I tried an experiment today, but it failed.

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(Robert Wozniak) #1

I tried an experiment today, but it failed.
I paused to press a neodynium magnet into an internal cavity, then continued printing so the magnet was completly encapsulated in the part… Unfortunatly The extrusion temp of the ABS is much higher than the operating temp of the neodymium magnet (80degC as I later learned) , and the magnet lost almost all of it’s magnetism… another one for the useless parts bin (I’m gonna need a bigger bin soon)

Well it seemed like a good idea.

(Robert Wozniak) #2

Ok… Does anyone know the melting temperature of an NFC RFID tag? I’m going to try to embed one of those next.

(Whosawhatsis) #3

The (important) metal parts will be fine. You’ll probably melt the plastic a little (at least enough to bond it), but I imagine it would survive. Those components need to be able to stand up to soldering.

(Dave Durant) #4

If it’s ABS, can you add a cavity that’s large enough to hold the magnet and a small printable square or something to cover the magnet up?

Do the print, insert the magnet, acetone-glue the square on…

(Normand Chamberland) #5

Interesting. I’ve been thinking of doing the same thing but with an hex nut (for a knob). How did you know when to pause the printer?

(Whosawhatsis) #6

@Dave_Durant Or just cover over it with ABS slurry.

(Dave Durant) #7

That too!

(Robert Wozniak) #8

@Normand_Chamberland
For this trial, I just found the layer number that was the end of cavity, and hit pause and retract at the right time… then continue after pressing in the magnet. A better method would be to add the proper statements to the GCode file.

(Robert Wozniak) #9

I’m thinking of trying @Dave_Durant 's idea, but applying the pad on top of the magnet. If it’s thick enough, it should insulate the magnet, and still allow it to be print encapsulated. I’ll also need to lower the bed temp as I’m printing at 120 degC with Aquanet on glass

(Whosawhatsis) #10

Between platform heat, latent heat in the recently-printed plastic, etc., I don’t think you’ll see that much improvement. Also, if you try to add acetone at those temperatures, it will boil.

(Daniel Osborne) #11

I knew heat could demagnetize, but I thought it required much hotter temperatures (like several thousand C). Thanks for sharing and saving others the same grief.

(Michael AtOz) #12

@Robert_Wozniak they sell RFIDs in glass capsules (the type that get injected into pets) not sure if I have seen an NFC one tho. Like https://www.sparkfun.com/products/9416

(Jason Ray) #13

I’ve tried this with bearings before

(Jonathan “se5a” Sorensen) #14

try it with pla, and a high layer height.
with the much lower extrusion temp you might get away with it. I’d be surprised if the the magnet is getting anywhere near the temperature of the extruder, and plastic is not a great conductor of heat.

(ThantiK) #15

The curie temperature of a neodymium magnet is WAY higher than ABS extrusion temps. There’s practically no way on earth that you demagnitized it. Look at the TC on the table here: http://en.wikipedia.org/wiki/Neodymium_magnet#Magnetic_properties

You’d have to reach 310C, possibly all the way up to 400C in order to demagnetize it.

Likely what happened, rather is that you’ve placed it too far into your printed object. Neodymium magnets, while strong, have awfully short throws to their magnetic field. Often less than 1CM. At most, you should have maybe 3-4 layers covering the magnet, no more.

(Robert Wozniak) #16

@ThantiK The Curie temp is where the magnet completly demagnitizes. Wikipedia is a great information source, but I’m relying on the manufacturer’s information. It probably would have been prudent to check it before I tried to embed the magnet. The bottom wall thickness was only 0.4mm, but I’ve since cut the magnet out of the part, and I can assure you that it has at most maybe 1/4 of its original magnetic strength. The magnets that I’m using (K&J magnetics) begin to lose their strength at 80 degC. I’m pretty sure I heated it to over 120 degC. K&J does offer specialty higher temperature magnetics.

(Nathaniel Stenzel) #17

Normand Chamberland, I want to print a pulley that fits on a nut. We have similar projects planned.

(Normand Chamberland) #18

@Robert_Wozniak Thanks. @NathanielStenzel Will try to monitor your updates about it!

(nathan burley) #19

Try samarium cobalt magnets instead? They have much better heat resistance:

http://www.first4magnets.com/samarium-cobalt-magnets-342-c.asp

(nathan burley) #20

same company also do neod. magnets for high temp environments (150oC):