Runaway X and Y axes during first print

Hello,

I just assembled my first printer, a Prusa i3 rework, and am trying to get my first print. Using the Marlin firmware with Pronterface/Slic3r for controlling the printer. I seem to have managed to do the mechanical calibration ok and tried to move on to the print.

When trying to print the 5mm wall for layer height calibration, the printer homes ok on all axes. Then it waits for a few seconds, and the x and y axes start to move. The problem is that the y axes moves straight INTO the triggered endstop, while the x axis just keeps moving until it crashes into the opposite side. The maximum movement range is constrained to 100 mm, so I don't see how it's going that far. As for the y axis, I can't imagine incorrect y direction logic being responsible since it treats the endstops it homes in on as the y_min endstop, as it should, which means it's trying to go into the negative y axis, knowing full well that the y_min endstop is triggered.

Does anyone have any ideas on how to deal with this? I'm reluctant to even run my printer now for fear that it breaks itself.

without starting a print, but just using the manual interface in Pronterface, can you home all the axes normally and move them to the extremes without issues?

Yep, they home fine manually. Also they only move in the positive direction from the home position: even the y axis. They move to the extremes no problem, though they also go beyond. I assumed overriding the "imaginary" endstops is a feature of the manual move commands, but I'm not sure.

Usually you can define the bed dimensions in your slicer and host software. I'm not familiar with Pronterface, only Repetier Host, but under the printer settings, it allows you to set the bed dimensions. In your slicer also, you should have settings to do the same. Once you've set those correctly (and restarted Pronterface), you should not be able to move past the point you specified. So for example, if you specify your max X is 180, then once you home X, you should not be able to move past 180 going the other direction. If it still goes past that, then something else is going on.

Do you have the proper jumpers installed for your micro-stepping settings. Micro stepping comes into play when calculating your steps per millimeter. If your firmware is expecting microstepping and you have no jumpers you will go beyond your endstops.

I have the regular Pololu drivers typically used on the RAMPS board, so I assumed it would be fine. Judging by the movement speed alone (i.e. I set the speed to about 1 mm/s and that's how fast it moves for homing) the stepping of the motors is what the firmware expects.

I've set the print area to be 100 mm in the x and y directions in both the Configuration.h file of Marlin and in the Pronterface slicer settings. However, the x axis still moves beyond that if manually prompted. I was pretty sure that's a feature of Pronterface though...

Edit: I've finally noticed the red line in Pronterface that seems to track where your extruder is: the trace of the extruder path is obviously scaled way down from where the extruder actually is, do clearly my axes moves faster than the software thinks. If lack of microstepping is indeed the issue, how do I solve that? I don't see any way of editting number of microsteps in either the Marlin Configuration.h file or the Pronterface slicer.

Edited 1 time(s). Last edit at 09/17/2014 10:57PM by anvoice.

Under the stepper drivers on the RAMPS board, there are places for 3 jumpers. To enable 1/16 microstepping, you need to put three jumpers for each stepper driver.

Never knew about that. Do you mean to the set of 6 pins (3 pairs) right under the stepper drivers? Do you think that's the reason the axis is moving out of range? Hope the local hardware store has jumpers...

Not sure that will solve the y axis jamming into the endstop, but worth a try.

Edited 1 time(s). Last edit at 09/18/2014 01:56AM by anvoice.

Yes, the six pins underneath each driver are for 3 jumpers. Since you are set for full steps, but your steps per mm is set for 1/16 stepping, that would cause the axis to try and move much further than it's supposed to.

Well, I got the jumpers in place, but my mega 2560 seems to have bricked. Pronterface can't connect, timeout error when uploading sketches. I'll try using an UNO as an ISP to burn it with the bootloader, otherwise I'm waiting for a new board... Thanks for the help so far.