Introduction: Hiding Messages in Magnets, Co2 Laser Blanked Neodymium Magnetic Fields.
A year or so ago I got a fishing magnet, (big old 2" x 1" Neodynium with a steel shell that redirected one pole around so all poles met the "bottom) problem was the magnet was shipped blank. Yep it was not a magnet or uhm.. it cansorta pickup a paperclip or two. (that's right they program the magnets by putting them in an extremely high magnetic field). This one must have missed the field, or somehow got hotter than boiling water. So i got to thinking about writing a magnetic field to it, but i had a fantasy of copping some youtubers such as rwg42985 https://youtu.be/2wQZ1ZCsrRo with high gaus writes, and then i got to seeing a thing about structured magnetic fields written to magnets via a cnc machine, such as Supermagnetman https://youtu.be/YZeODCG1LEs but before i got around to building a cnc rig to do this
And i got to thinking, my Hackerspace's Laser cutter is 80w, not enough to mark on the nickel that most neodymium magnets are coated/protected with, but might be able to hit the 180F-250F Curie point for small bits of the magnet. and possibly permanently wipe a small area. (I'm doing this with the hopes that I can eventually make some magnets with a pattern that repel or attract depending on rotation/distance/alignment. )
At this point i'm still dialing in the speed/power settings to get a good blank without overheating the rest of the magnets, but in about a dozen tests, its looking like its quite possible, and i've not been able to find anywhere anyone else is playing with this, but id be surprised if i'm actually the first.
The green/black you see in photos is a prepared stuff called Magnetic Viewing Film, and it can be found online on amazon and ebay and the likes. but be careful lots of folks show a big picture but you get a teeny square.
Step 1: Technique (sofar)
Using the laser at our hackerspace (Quelab), I put the magnet (1.26"D x 0.08"H) on the bed of the 80w co2 laser cutter, and focused it for just below the surface of the magnet.
I tried a few low power "cut's" (vector based square and circle.) Suspecting that the co2 laser could not even scratch the nickel coating that is on most neodymiums (which i found out was not true if i put tape over them first, not sure if it was concentrating the heat around the cut like a blanket or if the tape burning/carbon created enough of a chemical hotbed that the nickel was blackening) Anyway back to the settings.
I eventually found i had to blast them with a fair bit of power, our lasercut software does things by %power and then a speed setting which i assume is cm/second? I found that around 75% power and a speed of 9 got me a pretty good image, i then vector "cut" the word TEST into the magnet, and tested it with the film and verified it worked. I then ran about and showed everyone there my strange success.
Ive found that i can "raster" (more like dotmatrix) an image onto a magnet, but takes a 100% power and a very slow speed, and even then while the detail can be pretty high the visual ability of the Magnetic Viewing Film, is not so.
Please leave comments with suggestions and ideas to try, i'm next going to try the south side of a magnet engraved into quarters, with 1/2 the magnet blanked out, then flip the image and try it on a magnet on the north side, and see if i can make magnets that change how attracted they are based on rotation.
Participated in the
Epilog X Contest
3 years ago on Step 1
Try doing your cut over again a few times. The curie limit may not be hit on the first try. Repeated attempts may give higher resolution with less power. Just a thought.
I've visited Quelabs. I know the laser cutter you used. I was trying to revisit last weekend and go to the maker faire but things didn't work out the way I hoped. Maybe next year.
Reply 3 years ago
indeed, i have done some with multiple runs, its also possible that insulating it from the steel bed may be good too, may be wicking out the heat a bit. sorry for the delay on the reply, never saw the notification. Thanks for stopping by Quelab. it is a place near and dear to my heart for nearly 10 years now!