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How to learn CNC metal spinning forming technology

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Many peoples want to learn CNC metal spinning forming technology , but they can't find a good way or platform to learn .many metal spinner are engaged in hand spinning are curious how to learn CNC metal spinning quickly and what skills need to master in CNC metal spinning ,except you need to design the CNC metal spinning path in CAD software and make the CNC coordinate and program in Mastercam soft, you also need to know how to operate the CNC metal spinning machine. This article can help you to know the basic knowledge of metal spinning material , ,mold design and CNC metal spinning forming skills .

CNC metal spinning metal spinning with heating

① Metal spinning materials >>

Metal spinning material is important knowledge you need to know ,not all the metal types are suitable for metal spinning ,you need to know basic metal spinning materials. At first ,different metal has different spinning forming performance ,the value of hardness and tensile strength is bigger ,the spinning forming performance is worse ,the value of ductility is bigger ,the spinning performance is better .the higher value of hardness and tensile strength needs stronger spinning force to form .Second ,different metal have different unit price ,you can know the material cost and save the cost for you customer ,Third ,to know the metal other processing performance and mechanical properties ,you can choose the right metal to give customers a good metal spinning solutions .

CNC metal spinning blank sheet

Learn period : 1-2 weeks .

It takes one 1-2 weeks to know the density , unit price and spinning performance of different metals .so you can understand which metal is suitable to metal spinning and how to calculate the material cost of blank .

Density :  Aluminium - 2.75KG/M³ Titanium - 4.75KG/M³ Steel and stainless steel - 7.85KG/M³ Copper and brass - 8.95KG/M³

Unit price :  titanium >copper >brass >stainless steel >aluminium >steel .

aluminium - 3.43 dollars/KG  aluminium alloy - 4.15 dollars/KG  steel - 0.82 dollars/KG

stainless steel 304 - 2.67 dollars/KG   stainless steel 316 - 3.88 dollars/KG

titanium Ti1 - 19.4 dollars/KG   brass - 6.7 dollars/KG   copper - 11.9 dollars/KG

inconel 718 - 53.8 dollars/KG  Hardox - 2.09 dollars/KG

How to calculate the material cost of metal spinning

Material cost = Density*Unit price *πR²*T(R is the radius,T is thickness of blank sheet )

How to calculate the dimension of blank sheet and tube 

Many metal spinner are confused how to calculate the blank dimension of bland sheet or tube that used in sheet spinning or tube spinning .We can calculate the material cost after we know calculate the blank dimension ,metal spinning is divided into sheet spinning and tube spinning ,there is different to calculate the blank dimension between sheet spinning and tube spinning .

The dimension of blank sheet in sheet spinning

When we get a drawing or a sample ,we will know the final dimension metal spun products ,but how to calculate the blank dimension ,it needs experience to assess .The dimension of blank sheet includes diameter and thickness, there are two changes of blank sheet in sheet spinning ,the diameter and thickness of blank sheet will reduce after metal spinning, so we should need to calculate the dimension of blank sheet according to these two changes .

Blank sheet diameter :

No matter how blank sheet changes after spinning ,the total weight of metal spinning products is about same as blank sheet . 

Blank sheet weight = metal spinning weight + turning weight

Turning weigh refers to the Max edge or bottom edge are cut removed by turning.    

You can calculate metal spinning weight by UG engineering , or you can weigh the actual metal spinning sample .

Blank sheet diameter = blank sheet weigh / density /π/T

T is the blank sheet thickness

Blank sheet thickness : blank sheet will be thinning after sheet spinning ,when you know the actual thickness of metal spinning products (the thickness of the drawing ),we can calculate the blank sheet by the following formula

The blank thickness = the final thickness after spinning (the thickness of drawing ) / thinning rate

Convention spinning : thinning rate value is about 0.5- 0.8, the metal spinning forming angle is bigger and the height is higher ,the thinning rate is bigger .

Shear spinning : the blank thickness * sinα=the actual thickness after spinning

Neck spinning : neck spinning thickness will increase 10% -30%, the necking value = Max diameter -Min diameter ,the necking value is bigger ,the thickness increase more thickness .

Expanding spinning : expanding thickness will reduce 10-30%, the expanding value = Max diameter -Min diameter ,the expanding value is bigger ,the thickness reduce more thickness .

The dimension of blank tube in tube spinning

Tube diameter : if you used expanding spinning ,tube diameter is Min diameter ;if you used necking spinning ,tube diameter is the Max diameter

Tube height = products height + spinning lengthening10mm) + clamping height20-50mm

Material types and spinning performance 

Steel: DC03/DC04/SPCC/Q235/Q275/Q345/SJ235R/SJ275R/SJ345R

Aluminium: 1060/1070/1100/3003/5052/6061/6063/2024/7075

Stainless steel : 201/304/316/310/630

Special metal : Hardox ,Inconel 718 ,GH 3044

Inclusion : Except the material types are marked by blue need to make by heating ,other metal can be spun without heating ,aluminium ,copper is soft to spinning ,stainless steel is harder  aluminium and copper ,brass have stronger spring back than aluminium and copper ,but their ductility is still good .

All the aluminium must be use the H24 state( this aluminium is softest , so the ductility is best )

The best spinning steel is DC04this type can be used in deep drawing as the good ductility .

Stainless steel must use the DDQ, it means deep drawing quality ,the other stainless steel such as BQ, it means brushed quality ,it can be spun without good ductility ,you can buy Pohang stainless steel.>>

 

② Metal spinning mold design >>

Common metal spinning mold design

Learn period : 1-2 weeks .

It will take two weeks to learn CNC metal spinning mold if you know CAD design .

Spindle assemble ways : Mold is assembled in spindle by one location hole and six screws.

Spinning steps : You need to know to analysis the metal forming steps when the metal spun products of different shape .

Forming support point : the first touch material point of spinning roller in the CNC program must be support by exterior mold or interior mold to improve supporting force of the blank metal sheet or tube .(the second metal spinning forming needs to support by exterior or interior mold as well )

Mold hardness : mold hardness is higher ,the interior surface of metal spun products is smoother, you can choose different steel to make mold when spin the different metal ,mold material has 45#, 40cr, Cr12 ,Cr12mov .material cost is 45#<40cr< Cr12

The hardness of mold is not enough will make the mold deformation when the roller press the metal in the mold ,such as when we spin stainless steel ,the mold material is 45#, the mold will deform after stainless steel spinning and increase the gap between roller and mold that is setted by CNC program ,the stainless steel spinning will break if the gap increase . on the other hand ,soft mold surface will damage and scratch make the interior surface of metal spinning products scratch .

Mold accuracy : Mold needs to control the runout within 0.03mm. if the mold accuracy is not good ,the metal spinning products will have different thickness in any cross section, the edge will be inconsistent.

 

③ Metal spinning roller >>

Learn period : It will take one weeks to learn CNC metal spinning roller if you know CAD design.

Radius of roller

This is important parameter of metal spinning roller ,shear spinning needs R4-R6mmConvention spinning needs R6-R14mmshear spinning needs more spinning force than the convention spinning .The radius value of metal spinning is bigger ,the single point pressure of metal spinning roller is bigger ,the thinning rate is bigger .

If the metal is softer(such as 2-3mm aluminium or copper ) ,you can choose radius is about R12-14 mm to make convention spinning .If the metal is harder(such as 2mm -3mm stainless steel ) ,you can choose the radius is about R8-10 to make convention spinning . If the thickness is less than 1mm, you can Choose the R6mm, because bigger radius of roller will make the edge of sheet crinkle as the edge strength is not enough ,or you can choose bigger roller to spinning with a slide roller in the edge .

Roller hardness

Metal spinning roller needs higher hardness than mold ,because roller very point touch more times than mold ,so the hardness of roller material needs to achieve HRC58if you spinning stainless steel or the metal hardness is over stainless steel ,you hard better to make plating harder metal above spinning roller .

The hardness of roller is not enough will make the the exterior surface of metal spinning products scratches, the blank sheet can be pull and break after the exterior scratches.

Roller accuracy : roller needs to control the runout within 0.02mm. if the mold accuracy is not good ,the metal spinning products will have worse accuracy and different thickness in any cross section.

Basic roller material : Cr12mov ,DC53 ,SKD-1

 

④ CNC metal spinning path and debug>>

How to make a metal spinning path ,this is hardest technique ,not only you need to know the the performance of blank metal spinning materials ,but also you must to learn the metal spinning forming .even every shape can be form by different CNC spinning path ,but you can handle some basic principle and technique in metal spinning .

Rotate speed : bigger dimension ,thick and hard blank sheet or tube need to lower rotate speed ,such as stainless steel metal spinning needs lower rotate speed than aluminium .higher rotate speed can form metal with thicker thickness after metal spinning ,the exterior will be more smooth .

Feed speed : bigger dimension ,thick and hard blank sheet needs lower feed speed ,low feed speed can form metal with thin thickness after metal spinning ,the exterior will be more smooth .

The radius of roller : the radius of roller is bigger ,the thinning rate is less ,the edge is easy to break or crinkle . the radius of roller is less ,the thinning rate is big ,it is easy to break in the position that is close to mold .

The radius of single go forming path : the radius is bigger can reduce thinning , but the deformation is less and spring back is more obvious , the radius is less can pull the sheet seriously and make the sheet thin quickly ,it will will be break when the sheet is pulled too thin by roller .

The radius of single back forming path : Back forming path is helpful to maintain the thickness and make the sheet can hold the mold with less gap .

The gap between mold and roller after spinning : if the gap is too big ,the interior surface of metal spinning can not be pressed tight on mold ,the interior surface will not smooth .If the gap is too little ,the metal spinning machine will be loaded more spinning force ,the metal spinning machine will have a little shake and the exterior surface will have non uniform spinning lines.

How to judge the gap is right : at first ,when the metal spinning product is on the mold ,you can check the exterior spinning lines ,if the spinning lines is non uniform ,the gap is less .if the spinning lines is uniform ,you can use a hammer to knock on the different position metal spinning products , if the sound is clear echo ,the gap is bigger .second ,when the metal spinning product is took from mold ,you can check the interior surface to judge whether the gap is right .

How to improve the surface finish : you can add a last CNC metal spinning path with higher rotate speed and less feed speed .

How to improve the accuracy >>: to reduce the spring back and make the sheet hold the mold tight ,to keep the temperature maintain a stable value , if the temperature is not stable ,the metal spinning roller and mold have expansion and Contraction effect the gap ,so the gap changes will effect the accuracy of metal spinning products in the production .

Hope this article is benifit for you to learn CNC metal spinning .