You need to use the appropriate driver for a locally connected plotter.
If you configure an HDI nonsystem driver for a locally connected plotter and configure a printer in the operating system for the same locally connected plotter, the HDI nonsystem driver is unable to connect directly to the local port because the operating system print driver has control over it. The output is rerouted to the print spooler for the operating system.
If the plotter is connected to a serial port, make sure that the serial port is correct. The settings should match the settings of the plotter and should be appropriate for the cabling you have used. You can verify that these settings are correct by printing to the conflicting printer from another application.
Plotting from an HDI nonsystem driver through the spooler is similar to plotting to a file because there is only one-way communication with the plotter. Performance varies depending on the device.