When designing a product, its potential applications need to be considered. Aluminum die-cast parts can not only serve structural functions but also enhance aesthetics. Therefore, it has become a popular alternative to other materials. 

Due to the fact that modern computers are much more powerful than before, the processing time has increased several times. The pressed parts not only have excellent structural importance but also possess excellent aesthetic functions. 

You should clearly specify the purpose of the part on the die-casting machine. This can help you select the appropriate material and determine the appropriate tolerance for the design parameters based on your requirements. You should also consider the corrosion resistance, strength-to-weight ratio, conductivity, and other properties of the part. 

However, customers often end up paying for quality and strength that far exceed their requirements. Therefore, fully understanding the functional use of the parts will help you better comprehend the die-casting process.

For internal aluminum castings, appearance is not important. But for external castings such as shells or housings, appearance becomes very important. 

End users always have a preference for aesthetically pleasing products. Therefore, regardless of the performance of the components, consumers will give priority to the appearance. Hence, the external die-cast parts should have an attractive appearance. 

Therefore, when designing the parts, consideration should be given to the aesthetic aspect. Plan in advance the surface treatment effect you desire to achieve. Good surface treatment can provide additional protection against extreme weather conditions.

The assembly process of aluminum castings can be relatively simple or very complex, depending on the complexity of the parts. Traditional casting equipment has certain limitations on the types of parts that can be cast. Therefore, it was previously very difficult to cast complex details. 

However, complex parts can be divided into appropriate sections and then connected together through suitable assembly methods after casting. Some common die-casting assembly techniques include: 

• Fastening
• Thread 
• Welding
• Injection-molded metal components 
• Core drilling holes, etc.
  
  

Before starting the design, you must select a specific assembly technique for the die-cast parts. As the assembly method can significantly affect the design, please choose the appropriate assembly option that meets your requirements.

You should conduct a detailed cost budget analysis for the project. Because the budget issue directly affects every aspect of your manufacturing business. Your design must be based on the budget to meet the requirements of the budget. 

Experienced designers can significantly reduce the cost of die casting without compromising the quality of the parts. You should adhere to certain design parameters to avoid over-designing the parts and thus avoid unnecessary costs. 

For instance, adding grooves enables you to design lighter parts without sacrificing performance. It can also reduce material costs. Moreover, reducing or eliminating chamfers and sharp corners can significantly lower the costs and complexity of molds and casting processes.

Product design can vary significantly depending on the choice of materials. Each alloy has certain limitations. To achieve the best integrity and strength of aluminum die castings, careful design and execution are required. 

Depending on the composition of the alloy elements used in aluminum, its weight, fluidity, strength, conductivity, melting point and other properties may vary. However, not all alloy elements are suitable for casting materials. 

Some popular aluminum alloys that can be used for die-casting include:

• A380
• A383 (ADC12)
• A413
  
  

There are many other types of aluminum alloys available. You must choose the appropriate one based on your specific needs and budget constraints.

The draft angle is one of the important design parameters in aluminum die casting. It refers to the degree of taper or inclination between the core and the surface of the part and the parting line of the mold. We also call it the draft angle. 

The designer must provide sufficient ejection angles when necessary. Because without adequate ejection angles, the castings will be difficult to remove after solidification, and there is still a possibility of damaging the parts or even the mold itself.

When calculating the parting angle requirements, please take the following factors into account: 

• Generally, a common chamfer angle is adopted for most geometric features. 
• There are some exceptions for the interior walls and surfaces. In such cases, the ventilation volume is usually twice that of the exterior walls. 
• The draft angle requirements may vary depending on the alloy used for casting. You may need to calculate the draft angle based on the type of aluminum alloy you have chosen. 
  
  

The following will illustrate the standard tolerances for the internal surface draft angles of aluminum castings of different depths.

The standard tolerances for any alloy can be calculated using the following equation.

If you want to achieve a smaller draft angle, you can use precise tolerances. However, this requires more precise processing and incurs higher costs. Therefore, it is recommended to avoid using precise tolerances unless it is absolutely necessary. 

The accuracy tolerances for the internal surface draft of aluminum castings of different depths are as follows.

This is the formula for calculating the tolerance of part accuracy.

Please note that the draft diagram above has been exaggerated for better understanding of the concept. In fact, the draft diagram is very small and, if not observed carefully, it is usually impossible to notice at all.

The coordinated design of the moving mold and the fixed mold is of vital importance. Even if one of them is inconsistent, it will hinder the aluminum die-casting process. The design of the moving mold is usually more challenging. The structure of the fixed mold is relatively simple, but the moving mold needs to handle more components. When the material is injected into the mold, due to the pressure of the excessive material, the core may slip out, resulting in oversized dimensions.

The tolerances of the moving mold components depend on the linear tolerance and the projection area tolerance. Among them, the linear tolerance refers to the length of the mold core slider, while the projection area refers to the head of the mold core slider facing the molten material. 

The movement can be carried out along a linear direction perpendicular to the projection area. Therefore, it is best to keep the tolerance for moving the mold components at the minimum value of zero degrees. 

Due to the structure of the die-casting equipment, only relatively large or positive tolerances can be allowed during the production process. Based on certain projected area variables, the standard tolerances and precision tolerances are as follows. NADCA guideline.

The parting line is the position where the two halves of the mold come together to form the complete structure of the product. Due to the die-casting process, the formation of the parting line is inevitable. Because the design always includes at least two components.

The parting line clearly indicates the distinction between the moving die and the fixed die of the mold. The parting line tolerance refers to the maximum amount of mold separation that is allowed to ensure the proper execution of the aluminum die-casting process. 

When the material pressure tries to force the two halves of the mold to separate, the material will flow out from the separation point along the parting line. This is the flash defect in die casting. The casting requires additional finishing processes to remove the flash, risers, gates and overflow ports.The parting line tolerance is a function of the mold's projected area, which represents the separation surface where the molten material moves from one half-mold to the other.

The completely closed molds have no gaps between each other, so the tolerance of the projected area is always positive. The degree of mold separation depends on the mold shell pressure and the clamping force applied to keep the two halves of the mold closed.

The parting line tolerance will vary depending on the alloy, size and depth of the part. The recommended standard tolerance values and precision tolerance values for the die-casting parting line are as follows.

However, if the projected area of the die-cast part exceeds 300 square inches, please consult the die-casting factory (1935.5 cm²).

The machining allowance refers to the amount of raw material that can be removed from the finished aluminum die-cast part. The castings may have surface roughness and geometric shapes that deviate slightly from the actual design. Therefore, after die-casting, secondary processing is required to correct these errors.

The key point is that the best mechanical properties and density of the castings are located at the surface or near the surface. Therefore, the machining allowance should be carefully determined to avoid penetrating the less dense parts.

However, during the design stage, a certain amount of machining allowance must be specified for the machining and casting variables. If the machining allowance is too small, it may fail to meet the surface quality requirements, and there is a risk of leaving defects in the parts.

On the other hand, excessive machining allowance for the parts will increase production time, labor costs and overall expenses. Consulting with the die-casting supplier in advance will help you determine the appropriate machining allowance.

Generally, the minimum machining allowance should be 0.010 inches (0.25 millimeters) to reduce tool wear and minimize the porosity of the castings. The maximum machining allowance is the sum of the minimum machining allowance and the deformation of the castings.

The following is an example of the comparison of machining allowances at two different reference point positions.

However, some additional consideration is needed for flat and large parts. You can consult with your caster to assure the machining allowance values in this case.

Always try to keep the wall thickness of the entire component uniform. Uniform thickness is beneficial for the better flow and solidification of the metal. Therefore, the quality and integrity of the casting will be better. 

However, if you must provide variable wall thicknesses in your design, you should introduce a gradual transition in the form of rounded corners/radii instead of abruptly changing the thickness. Otherwise, sharp edges will remain in your design. 

In product design, there should be no sharp edges. This is because it will affect the flow of the metal and make it difficult to remove the mold after casting. However, if the walls meet at the parting line, these edges can be retained.

Although there is no absolute standard for wall thickness or thinness, it is best to keep it within a certain limit. The typical wall thickness range for aluminum die castings is 0.0787 inches (2.0 millimeters) to 0.1378 inches (3.5 millimeters). This also depends on the size and structure of the part. 

However, this may vary depending on the alloy of the casting, the configuration of the part, the size of the part, and the application. For instance, if the part size is small, it is possible to cast a wall section as thin as 0.020 inches (0.50 millimeters).

However, there may be exceptions to the maximum and minimum wall thickness for both small and large aluminum castings. If you encounter any issues, you can consult your casting factory.

Increasing the wall thickness will enhance the rigidity of the part. However, an excessively thick wall will delay the cooling process, thereby hindering the solidification process. Therefore, unless appropriate measures are taken, it will result in poor quality of the casting.

Thick walls will also increase the weight of the product. Therefore, product designers who focus on reducing the weight of components tend to prefer using thin walls. However, if the wall thickness exceeds a certain limit, the stiffness will be too low, and it is prone to warping during further processing.

The warping problem can be solved through gradual processing. However, the thin walls of the castings lack rigidity and strength. Installing reinforcing ribs can significantly enhance the rigidity of the thin walls, making them more stable.

However, modern die-casting technology is already advanced enough to handle most of the key design parameters. But these technologies should only be considered if they can ensure better performance or economic benefits for the parts.

Metal retainers and grooves are two common design features of lightweight component design. They can significantly reduce the amount of material required for manufacturing the components, while not affecting their integrity and strength.

Metal space-saving refers to the hollow spaces typically found within reinforcing ribs, which are used to reduce material usage and thereby decrease the weight of the component. The sections between the reinforcing ribs are of little use and can therefore be safely removed from the design.

When designing the metal protectors for the parts, the following points should be kept in mind.

• Avoid sharp edges on the metal protectors. Use rounded corners/radii with as large a radius as possible. The minimum radius should be 0.06 inch (1.524mm).
• Maintain uniform wall thickness around the metal protector. Try to make the thickness close to the usual recommended value.
• Provide an as large an undercut angle as possible.
  
  

The bag-like structure is another weight reduction technique. The thin-walled part can be used to replace the thicker part with holes, thereby reducing the amount of material required for production. However, the bag-like structure sometimes causes irregular shrinkage.

Therefore, you should carefully decide where to use the cavities. You can also use reinforcing ribs to enhance the structure of the cavities. This will increase the stiffness of the cavities and improve the metal flow. Reducing the amount of metal used can also increase the cooling speed, thereby shortening the production cycle.

• When two intersecting surfaces have sharp corners, using rounded corners or radii to connect them can prevent high stress concentration in that part of the mold or the component.
• Fillet/Radii: For any edges or corners along the parting line of the mold, no fillet/radii are required.
• Provide sufficient draft angle for the fillets that are perpendicular to the parting line.
  
  

You can design the fillet/radii in the parts according to the following guidelines.

Designers should follow the following design considerations to reduce the shrinkage of aluminum castings.

• In the design, excessive or thick sections should be avoided. If possible, the design should be revised to use thinner sections and core materials that save metal.
• Adding flat or vertical ribs to the wall can improve the feeding characteristics and reduce the tendency of shrinkage.
• Adding compression pins can reduce shrinkage in specific areas.

The following are some design considerations that should be taken into account when designing the bosses in the parts. 

• If a hole is required, try adding a hole at the center of the raised platform to achieve uniform wall thickness. 
• Provide larger rounded corners for the protrusions to allow the molten metal to flow in appropriately. 
• It is recommended to add ribs, as they can help ensure a good filling of the protrusion and also provide additional strength to the protrusion. 
• Provide sufficient ventilation for the protrusion so that the castings can be ejected more easily. 
  
  

This is a short video that explains the application and design process of the raised platform in die casting.

Designers should attempt to align these geometric features parallel to the mold ejection direction, or redesign the part to eliminate the need for the core/slide. The following example shows how to redesign the part to eliminate the requirement for side cores.
However, in some cases, you must introduce cores/slides to cast the features without the need for subsequent processing. You can design core slides or pull rods to eliminate the need for most (if not all) of the secondary processing operations. 

Therefore, the difficulties caused by the increased initial mold cost and the prolonged casting cycle can be mitigated by reducing the number of secondary processing steps. As a result, the repeatability of the parts has been significantly improved.

The side core-pulling mechanism and slider movement are usually driven by inclined pins or hydraulic cylinders. The inclined pins are mechanical devices used for the core-pulling/slider movement. The opening and closing sequence of the main mold can activate the inclined pins. 

Therefore, the inclined pins can be used without an additional power source. The production cost is also lower. However, the inclined pins may interfere with the disassembly of the castings, and they are only suitable for shorter slides. 

The top slider also has difficulty using pin joints and can only use springs. Using a hydraulic method can solve these problems. You can define a cycle and use the top slider. It will not interfere with the recycling of the castings. 

There are other motion methods that can be used for the core/ram. The designer must choose the appropriate motion method based on factors such as budget, production volume, part size, and the travel length of the core/ram in the casting. 

You can discuss with your die-casting factory to obtain appropriate suggestions regarding the design of the side core-pulling/slide mechanism. We also welcome your inquiries and will do our best to assist you.

The threads can be easily formed by an aluminum die-casting machine. The cast threads are usually limited to external threads that do not require precise level of fit.

If you need a specific precision grade for your part, you can always consult your die-casting factory. Secondary processing To achieve better precision, adjustments may be necessary. Additionally, the major diameter should follow the specified thread profile definition agreed upon by both parties.

The maximum and minimum tolerances for some ideal thread forming operations are as follows:

However, when creating threads, please keep the following points in mind.

• Additional trimming operations may be necessary to remove any burrs formed between the threads.
• Try to apply direct tolerances as much as possible instead of specifying the thread fit grade.
• These values include the tolerance limits for the moving mold components, parting lines and linear dimensions.
• When more stringent thread tolerances are required, please consult the die-casting factory.
• Keeping the threads at the parting line smooth can significantly simplify the manufacturing process. Since full-diameter threads are not necessary. Keeping the threads smooth allows the mold to move slightly without affecting the part.

The following chart shows the recommended external thread configuration.

• Clearly define all the specifications required by the die casting factory. Due to the large gap in the mold, the inserts usually require stricter tolerances. Please obtain the approval of the die casting factory to ensure that the tolerances of the inserts are sufficient. 
• If the customer wishes to provide the blades, please negotiate with the casting factory to ensure that the tolerances are in line with the suggestions of the casting factory. Because blades with inappropriate tolerances may seriously damage the mold. 
• Analyze the stress caused by the inserts. Ensure that these stresses do not have a long-term impact on the performance of the product. 
• The insert can be shaped in any way as needed to ensure that it provides sufficient anchoring force for the expected load conditions. 
• Avoid sharp corners and other features that may cause stress concentration in the parts.

The function of the push rod is to push the solidified casting out of the mold. Another function of the push rod is to clamp the casting to prevent it from bending due to the concentrated stress during the solidification process. However, the disadvantage of the push rod is that it will leave marks on the casting.

Therefore, designers should carefully select the position and size of the push rod based on the size, structure and other factors of the casting. When designing the push rod, the following guidelines should be followed.

• Place the ejector pin in the non-functional area of the casting, such as the bottom of a deep cavity, the overflow port, the protrusion, or the bottom of the rib.
• When removing the castings, the push rod will leave marks. Therefore, please do not position the outer surface of the castings towards the push rod.
• The recommended tolerance for the protruding or recessed pin marking is 0.015" (0.381 mm).
• Please follow the advice of the die-casting workers, as they can assist you in selecting the more appropriate size, position and quantity of the clamping pins.
  
  

The correct mold manufacturing method can significantly reduce the marks left by the push rod. However, these marks are still clearly visible. The original equipment manufacturer and the die-casting manufacturer should agree on the installation position of the push rod.

Also, please note that fringes will form around the top pin. Usually, unless the customer objects, fringes will not occur. The fringes of the top pin can be flattened to minimize their impact.

The ejector plate can serve as a supplementary component for the ejector pin, or it can be used independently. Usually, the casting factory uses the ejector plate as the installation surface for the ejector pin. Since the pressure is only applied to the ejector plate, the ejector pin will simultaneously push the ejector pin forward and retract the casting. 

The ejector plate can also operate independently without the need for an ejector pin. However, we usually only see it in micro-molding. The force applied by the ejector plate to the part is used to eject it. The advantage of this is that the ejector plate does not leave any marks on the casting like the ejector pin does.

• The surface (line thickness) of any letter or symbol should be at least 0.010 inch (0.254 mm) or larger.
• The height of the lines or symbols should be equal to or less than the thickness of the lines.
• If any text or decoration contains complex details or fine lettering, it may not be clear during the casting process. Therefore, please try to simplify them as much as possible.
• The draft angle should not be less than 10°.
  
  

Following these guidelines should be helpful for most situations. If you have any other requirements, you can always consult your casting factory for appropriate advice.