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Common CNC metal spinning problems and solutions

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Metal spinning technique and problem

This article introduces Metal spinning basic problems and technological difficulty , you can know the principle that why your CNC metal spinning path can’t form the sheet correctly ,this article can give metal spinning beginner an answer and settle ways when you have problems in metal spinning forming .

At first ,we need to learn how to form the shape .

Second ,we need to learn how to control the accuracy .

Here we go ....

double roller heavy duty CNC metal spinning forming

 

What is the hardest metal spinning forming products

Metal spinning have different shape , curve and function applied in different industry, many beginners to learn metal spinning are confused what is the hardest metal spinning products ,many beginners are lack of experience ,to know the basic knowledge can help you to assess the metal spinning project and reduce the cost of mistake .

 

Typical metal spinning products and solutions

 

1. Big flanging

big flange metal spinning problem

① Flange wide : Flange wide is big ,the flatness of flange is harder to control,the radius of flange is easy to break in the metal spinning process .

② Cylinder height : cylinder height is more than 80mm, it is hard to metal forming .

③ Air pressure holes : the metal spun product will hold and the flange radius position tightly ,it needs air pressure to demold from holes .

④ Flange radius : if the flange radius is less than 5mm,the blank thickness is thinning more in the flange radius position ,it is easy to break in the flange position if the thickness reduce too much .

⑤ Flange flatness : the metal springback will make the flange is not flat ,so we need to turn a angle in the mold according to the springback value .

⑥ Inclusion : Flange wide and cylinder height decides the difficult of metal spinning forming ,the value is bigger ,the metal Spinning forming is harder ,the radius of flange is little ,the thinning rate in is more in the flange radius .

 

2. High cylinder

High cylinder metal spinning problems

Metal spinning height : it is hard to spin when the height of stainless steel is over 120mm.the height of cylinder can achieve 150-180mm by metal spinning .aluminum and steel can achieve 400-600mm height after metal spinning forming .

Deep drawing blank : You can use a deep drawing blank as the first process ,then put the deep drawing blank in the metal spinning mold to make metal spinning ,it can achieve higher height than that made by metal spinning only .

Metal spinning path : metal spinning path includes go path and back path ,go path make the blank sheet reduce the diameter towards mold ,back path keep the blank sheet hold the mold tightly and reduce the gap between blank and mold ,other the thinning rate is big if the gap is too big .

The radius of go path : if the radius is little ,the deformation is obvious and springback is less ,but the thinning rate is big ,the blank will be break if the thickness is less ,if the go path is bigger, the thickness is thicker after spinning ,but the edge will crinkle as the strength of the edge is not enough .

Cutting the edge : the length of edge is not uniform after metal spinning many times of path ,you can use cnc turning tool to make the edge uniform , otherwise the long edge will break .

 

How to settle the deep metal spinning problem

① Edge crinkle : you can reduce the go path radius to increase the strength of edge .

② Bottom break : you can increase the go path radius to reduce the thinning rate , or you can reduce the gap between roller and mold , to make the sheet hold mold tightly ,you can use the the little hammer to hit the hold mold part ,if the sound is loud ,the gap is big .

③ Edge is not uniform : you will find the length is different in the edge after spinning many times like the image position .you can use CNC turning tool to turn the edge uniform .

Inclusion : deep metal spinning is hard ,you need to choose the right radius of go path ,and use the back path to reduce sheet thinning ,if you have the mold to make the deep drawing blank ,it can achieve higher height than metal spinning .

 

3. Shear spinning

shear metal spinning common problems

Shear spinning is a simple CNC metal spinning path ,you just choose the right gap ,spindle speed ,feed speed ,it can make the shear spinning successfully ,When the angel is big than 20º,you can choose the shear spinning.

Shaking line : you find shaking line on the exterior surface ,you can listen the shaking sound in the process , the gap is too little ,the machine will bear stronger force ,so the exterior line will have the shaking line .

Interior surface is not smooth : this is the blank sheet don’t touch the mold in the spining as the gap is big .

Metal backflow : if the bottom of metal spun produt and mold have gap ,it prove the gap is little ,you can increase the gap .

Morse taper : it is used to control the runout accuracy of metal spinning mold with +-0.01mm ,when you spin some cone (such as liner>>)needs high accuracy ,you can choose Morse taper to assemble mold on the CNC metal spinning machine .

 

4. Thin thickness

thin thickness metal spinning problem and solution

① Thin sheet metal spinning is easy to crinkle in the edge like the following image ,because the edge of thin sheet is soft . you can use little roller (roller radius is less 6mm) to spin ,little roller can form tiny and uniform rings in the blank sheet and improve the strength of the edge .

what is crinkle

② The other way is use the back roller to support the edge ,it can improve the strength of the thin edge .

③ You can spin a little edge as the first step to improve the strength .

 

5. Curve precision control

how to control the curve accurace of reflector

Metal spun products needs to control the accuracy of the shape or curve ,such as radar ,reflector,signal receiver. It is a dome shape usually .these products need the accuracy of CNC metal spinning lathe ,we choose the right RPM, feed speed and gap .we need to control the blank sheet to hold mold tightly with a little gap. Then you can choose a inspection tool that can be made by planar laser to check the shape accuracy .

If the accuracy is not qualified in some position like images , spring back is the main problem ,you can respair the mold to make the shape back to actual curve .

 

6. No-mold metal spinning

no mold metal spinning used in fan industry

No - mold metal spinning is applied in fan industry>> ,most of fan products have big dimension ,in order to reduce the mold cost ,no- mold metal spinning have a obvious advantage to form a fan components .

① Avoidance roller : it prevent the interference with mold when roller move follow the exterior curve of mold .

② Support mold : clamping press the sheet on the support mold and take the sheet spinning .

③ Back roller : it to make the support and make the flange flat .

④No mold : it save the mold cost in the fan industry.the separate mold design will be expensive like the right image .

 

7. Why need deep drawing to make the blank

deep drawing can improve the prodution efficiency of metal spinning

Reduce production time : Deep drawing is another metal spinning forming technique ,the mold cost of deep drawing is more expensive than metal spinning ,but the production efficiency is quicker than metal spinning ,so using a deep drawing to make a blank .you can make a blank like the image show ,it can save 1/3 - 1/2 process time of every piece.

Increase the forming height : On the other hand ,it improve the forming height greatly ,such as stainless steel 304,we can spin height at most 150-200mm height ,but when you use the deep drawing to make a first blank ,the height can achieve 250-300mm.

 

8. Necking spinning

necking metal spining problem and solution

Support point problem : spindle mold offer the support force in the support point ,if the gap is over 0.5mm between spindle mold and the first process blank ,the first process blank will crinkle quickly in the necking ,you will can’t finish the necking if the gap is big .

 

How to control the gap

① Control the accuracy of the first process blank : if the accuracy of the first process blank is not good ,some blank can’t put in the spindle mold ,some blank put in spindle mold with a big gap .

② Turning the support point of spindle mold to suit the first process blank with little gap as possible .you can put the first blank a little tightly by clamping force ,but when we finish the necking ,the diameter of support point of metal spinning product will be round after necking and it can be take easily .

③ Using the ambulacrum : ambulacrum is used to drive the motor and pulley ,it is softed than metal spindle mold and it have good abrasive resistance .

④ Using the hydraulic fixture : this is the best way to hold the first process blank tightly ,on the other hand ,it is easy to take of the metal spinning product that hydraulic fixture can open when we finnish necking .