Magnetize Pick-up/forming Tool

[mhammonds]

Hello Everyone!
I was hoping you could help me. I am designing a pick-up/forming tool for a machine I am working on. Because of the required geometry of the forming tool I elected to try and magnetize the tool so that it could pick up a steel spring and then place it into a spring retainer while forming the top of the retainer and capturing the spring. There really is no room for any type of conventional gripper mechanism and it seemed a logical way to go. However the forming tooling wants to be made of tool steel and hardened. I made a prototype and intended to just place permanent magnets inside it with the intention of magnetizing the whole head. It did not work and the forming tool seems to block any of the magnets field. I made the tool out of A2 tool steel. I have attached a Cross Section of the design. Is there another tool steel that would allow this to work or a method to magnetize the head? Please take a look and I welcome any and all suggestions. Thank you in advance.
Mike

 

[dgallup]

Can you make it out of a 400 series stainless like 440C? They have pretty high permeability and flux density.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[MagMike]

What type of permanent magnet material did you use? If the blue rings in your image are the magnets, it looks like they are pretty small relative to the tool. If they were not rare-earth permanent magnets, they were probably not powerful enough to magnetize a large enough volume in you tool.

 

[EdStainless]

Have you tried magnetizing the entire tool? In the days before modern magnet alloys they used Cr tool steels as permanent magnets. Wrap the entire tool with cable and give it a DC pulse and see how magnetic it becomes, you may have enough to do the job.

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Plymouth Tube

 

[RyreInc]

Looks to me like the tool steel is creating a return path for the magnet, bypassing the region of interest.

My best guess is to increase the inner diameter of the magnets (as little as possible) and bring them down far enough so they are flush with the lower surface of the tool (i.e. no steel on the bottom end of the magnets). This may give the field a chance to reach out into space instead of go through the steel only.

I made a crude drawing in my rotationally symmetric FEA software (using M19 steel and N45 magnets) and tested these ideas:

 

[MagBen]

agree with RyreInc. using paramagentic steel, e.g 3xx stainless steel. Or, simply putting the permanent magnet on the top of the tool such that no shunt effect.

 

[mhammonds]

dgallup....thank you for your reply. I have done some testing and I think changing to stainless will work much better. I already have a proto-type in the shop.

MagMike....thank you for your reply also....the magnets I show in the drawing I have already had changed to a larger magnet (neomydium ring magnet) .....they are rated to hold 16lbs each and I will have (2) of them. I did notice that in my design I was not making contact to the sides of the magnet with the head. There was a gap....and only making contact on the bottom. I made a steel sleeve and closed the gap. This allowed more surface contact to the head itself from the magnets. This made a big difference in the strength of the magnetism thru the head. Together with this change and changing the material I believe the problem will be solved. Once out of the shop.....I will post results.....

Thank you all again....

 

[mhammonds]

RyreInc...thank you for your time.....One other thing I did was reduce the thickness of the tool from the magnet to where I needed to pick up the spring. (as you suggest in your reply) I think this was also a contributing factor for the sucess in the changes made. What program did you use to show the magnetic fields?
Thank you again.
Mike

 

[RyreInc]

I used IES Magneto, but there is a free equivalent called FEMM.

 

[mhammonds]

EdStainless....
thank you also for your reply.....
That was the first thing I tried......it was not sucessfull.......although I thought it would be....we tried many different variations.....think the head was too big....same set up worked great to magnitize a screw driver...
Mike

 

[ndsram]

Dear mhammonds,
I suggest you look for low carbon steel 1008 or 1010 option, as it has got higher permeability and higher saturation magnetization. Please tell me, do you use some water as coolant. If you're using water, then this steel may get corrosion. In that case I suggest you to got for SS430.
I can help you in design on FEMM, if you could send me dxf file instead of dwg