dropping printer connections

Hello,  we have 3 Prusa i3 mk3 running on RS in our university printing lab. One issue we have been having is that RS will seem to randomly drop connections with the printers. Upon restarting the server on the computer, the connections will be reestablished. Unfortunately, since the common user doesn't have privileges to restart the server, they have to restart the entire computer. This is very time consuming, and can interrupt any ongoing prints.

Can you point us in the direction of some troubleshooting for these dropped connections?


  • Such connection problems are most likely caused by undervoltage. Especially if all connections are dropped. But normally server will reconnect after wards and your description does not sound like that. Run
    to see if you have problems with undervoltage. Not all undervoltages cause usb connection being dropped. If you know when it happened check /var/log/syslog - it will be noted there.

    Instead of restarting server it should also work to unplug usb and unpower matching prusa and reconnect. That would force both sides to reinit the communication chips so if the problem is the prusa communication or if it is the linux side would not matter. Eventually just unplugging and replugging usb would also do the trick. Hard to say without knowing what goes on.

    Hope this helps otherwise please describe more detailed if one or all are affected and which of the above works, which hardware is used...
  • Hello,

    The computer in question is running Windows 10.
    We have three printers, all the Prusa i3 mk3 model.
    Printer 3 stopped communicating a long time ago. We believe it is a hardware issue, but we haven't been able to identify it yet.
    Printer 1 has rarely dropped the server connection.
    Printer 2 drops the connection more regularly.
    I just tried the following procedure with Printer 2:
    Disconnected USB.
    Power-cycled printer.
    Reconnected USB.
    Temperature readout was displayed on dashboard.
    Attempted to print.
    Printer did not respond - no preheating - just sat idle.
    Issued M117 command - no response.
    Issued M104 command - no response.
    Repeated the above sequence several times.

    Restarted the computer.
    Sent a print job to the same printer.
    Job printed normally.

  • That sounds like the usb serial connector for that port crashed. Please make sure to use latest server version. Previous version would have reused last (crashed) serial instance while newer version will create a new instance so hopefully also restarts the driver, but I never have that problem so can not be sure. Deactivate and activate printer should then solve the issue. If that does not help with latest version try restarting server to test if that makes the port work again. If that also does not work the drivers are so crashed that in deed only a reboot makes them work again.

    You might try a different usb cable. Often also a source of problems especially if it is a long usb cable. Especially 5m cables are not really specified I think also they often work.
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