When many mechanical engineers design metal spun parts at the first time, they tend to overlook many issues. This article mainly introduces various technical problems in the design of spun parts.

1. Material selection

The structural strength, hardness, corrosion resistance of spun parts is mainly related to the metal type, metal thickness and the shape of metal spun.

①  Material performance

Different metal has different tensile strength, the tensile strength of stainless 304＞mild steel ＞ aluminum. Many people don’t know how to choose the right aluminum series , now we introduce the aluminum series in the following table. You can choose the right aluminum series according to the material performance.

② Materials spinning performance and tensile strength

The Spinning performance : 1100＞3003＞5052＞6061＞2024＞7075

The structural strength : 1100＜3003＜6061＜5052＜2024＜7075

③ Material grains refined

The grains of blank materials are refined after spinning, the hardness and strength are improved.

2. Structural design 

The design of thin-walled parts by metal spinning mainly needs to consider structural strength, which is mainly related to the type of material, thickness and the shape of the structural design, The design of structural shape is main aspect that beginners tend to overlook the most. If you want to design a perfect metal spinning product, you need to know how to analyze and determine the weak and strong areas of a product's structure.

① Weak area of structural strength

The position of the trimming edge and the bottom of the spun part are usually the structural weak areas of the product. The blue area is the weak area in the following image.

② How to improve the structural strength

Flanging design or the curve of trimming position undergoes sudden changes or bends, the structural strength will be improved.

3. Tolerance design

Many engineers don’t know how much precision to design for spun parts. They usually design it according to the accuracy of CNC milling and turning parts, actually the tolerance of metal spun products is worse than CNC milling and turning, the blank will have springback and the internal stress is not uniform when it is pressed and pulled by roller. The final diameter is bigger than the mold after spinning, the springback of materials is bigger, the final diameter of metal spun products is bigger. The cylinder curve will have a little cone like the blue line in the image, the edge have a littlet trumpet like the red line in the image.

On the other hand, the internal stress of metal spinning will make the weak area of structural strength deformation, actually the edge is oval and soft without flanging or rolling.

① What the factors effect the metal spinning tolerance

The accuracy of metal spun products is related to the diameter, structural design, materials types and thickness.

  ● The diameter is bigger, the accuracy is worse. 

  ● The strength of structure design is stronger or the thicker thickness spinning can improve the strength, it can reduce the internal stress effect. So stronger structural design and thicker metal spinning product have good precision.

  ● Different material types have different springback and and internal stress. Aluminum springback ＜ steel springback ＜ stainless steel springback ＜ titanium springback, springback is less, the accuracy is better.

② What the accuracy the metal spinning can meet

The accuracy of metal spinning product is better than welding or sheet metal, but it is worse than CNC turning, actual best diameter accuracy of metal spinning product can meet +-0.05mm, thickness tolerance can meet +-0.05mm. Most of metal spinning tolerance can achieve +-0.5mm.

How to control the metal spinning tolerance ＞＞

4. Deep drawing limit

All metals have fatigue strength. When the spinning roller repeatedly pull and press the work piece many times and the metal exceeds the ductility and fatigue strength, the spun material is prone to fatigue and cracking. This manifestation is more obvious in stainless steel and special materials＞, so the height of metal spinning had better to design short if it is allowed.

5. Size adjustment

Metal spinning usually requires adjusting the mold to adjust the size of the product. Metal spinning mold can reduce the diameter but can’t increase the diameter, so you can design bigger diameter if you have the plane to adjust.

6. Cost analysis

Metal spinning mold is cheaper than other metal forming, such as deep drawing and water expansion. The mold lead time is shorter. Of cause, the most of metal spinning production time is longer. So, If you have a small amount of metal products that need to be customized, spinning is obviously a better choice.

7. Surface treatment

The spinning surface will produce a slight and uniform indentation of the roller ( it is also called spinning line). In order to get the better smooth surface, you can choose the polishing to remove the spinning line.

Powder coating and painting are commonly used surface treatments, it is widely applied in stainless steel, steel, aluminum, Customers can choose different colors and gloss. Oxidation is often used in the surface treatment of aluminium, Electroplating is used for surface treatment of steel, mirror polishing and brushed is used for stainless steel. Surface treatment greatly enhances the corrosion resistance and appearance performance of the metal surface

8. Hole process

Most of the spun parts are used as shells, the holes are usually machined on their surfaces for assembly or welding. Stamping and three-dimensional cutting are excellent methods for processing spun holes. When the production quantity is small, three-dimensional laser cutting can save mold costs. When the quantity is large, the stamping production efficiency is more advantageous.

Someone ask why we don’t choose the CNC milling to make the holes. Because the spun part is a thin-walled component and it’s strength and rigidity is not enough to bear the cutting force, it is easy to shake by CNC milling processing. If you need to process metal spun production by CNC milling with a good accuracy, you need to design a good CNC milling fixturing to improve the strength and rigidity of metal spun product.