Aluminum alloy processing Cost control: Economic Analysis of Batch CNC and Aluminum Die Casting
In the manufacturing of precision components, aluminum alloy has become a core material in the electronics, automotive and robotics industries due to its low density, good thermal conductivity and easy recyclability. In the face of mass production demands, engineers and purchasers often find themselves in a dilemma regarding process selection: should they continue to use CNC milling/turning to achieve rapid iteration and high-complexity structures, or switch to aluminum die-casting to reduce the average cost per piece? This decision directly determines the BOM cost and delivery cycle. This article will deeply analyze the advantages and disadvantages of the two mainstream paths in batch scenarios based on material properties, process parameters and economic models, and provide practical selection basis.
The influence of material grades and pretreatment on costs
The first step in selection is not to directly compare the processes, but to lock in the material grade. Aluminum alloys of different grades show significant differences in cutting coefficients and die-casting fluidity, which directly affect the tool life and mold life.
Characteristics of common cast Aluminum grades
- A380/A360 It is the first choice for conventional die-castings, with good fluidity and low cost, but its fatigue resistance is average. It is suitable for appearance parts or non-load-bearing structures.
- ADC12 High-strength die-cast aluminum is often used in automotive parts, featuring good strength and corrosion resistance. The machining allowance is usually 0.5-1mm larger than that of A380.
- 6061/7075 (Casting variant) Although most of them are forging/extrusion grades, they are involved in a small number of complex-structured die castings, and the amount of grain refiner used must be strictly controlled.
Preprocessing strategy
For CNC machining, if raw materials are directly used, the costs of sawing and heat aging need to be calculated. It is recommended to use T651 or T6 state bar stock to eliminate residual stress and avoid machining deformation. For die-casting, parts with degassed melt (T65000 pieces) and regular shapes with uniform wall thickness. The core cost lies in the one-time mold investment.
Mold Design and Lifespan
- Die steel grades H13 or NAK80, hardness HRC48-52. The design life is typically 300,000 to 500,000 cycles, depending on the layout of the cooling water circuit and thermal fatigue control.
- Mold cost The cost of a simple die-casting mold is approximately 150,000 to 300,000 RMB. Complex multi-chamber molds can cost over 800,000 yuan. The delivery time for molds is usually 45 to 60 days.
Key Points of Die Casting Process
The injection speed needs to be precisely controlled. Slow filling avoids slag inclusion, and high-speed filling ensures fluidity. The typical injection pressure is 100-200MPa. After die-casting, quenching and artificial aging treatment are required to restore the strength to 230-260 mpa (ADC12).
Economic comparison: Breakeven point Analysis
The core of decision-making lies in finding the "break-even point". The following table, based on industry standard data, compares the cost structure per piece of the two processes under annual output (unit: RMB).
| Cost item | CNC milling/turning | Aluminum die casting | Explanation |
|---|---|---|---|
| Mold/Tooling investment | 5,000-20,000 & less;" | 200,000-500,000 | CNC fixtures are simple fixtures, while die-casting requires precise cavities. |
| Unit material cost | 15 yuan | 8 yuan | The utilization rate of die-casting materials is high (over 95%), and the scrap rate of CNC is relatively high. |
| Single-piece processing labor cost | 30 yuan | 12 yuan | CNC manual and machine depreciation is high, while die-casting has a high degree of automation. |
| Average mold cost per piece | 0.5-2 yuan | 20-50 yuan. | Mold cost/annual output, the larger the quantity, the lower the average cost. |
| Subsequent processing (milling) | "0 yuan | 15 yuan | The die-cast parts need to be milled twice to remove the gate and the mating surfaces need to be finely machined. |
| Total cost per piece | 45.5-47 yuan | 55-85 yuan. | In this scenario, CNC is more economical. |
Key Insights The above table is based on an annual output of 10,000 pieces. If the output is increased to 100,000 pieces per year, the average cost of die-casting molds will drop to 2-5 yuan per piece, and the total cost can be reduced to 35-45 yuan. At this point, die-casting will surpass CNC and become a better choice. Therefore, 30,000 to 50,000 pieces per year. It is usually the break-even range of the die-casting process. In addition, CNC can handle more complex geometric structures, such as internal cavities and thin walls
