USB Comms issues

I have just completed my first build, and currently in the process of dry testing.
The build is based on the Prusa i3 with arduino mega board and ramps 1.4.
I am running through windows 7 and can communicate and run the system.
The firmware I am now running is Marlin, however I did start with sprinter, and the same issues occurred in both version of firmware.
The issue I have is that during the machine seems to loose coms. It just stops.
This can be at various stages in the print, at first it was always when running a large tall print.
I have changed the bed shape, it is now set at 200mm cubed.

I have tried both pronterface and repetior, The g-code is produced in Slicr3 all looks good from the side.

when the machine hangs, the interface stops, it looks as if it is waiting for a responce.

Even killing the print, and resetting the ramps board will not clear the fault.
To regain control I have to tell the interface to disconnect, then physically disconnect the usb, wait 30 seconds and reconnect the usb cable. Then reconnect the interface.
On some occasions it fails to connect, then I have to restart the interface as well.
There is no pattern to how far through the print it is when it stops.

Can anybody through some light on this.

I am now starting to consider converting to LCD and SD card to bypass the USB issue.

I think it's a classic case of interference on the USB causes it to hang up. Do you get the Windows USB sounds?

There are a few things you can try, better quality USB cable, or even just a different cable, a shorter cable, use USB hub, add ferrites to the USB cable.

it could also be a fault on the RAMPS or just excessive comms errors. Printing from SD is certainly worth a try.

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Yep you could be right, the USB is quite long, also it runs over the top of the power supply. Will try a usb cable with a sheild.

Cheers

An update on my comms issues. I moved the power supply away from the usb comms input to the arduino. and also changed to the cable to shielded sb cable, Now it all work fine runs to the end of the print with no hang ups.
Thanks for your help.

I would still go with an SDcard for unattended prints. A comm failure is not a safe failure since the extruder still maintains temperature and requires you to be there to shut it down. Honestly, I don't know why there isn't a watchdog feature in most firmwares that can detect a comm failure and shut everything down safely in the event.

That's a good point. Its was always my intention to go sd card eventually anyway. Want to have this machine running in my shop window.