Printer stops and becomes unresponsive

I have a large printer (410 x 362 x 240 mm build volume) running Marlin on an Arduino + RAMPS 1.4. I have been trying to print something near the size of the build volume (the print is 398.7 x 300 x 227.5 mm). I am slicing the model with Simplify3D and sending the gcode to Octoprint running on a Raspberry Pi. I have also tried running the print directly from Simplify3D with the same result.

The problem is that the printer becomes unresponsive in the middle of printing the raft. I noticed I get a lot of:

• "Connection timeout during printing, forcing a line" (most common)
• "Error:checksum mismatch, Last Line: [line num]"
• "Error:Line Number is not Last Line Number+1, Last Line: 66"

Smaller prints don't exhibit this behavior. I've tried a few things thinking electrical / magnetic interference could be the cause:

• Moving the Raspberry Pi and its USB cable away from the stepper motors
• Replacing the stepper motor cables with ones that have stronger shielding
• Placing all of the electronics within a metal box to act as basically a faraday cage

Nothing has helped so far.

I have noticed that the above errors tend to happen during the long, slow moves across the build platform while building the raft. In between there is a shorter move where it changes direction. During those short periods, the errors stop for a moment and some gcode gets acknowledged (around three commands each time, though it's often used to resend missed or corrupted gcode).

Here are my current thoughts on the possibilities:

1. I could have a bad Arduino or RAMPS board. I got my Arduino board used and my RAMPS board came from gadgets3d with bent pins and incorrectly seated stepper drivers. I fixed the pins and drivers before I plugged it in, but it leaves me doubts to the quality of the board. I also had an endstop with the switch soldered to the board backwards which was causing the Arduino + RAMPS to reboot when the switch was triggered.
2. Perhaps Marlin is not processing gcode input or responding to it during the slow moves across the build platform. That would cause the timeouts I'm seeing. If this eventually fills its buffer, it could cause the other errors I am seeing.

Does anyone have any insight into this issue?

Thanks,
Marcus

I don't have a Pi and Octoprint configuration, but many with a MakerFarm i3v do. The error is a communication timeout in the Octoprint configuration. This thread should help - look within the last couple of pages in the thread.

http://3dprintboard.com/showthread.p...e-your-printer

As far as I can tell so far (the print I am attempting takes 29 hours), that was exactly the problem. At the slowest speed and the longest distance the printer travels, it takes 51 seconds to complete the move. I used 60 seconds as the timeout on communications, and it seems to be working well so far. Thanks for that! A configuration change is much preferable to buying new hardware.