Yet another magnetic hold down idea

Hello again. When I first started using my GF :glowforge:, I was a bit paranoid about the material moving while cutting. This was all before I thought about cut order. I looked around on the forum and sure enough there were all kinds of ideas to make hold downs. I liked the magnetic ones like the one by @pubultrastar the most

but I don’t have a 3D printer - but I do have a GF, right?

My idea was to create a sandwich of three 1/8” draftboard layers. The bottom layer would keep the magnet from falling out. The middle layer would hold the magnet. The top layer would be cover but also be the lip for when I want to hold down 1/4” material. I also cut four “pins” to make sure the alignment was correct.

I bought some very strong neodymium magnets from Amazon:

I got N52, since I was worried about the thickness of the 1/8” bottom layer. As it turns out, I could have used weaker. In fact if these magnets stick together by themselves, good luck getting them apart again. You need to slide them off with one of them behind some kind of ledge. I couldn’t with my finger strength, simply lift them off vertically. They come shipped with a 1/8” non-magnetic spacers so that they are easier to pull apart. But beware - the magnets can fly out of your fingers and attach to the rest of them if you’re not careful. This is another reason to have the magnet held in by that bottom layer and not epoxied in and directly exposed.

So the top edge (when looking at it from above) holds down 1/8” material while the bottom edge holds down 1/4” material. Moving is probably not an issue with big 1/4” boards but can be if we are using smaller remnants - or at least that’s what I’m predicting. For thinner material up to and including 1/8” you can place them directly on top and it will still grip the crumb tray with good force.

I also cut two curves on each side of the bottom two layers to provide a kind of “grip” when you want to lift them off.

Didn’t know what to put on the top layer, so I just engraved 1/8” and 1/4” to indicate ledge height and “N52 Neodymium” in case I forgot how strong it was - duh. Actually it’s so strong I want to make sure I don’t bring it near sensitive electronics, like… a… laser cutter…? No issues with that so far. I did some cuts where the head went right by them and it was not affected (as far as I could tell). I also marked up arrows on the lower two layers because orientation is a factor - the middle layer is longer than the bottom layer and the top layer is longer than the middle layer. The orientation of the pins is critical too - clean sides toward you, burnt sides to the sides as in the photo - because of the way the kerf was designed. On my .svg file I made two sets of four pins because they were so small I thought I might loose them or drop through the crumb tray and didn’t want to have to cut them all over again.

The whole thing was then glued together.

Here it is in action.

IMG_2531

Here are the .svg files if anyone is interested. Kerf is for 1/8” draftboard. Use at your own risk, okay? I have not tested every possible condition. Also try not to put these magnets near hard disks, mechanical wrist watches, and pacemakers - just to be on the safe side. Use weaker magnets if you feel uncomfortable. Also feel free to change the engraving to whatever cool design you like. If I do it again I think I’ll engrave something more inspiring on them.

GF Magnet Hold Downs.svg.zip (2.9 KB)

UPDATE: Okay, the .svg issue should be fixed now. It is now a .zip file. Uncompress and it should work fine. Big thanks to @ChristyM for the solution.

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Thanks for sharing. I moved this to the Free Laser Design category so people could easily find it.

:slight_smile:

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Thanks. The .svg file is still not uploading properly. Don’t know why but I lose stroke color (which I use to group cuts and determine cut order) and then it fills where it should be a stroke. I’m using Illustrator and tried both Save as… and Export as…

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I think you might need to zip it first (before uploading).

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Nice Design! I have the same magnets that I’m using “naked” right now. Thank you for sharing the drawing.

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Right - I’ll give it a shot!

UPDATE: I tried it and it works on my end! Let’s hope it works for everyone else as well! Thanks for the tip.

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Thanks, @tjleasa! Pretty strong stuff! Love your exhaust port and cap idea. Looks great!

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Thanks, It’s still working really nice. You may recognize the magnets. :slight_smile:

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I certainly do!

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Thank you!!

Fabulous! As another non-3D printer owner this rocks :slight_smile:

Will those magnets still hold down through a piece of 1/4"? I’m curious if they are strong enough to fight wobble in the materials - since having your stuff flat against the tray is best. I’ve ordered strong bar ones, but even those don’t register through 1/4". I’m curious about the rounds :slight_smile:

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Interesting but thinking of the look after the wars . neither magnet or hold-down pins have survived unscathed. I think of hold down pins as ablative and rarely surviving a dozen uses but the magnets have discovered a hole in the universe and often hide there among the lost socks.

The magnets in steel casing survive the best and focus the hold mainly down, while the steel casing is armor against being lasered. I have been looking at those high powered ones and thinking of using the steel flashing to make cases. I am thinking also that they might be good for making spice shelf refrigerator magnets.

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just salvage hard drive magnets.

you don’t even have to remove them from the metal plates. you can use the edge of the metal plate to hold down the material while keeping the magnet closer to the crumb tray. and you only need to overlap the tiniest little bit.

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Agreed! I disassemble all hard drives in my work and salvage the magnets. Everything else gets shattered, mangled and disposed of in multiple places. Very powerful!

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if you don’t have any old hard drives to dissemble, you can find them already salvaged on etsy or ebay.

just a sample listing, not endorsing this one at all. but $13 shipped to me for 10 of them.

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While patting myself on the back for salvaging some magnets from a very old hard drive, I misjudged their proximity. The sudden collision instantly rendered them a ball of shrapnel.

Are the magnets in newer drives less fragile?

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Thanks @deirdrebeth! I haven’t any 1/4" material in the house to test that, but that’s what the 1/4" ledge on the bottom side is for. If 1/4" plywood is warped in someway I doubt this design would be able to hold it flat. I have some 1/4" PG draftboard on the way so I’ll see how it goes with that. I’ll post here again with the results.

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i’ve used magnets out of everything from old 80mb IDE drives to newer SATA drives. i’ve never seen one shatter from them snapping together. not sure what happened or how old the drive you used was.

mine are still attached to the metal plates (i like the edges of the metal plates as hold downs). maybe that was part of it?

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:grin:Thanks for sharing, @rbtdanforth! I’ll post again to update their longevity. My GF :glowforge: rests on a steel table so my magnets stick there pretty readily and won’t crawl over to my sock drawer, but we’ll see.

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@shop - Wow, that’s neat!