Print is not straight

[flexchen 0]

Hi,

 

Last week I assembled my Ultimaker but found my print is not straight, I have tried some of solutions here but still have no luck to have the problem fixed.

 

This problem makes me unable to print anything with my new Ultimaker :sad:

I have already spent the whole weekend on figuring out the potential root cause:

1. Added 4 washers under X motor to avoid friction between belt and wood

2. Ran bed level wizard for many times

3. Rebalance the X motor pulleys

 

Two things I suspect are the Z axis rod is wobbling while bed is moving, also the drive nuts on the rod is not steady.

 

I have tried using glue gun to fix the drive nuts to tighten the rod and 2 axes, unfortunately, wobbling is still there and print is still bad... Is there any idea how to solve the issue?

 

Could you please advice me what else I can try?

 

Thanks a bunch!

 

[illuminarti 18]

If you've already checked that the belts aren't rubbing, then the most likely cause is that one of the X-Pulleys is loose.

Check that they are all properly tight, including the one on the motor shaft itself. I gather that UM now includes replacement grub screw for the pulleys, in case the ones included in the pulleys by default don't fix tightly enough.

I would try making a mark on each pulley and the shaft it is attached to with a sharpie, so you can see if there is any movement during the print. And I'd definitely avoid glue. Not sure how well that's going to attach anyway, but I think it's going ot cause more problems than it solves.

 

[gr5 2,002]

This problem you post about is very common and usually easy to fix. There are many causes. After seeing your picture it is almost certainly one of two problems: A) setscrews or B) rubbing belt.

You already addressed B but did you make sure the belt isn't twisting each time the X motor changes direction? It's the motor behind the robot in this picture (back right corner). Not only might you need to add the washers (which you did) but you might also have to slide the pulley closer to the motor. It should be as close as possible without touching the motor - mine are about .5mm from the motor.

But more often the problem is that the set screws aren't tight enough (as illuminarti says). You should do at least 2 of the following things:

1) tighten the hell out of all 6 screws (six! not 4, not 5, but six). Tighten it until you are almost to the point where you are afraid you will break something. The most common problem screws are the two pulleys on the short belt because the other 4 pulleys have half as much load (but they can slip also so tighten all 6).

2) Mark the pulleys: Use a sharpie (aka permanent marker). Put a tiny mark on each pulley and on each rod. Perhaps even photograph them or make a note of how perfect your marks line up. After printing another part that slides, recheck the markings.

3) Replace the existing setscrews with the extra ones. The extra ones are supposedly better (pointier, sharper) but I haven't used mine yet as the ones that came inside the pulleys are working fine for me.

 

[flexchen 0]

Thanks very much GR5 and illuminarti for so detailed and prompt reply!

You guy are genius! :-P After tightening all setscrews on rods, the print is close to perfection! I spent too much time on fixing the z rod, which is definitely in a wrong direction. Your solution really saved me lots of time!

There is still a small defects on my print, as you can see from the picture below, the top of the robot's head is a little bit melted by hot end when print ended, can I avoid this by tuning up the Cura settings or Ultimakers?

Thanks again!

 

[gr5 2,002]

This is a common problem with the UM robot. Because the antennae are so quick to print they don't have enough time to cool and they slump.

There are two parameters (maybe only one) you need to adjust to fix this:

1) Under Advanced, "cool" section make sure minimum layer time is at least 5 - 7 seconds is default (if fan is off then double these values).

The second parameter - probably the one causing your problem is

2) Under "expert settings", "cool" section set minimum speed to zero. Not only is there a bug in this setting for some versions of Cura, you probably don't need it with the newer ultimaker hot end design.

 

[flexchen 0]

Thanks a lot, gr5!

I tried one more time, when Cura was printing robot's antenna, the hot end was swamped by printing materials. Actually I tried gr5's suggestions, but looks like it might help some old versions of Cura, the melting problem is still there after applying the suggested settings.

I think the melted robot's antenna might be caused by the layer settings.

I am using the latest Cura 13.06.05, for some reason, the layer height is changed to 0.1mm in this version. I checked the settings in Cura 13.04, the default layer height is 0.2mm.

Once I changed the layer height back to 0.2mm in Cura 13.06.05, the melting problem is gone, however, which is expected, the print quality is worse.

I tried to use Flowthermostat Cura plugin, but looks like it is incompatible with the latest Cura, and temperature is always constant.

Any ideas to print the tapering top such as robot's antenna without losing quality? (layer height: 0.1mm)

Thanks in advance!

 

[gr5 2,002]

You should start a new thread.

What temp are you printing at?

I'm not sure if there *is* a fix. Those antennas are tiny and even though you print only one layer every 7 seconds, the head is still touching the antennas most of the time.

There is some new kind of head-cool-retraction setting in the new cura. I'm not sure what it does but I think it is supposed to rest above the part for 5 seconds to let the layer cool.

I guess I would manually lower the temp when the printer is almost done with the robot's head. I would lower to 185C and then when that is stable for a few minutes I would lower to 180 (if you hit 170 I believe Marlin shuts off the extruder so be careful). I would experiment with printing only the top of the head of the UM robot.

Another solution is to create a "cooling tower" where you print a small pillar next to the robot while printing the robot at the same time. The problem is then you will have stringing issues which have their own challenges (but can be dealt with nicely after some experimentation).