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  1. #1
    Super Moderator old man emu's Avatar
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    Print jumps 7mm in Y direction after initial layers

    Have a look at this part way print:

    Layer 2.6 labelled.jpg
    That's a scan of the object and I didn't get it square on the scanner.


    The black lines show the extrusion that was laid down as Layer 7 began to print (Z= 2.6). It was exactly 7mm down the Y-axis from where it should be. X position is correct.

    This is the Gcode for the print:

    Z-axis LHS plate.gcode

    This code printed OK last night, except for a corner lift. The bad print happened twice today. I've just done maintenance on my printer and the belts are tight. Remember that the first 6 layers printed correctly.

    Given that the room temperature where I was printing was 36C, could I have an overheat problem in the Y stepper? But the X stepper was operating under the same conditions. Both X and Y steppers were working hard as I was printing linear infill at 45 degrees.

    Any ideas as to what gives?

    Old Man Emu
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    But you won't outlast me!

  2. #2
    Super Moderator DrLuigi's Avatar
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    Had the same,

    Colin told me it could be that my rods arent oiled, that the stepper motors are off as pot meters go,
    Uhm and the belts that could be to tight or to losse,

    I guess thats it,
    Owye i also have a fan now on my makerfarm all the time when its on, a 120mm fan, it didnt do this anymore or not as frequent when i got the fan,

    Also perhaps try making the mm/s go slower like 40-45mm/s.

  3. #3
    Super Moderator Roxy's Avatar
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    I never have a jump of 7mm... But I do get a jump of 2 or 3mm if I'm not careful. Do you have your bed mounted on springs? I kind of need that because I need the extra time to react if I load some firmware that goes crazy. The downside is if you push too hard to remove a part, you might leave the bed shifted for the next print. And then part way through the print, it clicks over to where it wants to be and you get that layer jump.

  4. #4
    Staff Engineer printbus's Avatar
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    It's interesting that in October you were getting jumps in the X axis and now you're getting them in the Y axis. I'll throw out the same idea I had on the X-axis problem - make sure the belt pulley is tight on motor. It's at least easy to check.

  5. #5
    Super Moderator old man emu's Avatar
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    Everything's tight. I's just come out of the shop from its 10,000 mm extrusion service.

    Dr Luigi may have hit on the cause - room temperature too high. Roxy, what is the room temperature you are working at when you get your jumps? I was sitting in 36C without A/C, and 33% humidity.

    My steppers were pretty hot, but there were no unusual clicking sounds. That is to say, the steppers were not clicking, which is usual for my printer.

    If my belts were loose, or the steppers were missing steps, how do you explain the exact amount of displacement of the Y axis?

    Old Man Emu
    You may go past me,
    But you won't outlast me!

  6. #6
    Super Moderator Roxy's Avatar
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    Quote Originally Posted by old man emu View Post
    Everything's tight. I's just come out of the shop from its 10,000 mm extrusion service.
    You should be good for 10,000,000mm of extrusion service. Each 1Kg roll (at 3mm) is about 100 m. So 100 rolls is 10^7 mm.

    Quote Originally Posted by old man emu View Post
    Dr Luigi may have hit on the cause - room temperature too high. Roxy, what is the room temperature you are working at when you get your jumps? I was sitting in 36C without A/C, and 33% humidity.
    My room temperature is usually between 65 F and 75 F. It is more the bed temperature that affects my jumps. The bed gets hot enough to print, but it isn't really up to full temperature until I've been printing for 20 minutes. And then, it is probably a number of things factoring in. The bed and all the mounting hardware is getting warmer. But also, the thing I'm printing is getting higher up off the bed which means any curling up edge presses harder on the nozzle when you go across it. At some point, it is enough of a curl and enough leverage (because it is up above the bed) to click it back to where it wants to normally be. If you don't have a spring mounted bed, this is just an interesting anomaly for you.

  7. #7
    Engineer-in-Training gmay3's Avatar
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    OME, I have been having this exact same problem in the Y axis with mine lately, I have tried and failed many times to get the large extruder gear printed at 30% hexagonal infill and it fails as you have shown in the last 20 minutes of the print. So frustrating since its about a 2.5 hour print.

    I tried putting a fan near the RAMPS stepper driver heatsinks to see if cooling them down helped. This seemed to allow the print to only fail at 10 mins before being complete. (progress?) I do not have any active cooling on any of the stepper motors themselves.

    I also noticed that after the print failed while printing, I was able to pull the bed and cause the belt to slip over the teeth on the Y stepper gear and by doing this, the print error was even worse. Point being, I think the belt is heating up and becoming less rigid and allowing a little more flexibility in the belt.

    I've had this issue before with the set screw on the y pulley coming loose and causing this issue but I think this time it was because my y belt was just tight and now super tight. I've tightened it as much as I could and will try this print out again to see where we are.

  8. #8
    Staff Engineer printbus's Avatar
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    Quote Originally Posted by gmay3 View Post
    ... I do not have any active cooling on any of the stepper motors themselves.

    ...I think the belt is heating up and becoming less rigid and allowing a little more flexibility in the belt.
    One thought is to check how hot the Y-motor gets during your print. For those of us with the "hot" running motors, I found the Y-motor got the hottest of them all, likely since it is so boxed in when mounted in the frame. Maybe that heat is causing the Y-motor to skip or is soaking through the pulley to the belt?

    For a while I printed with a small desk fan angled towards the Y-motor, and then with a 40mm fan sitting on the table in front of the motor. Now the 40mm fan is mounted to a piece of wood that is in turn bolted to the bottom side of the v-rails. It only takes a small amount of airflow to keep the motor case at what feels like a reasonable temperature.

    EDIT: More info on mounting a Y-motor cooling fan to the v-rails is in this post of my build thread - Y MOTOR COOLING FAN
    Last edited by printbus; 11-24-2014 at 10:39 AM.

  9. #9
    Engineer-in-Training gmay3's Avatar
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    That's a good idea printbus! I will try moving the RAMPS fan to the Y motor to see if that helps.

  10. #10
    Engineer
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    I posted a printable Y motor fan mount not too long ago, for a 40mm fan. http://www.thingiverse.com/thing:498414

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