Happy holidays,
I am primarily experiencing motor issues and some software issues.

First, I cannot activate the motors from USB mode although the serial port is recognized and I have both uploaded the machine size and set the home point. Pressing Ctrl-C yields the message, 'regenerating preview queue'. This occurs while the commands are not read and

As a result, I have abandoned the USB approach and have switched to using the standalone SD card (which is the approach I want to use).

Anyway, I have followed Sandy's vimeo on how to do this by uploading the machine specs, setting the home positions, generating the g-code and then exporting the queue as a .txt file. I then upload this to the PolargraphSD shield and touch to turn on the motors. Here is where things get interesting. The left motor locks and the right motor does not fully lock, while they both (or make warbly, vibrating sounds.
Next, I load the SD file and initiate the process. At this point everything is frozen and nothing happens.

I have a feeling that there could be two problems here: A) power supply issues or B) motor issues. I am inclined to think that the first is the culprit.

I have read on Sandy's post about powering the SD standalone here: http://www.polargraph.co.uk/2014/01/external-power-input-on-polarshield/

As a result, I have tried these options: A) plugged a 9v 1amp power supply into the polargraphSD with no power to the arduino. B) 12V 2amp into the polargraphSD (I know this is too high). C) USB power to the Arduino and 9v 1amp into the PolargraphSD.

I suppose at this point, I am asking advice on what to do to troubleshoot this process. I will test each motor on my adafruit shield since I cannot test them on the polargraph shield, but as for the freezing I am at a loss.

Thank you so much for your comments.

Sandy, thanks for your reply

You are right it is a hardware issue. I connected the steppers to an Adafruit Shield v2 and they work fine. They actually work perfectly and I've been producing some nice drawings.

Anyway, I am perplexed as to why the polarshields are not working. (I have two which I purchased in the last year). I think it must be a problem with the 'easydriver' shields and/or the plastic terminal connections. I might try connecting without the terminal heads. Nevertheless, I am glad it is working. Thank you for in advance for your reply.

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I forgot to mention that the PSU is potentially the culprit. It is strange when I run 12V 2amps into the Adafruit board, the motors run cool; however, when through the polarshield they are quite hot. I know you recommend 2.66 amp, but those are hard to find. Maybe the adafruit board has a larger acceptance range?