Should I Use USB, Serial, Or Ethernet?
I recommend a good usb>serial adapter like the one pictured above. It's a smart adapter that maintains the port number Linux assigns to it eg: you plugin or power up your device and Linux assigns /dev/ttyS0 to your device and you configure Tux Plot or Cups to use that port. Next time you power up device Linux may assign /dev/ttyS1 to it now Cups print engine and Tux Plot are still trying to plot to /dev/ttyS0 and plot will fail. This adapter will maintain it's port number (in Ebay description) so it's always the same! It also has the FTDI chipset which is very Linux friendly.
This item is available on Ebay search “Startech FTDI”.
Another proven working USB>Serial adapter is found in this link from Walmart.
Triplite Keyspan USB>Serial Adapter
A null modem cable will also be needed if using the above adapter or direct from a REAL serial port on the back of your pc.
Take note of the cutter connection and order one with either 9 pin or 25 pin(25 pin shown) and male or female.
Please note these are my opinions only!
I state these opinions on years of experience in testing various cutting devices of both old and new technology.
For a small business just starting up I recommend a desktop pc and NOT a laptop as laptops are difficult if not impossible to expand other than via usb. Usb was mainly created because it's cheaper to produce and it is rarely superior to the old style REAL serial/parallel ports, they both need a dedicated control chip and added to cost of motherboards but made them far more reliable than usb.
If your cutting device has usb and serial/parallel and ethernet ports I would avoid usb if possible and use the REAL serial port with a serial null modem cable or parallel printer available on ebay etc $5 (Ethernet is always a good reliable port also).
If your desktop pc has no REAL serial port a pci or pci-express serial port expansion card on ebay costs around $10 giving you up to four serial ports and sometimes a parallel port also as shown below.
Cutting devices have had problems with reliability using usb ports and also usb>serial adapters like the counterfeit prolific pl2303 chip, also some manufactures of inexpensive cutters use $1 usb>serial internal adapter that has proven to be VERY unreliable! High end cutters like Roland/Graphtec etc mainly don't suffer from these issues. REAL serial/parallel and ethernet ports over come all those issues. If using ethernet port configure your cutter as a cups network printer (configured as: jetdirect, ipnumber, port 9100) and use Generic/Raw Queue then select cups printer in Tux Plot.
Watch Tux Plot install video on youtube or this website!