In die casting quality control,  every step is checked carefully. First, you check the right material like A380 or AZ91D. While making the parts, you watch how hot the melted metal is (like 750-950°F for aluminum) and how hard the manufacturer pushes it into the mold (between 2,000 and 10,000 psi).  You will use X-rays or ultrasonic testing to look inside without breaking the parts. Then, you will measure the parts with tools. It is within about 0.005 inches. Last, you look at the outside for problems like lines where the metal didn’t join well (cold shuts), and cracks.

This article explains the usual defects in die-casting and their causes with simple explanations. Understand how these issues occur and their effects on die casting quality.

Types of Defects in Die Casting

1.   Porosity

Typically, a porosity defect occurs because of the formation of small holes or gaps inside the metal during casting. Commonly, porosity defects are of two types:

• Gassporøsitet
• Shrinkage Porosity

 Gassporøsitet

Gas porosity occurs when some kind of gas or air is trapped in molten metal during solidification. For example, nitrogen (N₂) or oxygen (O₂).

These gases are trapped during the casting process. As the image shows, (a) demonstrates how air gets into the sleeve and mixes with molten aluminum (Al melt).

(b) Diecaster adds oxygen to replace air in the sleeve, which causes a reaction: 2Al(L) + 3/2O₂(g) → 2Al₂O₃. (c) This reaction forms a vacuum to reduce air entrapment. It also improves the quality of the material.

Shrinkage Porosity

When the part gets solid, there is a chance of shrinkage porosity. This happens often because of the incomplete filling of mold, which forms gaps.

Additionally, uneven cooling rates and solidification patterns are major factors that lead to shrinkage.

Furthermore, slow cooling sometimes causes larger shrinkage gaps. Because the metal cools down unevenly and causes distortion or cracks.

Standards for Porosity:

• The companies can accept parts with small holes that are less than 2% of their thickness.
• If porosity is below 0.5 mm in diameter, then it is good for structural parts.
• Try to maintain cooling rates of 5-10°C per second. This will help in preventing porosity during solidification.

2.   Shrinkage: What Happens When Metal Cools

Krymping occurs because metals freely expand when they are in molted form and contract when cooled. Faster cooling flow causes even more shrinking. Because of early solidification before significant contraction occurs. This issue also depends on what kind of metal you use.

For example, using aluminum metal, shrinkage can be around 1.6%–2.5%, while for steel, it can be 0.5%–1.5%. However, different alloys or environmental factors can influence shrinkage rates.

Dimensional Shrinkage

Dimensional shrinkage reduces the entire metal to a smaller size. This is caused by material contraction during cooling. For example, if you produce a metal rod in a 100 mm long dimension, it might shrink to 98 mm. It means there is a 2% reduction. This kind of shrinkage can also impact manufacturing precision.

Volumetric Shrinkage

When liquid metal pulls away internally while getting solid. It causes unnecessary spaces or voids. These issues are known as volumetric shrinkage. The voids look like air pockets in a sponge. They affect the part’s strength and weaken its structure without significantly changing its external shape.

Standards for Shrinkage:

• Measure enough shot weight to fill the mold properly in case of eliminate the chances of shrinkage.
• Check if the parts contain the accurate size and shape with minimal gaps.
• Apply an acceptable cooling rate (5–15 °C per second). It will avoid distortion.
• Most of the applications consider shrinkage below 0.3% in volume to meet their standard limits.

3.   Surface roughness

Surface roughness is the condition of a part’s surface, whether in rough condition or smooth. Manufacturers determine the levels of surfaces using parameters like Ra (average roughness) and Rz (roughness depth). For instance, most of these parts are accepted with Ra values between 1.6 and 6.3 µm, depending on their use.

Poor surfaces in parts happen because of several reasons, including die wear, venting, and air entrapment. Sometimes, manufacturers fail to replace old molds and place proper venting to escape air. This is why they fail to produce the expected demanded surfaces.

Standards for Surface Roughness:

• Match Ra values within the specified range for functional applications
• Inspect machine tools like mold, venting, cooling channels, etc., on a regular basis to ensure consistent surface quality.

4.   Dimensional Inaccuracies

When manufacturers fail to match the part size and shape with the profile, this issue refers to dimensional inaccuracies. Failure to maintain dimensions during casting can cause common problems, including warpage, distortion, and variations in thickness.

For example, if you use uneven cooling, this may bend the metal or twist (warpage). Distortion commonly occurs when pressure exceeds the consistency (1000-2000 bar) during casting. Similarly, if the molten metal does not fill the mold evenly, it creates variations in thickness.

Standards for Dimensional Accuracy:

• Apply proper cooling rates depending on the particular part needed.
• Meet Parts size requirements with tolerances of ±0.1 mm
• Add a uniform thickness within 1.5–3 mm, depending on the application.

Die Casting Quality Control Measures

Quality control in manufacturing comprises the stages of inspection. That helps you ensure parts meet required standards. These steps include inspecting materials, monitoring processes, and training operators.

Inspection and Testing

The quality of parts can be checked by dividing the process into two sections: in-process and final. The manufacturers can begin inspecting parts during production. They can find defects early. On the other hand, final inspections ensure the molded part is accurate and meets all specifications.

Additionally, manufacturers can use automated inspection systems, like vision systems and Coordinate Measuring Machines (CMM). These tools reduce labor costs and processing time as well as can improve accuracy and speed.

The CMM works by following a set of coordinated procedures. The engineers send commands using computers to the control unit. That then operates the machine following the guidelines.

Machines move the probe-carrying tool. This tool is used to collect precise measurements from the workpiece. The manufacturers then check the data to ensure if the workpiece meets specifications or not.

Material Control

It is important to inspect the chemical and mechanical attributes of incoming materials before using them in die-casting. Confirm the suitability of these metals and their compositions. For example, aluminum alloys can consist of 95% aluminum and 5% silicon. They offer tensile strength of 250–300 MPa and elongation of 5-7%.

Material certification and traceability are also important. This documentation ensures each batch of material can be traced back to its source. Additionally, you can verify them for compliance with standards.

Prosesskontroll

Constantly monitor each key process parameter to produce parts with consistency. Such as:

• Melt points around 680-720°C (1256-1328°F)
• Injection pressure as maximum as 100-150 MPa (1450-2175 psi)
• Cooling temperature up to 10-20°C/s (18-36°F/s)
• Cycle time is about 30-60 seconds.

Additionally, process control charts and data logging aid in tracking down all the important steps. These controls allow you to make drastic changes if needed to maintain product quality.

Operator Training

It is necessary to train your operators in order to maintain quality control. There are many training programs available on online platforms. That focuses on process control, troubleshooting, and quality awareness. By learning these skills, you can effectively detect errors early and ensure that the process runs smoothly.

SPC (Statistical Process Control)

Manufacturers integrate SPC into their process control. That involves using control charts and process capability analysis. They help them with monitoring and improving processes.

For example, in die casting, SPC can monitor injection pressure, cooling rates, and melting temperatures. This helps you to avoid variations in the final product.

Inspection and Testing Methods in Die Casting Quality Control

Visual Inspection

During visual inspection, manufacturers can examine part’s surfaces using magnifying glasses, microscopes, and borescopes. They can detect small details. For example, scratches (0.1-1.0 mm deep), cracks (0.05-0.5 mm wide), and other imperfections (porosity, pits) or uneven surfaces.

Dimensional Measurement

You can check the part’s size (e.g., length up to ±0.1 mm, width up to ±0.05 mm, height up to ±0.2 mm) and shape. For this process, dimensional measurement techniques are helpful.

These techniques involve several tools such as calipers, micrometers, and coordinate measuring machines (CMM). Additionally, you can use advanced technologies, like laser scanning, to measure with greater accuracy (e.g., ±0.01 mm).

NDT (Non-Destructive Testing)

NDT methods are cost-effective and preserve part integrity. They cater to inspecting the internal quality of parts without damaging them. These techniques can be:

• Radiography
• Ultralydtesting
• Eddy Current Testing

Radiography:

Radiographic testing involves X-rays (e.g., 100-400 kV). These X-rays can detect inside defects such as cracks or holes. The operator passes an X-ray beam through the part and creates an image. This method is commonly used to check issues in aluminum castings.

Ultrasonic Testing:

Ultrasonic testing uses sound waves (e.g., 2-10 MHz). These tests can determine the flaws in the inner side of metals.

Eddy Current Testing:

The operators identify surface and near-surface flaws in conductive materials using eddy currents.

Destruktiv testing

Manufacturers apply heavy forces to molded parts to check their strength. They keep testing parts until they break to determine how they will work under intense stress. These destructive tests are used for sampling, not every part. They include tensile testing, impact testing, and hardness testing.

For a tensile test, manufacturers measure how much force a component can handle until it breaks (e.g., 100-1000 MPa).

During impact testing, They note down the measurements. That a part bears and resists sudden shocks (e.g., 10-100 J).

Hardness testing helps in measuring how hard or soft a metal is (e.g., 50-100 HRB).

Case Studies and Best Practices

Case Studies

A real-world example demonstrates how powerful quality control systems help in determining part efficiency. For example, using automated porosity characterization can improve material quality assessment.

The image (a) section depicts porosity levels starting from 0.000 to 1.649%. In the meantime, section (b) visualizes hot spot FS times. That ranges between 0.000 and 9.328%. Benefiting from these analyses can really simplify your die-casting material quality.

Quantified Benefits

Quality control methods offer several benefits to both manufacturers and consumers. The common ones are:

• They reduce scrap rates by as much as 10 to 20%.
• Quality control processes help in improving overall yield by up to 5-10%.
• Manufacturers can reduce production costs and save around 10-20%.
• They get consistent quality parts every time.
• Reduce cycle time and require less maintenance.
• Monitor each part deeply while casting them.

Best Practices

Proactive quality control measures are important. They help you make consistent and high-quality parts. Some examples of best practices are:

• Maintain machine equipment and tools regularly to avoid defects and downtime.
• Continuous working improves procedures and reduces flaws.
• Always implement quality management systems, such as ISO 9001. These systems ensure consistent quality.
• Monitor defective areas and replace worn mold.
• Keep learning via training programs and develop effective skills that are needed to maintain quality.

Konklusjon

Die-casting quality control is very important. They make sure the parts are strong and meet the customer’s needs. As a result, consistency in quality brings many long-term benefits for manufacturers.

Additionally, these techniques allow them to find flaws early during casting. They can use several advanced tools to inspect and check the quality of the real-time equipment. For instance, calipers, micrometers, coordinate measuring machines (CMM), laser scanners, and radiography.