again print problems

Coincidentally, this week, I've experienced exactly the same problems with the X clamps failing.

1. Prints exhibited small X errors at first - front motor rod clamp was loose (but did not appear cracked to the naked eye) so motor axis slightly pointing to centre of machine, belt moves down to ride the pulley washer. Obvious belt stretching and tight spot particularly when carriage is in centre of X axis.
2. Eventually the belt slips one complete tooth and 2.5mm X errors occur.
3. I fixed the problem by tightening front motor rod clamp, realigning and retensioning.
4. The clamp failed completely a few days later.
5. I noticed front idler clamp had also failed.
6. I botched up the printer enough to get it working and printed new parts in ABS (today).
7. I was going to print parts in nylon tomorrow as they wouldn't crack in a month of Sundays (but may give other problems due to flexibility perhaps). I like neptunier's idea though, it would save a fair bit of time, so I shall think on.

(PS. Yes, the rods had been well degreased, twice!)

Nophead,
Yes I degreased everything, but it was just the bolt coming loose. I probably just overtightened it once I noticed it. I am sure it was sufficiently tight before it broke, I just didn't realize it would break and overdid it.

I am still getting a wavy pattern throughout my prints, but I dont know what to make of it. I want to say its always along the Y axis, as if the print table is wobbly but its not. It does not seem to be effected by print speed or layer perimeters.

Overall my prints are looking better and better and I was able to do a 7 hour print with no skipping last night once I centered the belts on the idler. I do wonder if there is some way to minimize this wavy pattern however.

Edited 1 time(s). Last edit at 07/11/2013 12:59AM by tbowren.

after a print yesterday evening the belt problem on the x axis occured again, but less then before. but theses screws i put in are not so good because they have a flat bottom. i ordered headless srews with a pointed end, they should do a better job of staying in place. i put in 4 because i dont know how stablle the plastik is on the x mottor side. also with 4, from whatever direction the forces come, youre on the safe side.
in addition the pla i have is faulty, it blocks the noozle every now and then. so you can imagine its a very good opportunity to train patience....
i took 2 pictures of the y belt. you are right, it is kinked. even if i push it a little, it stays so. i dont know whether you can see it on the photos.
could i use this belt [www.ebay.de] as well? it looks like the one i have on the mendelmax, that one is smoother. it is 5mm wide, 2.5 mm teeth.

michael

@neptunier,
The belt pulls the two X ends together at the front but that means they pivot around the Z bars and are pulled apart at the back. So the collars you added on the back bar will not do anything. However, the ones on the front will probably stop the rotation and so take the force off the back bar. So in actual fact the only problem clamp is the front X idler end.

The belt you linked to looks exactly the same as supplied, T2.5 polyurethane belt, however it appears not all T2.5 belt is the same, see page 154 here: [www.brecoflex.com]

@tbowren,
There certainly shouldn't be waves in the print. It is hard to see with such a complex shape. Sometimes the infill pattern will influence the outline if you only have a single outline and the infill is sparse. Have you got an example with a simpler shape?

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[www.hydraraptor.blogspot.com]

nophead,
i ordered this other belt and see what happens then. i will report.
yes the collars are mostly for the front. but when the threaded rod for the z axis is not perfectly straight, then there might be a little bit of turning movement around the z axis rod. there the collars in the back might help, but i dont know if that would be really a problem. but i like to be sure about things, and whether i need 2 or 4 collars, thats not a big deal.

michael

nophead,

yesterday i got the new belts and put them in. now they seem to work perfectly. i also strenghened the dibond with an mdf because with the original belts there was a slight movement in the y idler and y motor. but with this stabilisation the problem was still the same with the original belts.
the new belts are thinner and softer, you see the difference in one of the photos. i think they need less force to be in the right tension. therefore i think they are better for the delicate construction.
are there any disadvantages with softer/smaller belts? they are of course also t2,5.
i just read threedyprinter also had belt problems.

michael

Hi Michael,
I think more flexible is generally a good thing as long as they are not also more elastic. A thinner belt of the same construction will have less tensile members, so will be both. Brecoflex seems to have more wires but thinner. I assume the tensile strength and inelasticity is proportional to the total cross sectional area of the wires but the flexibility will be the inverse forth power of wire diameter. So I think it is possible to have more flexibility without more elasticity by using more thinner wires.

There are also second order effects like ringing in the belt as it behaves like a guitar string. That might be more of an issue with more flexible belts but it is hard to be sure as tension and resonant frequency come into play.

Going forward I have switched to Brecoflex as it seems more suitable. The mystery is what is different about your belt as it works fine on the machine I have here and hundreds of others. Please can you return it so I can analyse it and I will refund the cost and postage.

I also have received threedyprinter's belts. There is nothing obviously wrong with them when running them over a pulley by hand, so I will have to build them up into a printer to see if they behave any different.

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[www.hydraraptor.blogspot.com]

thanks nophead for your excellent support. the next days i will return the belt.

michael

Just wanted to give you an update on those new Brecoflex belts.

Thank you again for sending them out.

They feel much more flexible in my hands and wrap around the pulleys much easier as they can bend around a tighter radius.

When sliding the x and y carriages around, it is much smoother and I cannot get the belts to jump or ride off like I used to.

I can run the printer much faster now (70mm / s vs 40 mm/s) and the few prints I have made look very clean.

Thank you very much for the belts, I feel it has improved the printer greatly.