Drum repair (Z+)

Drum repair (Z+)
Difficulty	Expert
Duration	½–3 hours
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	JIS phillips #2 screwdriver 4 in (100 mm) zip ties Clear packing tape Doublestick tape Solvent Isopropyl alcohol Gloves Rags

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1. How to: clean an MZ/EZ/RZ drum to change colors

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There are many reasons a drum may need to be opened—to repair an issue, clean out old ink, transition to a new color, etc. This article outlines the common processes in disassembly, testing/cleaning, and reassembly, but does not go into specific maintenance (i.e. correcting the squeegee gap, replacing the squeegee gear, etc.)—those are separated out into their own tutorials.

The golden rule of drum repair is: only go as far as necessary, and no further.

Drum repair is inherently dangerous to the riso.

• Misassembling a drum and trying to print with it can result in totalling the drum and damaging the riso itself.
• Many of the individual components in the drum are quite delicate.
• The process is arduous and messy, and it's easy to make mistakes when fatigued or working alone (ask for help).

Doing as little as possible on drums is a good way of limiting the potential for error.

Evaluation

Before opening a drum it's important to create a plan of attack—to determine how much disassembly is required. A lot of assessment can be done before opening up a drum—both how it is functioning (1) mechanically, and (2) electrically.

Drum safety test (Z+)

The drum safety test is a quick test of all mechanical components of the drum. It is used to evaluate if it is safe to insert the drum in the riso. This test should be performed:

• Before and after doing any maintenance on a drum.
• On drums of unknown status (used drums, drums which have been shipped, or not used in a while, or might have suffered damage).
• On any drums which are behaving strangely (regularly printing weird, making strange noises, etc.).

If a drum fails any of the parts of this test it should not be run in the riso until it can be repaired.

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The drum safety test should be performed on the drum while it is sitting in the rails of the risograph (but not pushed into it). Remove the stencil by hand before performing this test.

① — Clamp

The tolerances inside the riso are very small (~1 mm for the separator needle and <5 mm for other sensors and components), and the drum is spinning very quickly—so anything protruding too high off the surface of the drum is in danger of getting caught in the riso. The clamp is already the part of the drum which protrudes the most—so anything wrong with the clamp can result in catastrophic failure.

1. The clamp should easily flip open when pressing the orange clamp lever, and snap closed when released.
2. The master ejection bar should lift up easily by hand and snap back down when released. Check that the ejection bar sits flat against the drum, and is not bowed out in the middle.
3. Check for the presence of two rounded metal clips near the center of the clamp (they can fall out, or become bent/mangled).
4. Check the two white wheels and white peg at the end of the clamp—the wheels should be unbroken and spin freely; the shafts they are mounted on should be parallel with the axis of the drum (not crooked).
5. Check that all 4 screws are in the clamp.

② — Screen

The drum screen is attached via two bars in the ends of the screen—each of which is attached at the front and rear of the drum. Anytime a tensioned surface is only attached in the corners like this, the bars will bow up slightly in the middle—it's important to make sure that the bars are not bowed up so high that they will catch on the separator needle.

6. The heavier bar (2 screws) should not raise higher than the surface of the metal lip of the clamp assembly next to it. Check it in the middle by dragging a finger tip from the surface of the screen mesh onto the clamp assembly—there should be a distinct step up to the clamp.
7. The thinner bar (4 screws), with the rubber strip along the edge, should not raise higher than the surface of the ejection bar next to it. Again, check in the middle, by dragging a finger tip from the surface of the rubber strip onto the ejection bar—there should be a distinct step up to the ejection bar.
8. Check that all 6 screws are in the screen, and that there is no damage to the screen bars.
9. Check around the screen for signs of major tears—if the mesh separates too high, it can also get caught in the riso.

③ — Rotation

When the drum is inserted into the riso, its rotation is unlocked, so that it can be spun during operation. When spinning, a series of internal rollers are engaged, which help distribute ink along the length of the drum. If the ink is very old/oxidized it can glue the rollers together, then when the riso tries to spin the drum it will either break the gearing inside the drum, or overload the main motor in the riso.

10. Click the manual unlock button (small round button at around 2:00 along the front blue/grey plastic flange) in and out a few times, it should move freely and snap back into the locked position when released.
11. Rotate the drum slowly in the print direction (counterclockwise) while holding down the unlock button. The drum should spin easily, and sound smooth during the whole rotation process. It can be compared to the feeling of rotating a working drum by hand. If the drum can only spin in the opposite direction (clockwise) it is a sure sign that the rollers are glued together by old ink and need internal cleaning (the rollers only engage when spinning in the printing direction).
12. While rotating the drum check for any major dents in the drum body—small dents won't cause additional damage, but heavy dents can deform the drum body enough that it can collide with the insides of the riso.