Die casting and CNC machining are two widely used manufacturing processes for precision metal components. There are significant differences in many areas, especially in production efficiency, cost control, product precision, and applications. Many customers may have doubts in selecting die casting or CNC machining for their designed parts.
CFS Foundry is a professional die casting and CNC machining manufacturer with years of experience. Relying on rich industry experience and a large number of practical project cases, we comprehensively analyze the main differences between die casting and machining, and guide you on how to select an ideal manufacturing process for your project.
Die Casting
Die casting is the process of rapidly injecting molten metal into a pre-designed mold cavity under high pressure. Once the metal cools and solidifies, the mold is opened to obtain the desired shape. The typical characteristics of the die casting process are “high pressure and high speed. The high pressure enables the molten metal to fill every detail of the mold cavity, thus allowing the production of complex-shaped and clearly contoured products. And the high-speed injecting and forming process makes die casting highly efficient and suitable for mass production.
Common types of die casting include aluminum die casting, zinc die casting, magnesium die casting, etc. Among them, aluminum alloy die casting is widely used in automotive parts, electronic enclosures, medical devices and other fields due to its moderate material cost and high strength. CFS Foundry has advanced die casting production lines, covering cold chamber die casting, hot chamber die casting and other types, which can adapt to the production needs of components of different materials and shapes.
CNC Machining
CNC machining (Computer Numerical Control machining) is a precision manufacturing technique that belongs to “subtractive manufacturing. It mainly controls the movement of the cutting tools through computer programming and removes excess materials by cutting, drilling, and milling on metal blanks, ultimately obtaining parts that meet the required dimensions and precision. The core advantage of this process is extremely high machining accuracy, which can finely trim the blanks, and is suitable for components with strict requirements on dimensional tolerance and surface roughness.
CNC machining metals could be both ferrous metals & non-ferrous metals. Main metals include carbon steel, alloy steel, stainless steel, aluminum, copper, and so on. The appropriate materials should be selected based on the performance, precision and cost of the parts. CFS Foundry is equipped with a variety of high-precision CNC machining centers, including CNC milling machines, CNC drilling machines and CNC turning machines. These machines can realize the integrated service from rough machining to finish machining, which is not available with the die casting process.
Die Casting vs. CNC Machining: Comparing Their Key Differences
1. Forming Method
This is the most essential difference between the two processes. Die casting is an extension of “additive molding”, although it involves cooling molten metal, the core is filled and formed, without a large amount of material removal. It directly molds the metal liquid into a shape close to the final product through the mold, and only requires a small amount of machining or no machining.
CNC machining is “subtractive forming”, it obtains the final product by removing excess materials from the blank. This difference directly leads to the shape of die-cast products being limited by the mold, but no large amount of subsequent machining is required after molding. The shape of CNC-machined products is limited by the machining capacity of the machine tool, but it has higher flexibility and can produce complex and precise metal components.
2. Production Efficiency
The production efficiency of die casting far exceeds that of CNC machining. During the die casting process, all the production steps, including mold closure, metal liquid injection, cooling, solidification, mold opening and removal, can be carried out automatically and continuously. Depending on the size of the product, a single set of molds can produce dozens or even hundreds of pieces per hour. For example, the die casting production of small aluminum alloy housings can reach 80-120 pieces per hour.
CNC Machining, on the other hand, is a piece-by-piece processing. Even if CNC machines are used to achieve simultaneous multi-position processing, the efficiency is still much lower than that of die casting. Taking the same small aluminum alloy housing as an example, the CNC milling processing of a single piece takes 3-5 minutes, and the hourly output is only 12-20 pieces. Moreover, the larger the product, the more obvious the efficiency gap becomes.
Therefore, die casting is more suitable for large production runs, while CNC machining is suitable for small to medium batch production with high precision.
3. Dimensional Accuracy and Surface Quality
In terms of dimensional accuracy, CNC machining is superior to die casting. The dimensional tolerance of die castings is generally within ±0.1 – 0.3mm, and the surface roughness is Ra 3.2 – 6.4 μm. If higher accuracy is required, subsequent machining is necessary to meet the requirements. However, the dimensional tolerance of CNC machining can reach ±0.001 – 0.01mm, and the surface roughness is Ra 0.8 – 3.2 μm, which can directly meet the requirements of components for precision instruments and high-end equipment.
But in terms of maintaining the accuracy of complex shapes, die casting is better. Die casting can form complex cavities, grooves, and thin-walled structures in one operation, and the dimensions of each part are consistent (the product qualification rate in batch production can reach over 95%). While processing complex shapes requires multiple clamping and changing of tools, CNC machining is prone to causing inconsistent dimensions of each part due to clamping errors, and the qualification rate is relatively lower (about 85 – 90%).
4. Cost Comparison
The main cost of die casting lies in the molds, while the cost of CNC machining lies in the labor and equipment wear.
Die casting requires the customization of dedicated molds according to the shape of the product. The design and manufacturing of molds are challenging, with long cycles and high costs. The cost of a typical aluminum die casting mold is approximately 3,000$~20,000$ dollars. At the same time, complex molds can cost over 30,000$ dollars. However, during mass production, the cost of molds per individual product is extremely low, and the material utilization rate is high (generally ranging from 85% to 95%). Therefore, the cost per individual product for mass production is very low.
CNC machining does not require custom molds, and the initial investment is low. Manufacturers only need to prepare the machining tools and fixtures. However, when producing in small batches, the processing time is long, and the labor cost is high. Besides, the material utilization rate is also low (generally around 60-75%). Therefore, the unit cost is relatively high. As the production volume increases, the unit cost will gradually decrease, but the reduction is limited and cannot match the batch cost advantage of die casting.
So, for small batch production (less than 1,000 pieces), CNC machining costs are lower. For large batch production (more than 5,000 pieces), die casting costs are lower. If production ranges from 1,000 to 5,000 pieces, it depends on the complexity of the product and needs to be calculated specifically.
5. Material Selection
Die casting is mainly suitable for processing low-melting-point metal materials, such as aluminum alloys, zinc alloys and magnesium alloys. Steel and iron are high-melting-point metals that would cause severe wear to the molds, which makes the die-casting process difficult and costly. Die cast products are mostly complex-shaped structural components and shell parts, such as engine blocks, transmission cases, phone body frames, and household appliance shells, etc.
The applicable material range of CNC machining is wider. Whether it is low-melting-point aluminum, zinc, or high-melting-point steel or iron, they can all be processed. The corresponding product types are mostly customized precision parts, such as precision gears, bearings, bolts, core components of instruments and meters, etc. CNC Machining can also be used for the secondary processing of die-cast products.
Tips on Selecting Die Casting or CNC Machining for Your Project
Choosing between die casting and CNC machining depends on your project’s volume, design complexity, and cost targets. Die casting is ideal for high-volume production of metal parts with consistent dimensions and smooth surface finishes. Once the tooling is made, unit costs drop significantly, making die casting highly cost-effective for large batches. It also allows complex geometries, thin walls, and integrated features that reduce secondary machining. Common materials such as aluminium, zinc, and magnesium make die casting suitable for automotive, electronics, and industrial components. However, the initial mould cost and longer lead time mean it is less suitable for low-volume or frequently changing designs.
CNC machining, by contrast, offers maximum flexibility and precision, making it perfect for prototypes, low-volume runs, or parts with tight tolerances. It requires no dedicated moulds, so that design changes can be implemented quickly with minimal extra cost. CNC machining works with a wide range of metals and is ideal when strength, accuracy, and surface finish are critical. For complex parts produced in small quantities, CNC machining is often more economical overall. As a professional manufacturer, CFS Foundry helps customers evaluate production volume, material requirements, and performance expectations to select the most efficient process for each project.
Cases Study
Case 1: Automotive Aluminum Alloy Wheel Hub Bracket (Die Casting + CNC Machining)
- Customer Requirements: Mass production of automotive aluminum alloy wheel hub brackets, with an annual output of 100,000 units, dimensional tolerance of ±0.05mm, and surface roughness of Ra 1.6μm.
- Process Selection: As a complex structural component with multiple mounting holes and internal cavities, this product features large batch volume and high precision requirements. Therefore, the combined process of die casting + machining was adopted.
- CFS Solutions: First, custom molds were used for die-casting the wheel hub bracket blanks to ensure complete product structure and excellent dimensional consistency. Then, CNC machine tools were applied to finish-machine key parts such as mounting holes and positioning surfaces to meet precision requirements. Meanwhile, an automated production line was adopted to achieve seamless connection between die casting and machining, reducing handling and clamping procedures.
- Result: The production efficiency reached 80 units per hour, with a product qualification rate of 99.2%. Compared with the customer’s original all-machining solution, the comprehensive cost was reduced by 40% and the delivery cycle was shortened by 50%.
Case 2: Precision Instrument Stainless Steel Gear (CNC Machining)
- Customer Requirements: Small-batch customization of stainless steel gears for precision instruments, with a production batch of 500 units, dimensional tolerance of ±0.003mm, and surface roughness of Ra 0.8μm.
- Process Selection: As a precision component made of stainless steel (a high-melting-point material), this product has a small batch volume and extremely high precision requirements. Thus, the CNC machining process was directly selected.
- CFS Solutions: High-precision CNC gear milling machines were used to complete gear turning, gear milling, drilling and other processes in one-time clamping, reducing clamping errors. In-line inspection equipment was applied during processing to monitor dimensional accuracy in real time. Finally, a grinding process was adopted to optimize surface quality.
- Result: The sample delivery time was 2 days, and the batch delivery time was 15 days. The product precision fully met the customer’s requirements, with a qualification rate of 98%, and the customer placed repeated follow-up orders.
Frequently Asked Questions
Q1: Can the precision of die-cast products reach the level of CNC machining?
A: The precision of die-cast products cannot reach the level of CNC machining. However, through the combined process of “die-casting + CNC machining”, the precision of the products can reach or even exceed the level of pure machining, while also taking into account the advantage of batch production. For example, the die-casting + machining products of CFS Foundry can have a precision controlled within ±0.005mm, meeting the needs of most precision products.
Q2: Is it more cost-effective to choose die-casting or CNC machining for small batch production?
A: For small batch production (less than 1,000 pieces), CNC machining is generally more cost-effective. Because die-casting requires a high investment in molds, small batch production cannot share the mold cost, and the unit cost is extremely high. For larger batch production, die casting is more suitable, and the unit cost is low.
Q3: How long is the production cycle for die-casting and CNC machining?
A: The production cycle of die-casting is divided into the mold manufacturing cycle and the batch production cycle. The mold manufacturing generally takes 20-30 days, and during batch production, it can produce dozens to hundreds of pieces per hour. CNC machining does not require molds, and sample production usually takes a week at most, and during batch production, it can produce ten to several dozen pieces per hour. The specific cycle depends on the complexity of the product and the precision requirements.
Q4: Which materials are suitable for die-casting and which are suitable for CNC machining?
A: Low-melting-point metals (such as aluminum alloys, zinc alloys, magnesium alloys) are suitable for die-casting. For stainless steel or other steel alloys, investment casting method is the alternative casting process for manufacturing. CNC machining materials have a wider application range, and almost all metal materials can be processed.
Contact CFS Foundry for Your Die Casting or CNC Machining Project
With rich experience and full capacities in die casting and CNC machining, CFS Foundry can provide customers with a one-stop production solution. Whether it is complex structural components for mass production or precision parts for small-batch customization, we can all meet the high-quality and timely lead-time requirements. Any inquiry on die casting or CNC machining services, pls feel free to contact us!
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