A4 Mendel

I've played around with designs for a while and taken them apart again when they were not quite what I wanted.
I'm building what I hope will be the final version now. Up in the Alps the temperature can drop a lot and cold draughts can ruin prints.
I wanted a slightly larger than the usual 200 x 200 build size. I didn't find an existing design that quite met my particular needs.
Last October my prints started warping on my Mendel90 with the colder weather so I built an enclosure to solve that.
This design incorporates the enclosure using it to add a bit of stability. Dibond and polycarbonate seemed like the best choices for the basic structure. I strengthened it with openbeam which also makes it easy to alter the placement of parts.

I just received the dibond sheets yesterday so it will be a while before it is finished.
I have seen a number of printers with the X carriage supported from below with the couplers compressed by the weight. It seemed to me better to support the weight of the carriage, rods etc. from above with the rods in tension rather than compression. I have supported the rods in 608 bearings from above. Wobble can thus be taken up by the couplings.

I made the end pieces of the X assembly with a lot of holes for playing with the design of the X motor and idler printed parts.


Please let me know if you see any silly mistakes :-)

Edited 1 time(s). Last edit at 06/28/2014 05:17PM by Ralph.Hilton.

Looks very tidy, nice job. My only comment would be; you have constrained the end of the lead screw, this is OK if your threaded rod is dead strait but it never is, this is a problem as it will cause Z wobble, I had mine running on 12mm rod with the lead constrained in bearing as you have and even with 12 mm smooth rods I got a wobble on taller prints, I changed the design and let them do what they want, wobble gone. Hey keep going it will be a nice printer when it's done, good luck.

Thanks, I was pondering a way to not constrain it while still suspending the X carriage weight from above.

Edited 1 time(s). Last edit at 07/09/2014 02:30PM by Ralph.Hilton.

This arrangement seems to give little constraint:


Edited 1 time(s). Last edit at 07/20/2014 12:24AM by Ralph.Hilton.

I find that if I put a nut on studding it doesn't sit at a perfect right angle, so it causes oscillation in Z movements as it rotates.

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[www.hydraraptor.blogspot.com]

I put a washer under the nut. The oscillation seems minimal. I suppose I'll have to wait until it is working to see if it works ok. I'm hoping that the 12mm steel rod will restrain Z wobble.

The rod can constrain angular wobble but the other form of Z wobble is up and down oscillation. I tried many z couplers on Mendel90 before settling on the current design and none had the first form, only the second.

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[www.hydraraptor.blogspot.com]