Axis 'slippage' on large prints

Hi,

I built RepRapPro Mendel last year and have been slowly tweaking it to get batter quality prints. However I've found that I get, what looks like, terrible belt slippage on the x & y axis on large prints.

As a test print I'm using this and the slippage appears to happen at the same z level each print, about a centimeter in and happens a couple fo times.



I've re-aligned the rods and made sure everything is sliding freely and I recently replaced the belts with higher quality GT2's with aluminim pulleys. I don't think the belts are too tight and the motors don't appear to be too hot.

I'm a bit flummoxed :\

Richie

Could it be that at that exact point the motors are making a few too fast infill-moves? I had the same problem. Slowing down my printing speed by 5mm/s fixed my problem.

Also, maybe adding a bit more power to the stepper motor could fix it, but I would first try to lower the printing speed.

If it is not a mechanical problem, this is the easiest to test, lowering printing speed (or when using Slic3r lowering the infill print speed) doesn't involve any physical changes to the machine.

Lowering the print speed is all well and good, but it's better to just lower the acceleration. I used to have the same problem and lowering the acceleration makes it so that the printer doesn't have to change directions as fast and I stopped having shifts. I'm using Marlin on a mendelmax 1.5 btw and i lowered the acceleration from 3000 to 1000

So, lowering acceleration, to what extent does that affect printing time? And what is the effect on the print? I can imagine a lot, but could you keep up the printing time by putting acceleration lower and print speed higher?

I suppose one could experiment with that, but with my experience lowering the acceleration doesn't noticeably affect print time or the print quality. It's not all that big of a change but it gives the motors a little more time to catch up.

Thanks for the advice. Lowering the print speed did help a little (I'll also try the acceleration for next print) but wathcing it through this time Its actually the material curling up when its thin and about to join across from front to back tenticles. I oversaw the print and manually squished down the curled up bits but occasionally the head would still catch on them.

I'm not sure if thats a product of too high/low head temperature(I print at B60 H190) or just that this model wont print well without supports.

I had the same problem a few times, and I am currently printing a part again because the guy who designed the part had the wrong measurement for an M5 nut in his design. Anyway, when I first printed the part I did it at 20% infill and the raised corners would curl up.

The second time (I'm sitting next to the machine while it's printing live right now) I used a 50% infill and it has zero curling!

I'm printing 3mm PLA with a 0.5 mm nozzle, 0.3mm layer height. Bed temp at 60º and hotend temp at 205º.

I hope this helps. All PLA is different, just like every machine and thermistor. So it's no 'sure shot'.