Hi and X-axis ends advice - Sloppy Pusa i3 parts...

Hi all, I'm new here.

I'm building a Prusa i3, I've just completed the mechanical build and about ready to start wiring. Before I do that though I'm not sure about the amount of play in the X axis smooth rods and axis ends that I have, and I'd like some advice.

The 8mm smooth rods were a sloppy fit in the two holes in both X axis ends from the start, so I put thin brass shims under the rods inside the ends to lift them up against the rounded roof of the ends. This tightened them up a lot but I notice that the weight of the x carriage and extruder is still enough to see movement between the smooth rods and the printed ends.

I'm thinking of sliding the rods out, putting a small amount of epoxy in the X rod channels and refit them while the x-axis is held straight (remove the extruder as well to take weight off it). I think this would lock the smooth rods in fine but wonder if there is a reason not too...

Is this sort of 'fixing' of sloppy parts with epoxy or similar glues normal for building these machines, or would I be better off to get two new x ends ?

Image of the X ends and brass shims attached via URL (couldn't get it inserted in post).
Photo


Martin

Edited 1 time(s). Last edit at 09/10/2014 09:11AM by mr.sneezy.

Do you know if the parts are made from ABS or PLA?
if ABS then perhaps make up some thick and gooey abs slury fill the holes with it, then press your rods in and let it dry overnight.
it should bond to the abs part, and fill the space.

if not ABS i have had luck with two part epoxy ( the dark grey and black stuff i think it's from 3m ) with PLA parts, not pretty but very very solid and bods to it well.
(repaired a 1kg spool holder with it)

which kit did you get? is that a Folger Prusa i3 kit? ( I got one from Ebay recently, great price )

Edited 1 time(s). Last edit at 09/10/2014 09:30AM by Waltermixx.

The printed plastic parts for my Pursa i3 Einstein variant came from a local guy (Morellitech) and are printed in PLA not ABS. ABS printed parts were not on offer in Oz when I wanted to buy the set, at least not anywhere I looked.

I didn't buy a complete kit, I bought bits from all over to keep cost low as practical. Complete kits seem to cost about $100-150 more than what can be done with careful selection from all sources.
I started by finding an i3 frame on Ebay, then bought all the rest to match, a good proportion did come from Morellitech locally at good prices.

Tonight I removed the x rods and poured a small amount of 30 minute epoxy into the ends and reinserted the rods (used Blu-tack to seal the outer holes). Tomorrow I'll know how well it worked.

Edited 1 time(s). Last edit at 09/11/2014 08:31AM by mr.sneezy.

I've completed the epoxy addition to the rod tubes in the X-ends. I did it over two nights so I could check alignment one side at the time, with the X carriage set close to the end being glued to set the rod spacing perfectly as possible. I'd only recommend doing the epoxy addition if you can be sure about getting the rods and ends in good alignment while the epoxy goes hard (parallel and with no twist).
I heated the rods slightly with a heat gun (slightly, like 60C or so) to help the epoxy flow down inside, while the frame was held sideways in a vise, until it just made it right through.

The result is vastly better than before. There is no wobble or free play in the X-axis now in any direction, it feels very rigid. The carriage also very free along the rods so alignment between them worked out well.
Cheers,
Martin

Edited 1 time(s). Last edit at 09/13/2014 10:49AM by mr.sneezy.

I just used the same black "LePages 10 Epoxy Steel" around the 5m nuts on the x-ends for the threaded rods, just to make sure they stay in place. Made sure none of it got in the threads, and that it had time to cure.
I also put the threaded rods in place so the weight of the x-axis was holding the 5m nuts in place. So far so good. If you find your 5m nuts are a little lose, this might do the trick.

I did tighten the X-axis lead screw nuts too, but did it by 'heat setting' them in with a heat gun (while on a 5mm thread off-cut). In fact I had to heat the nuts to fit them at all anyway, that part was too tight to press fit !

I used regular 30 minute epoxy in the X rod guides, it sets very well. 5 minute would not give me enough time to check alignments.

I think I'll have the control board this week and be able to continue.

I was going to heat my M5 nuts and press fit them into the x-ends, but they fit nice and snug as it was, I just wanted to make sure the did not loosen a bit when the carriage was going down. I did not want to heat the nuts and press them in, just in case i warped the flat printed base of the printed nut socket... i did not want the 5m rods to become skewed if i did not set the nuts correctly as it's a one time shot with heating... get it right or else.. So I chose to epoxy them in place... If the nuts do not fit, then yes you are pretty much forced to heat them up and melt them into place... but i had the option of going the other route. I checked them this morning and the epoxy is very hard, and my nuts are set in place.

Cheers.

I found a method that I could reheat the nuts and get them straighter, by heating the end of spare 5mm threaded rod first, then screw it in and wait till the heat transferred into the nut. It took a couple of goes to work out how much to heat the threaded rod to make the nut loosen slightly.

My control card arrived today

Hi,

Fixing the x-ends is the way to go, don't get new ones. as long as the x carriage slides ok along the x axis (and the rods don't move) then it should be fine. I (last year) bought my set of printed parts from morellitech and had a similar issue with the parts, but my x ads were so tight i couldn't even get them in without drilling the holes out. Once i did that i seemed to over drill them, then making my rods loose. I also had a problems where the bearing slots in the X ends has big blobs in them, making the bearings impossible to align perfectly. I happen to have (limited) access to a stratasys printer, and the owner kindly printed industrial quality replacement X ends for me. Morrellitech is a fine source for motors, belts and other hardware, although i am not sure about his print quality.

Recently (last few months) I have been selling Prusa i3 sets on eBay Australia. I'm not sure if you saw my listings there? (there is a multicolour set up now), but I have got my printer working hard printing sets (at a good quality).

I happen to live a few suburbs away from Morellitech which is interesting, he actually asked if I wanted to visit his workshop at some point, although that never happened. anyway, If you want some extra parts printed give me a shout, If its only a couple pieces i could do it for free (if you pay postage). I would like to help you out if there is any parts you need redoing. Your X ends look ok, and i don't think they need replacing if you can "fix" them somehow.

Also, I have built a couple Prusa i3s now (second printed by the first one) , and if you need any help with anything, chuck it on the forums or send me an email at stustu242@gmail.com.

Cheers,

stustu242