Huiwen CNC machining: What should I do if there is deformation during CNC machining of thin-walled aluminum alloy parts?

When processing thin-walled aluminum alloy parts, the dimensions are fully up to standard,  the fixtures warp  rebound as soon as they are loosened,  even slowly deform after a few days - this is  due to the machine tool's inability, but rather a combination of issues such as residual stress in the blank, structural rigidity, clamping pressure, cutting tool path,  process layout. The direct answer given by Huiwen Zhizao in the practical CNC machining of a large number of aluminum parts is: to solve the deformation of thin-walled parts, it is  enough to rely solely on adjusting the speed  feed rate. It is necessary to carry out full chain precision machining process control of aluminum alloys  blank screening to free state retesting. Below, we will explain the six key steps in three stages: pre machine operation, during processing,  post machine operation.

1、 Before starting the machine, screen the blank  press down on the source of deformation  the raw materials

Many hidden dangers in the processing of thin-walled parts are already buried before the parts are installed on the machine. Aluminum alloy sheets  forgings will retain residual stress inside during extrusion molding. Once a large amount of material is milled off during aluminum alloy CNC machining, the original stress balance is broken,  the parts will warp  bend towards the side with lower stress.

For CNC machining of high demand aluminum parts, priority should be given to using rolled aluminum plates that have undergone pre aging  stress relief treatment for thin-walled parts, avoiding rough blanks with large internal stress fluctuations; For high-strength aluminum materials like 7075, if the wall thickness is extremely thin, a low-temperature stress relief pretreatment can be added before rough machining. The blank allowance should also be reasonably planned to avoid excessive unilateral allowance causing stress distribution imbalance during cutting. Choosing the right blank  doing a good job in pre-processing is the lowest cost but easiest to save step in controlling deformation in aluminum alloy precision machining.

2、 DFM evaluates the structure in advance to compensate for the inherent lack of rigidity

Many thin-walled aluminum alloy parts have deformed due to the drawing itself: large areas of suspended thin-walled, deep cavity narrow ribs, unsupported flanges, naturally weak rigidity of the parts,  all cutting will cause the knife  vibration.

After receiving the drawings, conduct DFM manufacturability analysis  propose optimization for aluminum alloy CNC machining: when conditions permit, increase the transition corner of the thin-walled corner, add reinforcement bars at key positions,  design deep cavity process support structures; At the same time, distinguish between functional  non functional surfaces,  appropriately relax tolerances for non critical positions to leave room for CNC machining of aluminum parts. If the product structure cannot be changed due to project limitations, it relies on back-end processes to supplement - increasing auxiliary support, optimizing the cutting path,  repairing the inherent rigid short board of thin-walled parts processing.

3、 Change the mindset of clamping, don't let the clamping force create rebound

Ordinary tiger pliers are suitable for pressing thick walled parts with great force, but it is precisely the biggest taboo for processing thin-walled parts: the large clamping force forcefully flattens the thin-walled parts,  when the processing is qualified, the loose clamp immediately rebounds, which is the high-frequency rework reason for precision processing of aluminum alloys.

Aluminum alloy CNC machining should be matched  clamped according to the shape of the parts: vacuum suction cups are preferred for thin-walled flat parts,  surface adsorption is used instead of point compression to evenly distribute the force; Thin walled components with irregular cavities are supported by soft claws  imitation fixtures with additional support points. The support is only placed on the rigid parts of the solid body,  there is no pressure applied to the suspended area of the thin wall. During the precision machining stage, a portion of the clamping force can be appropriately released,  the positioning pin can be used to limit the position, allowing the parts to complete the final cut in a state close to natural stress. The springback of the aluminum parts during CNC machining will be significantly improved.

4、 The cutting path is customized for thin walls to reduce cutting force  thermal shock

Copying the parameters of thick walled parts is a common misconception in the processing of thin-walled parts: large cutting depth, large amount of material removal on one side, will generate a large lateral cutting thrust,  directly transfer the thin-walled top to the cutting tool.

The CNC machining of aluminum alloy with thin-walled cavities adheres to the separation of rough  fine machining: rough machining uses layered surrounding tool paths  symmetrical alternating material removal on both sides to avoid stress imbalance caused by one-sided hollowing. After rough machining, the workpiece is removed to release stress,  then semi precision  precision machining are performed; Precision machining with sharp hard alloy cutting tools, high speed, small cutting depth, low lateral cutting force,  sufficient cutting fluid to remove heat  prevent thermal deformation. The scientific cutting path is a key means to ensure the flatness  wall thickness uniformity of aluminum CNC machining.

5、 The stress release process cannot be omitted to prevent subsequent continuous deformation

Rough machining will leave a large amount of residual cutting stress. If rough machining is completed  precision machining is carried out directly, the stress will continue to be released during the finished product stage,  the part will slowly warp; Many factories skip the time sensitive process in order to reduce working hours, ultimately resulting in batch scrapping.

The standard processing rhythm for thin-walled parts is: rough machining to remove the vast majority of the allowance → workpiece removal for aging  stress relief → repositioning  clamping for semi precision machining  precision machining. For ultra-thin aluminum parts with a wall thickness less than 2mm, an additional "semi precision machining+secondary stress relief" can be added. This process cannot be arbitrarily removed in precision machining of aluminum alloys, as it directly determines whether the CNC machining dimensions of aluminum parts can be stable for a long time.

6、 Material selection should also make way for shape control

When it comes to the processing of thin-walled parts, the selection of material grades is often only driven by strength, while ignoring its impact on deformation. The common 6061 has good formability  relatively mild internal stress, making it suitable for general heat dissipation chambers  shells; 7075 has high strength, but its elastic modulus  residual stress level are also higher. When made  extremely thin walls, the tendency to warp is more obvious,  the requirements for stress relief  cutting path are more stringent; 5 series aluminum-plastic has good properties  is suitable for thin plates with certain toughness requirements, but the anodizing performance  work hardening need to be evaluated separately.

When selecting materials for CNC machining of aluminum parts, Huiwen Zhizao will consider wall thickness, flatness requirements, post-processing,  usage scenarios together, rather than simply selecting the highest grade based on strength. For aluminum alloy precision machined parts that are sensitive to deformation, materials with "just enough strength  more controllable stress" are often more worry free than blindly choosing high-strength grades,  can also reduce rework for subsequent thin-walled parts processing.

7、 Free state static retest, measuring the actual deformation amount

The processing of thin-walled parts cannot be judged as qualified based on the inspection results under the clamping state of the fixture,  the clamping external force will cover the real deformation. After all aluminum alloy CNC machining is completed, release all clamps  place the workpiece flat on the marble platform. Wait for the temperature to return to room temperature,  then check key indicators such as flatness, wall thickness, cavity contour,  hole position; For aluminum CNC machining samples with high precision requirements, add static retesting to observe the secondary deformation caused by slow release of residual stress,  predict the risk of dimensional changes after delivery in advance. Only by seeing the real data in a free state can we truly grasp the final stage of thin-walled machining.

Frequently Asked Questions (FAQ)

Q1: Why do thin-walled aluminum alloy parts deform after being processed properly  loosened?

Mainly clamping stress  residual stress in the blank. When compressed, the parts are forcibly constrained  a "qualified" shape. After loosening the clamp, the clamping rebounds,  the residual stress is redistributed after the material is removed, resulting in warping. So thin-walled machining emphasizes flexible clamping  stress relief processes.

Q2: Is it easier to deform thin-walled parts with higher rotational speed?

entirely. High speed, small cutting depth,  sharp cutting tools can indeed reduce lateral cutting force, but the prerequisite is that coarse  fine separation, symmetrical material removal, clamping,  cooling are all coordinated in place. Simply increasing the speed without changing the cutting path  clamping, the deformation improvement of aluminum alloy CNC machining is limited.

Q3: Do all thin-walled aluminum parts need to undergo aging stress relief?

The thinner the wall thickness, the higher the flatness requirement,  the higher the material strength, the more necessary it is. It is recommended to arrange stress relief for high-strength aluminum such as 7075  ultra-thin parts smaller than 2mm; The requirement for ordinary thin plates can be evaluated by DFM to determine whether to simplify them, in order to avoid unnecessary increase in precision machining costs of aluminum alloys.

Q4: Are vacuum suction cups suitable for all thin-walled parts?

Suitable for flat thin-walled parts with smooth surfaces; Irregular cavities  hollow parts are more suitable for multi-point support with soft claws  imitation fixtures due to air leakage  insufficient support. The clamping scheme should be determined based on the specific shape of the aluminum CNC machined parts.

Q5: How to determine whether a factory's thin-walled parts processing is reliable?

Check if it has undergone a preliminary DFM structural evaluation, if it has flexible fixtures such as vacuum suction cups/profiling fixtures, if it insists on coarse  fine separation  stress relief during aging,  if it has undergone free state static retesting. Only by recording these items can a stable aluminum alloy CNC machining supplier be established.

Returning to the title question: What should I do if there is deformation during CNC machining of thin-walled aluminum alloy parts? Monotonic machine parameters cannot solve the problem. The answer is to combine the six processes of blank control, DFM structure evaluation, flexible clamping, customized tool path, stress release,  free state retesting. Only by controlling the sources of residual stress, clamping force,  cutting force can we steadily improve the yield of aluminum alloy CNC machining, maintain the dimensional accuracy of aluminum parts CNC machining,  achieve reliable delivery of aluminum alloy precision machining.

Shenzhen Huiwen Intelligent Manufacturing Technology Co., Ltd. is a precision parts processing enterprise located in Shenzhen. It has a modern factory building of 20000 square meters  is equipped with 370+processing equipment (including multiple five axis machining centers  supporting testing equipment). It has long been engaged in practical thin-walled parts processing  undertakes various aluminum alloy CNC machining samples  bulk orders. It specializes in CNC machining of heat dissipation chambers, instrument housings,  thin plate aluminum parts. It can customize flexible fixtures, optimize tool paths,  implement stress relief processes for different thin-walled structures. The company has the ability to provide customers with full process services covering design, manufacturing,  assembly,  single piece sampling to mass production. Welcome to provide drawing consultation. We can provide 2D drawings, 3D models,  technical requirements to obtain DFM process evaluation  itemized quotations.