Hello all, I am new to the forum an

[Joan Porquer]

Hello all, I am new to the forum and I regret to tell that, although I am an engineering enthusiast and do play around with concepts for my engineering team to understand my needs from the market, actually I am a Marketing Director. I hope this is not a reason to reject my participation here.

I am working on a project that requires some sort of non-mechanical latching system, and the customer is asking to use magnets.

The idea would be to use a permanent magnet to attach to a moving part that needs to be retained at a certain position. The fix part would be an electromagnet with an iron core: the idea is to release the moving part that has attached to the core of the electromagnet by applying a current to the electromagnet with an inverse polarity to that one of the fixed magnet, provoking a repulsion force.

In this way, when the moving part carrying the permanent magnet enters in contact with the fixed unenergized electromagnet, the system would be attracted and thus remain in that position. As soon as the electromagnet receives a current, the repulsion force would make the system detach.

Is this just a stupid nonsense out of a ridiculous marketing mind?

Is there any literature I can find to understand how to dimension both elements?

Forum manager: if this topic is not in the right position please feel free to move it where it belongs.

Thank you all for your attention.

Regards from Barceona.

Joan.

 

[MagMike]

I realize the concept seems simple and straightforward, but the practical details to make this work are extremely challenging.

Unless minimal retaining forces are involved, it will require a lot of power to the electromagnet to produce a sufficiently strong repulsion force.

To evaluate feasibility, can you answer the following:
Approximately how much retention force is required?
How large is this going to be?
How much power is available to energize the electromagnet?

I am not aware of any literature that would directly address a design like this.

 

[IRstuff]

It's only slightly removed from the magnetic door locks that we have at work. You might want to buy a couple to see how they do it.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[Joan Porquer]

Thanks for your reply!

So it is clear that a dumb question is always more difficult to reply than a question from an expert, huh!

To put this into a more graphic terrain, just imagine a drawer into a cabinet that needs to be hold in the closed position with a pushing spring that would try to open it. The electromagnet is unpowered and the permanent magnet is keeping the drawer in closed position.

As soon as I want to open the drawer I switch the electromagnet on and the magic happens.

Those would be more or less the conditions. The dimension is in the order of centimeters or millimeters.

 

[Joan Porquer]

Hi IRstuff, thanks for your comment.

I have looked into those, and it seems that they use the current to keep the dore closed. As soon as the power is off the spring opens the door.

The problem is that this system is using power continuously and I want to make an energy efficient system. So I need to do it the other way around.

 

[IRstuff]

Still unclear about the level of retention force. Cabinet doors sometimes have magnetic latches, but they're relatively easily opened by pulling a bit harder. For stronger retention forces, ala tens of pounds of force, you run into the problems alluded to by MagMike.

The alternative is to use mechanical advantage to move the magnet away from the metal surface it touches. see Switchable Magnetic Base here:

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=824

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[IRstuff]

Magnetic door locks come either fail-safe of fail-secure. The latter stays locked with power off:

https://www.alibaba.com/showroom/fail-secure-magnetic-lock.html

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[EdStainless]

These were used commonly in signs to latch elements. There is a fine balance between the the holding force, current to unlatch, and the risk of demagnetizing the magnets.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed