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Electro magnet made from a microwave Transfor

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Gregory

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I would like to build a electro magnet from a microwave transformer.
Question
1
If I remove the winding with the fine wires and can I replace that winding with tha heaver winding and join the windings together does this give me a stronger magnet.
 

dr pepper

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If you mean increasing the number of turns then no that will weaken the field.
 

shortbus=

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You do know that you need to just use the "E" shaped core to make a transformer into an electromagnet don't you?
 

Gregory

Member
Yes’s I do understand the the e shape iron cor is required to make the electro magnet.
I am trying to make a electro magnetic vice for my milling machinewhich I require the vice to be very strong to prevent the Jobes from moving
I am trying to find out how to make a very strong magnetic vice.
Can you advise me.
Is it bettter to use Ac or Dc
Is the voltage important or current or both.
Is the wirer winding need to be thicker with less turned.
 

dr pepper

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Some surface grinders have magnetic vices, most tend to be non powered permanent magnet, there are some electric ones, I've seen just the 1, it was Dc.
Ac might work, the issue it has is that unless the poles are shaded the field will pass through zero, so if theres vibration the work may shift, the good side is that swarf is less likely to stick to the work.
 

shortbus=

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Is it bettter to use Ac or Dc
Was a die maker/machinist for my whole adult life. Don't know if this is a good idea for milling. Ussually magnetic chucks are only used for grinding. Milling puts much more force into the work.

For two reasons;

1. grinding has less real force(while still quite a lot) than milling.

2. the chips are smaller with grinding, what are you going to do about the chips sticking to both the work piece, the magnet and the cutter?

But to answer the AC/DC question, most of them are DC. That way you can reverse the polarity momentarily to release the work. Most work holding is done with pot type magnets, not an E type. The pot allows more of the magnetic force to work, Google electromagnetic grinding chuck.
 

shortbus=

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Some surface grinders have magnetic vices, most tend to be non powered permanent magnet, there are some electric ones, I've seen just the 1, it was Dc.
My experience over the years of doing this is just the opposite. Most are DC powered, they hold better and release better by pole reversal.
 

dr pepper

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I agree shortbus, I must have explained that incorrectly.
Braked motors have Dc brakes for the same reason.
 

schmitt trigger

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Short answer: Ampere-turns. You can trade one or another (within limits, of course)

What I would do? Measure the actual winding resistance. Let's say for the sake of simplicity, it is 100 ohms.
That means if you apply 50 volts, then 1/2 amp will flow. 100 volts, 1 amp.

You can think...hmmm, I'll try 200 volts. The problem is that as you increase the voltage, the power dissipation increases with the square of the voltage.
Eventually it will burn.

So you will require to empirically find what is the maximum power you can dissipate without burning the wire insulation.
Mind you, the wire inside the core will be perhaps 30C hotter than the outside.

That is the reason many power electromagnets are only rated for intermittent duty.
 

dr pepper

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There are probably examples on the net of this kinda thing.
 

shortbus=

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What is your advice for making a powerful magnet can it be made out of a microwave transformer
A work holding vice I don't believe can be made from a transformer, microwave or other type. A single transformer won't have very much holding force, and still has the problem of the chips sticking to the part being machined, causing bad finish and for small cutters the chance of breaking. And your cutter will become magnetized so chips will stick to it if not used with the magnet later.

This site shows what a work holding chuck looks like. The orange looking ovals are the coils. The centers of those ovals are one pole, the outside of the ovals is the other pole. They are all connected on the bottom side, to make a magnetic path. In use you would put the part so it covers the most poles to get the highest magnetic force. http://www.uptechengineering.com/electromagnetic-chuck.html

There is one Youtube of a guy doing it, but he is just using it to hold parts in his hand to belt grind them, not milling or other machine work. Belt grinding uses much less force than regular machining.
 

Gregory

Member
I have read the replies and and have to the conclusion that the magnet vice is out of the question.
Transferring my question to a magnetic bender .Can you help me with this project.
 

alec_t

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For the reasons given in post #13, I doubt it would be successful, unless you are planning to bend only very flimsy material.
 

shortbus=

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Can I use microwave transformers as a magnetic bender
A transformer micro wave or other is only good at being a transformer. That is what it was designed for, other electromagnetic things are designed for the job needed. Sorry....
 
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