Calibrating print position (Z+)

Calibrating print position (Z+)
Difficulty	Beginner
Duration	5 minutes
For series	Z+Any machine released with or after the RZ line, i.e. RZ/RV/EZ/EV/SF/SE and MZ/ME/MF/MH machines.
Tools	Ruler or loupe

This is the draft of an article, it is incomplete or in-progress.

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This is a part of the registration and alignment series of tutorials.

Calibrating the print position on Z+Any machine released with or after the RZ line, i.e. RZ/RV/EZ/EV/SF/SE and MZ/ME/MF/MH machines. machines can be done through test modes, while making a series of test prints.

In terminology the feed edge is the top of the page, regardless of paper orientation or the orientation of the printed image on it. So the axis along the direction of paper feed (from the feed elevator to the exit tray) is referred to as the "vertical” direction, and the perpendicular axis (from the front of the machine to the rear of it) is the “horizontal” direction.

For the purposes of this article, the terms left/right (along the axis of the paper feed), and up/down (perpendicular to the paper feed) will be used instead.

Strategies

Many different factors affect the final print position on the page. In the order of low-level to top-level they are roughly:

1. The position of the image burned onto the stencil.
2. How much stencil is fed under the clamp.
3. The angle the drum was rotated to when receiving the stencil.
4. The position of the MMUMaster Making Unit when loading a stencil (on two-drum machines).
5. Where the scanner starts recording an image (if scanning).
6. The timing of when the paper is fed to the drum.
7. Where the original is on the scanner (if scanning).
8. The user adjustments with the positioning buttons when printing.

The official service manuals for Z+Any machine released with or after the RZ line, i.e. RZ/RV/EZ/EV/SF/SE and MZ/ME/MF/MH machines. machines provide instructions for calibrating all of the above (and in what order) within the "Print position adjustment procedures" section of the OTHER PRECAUTIONS chapter (towards the end of the manual).

The following instructions present a simplified version of calibration, focusing on centering the printed image at the end, rather than calibrating each individual step along the way.

In practice, only two settings really need to be changed to get images properly centered:

• Home position (paper feed)—the default timing of when each sheet of paper is fed into the drum. This method works just the same way the print position buttons do—it just changes the neutral/starting position. Any adjustments to timing, however, carry a risk of increasing misregistration and/or paper jams, if pushed too far towards the end of the range.
• Write start position (master making)—this affects where the image is actually burned onto the stencil. This adjustment is quite dependent on all of the other master making settings—the clamp range adjustment, write speed, etc. and it has a limited range at which it is effective. If the burned area is moved outside of the printable area, the printed image will be cut off.

Best practice is generally to make adjustments to the home position (paper feed) first, and only adjust the write start position if the paper feed adjustments are getting to the extreme ends of the allowable range.

Procedure

Before starting this process, elongation/shrinkage should be checked, and calibrated if needed.

Determine the offsets

Firstly, the direction and distance of each required offset needs to be figured out.

1. If the riso has a wheel at the front the feed tray to control up/down positioning, turn it to the center position (referencing the sticker on the tray).
2. Start the riso up in test mode (turning it on while holding down the left and right print position buttons), with a working drum in, and a standard size of paper on the feed tray. Then run test mode 81 to create a stencil with the test grid and print a proof of it.
   • Alternately an original can be made (digitally for risos that print from a driver, or a physical original if the scanner bed is used) with a registration mark dead center on the page.
3. Switch into normal mode by holding the RESET key for 1 second.
4. Run 5–10 prints (both to ink up the drum and to evaluate the registration in the next step) using all the regular print settings, but without adjusting print position.
5. Filter through the prints to find one that seems typical for the set (i.e. not one that is a clear misprint, or very misregistered—if all prints have different print positions, then the registration may need to be corrected first).
6. Mark the feed direction on this print, and number it ① (this will be the first reference print).
7. Measure how far off the printed image is, and in what directions, and mark these on the sheet.
   • When using the test grid, measure to the edge of the printed area (which will likely be the cut-off ends of the grid lines).
   • When using the center mark, fold the sheet in half in each direction, and measure relative to this center mark.

Often the rough amount of offset is already known to the operator—it is whatever are the standard adjustments needed to before fine-tuning print position (the ones they make reflexively before even looking at the printed image). This can provide a quick shortcut to this process.

Since the riso moves in 0.5 mm increments with each button click (unless fine adjust mode is enabled), if the print position must always be shifted five clicks to the right, and two clicks up (for example), then the offsets are 2.5 mm to the right and 1.0 mm up.

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The former version of this tutorial is listed below, it goes through adjustment of the master making position, not the paper feed position. It will be removed as the above section is finished.

1. Enter test mode: hold left/right arrows on position adjustment control panel (for the first drum position, on a two-drum machine) while turning the machine on.
   • 0541 Vertical position
     This setting adjusts the default center position of the master on the long dimension of the paper. It is in tenths of a millimeter.
   • 0586 Horizontal position
     This setting adjusts the default center position of the master on the short dimension of the paper. It is in tenths of a millimeter. Positive is toward the front of the machine.