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astrodenny

Calibration Cube Issues - Drifting

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I've been trying to print a calibration cube but seem to experience the walls of the cube drifting from left or right.

Temp 220

Cura

Fill Density 20%

Print Speed 50 mm/s

Layer Height .2mm

wall thickness .8

Calibration Cube

http://www.thingiverse.com/thing:68445

On my first run, it seems that the cube would drift toward the left, leaving a stair step formation and not straight walls. I tightened up my X-Y motors and belts by shifting them as far down as possible. There were a few other problems before I canceled the print, but I think I have these squared away such as not sticking properly to the print bed and preheating before starting.

Before X-Y Belt Tightening

Before X-Y Motor Tightening

 

After the belt tightening, my left and right sides have improved signficantly. However, I'm now drifting up and down.

 

After X-Y Motor Tightening

 

My next approach is to tighten all of the x-y long belts and pulleys. However, am I missing something? I've reviewed the calibration wiki but would like to know what am I missing? Thank you

 

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It looks like you are either missing steps, and/or having the pulleys slipping. Did you slice it with 'Duplicate Outlines' or 'Joris' enabled, by any chance?

I'd start by making sure that all of your pulleys are properly tightened. Use a sharpie to mark the pulley and rod that it's connected to, and make sure the pulleys aren't shifting on the rods. Even when they seem to be tight, the pulleys can sometimes move. If you got spare grub screws with your printer, you may need to swap out some of the screws with replacements if you can't tighten the existing screws enough to stop slipping.

Also, make sure that all the belts are running smoothly, and not catching on the frame, or running up the sides of any of the pulleys.

Then, with the printer off, try moving the head by hand. You should be able to move it with fairly light finger tip pressure on each pair of sliding blocks - and the required force in both X and Y should be the same. If you can't, then check i) that the end caps aren't too tight on the axis rods; ii) that the axes and cross rods are square and level; iii) lubricate the rods with a little light sewing machine oil.

Once that is all taken care of, try reducing the travel move speed in Cura to about 100 mm/s, and see if that helps things. You should be able to go faster than that, but it looks like it's probably the travel moves between layers that are failing somehow, so start by slowing them down, and see if it helps.

Also, if you have an Ulticontroller, under the control->motion menu - what are your current AmaxX and AmaxY settings?

 

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Thanks for your response illuminarti,

I only ran this as a basic setting in Cura under "Normal" - duplicate outlines was not checked off and I did not have joris enabled.

I've tightened my pulleys, but I'm afraid I may have fiddled too many times to the point where I've lost track of what I've tightened and/or changed. I need to revisit this again. I was following the youtube video on belt tension as well as trying to get my belts to be parallel with the axes. I do have the backup grub screws included in the kit, which I'll swap out on all of the pulleys tonight. I'll also use a sharpie and test to see if they shift.

I haven't checked to see if belts are running up the sides of other pulleys, but have notices perhaps my X-Y short belts are too close to the walls. My long pulleys don't seem to rub up agains the frame at all. Then again, perhaps my pulleys are too far away from the bearings? I read in another post to get them as close to the bearings as possible. Currently, they're pretty far off from the end caps/innner frame/motor pulleys (5-10mm).

I've moved the print head and certainly cannot seem to get the smoothness down that the Ultimaker youtube video shows. This is defiitely an issue for me. I can move the print, but it takes more force than the video. This too is something I need to explore further. My end caps are definitely tight on the axis rods - the slider blocks were also painted - causing the slider block/belt tension levels to not adjust lower - on two of them I have to physically slide them upward/downward with my finger. I'm having a bad feeling paint could be part of it.

I'll also experiment with Cura abd reduce the travel speed. I have the ulticontroller, but did not make any changes to my AmaxX or AmaxY settings. Unfortunatley I did not check this before turning the printer off before having to leave the house. I returned, switched the printer on, and my current Amax settings are X=9000 and Y=9000

 

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What's your acceleration setting show as in the UltiController? I think that's Control -> Motion -> Acc, if I remember correctly.

I think it defaults to 5000.... you might try lowering that to about 3000 if so, and see if that helps any. In general though, it sounds like you need to just clean things up a little with you mechanics, and get everything sliding around smoothly. The print problems that you're having are almost certainly a result of overtaxing the steppers on some fast moves, due to the binding and rubbing that you mentioned. (And yes, there could be some pulley slipping in there too!)

Regarding belt positions... you just want to make sure that the pulley on the motor and the corresponding one on the axis are directly in line, so the short belt can turn smoothly as it passes from one to the other, without rubbing against the sides of either pulley. And then the pulleys for the long belts need to be lined up on the path through the sliding blocks, so that the upper and lower sections of belt are directly one above the other, and again the belt travels in a constant plane, and isn't being deflected to the sides as it passes over the pulleys. I.e., the long belts need to remain parallel to the closest side of the UM frame at all points of their length - top, bottom, as they clamp into the sliding blocks, and as they pass around the pulleys on each end.

 

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When we say "tighten the pulleys" we don't mean "tighten the belts". We mean tighten those set-screws. Tighten the hell out of them. All 6 pulleys for the slipping axis. Especially the two that the short belt goes around. Your shift is pretty small (only a few mm) so you have to check your sharpie marks carefully to see which pulley is slipping.

Also when you see the belts moving during printing, look to see if the belts are twisting at all each time they reverse direction. If so then your belt is rubbing the wood wall. Fix this by adding washers under the spacers and making sure that the pulley on the motor is as close to the motor as possible without touching the motor.

 

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Ok guys here's what I've done:

1) Replaced all pulley grub screws with the new silver ones included in the ultimaker kit.

2) Aligned all pulleys, including the motor pulleys so they are pulling their corresponding belts straight. Tightened them as best as I could and will tighten more!

3) Marked all pulley positions with a black sharpie

4) Discovered the Y motor pulley's grub screw was all the way in, but not very tight!

5) Made sure to check each long belt so that they were parallel with their corresponding axis.

6) Checked short belts and corresponding pulleys for any friction against the frame or end caps.]

7) My slider blocks' c clamps where extremely tight around the ends of each axis - I loosened them slightly

8) Recalibrated the print bed

9) Preheated the PLA to 210-220

10) Tightened belts, but not overtight (refered to video on tight belt "sounds" when pulled back)

11) Lightly oiled the axis

12 ) Reduced print speed to 100 mm/s

13) Tightened short belts (but not overtight) on pulley motors

Here is what I got ... after all that I was jumping for joy and things at least looked much better ... until of course, my bowden tube came out! So this is a partial print, but at least you'll hopefully notice the improvements:

IMG 1890

IMG 1889

IMG 1888

IMG 1887

IMG 1886

Let me know your thoughts. As you can see, once the tube popped, it stopped feeding. I paused the print, tried to carefully get the tube back in but it became too much of a project without moving the print head around and misaligning the work. I have to say, the blue horseshoe clamp is frustrating - in my case it does not fit - it's just too tight and thus pops off. Frankly I'm not sure how much of a difference it makesbut I will be looking for a better solution. I saw one post where someone used a zip tie. If there is a printable substitute, I'd like to consider that.I also seem to have lost a motor spacer in the process, which I'm still looking for that dissappeared off my desk (just used the screw and washer for now).

Anyways, please take a look at the print and let me know your thoughts.

 

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Well, it looks a lot better - up until the point where it stops looking better :-)

Its a bit hard to see the sides, but it seems pretty clean - the top looks like it might be under=extruded a bit, but it's hard to tell, as it was also the first layer going down over infill, and that never extrudes really well anyway.

Once you get the Bowden sorted out, do the print again, and post the results, and we'll advise further on any extra tweaks.

Well done for working through all the issues :-)

 

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I think it used to default to 3000 - but at some point got increased to 5000 as a default. I need to hunt that down, because I'm not sure that isn't a big part of the reason people are having more and more skipped steps issues....

 

Acceleration is set for 5000. I'll lower this to 3000 as an experiment and I'm going to make adjustments with pulleys and belt positions now - I'll report back and let you know. Thanks!

 

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Yes, it did - Daid changed it to 5000 in December for the Cura 12.12 firmware.

I wonder if that isn't a bit on the high side.... at least in conjunction with x/y/z moves as well. Might be something to try changing when troubleshooting skipped-step problems (once loose pulleys and gross mechanical issues have been ruled out).

 

I think it used to default to 3000 - but at some point got increased to 5000 as a default. I need to hunt that down, because I'm not sure that isn't a big part of the reason people are having more and more skipped steps issues....

 

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I built a fresh Marlin within a few days of Christmas and my default accelerations are 3000 and max accel is 9000. These values have always worked fine for me. I increased my Z accel and speed since then.

 

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Yes... but its hard coded to 5000 as the default in the UM fork of Marlin now. If you've previously saved your defaults into the EEPROM, then those are going to take precedence over the hard coded values, even after a firmware upgrade.

However, if you haven't ever written to the EEPROM, then you get whatever is coded in Marlin each time you boot up.

I'm actually running at 5000 at the moment, and not really having any problems. But I've got everything pretty well bedded in.

(The max acceleration doesn't really do much, btw. The acceleration you get is the lowest of the max acceleration for any axis involved in a move, and the 'one true' acceleration speed. Since the default max for x and y is 9,000 and the max for e is 10,000, in practice you get acceleration at the requested 5000 (or 3000) rate. Unless you also move in Z, which has very low acceleration, in which case you the low z rate applied to all axes).

 

I built a fresh Marlin within a few days of Christmas and my default accelerations are 3000 and max accel is 9000. These values have always worked fine for me. I increased my Z accel and speed since then.

 

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Illuminarti,

Here is my latest cube after solving the bowden tube problem:

IMG 1898

IMG 1905

IMG 1902

IMG 1909

Much better! No drifting and it seems the sides are straight/clean. However I'm experiencing a slight bending around the corners. If you look close you'll see that some of the corners are not sharp, but bend slightly. Note that one of the sides was scratched by accident as my print was bonded to the print bed - accidentally scratched it while trying to remove. As for the corners, it seems like when it makes its final turn, something is too tight?

 

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I'm glad to hear you're getting better results. Prints are looking pretty nice now, and everything is pretty much where it's supposed to be on each layer (which is a good sign!) :-)

Not sure about the corners... might be a little bit of ooze and over extrusion... perhaps due to printing the perimeters a bit too fast, causing pent-up pressure which oozes out as the printer slows down for the direction change.

Maybe try printing a touch slower, and/or cooler, and see how that effects the results?

 

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