Image forming device with multimode duplexer

1. A method of duplex printing in which a media substrate is partially expelled from an image forming device, said method comprising:

transferring print material to a first side of one media substrate after a preceding media substrate has been partially expelled from said image forming device and moved into a duplex path of said image forming device; and

varying gaps between said media substrates as said media substrates are moved through said image forming device, at least some of the gaps determined based on timings between a fuser and an exit roller that each share a common motor.

2. The method of claim 1 , further comprising:

transferring print material to a first side of said preceding media substrate prior to said preceding media substrate being partially expelled from said image forming device and moved into said duplex path of said image forming device; and

transferring print material to a second side of said preceding media substrate;

wherein varying gaps between said media substrates as said media substrates are moved through said image forming device comprises varying a first gap and a second gap between said media substrates, said first gap being a distance between a trailing edge of said preceding media substrate and a leading edge said one media substrate and said second gap being a distance between a trailing end of one media substrate and a new leading edge of said preceding media substrate after inversion.

3. The method of claim 2 , wherein said second gap is greater than said first gap.

4. The method of claim 2 , wherein said second gap is substantially equal to said first gap.

5. The method of claim 2 , further comprising:

partially expelling said one media substrate from said image forming device and moving it into said duplex path;

transferring print material to a second side of said one media substrate;

wherein varying gaps between said media substrates as said media substrates are moved through said image forming device comprises varying said first gap, said second gap and a third gap between said media substrates, said third gap being a distance between a new trailing edge of said preceding media substrate after inversion and a new leading edge said one media substrate.

6. The method of claim 5 , wherein said third gap is smaller than said first gap.

7. The method of claim 5 , wherein said third gap is the distance needed for toner patch sensing.

8. The method of claim 5 , wherein said second gap is substantially equal to said first gap and said third gap is smaller than said first gap.

9. The method of claim 5 , further comprising:

transferring print material to a first side of yet another media substrate;

wherein varying gaps between said media substrates as said media substrates are moved through said image forming device comprises varying said first gap, said second gap, said third gap and a fourth gap between said media substrates, said fourth gap being a distance between a new trailing edge of said one media substrate and a leading edge said yet another media substrate.

10. The method of claim 9 , wherein said fourth gap is the distance needed for toner patch sensing.

11. The method of claim 9 , further comprising switching a transfer voltage of said image forming device from a first voltage to a second voltage, wherein said fourth gap is proportional to the time to switch said transfer voltage.

12. The method of claim 9 , wherein said fourth gap is the distance needed for sensing the edges of the media sheets.

13. The method of claim 5 , wherein said third gap is the distance needed for sensing the edges of the media sheets.

14. The method of claim 1 , further comprising moving the media substrate in a vertical direction after transferring print material to the first side.

15. The method of claim 1 , wherein the method comprises a two-image print job.

16. The method of claim 1 , wherein the method comprises a three-image print job.

17. A method of duplex printing using an image forming device, said method comprising:

transferring print material to a first side of a first media substrate;

partially expelling said first media substrate out of said image forming device and into a duplex path of said image forming device;

adjusting a gap between the first media substrate and a second media substrate based on timing of a motor that is shared between a fuser and an exit roller; and

transferring print material to a first side of the second media substrate while said first media substrate is into said duplex path.

18. The method of claim 17 , further comprising varying an interpage gap between said media substrates as said media substrates are moved through said image forming device.

19. A duplex image forming device comprising:

a plurality of image forming units disposed along a primary media path and transferring print material to a media substrate;

a duplexer returning said media substrate to said primary media path; and

a processor controlling said image forming device;

wherein said processor is programmed to vary gaps between media substrates as said media substrates are moved through said primary path and said duplexer of said image forming device, a size of at least some of the gaps being determined by a timing to adjust voltages between two of the plurality of image forming units that share a power supply.

20. The duplex image forming device of claim 19 , wherein said processor is further programmed to partially expel said media substrates from said image forming device.

21. The duplex image forming device of claim 19 , wherein said processor is programmed for a two image printing sequence.

22. The duplex image forming device of claim 19 , wherein said processor is programmed for a three image printing sequence.