Mounting a Wade's Extruder using magnets?

I finally got my Mendel up and stably printing! In the course of trying to dial it all in, I had to disassemble the extruder many times to floss the bolt teeth, clean out the nozzle, etc.

I'm pretty fed up with having to take the whole darn thing apart just to get it off the carriage, so I'm trying to find other ways to mount it. I saw Tony's horizontal wade mount, which is pretty cool, until I saw that the front bolt has to be recessed in order to clear the large gear! So I still need to take the gear off to take the extruder apart?

So here's my thought: can we mount the extruder to the carriage using rare-earth magnets instead of bolts? Same dimensions, mounting scheme, etc., but it would pop off if needed. i was thinking of magnets mounted in the bolt holes of the carriage and the mating holes in the extruder mount.

Secondary benefit would be to provide a fail-safe if the nozzle were run into the bed too hard, it would just pop off...

I couldn't find anyone talking about this, is there something big I'm missing as to why this wouldn't work? I don't have any magnets to try it yet, but I can work on it this week if nobody can give me a good reason why not. Maybe the magnets would be too close to the heat and would lose their magnetism?

Nik

I'm not sure a magnetic connection would hold up. However with that horizontal adapter plate I designed, you can still get to the screw without taking the large gear off if you flip the small gear around and mount the gears close to the side (using maybe one washer between the large gear and the bearing). The main reason I had to recess that bolt was to make it more flexible with the distance between the large gear and the base and allow the large gear to be removed without having to unscrew that bolt.

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Tony Buser http://tonybuser.com * http://reprap.org/wiki/User:Tbuser#Projects

I think mounting the extruder with magnets would work fine. The mounting needs to be stiff enough to handle the abrupt direction changes without sliding around, so I do think the rare earth magnets would be needed. Try it and let me know how it goes? With pictures maybe?

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I'm building it with Baling Wire

I have a lasercut plywood carriage and extruder and I have cutoff m5 bolts and made a slot with a hacksaw (so it is like a grub screw). I screwed these part way into the carriage to make posts that the extruder slots onto. I then have a hook and eye each side of the carriage to hook the extruder in place. The screws prevent lateral movement and the hooks hold it on. This works quite well and it only takes seconds to remove the extruder.

Greg, sounds interesting. Pictures? Especially disassembled, would be great!

If you're going to use magnets, you need to constrain the extruder in the X and Y directions, so that it doesn't get knocked about while printing.

Otherwise, your nozzle will never be in the same place twice after any sort of obstruction is encountered.

You mean the X axis, as the Y axis is the bed. I don't think the Z axis has any impact.

Maybe we could do something with brackets or something. Or like this:



Where A is a piece of metal and B is a magnet. This would make swapping devices easy.

I haven't been able to pick up any magnets this week, but I was thinking of trying out something that was essentially Tony Buser's bracket bolted to the carriage as normal, but instead of another set of bolts from the bracket to the Wade's body, that there would be magnets between the two (i.e., glue magnets in the corresponding bolt holes so that they line up without any extra hardware).

Does anybody have any experience with the makerbot 3mm magnets? I was thinking of something along those lines: small and powerful magnets. Those guys seem to have success with the magnets holding down the build platform, so I would expect them to work similarly well to hold the extruder body in place against the bumps and catches during printing.

Bart: I mean that if the extruder is not held in place in the X and Y directions, the extruder could move relative to the carriage when bumped in one of those directions.

Yes, the extruder itself does not move in Y, but it moves relative to the bed in Y. If the extruder barrel hits the printed object, the extruder will slide about on the carriage, no matter what magnets you have, if it's not held in place by something else.

You need to provide some sort of mechanical interface along with the magnets. The same is true of the Makerbot build platform, where they have holes in the wood build platform that mate up with bolt heads on the carriage assembly.

Think of it like a lego piece. Movement in the X and Y on a pair of stacked lego bricks is held in check by the buttons on top of the bottom piece and the bottom outside edge of the top piece. Pull them in the Z and they pull apart.

I think this idea is workable.

We could modify Tony Buser's horizontal adapter plate to include two posts and places to attach one (or more) magnets.
The Wade Extruder would have to be modified slightly as well to match up but I think it would be very usable.
If a real head crash occurs the extruder should be pushed up before destroying the bed and otherwise (since it is restrained from moving in the X and Y directions with two (or more posts) can only be pushed up, and then only when a head crash occurs.

I have a bunch of rare earth magnets that I was planning on using with my heated bed but have decided to use clamps instead so I think I will play around with this idea.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

For the last 6+ hours of printing, I have been using a snap together clamping mechanism to mount my extruder. It does need provisions to stop side-to-side motion, but the clamp itself works.

With the amount of mass on an extruder head, plus the push/pull from dragging the filament, it might take a relatively big magnet. Given my results with a plastic snap together assembly, I would say a magnetic mount is doable but clamps might be a lighter, more compact, and easier to make solution.

The prototype could definitely benefit from design and print-ability improvements, but here is the current version I'm printing with: http://www.thingiverse.com/thing:4944

Look at the third from last and last pictures to see how I have used the clamps. My extruder just snaps onto the x-axis carriage. Since taking these pictures, I have melted little bumps into the x axis carriage to prevent the extruder from sliding along the x-axis during prints. I need to update the files to reflect this addition, but I'm working on bigger problems at the moment.

Arvin Wrote:
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> Greg, sounds interesting. Pictures? Especially
> disassembled, would be great!


Here is the carriage with the "posts" (only 1 is really a post)


This shows the hooks on the extruder:


Here is the hook and eye attachment: