Duplex printing is when you print on both sides of a page.
Some printers which do duplex printing require that you send
them special commands to force this mode. This is usually
done by the FILTERS. The ifhp
filter makes a stab at sending the PJL or PostScript commands
to the printer. Many people have reported problems doing
duplex printing, so here is a check list.
Make sure you have enough memory for the worst case
print job. Usually the printer has to rasterize both
pages before it can produce an impression. It may require
much more memory than you expect.
Check your printer manual to discover the EXACT form
of the enter duplex mode command
and make sure that either the command is part of the job
(PJL language at the start of the job, postscript header,
etc), or that the filter generates the correct form.
Note there is a PostScript Printer Description file
(PPD) for most printers that support PostScript, and they
even have the PJL and PostScript code for this in the PPD
file.
It has been observed that even with what would
apparently be sufficient memory, that many duplex jobs
print 'oddly', that they are not aligned on the same side
in the same way, etc etc. This may not be the fault of
the software, but of the support for duplex
operation.
Read the ifhp
documentation, and create a configuration section in the
ifhp.conf file for your
printer.
I know this is painful, but until there is a uniform way
to get the correct commands extracted from either PPD or some
other database then this appears to be the only way to do it.