Current MakerBot machines use an ATmega8U2 for USB communication. The ATmega8U2 is programmed with a custom VID/PID pair that identifies the type of machine.
Some Thing-o-Matics and many other popular brands of 3D printers are based on the Arduino Mega. The Arduino Mega also uses an ATmega8U2 (or a close relative like a ATmega32U2) with a custom VID/PID pair.
Older MakerBot machines use a generic USB serial cable based on an FTDI chip.
| VID | PID | Device |
|---|---|---|
| 0403 | 6001 | FTDI FT232BM/L/Q, FT245BM/L/Q, FT232RL/Q, FT245RL/Q |
| 0403 | 6010 | FTDI FT2232C/D/L, FT2232HL/Q |
| 0403 | 6011 | FTDI FT4232HL/Q |
| 0403 | 6014 | FTDI FT232HL/Q |
| 2341 | 0010 | Arduino Mega |
| 23C1 | D314 | Replicator |
| 23C1 | B015 | Replicator 2 |
Information on FTDI VID and PID combinations is from
Technical Note TN_100
USB Vendor ID / Product ID # Guidelines
http://www.ftdichip.com/Support/Documents/TechnicalNotes/TN_100_USB_VID-PID_Guidelines.pdf