Calibration problems

#1
I just finished building my gMax printer (after getting it from the kickstarter a year ago), but am having some troubles calibrating it.

first: It seems my table is bent such that the X-axis edges are about 3mm lower than the center of the x-axis. The y-axis is level all the way across. Does anyone know how to fix this or will I need to get a new table? (If I need a new table, any ideas on a good, cheap replacement?).

Second: I was having issues with skipping and my layers becoming mis-aligned (sometimes by 1/4 inch or more). The calibration page suggested adjusting the potentiometer if skipping is heard, after some internet research describing under powered and overpowered motors I spent most of two nights trying to adjust the motor so it wouldn't skip. I now have run into a problem where the motor makes terrible noise it's receiving power at any point and pushing/pulling the table, even very gently, results in very loud "skipping" noises and the motor not working at all. Did I break the motor controller or the motor? I have been unsuccessful at getting my printer out of this state.

Thanks in advance for your help.
 
#2
You are probably building a gMax 1.0 because you got it a year ago. I only have experience with the 1.5. But I will do my best to help you out.

#1 Could you link a picture? I am not sure what you mean.
first: It seems my table is bent such that the X-axis edges are about 3mm lower than the center of the x-axis. The y-axis is level all the way across. Does anyone know how to fix this or will I need to get a new table? (If I need a new table, any ideas on a good, cheap replacement?).
#2 Your acceleration is set to high in slic3r. You tried to fix this problem by sending the motor more current. Current makes things hot especially the drivers. The stepper drivers have a thermal "shutoff". If its too hot they slow down significantly. You may just need to turn the current down, turn up the thermal shutoff to the maximum setting, and lower the acceleration settings in slic3r. Download the slic3r configurations from http://gcreate.com/downloads/slic3r-1-1-6-config-file/. This is the oldest slic3r config I am assuming for the gMax 1.0. You may have broken the driver. But give this a try first.

I am not sure which version of the build manual you have. The very last step. #14 goes over calibrating the drivers.
http://gcreate.com/downloads/gmax-build-and-calibration-manual-1-4-1/

I have been looking for the characteristics of a broken stepper driver online. I have never burned one. I basically found... They don't work at all. If anyone knows please fill me in. I turned my thermal shutoff to the minimum and moved my y-axis back and forth. When the shutoff kicked in, it just slowed things down for a few seconds. It did make a horrible sound briefly one time. But my shop is very cold, just my fingertips could probably cool the driver sufficiently.
 
#3
Thank you for the advice.

#1: I uploaded the photos of the table upside down on my granite counter to Google Drive (here: http://goo.gl/mNG0J7). You can see that the edges are raised off the counter, I did not touch the table between any of the photos.

#2: I was worried I may have broken the stepper driver. I wasn't able to find the speed setting in slic3r until after the problems occurred. I was already using the gMax slic3r config, though I was using the 1.1.7. Perhaps the gMax 1.5 can handle the higher speed?
 
#4
The commonly used term for what you are calling the table is the bed and it looks like yours is warped significantly. You might be able to get by with this bed for small test prints by starting the print in a fairly level spot. You will likely need to replace the bed before you print anything large. I'll suggest a few options below. All of these options are explored in various sections of this forum and Gmaxers have adopted a variety of solutions.

- Buy a new piece of acrylic. My original bed warped too so even if you buy a new piece it might eventually warp.
- Add an aluminum frame/support structure to minimize the bed warping.
- Replace the bed with something less prone to warping (and cheaper than acrylic). Glass and MDF (manufactured wood) are two options. I replaced my bed with glass. Prints easily stick to acrylic but won't stick to glass without assistance. I've had great success by spreading a thin layer of glue-stick on the glass.

Chris
 
#6
Glad to know this is a common problem (and to learn the correct terminology). I'll pick up some MDF from Home Depot this week.

As for the stepper driver. I took my 2nd extruder stepper driver (since I only have one extruder right now) and used that as a test. My Y-axis motor seems to be mostly fine now, there's just one problem.

When I home the Y-axis it goes correctly to the Y-axis endstop and stops there; however, when I manually control the printer (using repetier-host as I don't have the built-in LCD) the controls seem to be reversed for the Y-axis only. Since it homes to Y0 I am unable to go into the negative coordinates, but making the bed go in the positive Y direction ends up sending it to the Y-axis endstop rather than the backside of the printer.

Any idea what's going on here and how to fix it? Is it due to the stepper driver? They looked the same so I didn't think it'd be an issue.