In this article, we go over key considerations of die casting design optimization. Learn how carefully you can follow them, adding the right draft angles, wall thicknesses, and placing cooling channels.

Die Casting Process in 4 Steps

1. Melting and Alloying

The first step in die casting is to melt the metals. Manufacturers melt aluminum at 660°C or zinc at 420°C.

They keep the metal at a temperature (between 50 and 100 °C ) that is just above the melting point to prevent overheating.

Additionally, they add other alloying elements to increase the part strength. Such as magnesium (1–4%) or copper (0.5–3%).

2. Injection

The manufacturers pour molten metal pallets into the mold. They apply high pressure, typically between 10,000 and 20,000 psi (pounds per square inch).

However, the injection speed can fluctuate around 1 to 10 meters per second. It also depends on the level of detail and size of the mold.

Focusing on these parameters allows you to fill the mold. Because proper flow eliminates defects like air bubbles.

3. Solidification and Cooling:

After filling the die with molten metal, manufacturers leave them to cool down and solidify. Particularly, they set cooling rates according to material and mold design. That usually ranges from 50°C to 150°C per second.

However, applying faster cooling can reduce grain size and increase strength in part. At the same time, excessive cooling can reduce ductility. This is why temperature control is important and should be between 150°C and 250°C. So that you get uniform cooling and prevent warping or cracks.

4. 배출

Once the part solidifies, the manufacturers eject it from the mold. They use ejector pins that forcefully push out the molded part without causing any damage. This force usually ranges between 500 and 5,000 kg in accordance with part size.

Additionally, manufacturers carefully control this force to avoid deformation or surface damage. They also monitor die temperature during ejection. So that the part does not cross the maintained heat (above ~100°C for most metals) and avoids sticking or bending.

Die Casting Design Optimization Rules

Material Selection and Properties:

You can use different alloys for die-casting techniques. Each metal has particular properties like strength, melting point, and structural bond. That makes it necessary to match them with project needs.

Here, we have mentioned the most common metals in die casting and their comparisons in a table.

Geometric Design Rules:

1. Wall Thickness Variations:

Manufacturers add uniform wall thickness in designs to prevent defects. For example,  warping and uneven cooling. They use a thickness of 2–4 mm for most aluminum parts, while for zinc, 1–3 mm is optimal.

It is important to avoid sudden changes in thickness. Use gradual taper or fillet with a radius of 1–3 mm for transitions to decrease stress concentrations.

2. Ribbing and Stiffening

You can improve heat dissipation and strength in part via ribs and reduce the need for thicker walls. Keep their thickness around 0.6 times the adjacent wall thickness. This step will ensure sufficient strength while avoiding sink marks.

Additionally, do not exceed rib height of 2.5 times the wall thickness. This will help you maintain a solid foundation and avoid distortion. Furthermore, add proper space (at least 2–3 times the rib thickness) for the rib. This space lets the metal flow smoothly and makes cooling effective.

3. Undercuts and Draft Angles

Because undercuts can make the ejection process complicated so minimize them whenever possible. If this is not avoidable, then you can use slides or lifters.

Similarly, right draft angles smooth ejection operations and protect parts from damage. You can add 1–3° Draft angles for internal surfaces and 2–5° for external surfaces.

Stress Analysis of Die Casting Parts

1. Finite Element Analysis (FEA)

Manufacturers use various tools to predict stress, deformation, and defective areas in parts, whereby finite element analysis (FEA) works well. These tools are powerful and help locate errors in real-time before production.

First divide the parts into small sections, then begin analyzing deeply. Find how forces, pressure and temperature can affect the part. It is better to keep enough mesh size in FEA with element size as much as 1 to 5 mm. This is also based on part complexity.

FEA tools aid in getting accurate designs that can handle injection pressure and thermal stress during cooling.

2. Fatigue and Fracture Analysis

Manufacturers pass the molded parts through several fatigue and fracture tests. So that they make sure the parts last long and can handle repeated loads or external stresses.

Additionally, this part should contain a design that can combat cyclic loads. Depending on its application, it must withstand at least 1 million cycles without failure.

Among several alloys, aluminum (90–100 MPa) or zinc (55–70 MPa) with higher fatigue strength are most commonly used. If you control stress concentrators in design, this will further enable better fatigue resistance. Also, you can include fillets (1–3 mm radius) at sharp edges.

Thermal Management and Cooling Systems

1. Cooling Channel Design

Placing cooling channels near the die surface, typically within 10-15 mm. By doing this, you can reduce cooling time and maximize heat transfer. These optimizations ensure uniform heat dissipation and avoid the risk of warping or shrinkage during casting.

Furthermore, you can set the diameter of cooling channels around 8–12 mm. This measurement creates consistency in cooling flow without causing pressure drops. Also, try to maintain the flow rate of cooling fluid (oil or water) at 4–8 liters per minute. So you can get effective cooling and avoid hotspots.

2. Temperature Control

Add accurate temperature controls in designs. Because right temperatures also aid in producing consistent cooling and decrease thermal stress in parts. Also include sensors within the die. For instance, thermocouples.

These sensors help the manufacturers monitor temperature. That should be around 150°C to 250°C for aluminum and 100°C to 200°C for zinc alloys.

Uniform die temperature provides even cooling and avoids cracks or distortion. Additionally, incorporating automated cooling systems regulates the flow. They allow you to produce high-quality cast parts.

Importance of Simulation and Analysis Tools

1. Computational Fluid Dynamics (CFD)

Designers use computational fluid dynamics (CFD) to check how well the design works. This tool helps them in analyzing metal flows within the die cavity. They can also find defective areas like air entrapment, uneven filling or turbulence.

Further, they analyze flow velocity, which should be between 30 and 50 m/s. That improve mold filling and reduce defects.

They also study cooling patterns to focus on regions of heat transfer. This rate must be around 50 °C/s to avoid incomplete filling or shrinkage.

CFD further caters to refining gate systems and runner designs. They ensure optimal metal flow and minimize the risk of voids.

2. Design of Experiments (DOE)

Design of Experiments (DOE) are the tools that can systemically check the design performance and parameters. They help in finding the best solutions with minimal prototypes.

The key parameters of each design are different. For instance, cooling rates, injection force, or die temperatures. The study via DOe shows how they affect part quality.

Furthermore, using DOE, manufacturers can adjust wall thickness, rib dimensions, and draft angles. This tool helps minimize the need for expensive trial-and-error approaches.

Design Tips for Die Casting

Parting Line and Parting Surface Design

Proper parting lines prevent damage during part removal. It is recommended to place the parting line 5–10 mm away from fragile or critical features like ribs or deep cavities.

Also, you can use position parting line in flat low-stress arise. For example, the middle or bottom of the part.  This will smooth part removal using minimal force (500–5,000 kg).

A minimal addition of a parting line can make your design less complex and improve manufacturing efficiency.

Draft Angle and Taper Design

Guidelines for Different Materials:

Die casting Manufacturers set draft angles in design according to the material being cast. These are varieties and depend on project requirements. For example, for aluminum, they add 1 to 3 degrees, and for zinc, a slightly smaller range (0.5° to 1°) is good.

Impact on Ejection Forces:

Draft-angle mechanisms can affect design capabilities. Adding a right or moderate angle, such as 2°, reduces friction, ejection force, and risk of damage. They make it easy to remove parts, preventing surface defects or distortion.

Fillet and Radius Design

1.   Stress Concentration

Avoid adding sharp corners in designs. They can create stress concentrations. That causes cracks or failure. Instead of this, use rounded edges or fillets. These corners allow better-molten flow and distribute stress evenly. As a result, you get durable parts, reducing the likelihood of breakage.

2.   Recommended Radii

Manufacturers add a radius that is proportional to the part size. They usually add a minimum radius (0.5 mm) in small parts to make smooth transitions and better mechanical strength.

For the more significant part, radii of 1–3 mm work well. It decreases stress points effectively.

Rib and Boss Design

Optimizing Rib Dimensions:

Optimize rip dimensions in thin, and it must keep 50% thickness of the wall thickness. Proper spacing is also necessary; it should be 2–3 times the rib thickness. This process smooths metal flow and reduces cooling time.

Preventing Cracking:

The manufacturers ensure the rib base contains a smooth transition with a minimum radius of 0.5 mm. This helps in distributing stress more evenly. They avoid sharp transitions to reduce cracks under load.

Hole and Pocket Design

1.   Ejection Considerations

You can avoid sticking by providing enough clearance (typically 0.1–0.3 mm) for core pulls and ejector pins.

2.   Preventing Sink Marks

Manufacturers keep hole depth uniform and not exceed 2–3 times the wall thickness. They also reduce excessive thickness variations to minimize surface defects. Also, there must be 5 mm-distance among each hole to prevent sink marks.

Venting and Overflow Design

Purpose of Venting:

Vents help in escaping trapped air (around 2-5% of the cavity volume) during casting. They prevent air pockets and ensure even fillings.

Overflow Design:

Overflow channels collect excessive metal (about 5-10% of the total fill) during the casting process. They prevent voids, which are the empty spaces inside the part, from occurring due to uneven filling.

Real-World Examples of Die Casting Design Optimization

자동차

Manufacturers opt to increase engine block weight by up to 15-20%. This weight reduction increases fuel efficiency by around 10% and performance via better heat dissipation and reduces engine load.

항공우주

Optimization techniques for aircraft landing gear can improve fatigue resistance by around 50%. It also increases strength by 30% and weight by 25 % than old designs.

Consumer Products

Manufacturers can make smartphone casings up to 0.5–1 mm thinner and more durable. They maintain their structural integrity and sleek, eye-catching layouts.

Quantifying the Benefits:

Optimization processes reduce part weight overall production (15% cost savings). It offers better performance and depicts the actual benefit during casting.

결론:

Die Casting Design Optimization is a beneficial technique that allows you to make an ideal design. It improves the part efficacy and allows you to produce accurate parts, reducing manufacturing costs.

The parameters that are included in this optimization can be cooling channels, ribs, fillets, controlled die temperatures, and so on regarding the casting process. However, each aspect may vary and can be determined according to the project’s needs.