How to choose CNC processing technology for aluminum alloy in 2026? Comparison of cost between precision milling pure cutting after dismantling die-casting by Shenzhen manufacturers

CNC parts processing, Shenzhen CNC processing, humanoid robot joint shell processing, Shenzhen Huiwen Zhizao has been deeply involved in robot structural component processing for many years. We have been in this industry for many years, the answer is actually complicated: when choosing the process for CNC machining of aluminum alloys, it is a matter of "pure CNC mold making" - first look at three things: how large the batch is, how thick the wall is, whether it is subjected to force. For sampling extremely small batches, pure aluminum alloy CNC machining is the most flexible; Thin walled shell measurement, precision milling after die-casting is the most cost-effective; For thick walled load-bearing components, liquid forging CNC machining are more suitable. Each of the three routes has its own battlefield, if you choose the wrong one, either the cost cannot be reduced the accuracy cannot be maintained. During the preliminary review by the technical department, three questions are usually asked: how many pieces of this item are needed per year, what is the thinnest wall thickness, whether heat treatment welding are required in the future. After answering in three sentences, the process route is basically determined.

1、 What are the differences among the three process routes

Many first-time buyers looking for CNC machining manufacturers in Shenzhen may be confused when they receive a quotation - for the same part, a pure CNC quote of 500 yuan, a precision milling quote of 80 yuan after die casting, a precision milling quote of 120 yuan after liquid forging. So much difference, exactly is the difference?

Essentially, it's one thing: how to shape materials how to refine mating surfaces.

The logic is complicated: CNC is "cutting out parts the entire aluminum material", with a material utilization rate of less than 40%, most of them are sold as chips; The mold process is "molding first then repairing", most materials are in place at once only the mating surface is refined. The savings are in rough machining hours, but the mold cost needs to be amortized in batches.

2、 Pure CNC wins in sampling, loses in batch accounting

The advantages of CNC machining of pure aluminum alloy are zero mold cost, fast drawing modification, the ability to produce any material structure. In the prototype stage, there are three to five pieces, programming can be done on the machine without waiting for the mold.

But the cost structure is linear - one piece per hour, one hundred pieces per hundred hours. It is surprising that a piece of aluminum material with a large removal amount, such as a joint skeleton, weighs 2kg leaves 200g after cutting, totaling several thousand pieces.

When to choose pure CNC:

Annual demand of less than 50 pieces

The structure is still iterating there may be changes to the diagram

High precision requirement (within ± 0.01mm)

Urgent order, unable to wait for mold cycle (mold usually takes 25-45 days)

When to choose pure CNC:

Annual demand of over 100 pieces, structure finalized still in pure cutting - equivalent to paying full tuition for each piece of "whole piece material picking parts"

3、 Die casting is cheap, but porosity heat treatment are two hard constraints

The strengths of die-casting are thin walls complex shapes. 0.5-1.5mm wall, dense heat dissipation teeth, thin-walled shell, one-time molding, high efficiency, lowest single piece cost. Aluminum alloy shell CNC machining parts such as radar housings gearboxes are widely used.

But two constraints must be known in advance:

Firstly, internal pores. Die casting has a fast filling speed, the metal liquid sprays gas at high speed in the mold, resulting in more obvious shrinkage in thick walled areas. The mechanical properties are discounted, the tensile strength is only about 60% -70% of the same grade forged.

Secondly, it cannot undergo heat treatment has poor welding performance. Pores will bulge deform during T6 heat treatment at high temperatures, anodizing is also prone to foaming blooming. So for the main load-bearing, heat-treated, welded parts, the die-casting route should be carefully considered.

When to choose die-casting+CNC finishing:

·Annual demand of over 500 pieces

·Thin walled shell with a wall thickness of 0.5-3mm

·Non main load-bearing components, exterior components

·No T6 heat treatment required

4、 Liquid forging: a middle path reserved for thick walled load-bearing components

Many people have heard of liquid forging (squeeze casting), but it solves the middle ground of "insufficient die casting too expensive forging".

The process principle is simple: the metal liquid is slowly filled under high pressure solidifies while being pressed. Because it crystallizes under pressure, with sufficient shrinkage, fine grain size, dense structure, mechanical properties similar to forgings, it can also undergo T6 heat treatment can be welded.

The cost is about 50% higher than die-casting, but 30% -60% cheaper than pure aluminum alloy CNC processing. The mold cost ranges 50000 to 150000 yuan, which is more expensive than die casting but much cheaper than free forging.

When to choose liquid forging+CNC:

·Load bearing components with a wall thickness of 5mm more

·Annual demand of 100-5000 pieces

·T6 heat treatment welding is required

·Joint, bracket, skeleton other load-bearing components

Thin is its stage, thick walls bear the force. Five axis machining with precision milling on the key mating surface, without cross process rotation of the benchmark.

5、 Case: What is the cost difference among three routes for the same joint brace

Give a specific example to calculate the account.

Parts: Humanoid robot knee joint bracket, made of 7075 aluminum alloy, with a wall thickness of 8mm, a maximum outer shape of 120mm × 80mm × 40mm, a critical mating surface tolerance of ± 0.02mm.

Conclusion:

·Annual demand of less than 100 pieces: pure CNC is the most cost-effective, no need to mold

·Annual demand of 300 pieces: Die casting+CNC has passed the break even point, net savings

·Annual demand of 300 pieces T6 heat treatment required: Die casting cannot be used, liquid forging is used. If the annual demand exceeds 500 pieces, it will save money compared to pure CNC

That's why we say 'ask about batch first' - when the batch changes, the answer is completely different.

6、 5 things to confirm before quoting

1. Batch annual demand: A few pieces per time, dozens of pieces per year, thousands of pieces per year, the answers are completely different. First, clarify the scale, otherwise the quotation will be incomparable.

2. Wall thickness stress level: The thickness of the thinnest wall, whether it is the main load-bearing component, whether there are impact fatigue requirements determine whether to use die casting liquid forging.

3. Subsequent process requirements: whether T6 heat treatment, welding, anodizing powder coating - die castings cannot be made T6, which is the most prone to stepping on pits.

4. Material grade: 6061 7075? The specific grade directly determines the molding process surface treatment effect, the three words "aluminum alloy" are equivalent to writing them.

5. Consistency requirements: Should the first article be reported in full size, how should batch inspection be carried out, should process records be kept for repeat purchases? Especially in the small batch stage, it is necessary to make a decision first.

7、 Huiwen Zhizao's approach: plan the mass production route during the sampling stage

Shenzhen Huiwen Intelligent Manufacturing Technology Co., Ltd. is a manufacturer of robot structural components in the field of CNC machining in Shenzhen, providing integrated hardware component services design, intelligent manufacturing to assembly. All three process routes have their own equipment:

·Die casting: 15 die casting machines, 160T-800T

·Liquid forging: one 400T one 1600T each

·CNC precision repair: More than 370 equipment, including 161 five axis linkage 3+2 five axis machining centers in total

·Testing: 13 Zeiss CMM+over 50 testing equipment

Both precision milling after die-casting liquid forging+CNC composite processes can be connected in the factory, without the need for outsourcing the blank pulling it back for precision repair, the benchmark does cross factories.

More important than equipment is the process connection. The habit of Huiwen Zhizao is to discuss the subsequent mass production route with the customer during the sampling stage: if this part needs to be mass-produced in the future, the sampling structure should be reserved according to the requirements of the mold process - the die-casting part should leave a draft angle to avoid local thick wall material accumulation, the liquid forging part should plan the stress surface runner position.

The prototype is first rapidly verified using pure aluminum alloy CNC machining, after shaping, the blank is converted to die casting liquid forging, the key surface is precision machined with five axes. When delivering the parts, the three coordinate inspection report will be sent with the goods, the first piece data will be retained. For repeat purchases, the same set of process parameters will be used.

Common Misconceptions

The first misconception is that "mold parts" cannot be used as load-bearing components. Ordinary die castings are indeed limited by porosity, but liquid forging has a dense structure that can be T6 welded, load-bearing components have their own positions.

The second misconception is that opening a mold is definitely cost-effective. The mold cost is a one-time investment, the algorithm is simple: mold cost ÷ cost savings per piece relative to pure CNC=breakeven production. If the output exceeds this point, the mold route will be net saving; Stuck below this point, pure CNC is more suitable.

The third misconception is that the sampling process is directly postponed to mass production. There is no problem with using pure CNC for sampling, but if the structure is designed completely according to cutting logic, it often needs to be changed one round when turning the mold - draft angle, wall thickness uniformity, fillet transition. The earlier you consider rework, the less likely it will be.

Frequently Asked Questions

Q: How many batches should we start considering mold making? There is no unified cutting point, look at the parts. A hundred pieces of thin-walled exterior parts can be counted as die-casting accounts; Liquid forging is often more cost-effective for thick walled load-bearing components with an annual demand of over 200 pieces compared to pure CNC. Provide the annual demand drawings to the processing factory, ask them to calculate the breakeven production for you to see.

Q: Can liquid forging parts be heat treated welded? Okay. Liquid forging has a dense structure, supports T6 heat treatment, has significantly better welding performance than die-casting parts. This is a prerequisite for its use in load-bearing components such as joints skeletons.

Q: Can die-casting parts be used as load-bearing components at all? No. The die-casting of non main load-bearing shells, brackets, heat dissipation components is fully sufficient; For the main load-bearing, impact bearing, heat-treated parts, liquid forging forging should be selected.

Q: How is the mold fee generally amortized? The mold fee shall be reported separately, with a one-time investment, then the processing price shall be reported by piece. To determine whether it is worth it , divide the mold cost by the amount of money saved per piece compared to pure CNC to obtain the breakeven production, compare it with the expected purchase quantity.

Q: What type of robot parts projects is Huiwen suitable for? Structural components such as humanoid robots quadruped mechanical dogs can be assembled single piece sampling to medium to large-scale production, providing hardware component services that integrate design, intelligent manufacturing, assembly; The software algorithm control parts are led by the client team, while we collaborate on hardware.

Summary

The differences in the three process routes are essentially differences in batch size, wall thickness, stress characteristics: pure aluminum alloy CNC processing is flexible but expensive, suitable for sampling extremely small batches; Precision milling after die-casting is cheap efficient, suitable for measuring thin-walled non load bearing parts; Liquid forging+CNC dense heat treatment, suitable for thick walled load-bearing parts to take the middle route. At the sampling stage, the R&D team clearly explains the expected batch size, stress requirements, subsequent processes, together with the processing plant, determines the migration path before entering the quotation mold review.

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