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Published by VMT at Dec 17 2025 | Reading Time：About 2 minutes
When you plan to manufacture metal parts with thinner walls and higher machining difficulty, there are usually two common manufacturing methods to consider: CNC machining and thin-wall casting. So, to deal with different materials, wall thicknesses, precision requirements, and applications, how would you choose between CNC machining and thin-wall casting? But like any manufacturing process, you need to learn a lot before deciding which process works best for your parts.
This article will guide you through CNC machining and thin-wall casting, including their definitions, pros and cons, recommended wall thickness ranges, typical applications, as well as cost factors, helping you clarify whether they are the right processes for your project.
In engineering, thin-wall structures refer to large load-bearing assemblies made of thin plates, shells, or profiles. However, in manufacturing, we typically classify metal components with locally thin walls and high machining difficulty as metal parts of thin wall structure ( also thin-wall metal parts).
For metal parts, there is no universal definition of thin-wall thickness. Thin-wall characteristics depend on factors such as material properties (aluminum, steel, and titanium behave differently), overall part size, machining method, and especially the ratio of wall thickness to wall height or length (which is more important than the absolute thickness). Although standards vary by material and application, a metal part is generally considered thin-walled when the wall thickness–to–height or length ratio is approximately ≤ 1/10–1/20, with absolute wall thickness typically ranging from 0.5 to 2 mm, depending on the material and process.
Thin-walled metal parts have small wall thickness, low stiffness, and are easy to deform. Because of this, the choice of manufacturing process has a direct impact on dimensional accuracy, mechanical performance, and cost. The most common manufacturing processes include CNC machining, thin-wall casting, EDM, plastic forming with finish machining, and additive manufacturing. Among them, CNC machining and thin-wall casting are the two most widely used and most mature processes.
This is mainly because the other methods have clear limits. EDM can reach very high precision, but it is slow and expensive, so it is not suited for mass production. Plastic forming can improve material properties, but it requires high tooling cost and cannot match CNC in flexibility. Additive manufacturing can create very complex shapes, but it still has higher material cost, lower surface quality, and slower production.
In contrast, CNC machining offers excellent accuracy and great design flexibility. It works well for complex parts, tight tolerances, low or medium volume production, and parts with short life cycles. With proper tooling and process optimization, deformation can be effectively controlled.
Thin-wall casting, on the other hand, is very efficient for producing complex shapes at large volumes. It can form thin and intricate structures directly, uses material efficiently, and delivers very low cost per part. It is a strong fit for lightweight design and high-volume production.
These two processes are therefore the most practical and widely used solutions for thin-walled metal parts today.
CNC thin-wall machining refers to using cuttIng tools (where tool movement is controlled by computer programs) to remove material from a solid metal block or plate, forming thin-wall structures . The typical workflow includes CAD → CAM Programming → Workpiece Setup → Machining (turning, milling, drilling).
If you consider the CNC machining rather than thin-wall casting for your thin-walled metal parts, you may find following advantages of it:
It is suitable for nearly all metals, including aluminum, copper, titanium, stainless steel, and high-temperature alloys.
Modern CNC machines have high positioning and repeatability accuracy, and the entire process is controlled by computer. Tool offsets, thermal compensation, and in-process measurement can all be used to minimize errors. As a result, CNC parts achieve precision levels that casting cannot match.
Cutting generates clean, continuous material removal, which avoids rough grain boundaries, porosity, or shrink marks typically found in cast parts. This allows many parts to reach their required surface finish without extensive post-processing.
High repeatability and consistent quality due to fully digital control.
CNC parts often have superior mechanical properties.They are usually made from forged, rolled, or heat-treated stock, which has dense microstructure and uniform grain orientation. These materials typically offer higher strength and better fatigue performance than cast materials, which may contain porosity or coarse grains.
Design changes in CAD/CAM can be made quickly without creating new molds.
However, there is no perfect manufacturing process, and for thin-wall metal parts, CNC machining has the following disadvantages:
Thin-wall features have low stiffness. During cutting, they are more likely to vibrate or deflect, which can affect dimensional accuracy. This makes it necessary to use carefully controlled cutting parameters, proper tool geometry, solid fixturing, and effective cooling.
Limited tool reach, making it difficult to manufacture complex internal cavities or intricate 3D geometries.
CNC removes material through step-by-step cutting. This takes time, and thin-wall parts often require multi-axis machining, multiple setups, and tight process control. As a result, the cost per part is usually higher than casting.
Thin-wall casting is an advanced application of traditional casting methods(such as die casting, sand casting, investment casting, and lost-wax casting). Usually, molten metal is poured into a pre-designed mold and allowed to solidify. The full process includes mold design, metal melting, pouring, cooling, mold removal, and post-processing.
If you consider thin-wall casting rather than CNC machining for your metal parts of thin wall structure, you will find following advantages of it:
Once the mold is built, the marginal cost per part becomes very low, making casting highly economical for mass production.
It can form complex internal geometries that are impossible or extremely difficult to machine, reducing the need for assembly.
As metal is poured directly into the mold cavity with minimal waste (and scrap can be remelted).
You may find the following disadvantages of thin-wall casting:
Very thin walls cool and solidify quickly during casting. Because the metal loses flowability before it reaches all areas of the mold, defects such as misruns or cold shuts can easily occur.
Cast parts shrink during solidification, and the final size is affected by mold wear, temperature changes, and metal flow conditions. These factors make it difficult for casting to achieve the tight tolerances that CNC machining can provide.
The metal solidifies against the mold surface and can form grain marks, porosity, and other surface defects. As a result, cast parts usually require additional machining or polishing to reach the final surface quality.
Aluminum, zinc, and magnesium are common casting materials, while titanium and high-temperature alloys are more difficult to cast.
Dimensional stability depends heavily on mold conditions, pouring temperature, and operator skill, leading to greater variation between parts.
Mold fabrication is expensive and time-consuming, making design changes slow and costly.
The theoretical limit for thin-wall thickness in CNC machining can reach to 0.01 mm, but actually it is difficult, requiring multiple shallow cuts, slow feed rates, and is very costly. For commonly recommended thicknesses for CNC machining of thin-wall metal parts, please check the table below:
Table 1: Recommended Wall Thickness for CNC Machining
| Material | Recommended Wall Thickness | Notes |
| Aluminum | 0.8 mm (down to 0.5 mm for small parts or special setups) | Easier to machine; suitable for very thin structures. |
| Steel / Stainless Steel | 1.0 – 1.5 mm | Harder and tougher materials require thicker walls. |
| Titanium | 1.5 – 2.0 mm | High vibration tendency during machining; requires greater stiffness. |
| - | Aspect ratio of the most commonly used material- aluminum | For aluminum, recommended height-to-thickness ratio: 3:1 to 4:1 to avoid deformation or chatter. |
The wall thickness of castings is primarily influenced by metal fluidity, part dimensions, and the casting method. In the laboratory or using special high-fluidity alloys and advanced die-casting techniques, theoretically, thicknesses of 0.5 mm or even thinner can be achieved. The following lists the generally recommended thicknesses for different situations:
Table 2: Recommended Wall Thickness for Thin-Wall Casting
| Casting Method | Recommended Wall Thickness | Notes |
| Die Casting | 1.0 – 2.0 mm | Best method for thin-wall casting; depends on alloy and part size |
| Sand Casting | 3 – 5 mm (steel may require ≥ 8 mm) | Poor metal flow and uncontrolled cooling lead to thicker-wall requirements |
| Investment Casting (Lost Wax) | ~1.5 mm | Capable of thinner walls with finer feature definition |
CNC thin-wall machining is primarily used for high-precision production and is essential for manufacturing fully functional, dimensionally accurate parts that meet strict specifications. In contrast, thin-wall casting is more suitable for large-scale production or components with complex internal geometries. Both processes are widely used across aerospace, defense, consumer electronics, medical devices, and the automotive industry. Below are common applications in these sectors:
CNC Thin-Wall Machining does not require molds, but the cost per part is relatively high. The key is selectivity: for each dimension that requires strict tolerances, you should carefully analyze its cost-effectiveness. Thin-Wall Casting cost-effectiveness depends on the specific situation. The upfront cost for molds is high, but the per-part cost is low, making it more suitable for larger production volumes.
In summary:
For thin-wall parts, as wall thickness decreases, mold costs for casting increase, and CNC machining costs also rise. Therefore, you should evaluate the process choice based on wall thickness, part complexity, and production volume to determine the most cost-effective solution.
As a CNC machining factory, VMT is committed to providing high-precision custom alloy parts (CNC precision machining thin-walled metal parts, surface finishes, etc.) for various industries. With professional knowledge, advanced CNC equipment, a strict quality control system, and exquisite surface treatment processes, we can meet all your prototype design and production needs. Contact VMT to require a free consultation or quote, we provide 24/7 service.
What is the minimum wall thickness for machined parts?
For CNC machined parts, wall thickness directly affects strength, accuracy, and cost. In most applications, the recommended minimum wall thickness is 0.8–1.0 mm for metals such as aluminum and brass, and 1.0–1.5 mm for steel or stainless steel. While thinner walls are technically possible, they often require slower machining speeds, specialized tooling, and additional quality controls. From a customer perspective, maintaining a reasonable wall thickness helps ensure dimensional stability, reduces the risk of deformation during machining, and shortens lead times—ultimately lowering overall project costs while maintaining part performance.
What is the minimum wall thickness for castings?
Casting typically allows thinner walls than machining, but it comes with process limitations. Depending on the casting method, minimum wall thickness usually ranges from 0.5–1.5 mm. For example, die casting supports thinner walls, while sand casting requires thicker sections for proper metal flow. However, extremely thin walls increase the risk of defects such as misruns, porosity, or incomplete filling. Customers should balance design freedom with reliability, as slightly thicker walls often result in higher yield rates, better surface quality, and more consistent production outcomes.
What are the differences between CNC machining and casting?
CNC machining and casting serve different manufacturing needs. CNC machining excels in precision, tight tolerances, and complex geometries, making it ideal for prototypes, low-to-medium volumes, and high-performance parts. Casting, on the other hand, is more cost-effective for high-volume production and thin-wall structures with simpler tolerances. From a buyer’s standpoint, machining offers flexibility and accuracy, while casting delivers scalability and lower per-unit cost at volume. Choosing the right process depends on production quantity, functional requirements, and budget expectations.
What is thin-wall casting?
Thin-wall casting is a manufacturing technique designed to produce metal parts with reduced wall thickness while maintaining structural integrity. It is commonly used in industries such as automotive, electronics, and aerospace to reduce weight and material usage. The key advantage for customers is cost efficiency in mass production, as thin-wall designs minimize raw material consumption. However, success depends heavily on mold design, alloy selection, and process control to avoid defects and ensure consistent quality.
How to avoid excessive costs in thin-wall CNC machining?
To control costs in thin-wall CNC machining, smart design decisions are essential. Increasing wall thickness slightly where possible improves rigidity and machining efficiency. Avoiding unnecessary deep cavities, sharp internal corners, and extreme tolerances also reduces machining time. From a customer’s perspective, early collaboration with an experienced CNC machining service helps optimize designs for manufacturability. This approach minimizes rework, shortens lead times, and delivers high-quality thin-wall parts at a competitive cost—without compromising performance or reliability.
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