Focus on Duplex

Duplex means printing on both sides of the paper, which is opposite to simplex, which is printing on one side. Duplex printing is highly desirable in that it reduces paper consumption and the amount of paper in file cabinets. Duplex printing difficulties are a perennial issue: people try to get the printer to print on both sides of the paper, but it doesn't happen. Here is some information based upon my years of dealing with that.

First determinations

First and foremost when dealing with this issue is to assure that the printer is capable of duplex printing: not all printers are. How can you tell? With HP printers, you can tell from the model number. An example is model number 4015dn: here, the 'd' means that it is a duplex capable printer (and 'n' means it operates over networking). Workgroup printers that do duplex will often have a duplexer that is added to their paper path, being a conspicuous, boxy thing hanging off the end of the printer.

What governs duplex in print job processing

So, what actually does control duplex printing?
In PostScript printing, it is the PostScript itself... The PostScript gets generated by the application software in conjunction with the PostScript printer driver installed on the computer where the print job is being created. That driver allows you to select duplex, commonly in an options presentation. What this does is generate the following PostScript instruction: 

%%BeginFeature: *Duplex DuplexNoTumble
 <</Duplex true /Tumble false>>
   setpagedevice
%%EndFeature

What if the PostScript does not contain that duplex instruction?
In this case, one of two things will then govern duplex. First, the PostScript driver may generate PJL which tells the printer to do duplex. PJL is HP's Printer Job Language, which consists of lines of simple text, presented to the printer ahead of the job proper, which tell the printer to handle the job in a certain way. Many printer brands other than HP understand PJL. The PJL instruction for duplex is: 

@PJL SET DUPLEX=ON
The next natural question is, what happens if not even this PJL is sent with the job?
In this case, the duplex-capable printer will follow the duplex configuration parameter which the printer administrator set into it. This is a default, governing what to do if nothing in the job says what to do. Commonly, printers capable of duplex are configured to print duplex by default, which is common sense in that it saves paper. Note well that this printer configuration value is a default, not a mandate: any plex specification that comes with the job overrides this.

But what if the printing is IPDS rather than PostScript?
In this case, the print server controls duplex, according to what it found in the job originally submitted to it (which may have been PostScript, PCL, etc.). This is AFP stuff, which the server administrator would have set up.

Troubleshooting no duplex

If you are certain that the printer is duplex-capable, proceed as follows:

  1. If PostScript, look for duplex in it.
    The best approach is to do a "print to file" and then inspect the contents of the file for the duplexing instruction illustrated earlier. With most of the cases I've seen, it has been the case that the job did not contain such an instruction, or did have such an instruction earlier in the job but then had an instruction which turned duplex off in the bulk of job printing, via: 
    %%BeginFeature: *Duplex None
 <</Duplex false>> setpagedevice
%%EndFeature
    due to how the application wanted output to be produced.
  2. Assure that you have the appropriate PostScript driver
    You should obviously not be trying to use a driver that is specific to a Ricoh printer model when you want to actually print to a certain HP model. You can do one of the following:
  3. Try your job on another printer of the same technology.
    For example, you tried the job on the HP printer that is near your office. Try submitting the job to another HP printer or other PostScript type printer in the environment. If you have the same problem, the issue is with what you are sending, not the printer.
  4. If all else fails, confer with a printing expert.
    There should be someone in your organization who is very familiar with printing technology, and can quickly unravel minor mysteries. But don't expect the person in your organization who is responsible for the printer to be able to help: often, they are just the people who clear paper jams and replace toner cartridges, who don't have printing technology expertise.
Back to the Printing page