Neodymium Magnets for Holding Glass Build Plate to Onyx

[inventabuild]

Anyone know if it will cause a problem if I use Neodymium Magnets to hold the glass build plate to the Onyx heated bed? Here's a pic showing 3 sets of magnets I used in place of spring clips (1 is at the bottom of the pic and the other two are in the upper left and right corners):

A few advantages:

1. Once the magnets are glued down to the top of the glass and the underside of the Onyx, the glass will go onto the Onyx the same way every time. Therefore calibration compensations for any imperfections in the glass and Onyx can stay accurate.

2. Magnets deflect the glass much less than the spring clips if you have an uneven Onyx.

3. It will be easier to put the glass on and take it off (not saying that it really needs to be any easier than it already is, but yeah it will be easier).

Potential downfalls:

1. Magnets introduce magnetic fields into an environment rich w/ electrical wires although they appear to be far enough away from everything that they will not cause a problem.

2. Magnets will degrade if they get too hot. Max operating temps for Neodymium magnets range anywhere from 80 C to 200 C depending on the grade.

The Thermal Characteristics table on the following page shows the max operating temps of the different grades

http://www.kjmagnetics.com/specs.asp

Any thoughts?

[vile_fly]

Not a great plan, unless you plan on replacing the magnets regularly. The magnets I bought from the very same company destabilize at around average bed temps. My n52 magnets came with the note "Neodymium magnets will lose their magnetic properties if heated above 175F / 80 C."

Still, it is a nice idea. You could try wrapping the magnets in an insulator to protect them.

As for the interference issue, those magnets would have to be in motion to create a problem.....so no problem there.

[inventabuild]

Thanks for the feedback. So long as all I have to lose are the magnets themselves I'll continue giving it a whirl. Right now I'm only printing PLA w/ a bed temp of 60C although I'll probably have to explore the higher operating temp magnets if I start printing ABS and other plastics.

[Nylocke]

You could use hightemp ceramic magnets, though they aren't as attractive as neodymium

[inventabuild]

Thanks for the suggestion, I will look into that.

I also suppose electromagnets could be built into the heated bed unless electromagnets act as moving magnets which vile_fly cautioned against.

Also, embedded electromagnets would add to the cost of the bed and the cost / benefit ratio would need to be favorable.

[inventabuild]

This company has ceramic magnets with an operating temperature up to 450 C although I don't know their strength relative to the Neodymium magnets:

http://www.allmagnetics.com/ceramic.htm

[Nylocke]

From the same people, they have 280 C neo ones, http://www.allmagnetics.com/neodymium.htm, also try the smco ones, they are just a bit weaker than the neo ones, but rated to 800. (The max energy product (BH rating) is a "good" testament to the magnets attraction force at peak) (make sure you dont get sintered SmCo magnets if you get them, they are prone to thermal shock, Get the bonded ones)

[vile_fly]

Wow. Guess I didn't do enough materials research on this one. Looks like there ARE magnets out there that might do the trick.

[Nylocke]

You should always do research before talking out of your ass it can hold new possibilities and save you from looking like an idiot as an added bonus.

[mattnewby]

Some grades of neodymium (NdFeb) magnets will maintain their performance up to temperatures as high 230 degrees celsius, while Samarium Cobalt (SmCo) will operate up to 300 degrees celsius

There is a couple of useful tables here:

Neodymium - http://www.first4magnets.com/tech-centr ... agnets-i91
Samarium cobalt - http://www.first4magnets.com/tech-centr ... gnets-i112

[Jimustanguitar]

You're also forgetting that the Onyx bed only reaches its set temp in the center of the bed. I've measured as much as a 10 deg C difference between the center and perimeter with an infrared thermometer. Even with the first magnets you suggested, if your bed is at 80, the magnets would probably only get to 75 or so at best. It depends on how stable they are at temps approaching their max.


Side note: You really think that the little binder clips are warping a sheet of glass at the edges? (Don't get me wrong, the magnet idea is really cool, and I want it too. I just don't know that it solves a problem other than always having to keep tabs on those pesky clips.)

[626Pilot]

It might be problematic. The Onyx is, among other things, an antenna. When the RAMBo rapidly switches current on and off through that antenna, it creates an oscillating electromagnetic field. I found that putting some small neodymium magnets on it while it was turned on resulted in the magnets jumping around. It was fun to watch, but using Nd magnets to hold down the glass could have unpredictable results.

(really grouchy stuff)

Please don't.

[Nylocke]

I'm not grouchy :'(

[Eaglezsoar]

You should always do research before talking out of your ass it can hold new possibilities and save you from looking like an idiot as an added bonus.

Not grouchy?

[626Pilot]

Let's all shake hands and pretend it didn't happen. There is a place for tearing into people and it's called YouTube. (Ask me how I know.)

As for holding down the plate, it's always a tricky question. I use printed plastic clips, but they take away a little of the available print surface and can cause problems with effector-mounted fans. I wish there was a solution that would hold down the glass without adding complications like that.

[Nylocke]

For the record, I was not angry or grouchy while saying that, it was more sarcasm... :'(

[inventabuild]

626Pilot, thanks for the info...reverted back to metal clips.