The parallel port is a crucial part of the control system for plasma cutters, such as those manufactured by PlasmaCAM in Colorado City, Colorado. PlasmaCAM makes a cutting table, automation electronics, and software to control plasma cutters, and they interface their cutters to PCs using parallel ports.
There are several reasons why parallel ports are preferred in this application. First, the PlasmaCAM uses servomotors on their x- and y-axis with encoder feedback for accurate positioning and contouring, and these motors require bi-directional communications simultaneously, a capability not available on USB. That bi-directionality enables a closed loop system that can communicate to the PC if the cutting head contacts an obstacle that causes the table to bind or the motor to slip — important for reducing waste and increasing safety.
In addition, newer interface technologies such as Firewire, USB, and Ethernet are less desirable in this application because they use higher frequency signals that are readily affected by electromagnetic interference.
Finally, PlasmaCAM also prefers the physically stronger parallel port cable and positively-securing connectors found in parallel port connections.
The LAVA Parallel-PCI and Parallel-PCIe boards are ideal in this setting. But note — not all parallel ports are equal here: some parallel port adapter cards in the market have insufficient port voltage levels, and all, or virtually all, USB-parallel interfaces also lack the required voltages. Better to go with LAVA.