Help designing electromagnet pick up tool(pen)

[myles240]

I am a total newbie to electromagnets. I am a Machinist and need a way of cleaning metal chips out of T-slots on machines. I could not find a tool to buy (I did find one listed from Spap-on but it has been droped for some time). So I am trying to build one. I would like to use 2 AA bateries (pen light design) and keep the overall width of the electromagnet under .5" so that it can fit in the T-slots. Length is not an issue and I am not sure what is more important,pull or area for the chips to attract to. Any help to where I could buy the tool,just the electromagnet, or tips on the design would be greatly appreciated. Just keep in mind I am a Machinist...so keep the words simple! Here is a link to all I could find for off the shelf electromagnet in .5". But it is 12V...will it work for me @ 3V?

http://www.newmantools.com/magnets/emr.htm

Myles

 

[dgallup]

I just modeled the device as stated:

The original design of #30 copper wire, on a 1/4 inch bolt, 5 layers, and 1.25 inch coil height should operate as follows.
1.75 watts
3 VDC
0.58 amps
5.143 ohms
613 turns total
358 ampturns

I added a .001" thick burr .01" away from the pole face so I had something to calculate the attraction on. I used 1010 cold rolled steel material properties for the bolt and burr. Without any outer shell, it produced .06 N attraction. With an outer shell .030" thick and a .125" thick end cap, also 1010 CRS, the attraction on the burr increased to .2 N. Too bad there is no way to attach files on this site or I could give you a nice flux distribution plot.

 

[MagMike]

Hello dgallup,

Here is a workaround that might be worth considering for uploading that flux distribution plot:
faq559-1177

 

[myles240]

There is a picture of a 3D model on this site

http://multiterra.mooload.com/file.php?file=files/1134101668/Assembly2.bmp

You have to click on the little words "click here to download" in the center of the page surrounded by a bunch of advertising. I have a .5" Dia head X .5"long press fit to a 1/4" Bolt(with the head machined off). A plastic nut whitch leaves me with a 1.5" long coil of #30 copper magnet wire. How would you suggest I attach a outer shell and end cap? I never tried but if the site allows me to upload exe files I could upload a model that you can rotate around and look at.

 

[myles240]

Hey they do allow exe files! After you run the file you will be looking at it from the end. Just rotate it around with your mouse. Zoom is the scroll wheel or use the commands on top if you dont have a wheel mouse.

http://multiterra.mooload.com/file.php?file=files/1134103372/Assembly2.exe

 

[dgallup]

Here is the link to the flux distribution plot. My model is not exactly like yours since I did not have time to remake it after seeing your model. In my model the bolt face is flush with the end of the coil. In the left hand plot the shell has material properties of air (like it isn't even there) and in the right hand plot it is 1010 CRS. You can see the radical difference a flux return path makes. I think you would be better off with a slightly smaller bolt since you are not saturating it. That will let you add the shell without going over your .5" OD which my shell exceeds (.56 OD). Also, try to minimize how far the bolt protrudes from the end of the coil and carry the shell down just as far.

http://multiterra.mooload.com/file.php?file=files/1134168973/bolt.jpg

 

[myles240]

So if I understand you correctly I can turn down my bolt to about .188" ,cut off the extra threads on the bolt,and slide on some heatshrink and then slide on a steel sleve. Or does the sleve need to be capped at one end?

 

[myles240]

Here is a pdf if the sleve has to be attached...see if i am on the right track.

http://multiterra.mooload.com/file.php?file=files/1134184633/Assembly1.pdf

 

[dgallup]

One end needs to be capped and the other end, where you are picking up the chips, uncapped. You can have a non-magnetic cap on the working end but keep it very thin. The working flux is going to be between the ends of the core & the shell. Try to have about the same cross sectional area in each.

For better battery life you may want to go to finer wire and more turns. Just a single gage number will make a significant difference because the resistance/length goes up and the length of wire goes up. The total number of amp-turns will decrease only slightly, mainly because there is less total copper and more insulation in the winding window with the finer wire. You don't really need any heat shrink (assuming you are using enamelled magnet wire) but it will help keep things in place. Or you could varnish the wound coil.

 

[EdStainless]

The back end needs to have a magnetic cap/plug that connects the center pin with the shell. At the pickup end you should have an air gap between the center pin and the shell. The air gap is where the field strength will be the highest.
I would wind with very fine wire and keep the coil as close to the center pin as possible. Coat the windings with resin (urethane or epoxy) and shove it all together. Make sure that the air gap at the working face is sealed.
You could put a thin piece of Al or brass on this face to protect it, but keep it very thin.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm