This was originally written for the Windows version of Cura 2.3. For OS X (Apple) version see the bottom of this page or click the hyperlinked text.
Note: This isn't a reliable method but it does work sometimes at least for the Windows version. Unplugging and plugging in the USB cable is sometimes needed to get Cura 2.3 to see the printer. Even if Cura 2.3 does see the printer, Cura 2.3 may still not display the current status of the printer. Getting prints to actually start printing seems to fail more often than not.
Maybe this will help someone that wants to use Cura 2.3 and wants to spend the time experimenting.
Cura developer is recommending not to print through USB anymore. This part of function is now working as plugins module.
USB printing not working on Cura 2.3
Original USB Printing plugins will communicate with STH500, which is a firmware update program for AVR. However, this program does not close serial port correctly before plugins started baud rate detection. This problem will cause USB port cannot open and failed detecting USB printer.
Comment out Line 301 will solve.
File: C:\Program Files\Cura 2.3\plugins\USBPrinting\USBPrinterOutputDevice.py
Line 300-302: (Before):
programmer = stk500v2.Stk500v2()
Line 300-302: (After):
Only Line 301 is to be changed by adding a hash character, #, at the beginning of the line.
#programmer = stk500v2.Stk500v2()
You can also download an already modified file USBPrinterOutputDevice.py and overwrite the existing file. Make a copy of the original in case something goes wrong.
Connect printer via USB, start Cura application. You can find both “USB Printing” and “Save to file” button on right bottom.
The following instructions were provided by Bruce Johnson. Thank you Bruce.
OS X doesn't let users edit files in Applications packages without higher authorization. (This may be a 10.12 thing) Mac editing of USBPrinterOutputDevice.py: Start Terminal. enter 'cd /Applications/Cura.app/Contents/Resources/plugins/plugins/USBPrinting/' then enter 'sudo open -e USBPrinterOutputDevice.py' which will open the file in TextEdit.
Follow Solution 1 from above and then save the file.
After the sudo command you'll be asked for your password.