1 Topic by Trevor.James

  • Trevor.James
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Topic: Skipping Y and X axis

So,

I am using my Solidoodle 3 for printing the first time today.  After a bunch of problems with not sticking to the plate, I finally figured out how to calibrate my level, and set the first layer depth properly.  So things are looking good there.

I now have found a new problem.  My print head will just randomly offset itself during the print.  It will print perfectly for the first 10 layers, then it will offset on the Y axis and try printing the rest of the layers 8 mm to the front.  This of course results in the extruding ABS just going everywhere but where it should.  I thought it was just a Y axis problem until my X axis just jumped about 30 mm to the right as I was trying to troubleshoot.

I don't think it is a mechanical problem.  A loose belt might result in slippage and get a few mm offset, but not 30 mm straight to the right.  I think there is a loose cable, or something weird going on with the electronics that is sending false info to the motor.

It might also be a dropped command.  I don't know how the code is written, but does it work like this?:
Sent commands:
-forward
-left
-right
-back
-next layer
-forward
-left
-right
-back
-next layer
-forward
-left
-right
-back
-next layer
-etc.

Because if so, missing out on one of the -back commands would cause the entire thing to start printing offset by whatever that back distance should have been.  I don't know if this is the problem, but I know it isn't mechanical and since I am an ME, where my expertise ends.


Has anybody ever run into this problem and know what causes it or how to fix it?

2 Reply by Trevor.James (edited by Trevor.James 2013-03-24 07:45:19)

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Re: Skipping Y and X axis

I have included a picture of the latest failure

Also included is what those layers are supposed to look like.

It seems to be printing the layers fine, it is just shifting the offset with each layer for some reason.

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3 Reply by pcpoirier (edited by pcpoirier 2013-03-24 11:00:57)

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Re: Skipping Y and X axis

Shut off the power and move the carriage all the way x and y.  If it is not smooth, you need to clean and lube the rods as well as adjust the belt tension.  the y axis belts have to have the same tension or it will jam.  the machine doesn't know if it lost its place(open loop) and it will keep going out of place until homed


http://wiki.solidoodle.com/tutorials

4 Reply by op7ical

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Re: Skipping Y and X axis

It is generally better to post these kinds of questions in the Help/Repair section - we are happy to help out, but it just keeps things organized better that way.

There are various causes for skipping.  If both x and y are shifting, it may be a communications or electronics problem.  Mechanically, they are not really interdependent so it is strange that they would both simultaneously act up.  It may be worthwhile to try printing on a completely different PC to see if something is interrupting the software periodically, or something is wrong with the USB connections, etc.

I had an issue recently with y-axis skipping which was created by the stepper driver overheating.  To fix it, I just pointed a PC fan at the board, and the problem disappeared instantly.  Some people have previously reported skipping issues related to board communication dropouts when it overheats.

I would definitely suggest trying to cool your board down.

5 Reply by ronsii

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Re: Skipping Y and X axis

Hi Trevor, Hard to tell from the pics, but if the extruder is overextruding it will print just fine until the printhead builds up too much extra plastic for the hotend to 'push' its way over... that would explain both x and y axis losing steps. Below are a couple of links to Ian's site on how to calibrate the extruder.


http://solidoodletips.wordpress.com/201 … libration/

http://solidoodletips.wordpress.com/201 … flow-rate/

6 Reply by Trevor.James

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Re: Skipping Y and X axis

Good point about the forums, I guess I should have placed this thread there.  Do you know how to move threads?

I don't think it is a flowrate problem.  It seems to be purely an offset issue.

Also, I think it is just on the Y axis, as the only time it messed up on the X axis was when I was fiddling with it during troubleshooting, so that problem may have been my fault.

I have another print as seen below.  This is supposed to be the thumbscrew piece:

soliforum.com/topic/242/thumbscrew-to-level-bed-from-beneath/

As the pictures hopefully show, it went fine for about 20 minutes, then the Y axis offset started shifting, forward at first, then back toward center for the last few layers.

The layers themselves seemed to be fine, they just get laid down at different Y offsets.


I think you might be right about the board overheating.  I modified my cover to only cover the build area and leave the board/spool in the back exposed.  This time it got 20 minutes into the print before the problem occurred vs. the usual 5 mins.  So, I am going to try printing  for 5 minutes, pausing, waiting for it to cool, and the resuming.  If that fixes the problem, I know it is temperature buildup in the control system.

Also, I have a 5 Volt fan from an old laptop that would fit perfectly and cool the board.  Do you know where on the board I can tap off 5 V?

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7 Reply by Rincewind

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Re: Skipping Y and X axis

I am having the same problem printing from an ARM tablet (check here. I did some troubleshooting and I suspect there is a problem with USB voltage levels.

Can you try printing from a different computer?

In any case, check the trimpot voltages and see if they are in the correct range. Please post back because I'm also very interested in how the situation evolves.

8 Reply by danny

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Re: Skipping Y and X axis

I'm having the same problem but only in the X direction.

seems that it's not a carriage sticking thing, but an overheating thing.

it seems that sometimes commands sent to the X carriage are just ignored. (so pressing home all I've had Y home, Z home and X not move until I've pressed it a few more times).

this random ignoring commands sent to the X axis really messes up models..

I've recently added heatsinks to the pololu drivers, and I think that I might have been able to print for a bit longer before this problem showed up.

I also put a large C Clamp onto the X stepper (which gets hot) and found that heat sinking this might help also...

but of a loss as to what to do now!!

I suppose I need to get a fan and do some active cooling of the electronics rather than just the passive cooling, maybe the same on the steppers