BRIGHTSTAR
PROTOTYPE CNC CO., LTD
+86 137 5010 5351
EN
May. 19, 2026
Thin-walled parts are among the most troublesome types in CNC machining. Whether it is thin-walled housings for aerospace applications, enclosures for medical devices, or lightweight structures for robotic joint arms, thin-walled parts are always prone to deformation, vibration, and dimensional non-conformance.
A thin-walled aluminum part with a wall thickness of only 1 millimeter may deform due to clamping force and spring back after release; it may expand due to cutting heat and shrink after cooling; it may bend due to cutting forces, resulting in uneven wall thickness. The consequences of these problems are: high scrap rates, increased costs, and delayed delivery.
So how should thin-walled parts be designed? How should they be machined? Are there proven tips to avoid deformation and improve yield?
This article will summarize 8 practical tips for thin-walled part CNC machining from both design and process perspectives. Whether you are an engineer or a procurement professional, understanding these tips will help you obtain more stable and economical thin-walled parts.
Before diving into the tips, understanding why thin-walled parts deform helps us solve the problem at its root.
Three main causes of deformation in thin-walled parts:
When you clamp a thin-walled part with a vise, the clamping force causes elastic deformation of the part. After machining, when the vise is released, the part springs back to its original shape, but the features that have already been machined will shift from their correct positions.
This is the most common cause of deformation. The thinner the wall and the larger the part, the more obvious the clamping deformation.
The cutting tool applies a certain amount of force to the workpiece during machining. For thin-walled parts, this force is sufficient to cause the wall to bend or deflect. When the tool leaves, the wall springs back, resulting in an uneven machined surface.
Raw materials contain internal residual stress. When a large amount of material is removed by cutting, the stress redistributes, causing the part to warp or twist. This deformation may occur immediately after machining or gradually appear after several days of storage.
Aluminum alloys, titanium alloys, and stainless steel all have this problem, with aluminum alloys being the most problematic.
Understanding the causes of deformation allows us to take targeted measures.
This is the most direct method. If your part has a wall thickness of only 0.8 millimeters but does not functionally require such a thin wall, increasing the wall thickness is the simplest and most effective way to solve deformation problems.
Recommendation: For aluminum parts, wall thickness should preferably not be less than 1.2 millimeters. For steel and stainless steel, wall thickness should preferably not be less than 1 millimeter. For plastics, wall thickness should preferably not be less than 1.5 millimeters.
If lightweighting is a hard requirement and wall thickness cannot be increased, consider adding reinforcing ribs. Ribs can significantly improve part rigidity while adding very limited weight. Rib height is generally 3 to 5 times the wall thickness, and rib thickness is similar to or slightly thinner than the wall thickness.
Case study: A 200 millimeter long thin-walled housing with a wall thickness of 1 millimeter deformed severely after machining. After adding cross ribs internally, deformation was reduced by 70 percent while weight increased by only 8 percent.
For designs where wall thickness cannot be increased and ribs cannot be added, temporary supports can be used during machining.
Method: Design temporary connecting ribs between thin-walled areas or between thin walls and solid areas. These connecting ribs act as supports during machining, preventing thin walls from vibrating or deforming. After machining, these connecting ribs are removed manually or by CNC.
Recommendation: The thickness of connecting ribs should be 30 to 50 percent of the wall thickness, and the length should be as short as possible. Be careful when removing connecting ribs to avoid damaging the thin-walled surface.
This method is very common in mold machining and is also suitable for thin-walled structural parts.
Clamping deformation is the most common problem with thin-walled parts. The key to solving this problem is to distribute clamping force over a larger area or change the direction of the clamping force.
Standard hard jaws have a small contact area and easily cause local deformation. Switching to soft jaws (aluminum or copper material) allows them to be machined to match the part contour, providing a larger contact area and more uniform clamping force distribution.
For thin-walled parts with complex shapes, design dedicated fixtures where the clamping surface fully conforms to the part contour. Although the cost is higher, this investment is worthwhile for production quantities.
For flat thin-walled parts, vacuum chucks are ideal. They use atmospheric pressure to hold the part on the chuck, with clamping force evenly distributed across the entire bottom surface, causing almost no deformation. Vacuum chucks are suitable for flat parts such as aluminum plates, steel plates, and plastic plates.
For extremely thin-walled parts, the part can be fixed in low-melting-point alloy. After machining, the part is heated above the alloy's melting point, the alloy melts, and the part is removed. This method completely eliminates clamping deformation.
The machining sequence has a significant impact on the deformation of thin-walled parts. A reasonable sequence can reduce deformation caused by stress release and cutting forces.
First remove most of the stock material. After rough machining, allow the part to rest naturally for a period of time (several hours to a day) to allow residual stress to fully release, then perform finishing.
If the part is symmetrical, use a symmetrical cutting strategy whenever possible. For example, when machining a cylindrical thin-walled part, machine the inner and outer walls alternately rather than finishing the inner wall completely before starting the outer wall. Symmetrical cutting balances cutting forces and reduces deformation.
Machine the more rigid areas first, then the less rigid areas. This way, when machining the thin-walled areas, the overall part already has some rigidity.
For very thin parts, consider using multiple setups, machining only a portion in each setup, releasing the workpiece between setups to relieve stress. Although this increases setup time, it can significantly reduce deformation.
Cutting parameters have a direct impact on the deformation and vibration of thin-walled parts.
Reduce depth of cut
The greater the depth of cut, the greater the cutting force. For thin-walled parts, it is recommended to use a small depth of cut, typically 0.1 to 0.3 millimeters. Although this increases machining time, it can avoid vibration and deformation.
Increase cutting speed
While keeping the depth of cut small, cutting speed can be increased. High-speed machining produces thinner chips, lower cutting forces, and heat is more easily carried away by the chips.
Use climb milling
With climb milling, the cutting force direction is downward, helping to press the workpiece onto the worktable. With conventional milling, the cutting force direction is upward, potentially lifting thin-walled workpieces. For thin-walled parts, climb milling is safer than conventional milling.
Control feed rate
Excessively high feed rates increase cutting forces; excessively low feed rates cause tool friction and heat generation. Find the appropriate feed rate to control cutting forces while maintaining efficiency.
Tool selection directly affects the machining quality of thin-walled parts.
Use sharp tools
Dull tools generate higher cutting forces and are more likely to cause deformation. For thin-walled parts, it is recommended to use new tools or freshly resharpened sharp tools.
Use small diameter tools
Small diameter tools generate lower cutting forces and are more suitable for thin-walled machining. However, small diameter tools have poor rigidity and are prone to breakage. A balance needs to be found between tool diameter and rigidity.
Use multi-flute tools
Multi-flute tools have a smaller chip load per tooth and produce smoother cutting forces. For aluminum thin-walled parts, three-flute or four-flute end mills are good choices.
Use variable-pitch tools
Variable-pitch tools can disrupt the regularity of cutting vibration and reduce chatter. For thin-walled parts that are prone to vibration, variable-pitch tools are very effective.
Cutting heat causes workpiece expansion, followed by contraction upon cooling, resulting in dimensional deviation. For thin-walled parts, this effect is even more pronounced.
Use high-pressure coolant
High-pressure coolant removes cutting heat in a timely manner and also aids in chip evacuation. For aluminum thin-walled parts, water-based coolant is recommended.
Use minimum quantity lubrication
For certain materials, minimum quantity lubrication can provide adequate lubrication while reducing coolant usage. Minimum quantity lubrication generates less heat and is suitable for thin-walled machining.
Preheat before machining
For thin-walled parts with extremely high precision requirements, the workpiece can be preheated to the operating temperature before machining. This way, the thermal expansion state of the part is consistent during machining and in service.
Use multiple finishing passes
For extremely thin-walled parts, finishing can be divided into multiple passes, removing only a very small amount of stock each time, allowing the workpiece to cool between passes.
For materials with high residual stress, heat treatment is the fundamental method to solve deformation problems.
Stress relief for aluminum alloys
Aluminum parts can undergo stress relief annealing after rough machining. The temperature is generally 300 to 350 degrees Celsius, held for 2 to 4 hours, then slowly cooled. This process releases most of the residual stress.
Stress relief annealing for steel parts
Steel parts undergo stress relief annealing after rough machining at temperatures between 550 and 650 degrees Celsius, held and then slowly cooled. For high-alloy steels, more complex heat treatment processes may be required.
Cryogenic treatment
For aluminum parts with extremely high precision requirements, cryogenic treatment can be considered. The part is cooled to approximately minus 180 degrees Celsius, held for a period, then slowly returned to room temperature. Cryogenic treatment can significantly improve dimensional stability.
Note: Heat treatment should be performed after rough machining and before finishing. If finishing is done before heat treatment, part dimensions may change.
Different materials have different adaptability to thin-walled machining.
Free-machining materials
Brass, aluminum alloys such as 6061 and 7075, free-machining steels, and similar materials have low cutting forces and are suitable for thin-walled machining. If functionality allows, prioritize these materials.
Avoid difficult-to-machine materials
Titanium alloys, Inconel, 304 stainless steel, and similar materials have high cutting forces and severe work hardening, making thin-walled machining extremely difficult. Unless absolutely necessary, avoid using these materials for thin-walled parts.
Consider material rigidity
The elastic modulus of a material determines its rigidity. Steel has an elastic modulus of approximately 200 GPa, while aluminum has approximately 70 GPa. At the same wall thickness, steel parts are three times more rigid than aluminum parts. If a thin-walled part is prone to deformation, consider switching to a material with higher rigidity.
Original situation:
An electronic device housing with a wall thickness of 1 millimeter, dimensions 150 millimeters by 100 millimeters by 40 millimeters, made of 6061 aluminum. Original process: clamped with a vise, completed internal and external machining in one setup.
Problems:
After machining, the four corners of the housing were warped, with flatness out of tolerance by 0.3 millimeters; side wall thickness was uneven, thin on one side and thick on the other; there were obvious chatter marks on the surface.
Optimization plan:
The following combination of measures was applied:
· Added internal cross ribs without changing wall thickness
· Switched to vacuum chuck for fixturing, eliminating clamping deformation
· Rough machined, then stress relief annealed, then finished
· Switched to small diameter three-flute end mill, climb milling, depth of cut 0.2 millimeters
· Used high-pressure coolant
Results:
Flatness improved from 0.3 millimeters to 0.05 millimeters; wall thickness variation improved from 0.15 millimeters to 0.02 millimeters; chatter marks disappeared; yield improved from 50 percent to 95 percent.
Q: What is the minimum wall thickness for thin-walled parts?
This depends on the material, part size, and machining equipment. Generally, for aluminum, it is recommended not to be less than 1 millimeter; for steel, not less than 0.8 millimeters; for plastics, not less than 1.5 millimeters. Special processes can achieve thinner walls, but costs will increase significantly.
Q: How can I tell whether a thin-walled part needs reinforcing ribs?
If the aspect ratio of the part is greater than 5 times the wall thickness, or the unsupported overhang length is greater than 10 times the wall thickness, ribs are recommended. A simple method is to press the thin-walled area with a finger; if noticeable elastic deformation is felt, reinforcement is needed.
Q: Are vacuum chucks suitable for all thin-walled parts?
No. Vacuum chucks require the bottom surface of the part to be flat, with no through holes or gaps that cause air leakage. For parts with holes or uneven surfaces, sealing strips need to be used, or other methods need to be adopted.
Q: Can thin-walled parts be straightened after machining if they deform?
Yes. For aluminum parts, manual or hydraulic straightening presses can be used. For steel parts, thermal straightening can be used. However, straightening adds cost and may affect surface quality. It is best to avoid deformation during machining.
Q: How thin of a thin-walled part can you machine?
Brightstar has extensive experience in thin-walled part machining. We can routinely machine aluminum parts with wall thickness down to 0.8 millimeters and steel parts down to 0.5 millimeters. Thinner parts require specific evaluation.
CNC machining of thin-walled parts is indeed more challenging than ordinary parts, but with reasonable design and process planning, high-quality parts can certainly be achieved.
Let us review the 8 key tips:
1. Reasonably increase wall thickness or add ribs to improve rigidity at the design source
2. Add temporary supports in thin-walled areas and remove them after machining
3. Optimize fixture design, use soft jaws, vacuum chucks, or low-melting-point alloy
4. Arrange machining sequence reasonably: rough before finish, symmetrical machining, multiple setups
5. Choose appropriate cutting parameters: small depth of cut, high speed, climb milling
6. Use the right tools: sharp, small diameter, multi-flute, variable-pitch
7. Control cutting heat: use high-pressure coolant or minimum quantity lubrication
8. Stress relief heat treatment: stress relief annealing or cryogenic treatment after rough machining
These tips are not isolated; often a combination of several tips is needed to achieve the best results. For critical parts, it is recommended to communicate with your machinist during the design phase to develop the optimal solution together.
Ready to Machine Your Thin-Walled Parts?
Whether your thin-walled parts are made of aluminum alloy, stainless steel, or plastic, Brightstar has extensive machining experience.
Email Amy: amy@brightstarprototype.com
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