Calibrating print position (RP-RN)

Calibrating print position (RP-RN)
Difficulty	Beginner
Duration	5 minutes
For series	RPRN
Tools	Ruler or loupe

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

Calibrating the print position on RPRN 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.

Procedure

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

Determine offsets

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

1. Turn the riso on and load a working drum. Then lower the feed tray, and fill it with paper of a standard size.
2. If the riso has a wheel at the front of the feed tray to control up/down positioning, turn it to the center position (referencing the sticker on the tray).
3. Turn the riso off, then start it 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 50 (type in 50 + START) to create a stencil with the test grid and print a proof of it.
   • Alternately a stencil can be made (using a scan or from the driver—whichever is typical for how the machine is used) with a registration mark dead center on the page.
4. Switch into normal mode by holding the RESET key for 1 second.
5. 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.
6. 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).
7. Mark the feed direction on this print, and number it ① (this will be the first reference print).
8. 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.

Calibrate the left/right print position

On RPRN machines, the left/right print position is adjusted in the master-making process, by changing the write start-position (how far along the stencil that the riso begins burning the image).

1. Turn the riso on in test mode (hold the left and right print position buttons while turning it on).
2. Run the test mode for "write start-position adjustment" 281 (type in 281 + START) and jot down the current value.
3. Adjust the value according to the offsets (with the test still running, type in the new value and hit START; the ✱ button will flip the sign between +/-).
   • Increasing the value by one (+1) will move the printed image to the left (burned image closer to the clamp) by 0.1 mm.
   • Decreasing the value by one (-1) will move the printed image to the right (burned image further from the clamp) by 0.1 mm .

For example if the current value is +8 and the image needs to move to the right by 0.5 mm, the new value should be +3.

4. Turn off the riso.
5. Use the #Determine offsets section above to create a new stencil and test print. Mark the feed direction, number it, and measure and mark the new offsets.
6. Repeat to fine tune as needed.

Calibrate up/down print position

Calibration of the up/down position is handled with the TPHThermal Print Head print position (also part of the master-making process).

1. Turn the riso on in test mode (hold the left and right print position buttons while turning it on).
2. Run the "TPHThermal Print Head print position adjustment" test mode 294 (type in 294 + START) and jot down the current value.
3. Adjust the value according to the offsets (with the test still running, type in the new value and hit START; the ✱ button will flip the sign between +/-).
   • Increasing the value by one (+1) will move the printed image up (burned image closer to the back of the drum) by 0.1 mm.
   • Decreasing the value by one (-1) will move the printed image down (burned image closer to the front of the drum) by 0.1 mm .

For example if the current value is +2 and the image needs to move down by 0.3 mm, the new value should be -1.

4. Turn off the riso.
5. Use the #Determine offsets section above to create a new stencil and test print. Mark the feed direction, number it, and measure and mark the new offsets.
6. Repeat to fine tune as needed.

Additional adjustments

In addition to the above, it may be useful to read the official documentation on calibration of the following:

• Master clamp range—how much stencil is fed under the clamp (this is important in making sure stencils can be loaded and removed properly, especially in two-drum machines).
• FB scanner start position—where the scanner bed starts "seeing" the image, in the left/right direction.