Sucking disc solenoid?

Gallery, Projects and General > How do I??

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Lew_Merrick_PE:
Martin,

1) Commercial electromagnets are measured by lifting essentially pure iron with a machined smooth surface in a fixture that makes intimate contact between the face of the electromagnet and the plate using a load cell to calculate the force. If the part you are wanting to life is not pure iron (i.e. it is steel with some alloying agents), you will not reach maximum force. If the part you are wanting to life does not have a perfectly flat and smooth surface, you will not reach maximum force. This is the first issue.

2) Quite a few vendors of commercial electromagnets lie through their teeth as to the lifting power of their units.

Electromagnets (and other inductors) are all about amp-turns. At 12V, 3W is (3/12 =) 0.25A (in quick & dirty numbers). With enough turns, 0.25A is enough to lift a 2.5 kgF (5.5 lb or 24.5 N) load. Please note the qualifier with enough turns. The resistance of the magnet wire acts to reduce the active voltage in such a circuit. The heat generated by the inductor is I²r (I being current, r being resistance). Balancing these to come up with an "optimum" inductive magnet is no trivial task.

While I am sure that there are good, honest companies in China, my overall experience dealing with Chinese manufacturers is that there is no aspect of design requirements that they will not shortchange upon if they feel they can get away with it (and shave a few more pennies into profit). Please believe that I can make citations in this regard all day long. Caveat emptor is the only "rule" many businesses in China regard as functional.

Arnak:
Hi Andy & Lew,

Andy, thanks very much for the Pick up tool, brilliant. :clap:

I will make a couple of those. :bow:

Lew, thanks very much for the info, it seems obvious that this magnet must be faulty.
It can only just pick up 6" steel rule if touched in the middle, now that can only be a few grams let alone a KG. :bang:

You make some good points regarding the spec of those magnets as well, I don't know about being short a few turns more like a few hundred. :palm:

I think that in this case the only sucking bit is me being the sucker who brought it. :doh:

Martin

DavidA:
This may sound a little silly, but is your rule steel or stainless steel ?

Have you tried to lift other items ?

Dave.

P.s. Don't laugh. People have been caught out by simpler mistakes before today.

doubleboost:
When i was at tech classes
We were told sucking was for sex :bugeye: :bugeye:
In the motor trade we had depresions :( :( :(
He then said you lot make me depressed
I will never forgett those words of wisdom :doh: :doh: :doh:
John

Arnak:
Hi DavidA,

Good thought that but the rule is steel.

I appreciate that mistakes like that are easy to make, that's why I make so many. ::)

I won't make any comments about the sex is for sucking as I'll probably end up getting banned. :drool:

Martin

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