X Belt running off and corners are rounded

I finished the build of my mendel90 a month ago, and I am still calibrating because of issues. FYI: My mendel90 is 10cm higher than a normal one.

Picture:

So I got 2 problems, my X belt runs off if I tighten it, and the other one is my cornering problem.

The X belt runs off because if I thighten it, the X motor bracket twists clockwise a bit, making the pulley not being parallel to the belt which in its turn makes it run off. I tried to fix this by tightening my clamps, but they broke off so I had to come up with a new solution. I designed a part which acts like a nut trap, but only for the rods. One end goes into the X-Idler, and in the other end goes the rod, making it basicly impossible to move the rod. Even with this part installed, the X-motor bracket twists, although a littlebit less. It seems like the bottom part of the barclamp thing flexes a bit, making it possible for the part to twist. Any ideas how I can solve this?

My second problem is/are my corners. A picture to illustrate my problem:

As you can see, my corners are little circles instead of pointy. I tried increasing and reducing temp, increasing and decrease extrusion multiplier, increase and decrease XY-jerk, increase and decrease speeds, thightening my belts (and the problem above occured), and I am currently fiddling with the extruder advance setting (I think this won't help either because the extruder advance only works, visibly, at infill and not perimeters). The only thing that slightly reduced my problem was increasing acceleration. I had it at 1500mm/s² and it is at 3000 mm/s² now, but I still have those round corners, only slightly less. Any suggestions here?

Did you degrease the rods? I don't have a problem with the idler slipping.

I didn't understand your description of your "acts like a nut trap" solution. Perhaps a close up photo would make it clear.

To make the belt run in the centre I shim the penny washer as the M4 bolt will be at a slight angle because the nut trap is an interference fit but the rest of the hole is a clearance fit. An off-cut from the 0.5mm polypropylene strips works well, as does a piece of the skirt extrusion about 0.4mm high.

I don't know what the corner problem is. How fast are you doing the outline? What are your belts made from, they look an unusual colour for T5 timing belts?

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Yes i did degrease the rods, but it didn't help. My belts are normal, black, T5 belts.
In the attached file is the thing I made for the rods, it isn´t well made though, I had to make the center hole bigger because my printer made them smaller somehow. I thought this was a calibration failure but other holes are perfect. Anyhow, this part acts like a solid stop for the rod, and to function, your rod has to be at the right length. I made mine a little too short, but I filled the gap with some metal rings.

Edit: I print perimeters at 45mm/sec now, but I tried it at 10mm/s without change.

Oh and my belts are from reprapworld.com

Edited 2 time(s). Last edit at 04/13/2013 04:10PM by TheHawk.

Did you ever solve your corner problem? I'm having similar problems on my Mendel90. Increasing the acceleration from 2000 to 4000 has made it a little better.

Have you already found out the solution to the corner problem? I've had the similar problem in my Huxley printer.