-walled castings, strong corrosion resistance, good mechanical properties, high thermal and electrical conductivity, and high strength at high temperatures

Magnesium: Easy to machine, high strength-to-weight ratio, lightest among commonly used die-cast metals

Copper: High hardness, strong corrosion resistance, the best mechanical properties of commonly used die-casting metals, wear resistance, and strength near to steel.

Lead and Tin: High density and extremely high dimensional precision can be used as special corrosion protection components. For public health reasons, this alloy cannot be used in food processing and storage equipment. Alloys of lead, tin, and antimony (sometimes with a little copper) can make hand lettering in letterpress printing and bronzing.

The upper mass limits for die casting with aluminum, copper, magnesium, and zinc are 70 lbs (32 kg), 10 lbs (4.5 kg), 44 lbs (20 kg), and 75 lbs (34 kg), respectively.

Advantages and Disadvantages of Die Casting

Advantages of die casting

The advantages of die casting include that castings can have excellent dimensional accuracy.

Usually, this depends on the casting material. Compared to other casting processes, die casting produces parts with smooth surfaces and a fillet radius of approximately 1-2.5 microns. Die casting can produce parts with wall thicknesses of about 0.75 mm, compared to a flask or permanent mold castings. It can directly cast parts of internal structures, such as wire jackets, heating elements, high-strength bearing surfaces. Other benefits include reducing or avoiding secondary machining of parts, the production speed of castings, the tensile strength of castings (strength up to 415 MPa), and the ability to cast high-flow metals.

Disadvantages of die casting

The biggest disadvantage of die casting is its high cost. The price of die casting equipment (die-casting machines) and molds and mold-related components is relatively high compared to other casting methods. Therefore, die-casting manufacturing has high economic value only when mass-producing parts.

Other disadvantages include: the die casting process is only suitable for relatively fluid metals, and the casting mass must be between 30 grams and 10 kilograms. There will always be voids in the last batch of castings in normal die casting. Therefore, no heat treatment or welding can be performed because the gas in the gap will expand under the action of heat, causing internal micro-defects and peeling of the surface.

Hot Chamber Die Casting and Cold Chamber Die Casting

There are two different ways of making parts in die casting: hot chamber die casting and cold chamber die casting. In both manufacturing processes, the molds are sprayed with a release agent prior to the casting process to ensure that subsequently cast parts can be easily removed from the molds. However, the melt is not poured directly into the mold cavity but first poured into the casting cavity of the die casting machine. From there, the alloy is pressed into the mold by a piston (a so-called casting group) through one or more channels. The difference between the two processes is the structure of the casting chamber, as described below.

Hot Chamber Die Casting

In hot-chamber die-casting, its metal pool is a molten state of liquid, semi-liquid metal that fills the mold under pressure. The advantages of this system include high cycle speed (approximately 15 cycles per minute), ease of automation, and ease of melting the metal. Disadvantages include the inability to die-cast metals with higher melting points and the inability to die-cast aluminum, which would carry iron out of the molten pool. Thus, hot chamber die casting machines are generally used for alloys of zinc, tin, and lead. Moreover, hot chamber dies casting is difficult to use for die casting large castings, which are usually die casting of small castings.

Cold Chamber Die Casting

Cold chamber die casting can be used when die casting metals that cannot be used in the hot chamber die casting process, including aluminum, magnesium, copper, and zinc alloys with higher aluminum content. The metal needs to be melted first in a separate crucible in this process. A quantity of molten metal is then transferred to an unheated injection chamber or nozzle. These metals are injected into the mold by hydraulic or mechanical pressure. 

The biggest disadvantage of this process is the long cycle time due to the need to transfer the molten metal into the cold chamber. Cold chamber die-casting machines are also divided into vertical and horizontal types. Vertical die-casting machines are usually small machines, while horizontal die-casting machines have various models.

Application Areas of Die Casting

Die casting is mainly used for mass production, i.e., for casting many parts of the same type. High casting quality is achieved despite the high pressure used in the manufacturing process. The die casting process is particularly suitable for producing very thin (up to 1 mm) (lightweight) parts.

Most commonly, die-cast components such as wheels, cylinder blocks, cylinder heads, valve bodies, and manifolds are manufactured for the automotive industry. In addition, other industries use die castings:

• Aerospace
• Household appliances
• Furniture
• Electrical tools
• Electronic products
• Mechanical
• Lighting technology

In the future, foundries will be interested in other industries such as electric vehicles. This offers great potential for light metal castings.

Choose a Trusted Die Casting Company

Die casting has been widely used in manufacturing since the 19th century. As a top die casting service provider in China, JTR has been providing customers with complete die casting solutions for many years. High-quality die casting service is the key to our profitability. So if you need to implement your design, you can contact us. You just need to complete the design or creativity, and we will do the rest.

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