Print position

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

Print position refers to where the image is placed on the printed page. On digital duplicators, the print position can be adjusted after a stencil has been made, either with directional arrow buttons or with mechanical adjustments on the feed tray (for some older models).

Print position is a translation along two axes (for rotation, see Skew).

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.

Adjustment

There are two systems to control print position while printing: digital positioning, and manual positioning. Which is used depends on the model of the machine.

• Digital positioning uses arrow keys on the control panel to move the print—each button click will move the image a set unit in a cardinal direction on subsequent prints. All duplicators have digital control on the left/right axis (along the length of the paper path) by changing the timing of the paper reaching the drum. Higher level models also also have digital control in the up/down axis by moving the drum itself forward and back in the riso.
• Manual positioning is used in older and more limited models to adjust the up/down print positioning. It functions by turning a dial on the paper feed tray that moves the whole stack of paper forward and back.

Two images should be added here, one of the print position buttons (either 2 or 4 button arrangements) and one of the feed tray positioning dial.

Fine adjust mode

The highest model risos have an optional setting called "Fine Adjust Mode" which changes the fidelity of digital positioning. Normally each button press will move the image 0.5 mm in any direction; with fine adjust mode enabled the movement changes to 0.1 mm. For risographs that have the option (usually those with touch screens) it can be enabled by changing the value of test mode 168 to 1.

Calibration

If the print position consistently needs to be adjusted roughly the same amount, in the same direction (even on different drums) then base print position (AKA where things print without any adjustments) is likely out of specification. Recalibrating it will recenter things (on average) so that it only takes a few clicks (less than 1 mm) of the print position buttons to get the image properly placed.

Sometimes it’s even necessary to recalibrate, when the print position falls outside of the adjustable range—when the position adjustments are maxed out and the print still isn’t in the correct spot.

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. The timing of when the paper is fed to the drum.
6. The user adjustments when printing, with the positioning buttons.

Calibration can be a chasing game, because all of those things are codependent: changing one often has repercussions in the rest.

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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 an "Other Precautions" chapter towards the end of the manual.

In practice however, it is often sufficient to calibrate only two things: the paper feed "home" position, and the stencil-making "write start" position.