Tuning my printer

[Geertjan]

I have a few printing problems caused by either software/slicing issues or deformation caused by the printer itself (backlash).
Perhaps you guys can help me out. I have made pictures of the problems.
Single wallobjects print fine but as soon as I start filling these structures I run in the following problem.
I have gaps between the rim and the fill. Sometimes even the rim layers do adhere.
This might be a slicer problem but I don't know how to correct it.
If I a print a cogwheel the teeth are irregular and on a larger scale I have what I think is backlash.
I hope the pictures offer some clues.

The edge of this flower should be sinusoidal but the print is not.

gaps between rim and fill and irregular cogwheel teeth

Gaps between rim and fill

[dognotdog]

The gaps between the perimeter and fill are odd, i usually get the opposite effect. Which slicer are you using? I'm using slic3r, and that often does weird stuff.

The irregular geometry in the first two pictures looks like backlash indeed. To solve that, lawyer up, hit the gym, delete facebook. Or, rather, make sure the sliders slide freely, apply PTFE lubricant (especially the central "rail", which absorbs the lateral forces), and tighten the timing belts. I've found that adjusting the stepper current is mostly futile, as you have only a very small band where it works properly, without steploss and without overheating.

[danielkschneider]

With respect to the first picture: Print the first layer real slow, like 12 mm/s? In addition,nozzle real close to print bed:1 sheet of paper.

If the first layer is off, then the rest can follow IMHO

SFACT can do this (speed section)

[Geertjan]

I use slic3r. Mainly because it is easy to use. Seems I have to delve into Sfact:-{ Regarding the backlash; I have lubricated all the sliders with PTFE many times. adjusted the bolts that hold the Y axis. The belt on the Y motor is pretty tight. I have my doubts about the X axis belt. It seems tight enough but during printer I observe a slight flexing up and down.
I have tuned the stepper current just above the minimum energy where the motor begins losing steps. I agree with dognotdog that there is not much to tune. Still I have troubles with the Z axis movement. When printing an object with a fill after about 15 layers the nozzle object distance becomes so small that it touches the plastic. Strangely with a single wall object i can print at any hight without the problem of the nozzle touching the object.
Slower printing also reduces the rim/fill gap.

[dognotdog]

If you get too much material, maybe reducing the "extrusion multiplier" in the filament settings helps. I have to set this to 0.95-0.97 to avoid too much material being deposited, else solid infills start bulging upwards after a few layers. Though in general, I do not worry about the nozzle touching the plastic. At least on my felix, the whole X-axis carriage can twist along the axis quite a bit, only the weight of the extruder is pushing down the nozzle. It can easily lift 0.5 or more mm when it "runs over" already printed parts that happen to bulge, and the extrusion itself also forces it up enough for things not to get stuck, in my experience.

I have also found that the Z-axis steps/mm in the firmware is not technically correct, if the M8 threaded rod is up to spec. For 1.25mm per revolution, it should be at 2560.0, but the firmware has it at 2580. I don't know how accurate the threading is, but just as with the X/Y axes, it might be a good idea to measure the actual movement and calibrate for that.

On the X axis, I had to fine tune height of the pulleys at both ends to match the holes in the carriage, and so the belt doesn't rub on anything, either. I have also replaced the bearing mount on X with the "improved" version that doesn't stick out to the sides, with the side effect that the bearing now has some play up and down, as well as the washers are free to rotate should the belt touch them. I also slightly loosened the bolts at the Y-axis bearings, to also allow the washers to turn, with no ill-effects so far.

On my prints, I can not see backlash on X, but it is visible to the eye on Y with round features, though not bad enough to try to further fine-tune it.

Now I just have to get rid of the Z wobble somehow, and all is well

[Geertjan]

Thank you dognotdog. I tried the extrusion multiplier with a lower value and indeed it improved a little. At least the nozzle is not ploughing throug the plastic. Indeed the carriage can hop over bumps but when it does it takes small amounts of plastic with it from the print producing spiderweb thin threads i did like to avoid. What i do when i see this happening I give the z axis spindel a small turn by hand. Not very ellegant. I am not up to changing the firmware but perhaps guillaume can investigate.
I will try to align the x axis pulleys this weekend

[Lioric]

The is backlash indeed. Im using 0.25 for X and 0.15 for Y and that solved the incorrect arcs and circles (and bulged corners), just measure your values and apply them. You don't need to modify the firmware, just search this forum for the instructions that I posted a a couple of weeks back for how to calibrate the actual stepper distance (steps per mm), you can do that even directly from RepetierHost (Config Menu -> Firmware EEPROM configuration)

About the height issue, yes I have experienced the same issue, after several layers the nozzle starts to hit the printed part, so far I tested with several configurations and managed print up to a 10cm object without the nozzle to detach the object from the bed

[Geertjan]

After a lot of testing I still experience backlash and resonance. I lubricated all the sliders many times. Tried different tensions on the x and y belts. aligned the x axis belt because it was touching the washers of the pulley. Especially when the table (y axis) changes direction there is a noticeable vibration in the bed. On the x axis I can feel a slight vibration. I haven't removed the kepton tape in the sliders and I am a bit reluctant to remove it. Should I remove it or are there still other options to pursue?
Adjusting the extrusion multiplier soloved the problem of the extruder running into the printed part.

[Geertjan]

Ok, removing the kepton tape from the Y slider and replacing it is worth while. The Kepton tape had crept out and was rubbing the aluminum rail. Because I first tried to combat the vibration by putting more PTFE spray on the rail there was now to much lubricant in the slider. The Kapton didn't stick anymore and was forced to the side. Y axis is running smoothly now. I suspect de vibration in the x axis slider has a similar cause.

[Kjetilei]

Thanks for the input!

Do you know the tickles of your Kapton tape? I have never been able to find the "hot spot" for my sliders with the Kapton tape I have been using (it's quite thick).

Do you have any photos of before and after prints?