①It Should Be Able To Ensure The Accuracy And Precision Of The Workpiece Being Processed.

①It should be able to ensure the accuracy and precision of the workpiece being processed.

The process of CNC processing aluminum alloy is relatively simple on the surface. However, as long as the parameters are adjusted slightly wrong, the accuracy of an entire batch of products will be completely wrong. Such rework is more expensive than making a new mold.

Why is aluminum alloy CNC processing more difficult to chew than steel?

Aluminum alloy is a material with relatively low hardness and very fast thermal conductivity. During the cutting process, it is very easy for the tool to adhere and produce burrs.

When most domestic machining workshops use CNC machine tool milling and CNC machine tool turning to process aluminum parts, many practitioners who are new to the industry often habitually directly apply the cutting parameters for steel. This approach will cause the service life of the tools used to be greatly shortened, basically by half.

At that point in time in 2024, there is an electronics factory here in Suzhou. They have a batch of radiator shells made of 6061 aluminum alloy. They have changed the processing technology from manual milling to computer-controlled CNC processing. In this way, the range of dimensional errors is much narrower.

From the previous precision of plus or minus 0.1 millimeter, it was suddenly so tight that it could only accept the accuracy requirement of plus or minus 0.02 millimeters. However, when trial production was first started, the spindle rotation speed was not slowed down quickly. As a result, among the first 300 products, the proportion of scraps was frighteningly high, directly reaching a serious situation of 12%.

G code feed speed is most easily ignored

In the G code program, the value F is used to control the forward speed of the tool. For processing materials such as aluminum alloy, experts recommend that the cutting speed should be maintained in the range of 200 meters per square meter to 400 meters per minute.

However, many skilled workers on site tend to directly copy the old experience in processing steel parts. As a result, the given F value becomes too high, and finally the tool tip breaks and is damaged after only a few uses.

In a factory in Shenzhen that specializes in producing drone casings, they use three-axis CNC to mill 6061 aluminum alloy material. When the feed speed was adjusted from 800 mm per minute to 500 mm per minute, the processed surface roughness also improved significantly, with the value reduced from Ra1.6 to Ra0.8. At the same time, tool consumption was directly reduced by 40%.

Choosing the wrong coolant concentration equals nothing.

During CNC machining of aluminum alloys, the concentration of coolant usually needs to be controlled within the range of 5% to 8%. If this concentration is set too low, aluminum chips will adhere to the surface of the part, leaving scratches. On the contrary, if the concentration is too high, the workpiece will appear whitish and discolored. In this way, customers will directly return all unqualified batches when inspecting the goods.

There is a factory in Dongguan that specializes in making middle frames for mobile phones. In 2023, they changed the cutting fluid to a low-concentration water-soluble cutting fluid that can be dissolved in water. Since the surface quality has been improved, the number of customer complaints per month has dropped from the original more than 30 orders to single digits. As a result, in just one year, they have saved more than 200,000 yuan just in terms of shipping costs for returns and exchanges.

How to choose tool material and geometry

Because the thermal conductivity of aluminum alloy is five times that of steel, a large amount of heat is generated during cutting. Faced with this situation, the coating material must be selected within the TiAlN or DLC range.

If you choose an uncoated carbide blade, there is absolutely no way the tool can withstand high temperature damage. Specifically for large-diameter milling cutters, the rake angle must be designed to be a value of more than fifteen degrees. Only by doing this can we ensure that the chip discharge work becomes very smooth during the cutting process.

In a workshop in Hangzhou that produces automotive aluminum parts, after switching to a four-edged milling cutter with DLC coating, the useful life of a single tool was extended from 800 pieces to 1,500 pieces. At the same time, the proportion of tool cost in the total processing cost was also reduced from 18% to 9%.

How to lock tolerance and repeatability

The contract tolerance of CNC aluminum alloy parts is generally within the range of plus or minus 0.01 mm to plus or minus 0.05. Because the elasticity of aluminum alloy is relatively large, if the clamp is locked too tightly, the workpiece will be deformed. However, if the clamp is too loose, the tool will be bent. Because the clamping force is not well grasped and controlled, the accuracy is prone to floating and instability.

There is a supplier unit of aviation aluminum parts in Chengdu. This unit uses five-axis CNC turning and milling technology to manufacture mixed-type parts. It conducts full inspections on each batch of 200 parts produced. Its CPK value has been maintained at a high level of above 1.67 for a long time, so there have been no complaints from customers.

How to calculate the cost so as not to suffer a loss?

The cost of a single piece of CNC aluminum alloy is equal to the apportionment of tooling during material processing plus post-processing costs. Complex shapes require a long cutting time and the unit price is naturally high. Don’t miss out on the post-process of EDM wire cutting and deburring when quoting.

In the year 2025, the average domestic processing fee for CNC aluminum alloy parts will be between 8 yuan and 15 yuan per minute. If your product structure is very complex, the quotation will exceed 20 yuan per minute. When many customers go to compare prices with three suppliers with drawings, they often choose the manufacturer with the lowest price.

However, those who quote the lowest prices usually hide the cost of tool wear and the risk of production scrap rates in their profit margins. When settlement is made at a later stage, they will often increase the price even more.

May I ask what is the current scrap rate of your workshop when CNC processing aluminum alloy parts? You are welcome to talk about the relevant parameter settings in the comment area. If you find it useful, please give it a like and forward it to peers in the industry.