| 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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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.
Doing as little as possible on drums is a good way of limiting the potential for error.
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 mechanically, and electrically.
The first step of any drum work is to test the mechanical components with a "drum safety test."
The drum safety test is a quick test of the most critical mechanisms in the drum. It is used to evaluate if it is safe to insert the drum in the riso. This test should be performed:
The drum safety test is most easily 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.
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.
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.
④ — Ink
Lastly, check for signs of separated ink. This can appear as an oily residue on the surface of the drum body (usually underneath the drum when it's in the locked position), inside the ink tube holder, in the ink tube itself, or even in the drum case. If a drum has heavily separated ink in it, it's quite likely it needs an internal cleaning before it will ink properly, and that it might be heading toward more issues.
It's also important not to use separated ink tubes in drums, as this will cause further issues with them. Instead, separated ink should be remixed before use.Most of the internal components of the drum can't be easily accessed without disassembling it, however there is a display window through which much of the key mechanism can at least be seen.
Removing the ink tube from the drum, there is a small plastic panel inside, along the bottom of that channel—it can be clicked out, much like the battery cover on a remote control. Shining a light in here will expose the inner rollers and the ink and overflow sensors.
If it is safe to rotate the drum in the riso (it has passed the § Drum safety test), it can be turned once without a tube in, using test mode 892. Looking into this window while the drum rotates can give a sense of how the ink is moving inside the drum: the bead of ink should roll clockwise, while the squeegee roller rotates counterclockwise beneath it.
The drum should not be rotated too many times without an ink tube in, as this can cause the riso to try pump ink, filling the pump with air instead, and locking it up.
Using test mode, many of the electrical components in a drum can be tested without fully disassembling it. Additional electrical tests can be completed with the drum disassembled (described in a later section).
The following table outlines the components and the unit tests for them.
| Test mode | Component | Description | Causes for failure |
|---|---|---|---|
811 |
Ink cartridge set switch | This test should read ONFast beeps and an analog display of <code>╷╷╷╷</code>. when the ink tube is clicked in, and OFFSlow beeps and an analog display of <code>oooo</code>. with no tube. This is a good test to run first, to evaluate if the drum is connecting with the riso at all. |
|
809 |
Ink sensor | The longer sensor needle, which detects the ink in the reservoir. If the longer needle is touching the ink in the reservoir it should read ON, and OFF if not. If it is not detecting, the riso will try to pump ink whenever the drum is spinning (assuming there is an ink tube which is recognized and has not been marked as empty). |
|
810 |
Overflow sensor | The shorter sensor needle, which detects if the ink in the reservoir has built up too high. If the shorter needle is touching the ink in the reservoir it should read ON, and OFF if not. If it is detecting the riso will throw a T/P04-513 error—the "ink overflow" error and stop printing. |
|
882
|
Inking motor | This test will run the ink pump motor when activated—which can be heard as a high pitched whirring inside the drum. This test should only run for a split second, or ink can build up inside the drum (as drum is not spinning during the test). Some models of riso will automatically end the test after 0.5 seconds, but others will not. If the test runs longer than 1 second, immediately hit STOP to end the test. |
|
1211 (protected areaThe protected area test modes are accessed by first running test mode <code>9874</code>.) |
Drum memory | This test reads the first four digits of the drum serial number from the memory stored on the drum PCB. It can be used to evaluate if the riso can read the drum memory on the drum PCB. It should be performed with the front door closed (to make sure the riso has locked the drum in place). The value should be a positive number (and correspond with the first half of the 8-digit serial number printed near the back handle of the drum). |
|
Failure of the drum PCB, drawer connector, or wire harnesses—or the drum PCB being unplugged—are possible causes of misfiring of all of the above components—and have not been included in the "causes for failure" listings. The above tests do not account for: issues with the RFID reader or antenna (which recognizes the ink tube) or the actual values in the drum's memory. | |||
This article should probably be split up into at least two additional articles. One for the drum safety test (Z+) and another for common drum issues. They will unfortunately be dependent on this article for the disassembly process—but many of the other tutorials probably will be too.
Combining: (1) observations of the issues the drum has been having during operation, (2) the mechanical safety test, and (3) the electrical component test—can reliably diagnose most drum problems. And once the problem is identified, the technician can determine what sort of repair is necessary, again minimizing disassembly as much as possible.
The following charts describe the most common drum issues, their possible causes, and how much disassembly they require.
| Issue | Behavior | Cause(s) | Procedure |
|---|---|---|---|
Ink overflow |
The riso throws a T/P04-513 error message and refuses to print with this drum.
|
Ink has built up inside the drum to the point that it is contacting the shorter ink-overflow needle, but is not yet in contact with the ceiling of the chamber visible through the viewing portal (see § Portal access above). | Disassembly may not be required, instead, the excess ink can be "printed out".
|
| Ink has built up so high in the drum that it is in contact with the ceiling of the reservoir chamber and/or ink sensor PCB. | The drum needs to be disassembled through to accessing the rollers, and cleared out from this point. The squeegee gap should also be checked/calibrated at this time. | ||
| See ink overflow for more information about this issue. | |||
Drum not inking |
Even with multiple inking, printing, and cleaning attempts, no ink is coming through the drum. | The pump is filled with air, and is not successfully pulling ink from the tube (this is very common in brand new drums). | Disassembly may not be required, instead the pump needs some help being primed with fresh ink.
|
| The ink sensor is reading ON even with no ink in the drum (see § Electrical evaluation above)—thus the riso falsely believes that there is already ink in the drum, and thus is not pumping any additional ink. | Disassemble through Removing the ink sensor to ensure that the ink sensor (long needle) is properly positioned, and there is no ink buildup on the ink sensor PCB. If there were no clear issues, proceed to the internal electrical test to confirm the ink sensor is working properly. | ||
The ink pump motor has failed (see § Electrical evaluation above), so the riso is trying to pull ink, but the pump is not actually running. In this case the riso is likely throwing a T/P24-539 error.
|
First check all the connections with the drum PCB, to make sure the ink pump motor is not merely unplugged in the front of the drum. If this is not enough, disassemble through removing the drum body and make sure the ink pump motor and encoder sensor are properly plugged in inside the drum. If necessary, proceed through separating the ink pump & motor to the internal electrical test to test the ink pump motor in isolation. | ||
| The ink pump is clogged (or has a bad seal/gasket)—the riso is running the pump but no ink is being pulled. | Be sure to try the previous instructions a pump filled with air first. If that fails, disassemble through separating the ink pump & motor, then run the "mechanical test of the ink pump" described in that section. The pump may need internal cleaning, in the taking apart the pump stage. | ||
| The nozzles or internal plumbing of the ink distributor may be clogged—usually this looks like the drum inking well in one or two stripes side-to-side (parallel to the axis of the paper feed), but remaining dry in the other areas. | Disassemble through removing the drum body, then clean the nozzles of the ink distributor with solvent. It may be necessary to continue through separating the ink pump & motor, so that the "mechanical test of the ink distributor" can be performed. | ||
| The squeegee roller is not rotating, so ink is not being distributed along the length of the drum. This appears often as thin inked lines at each of the four nozzles, but no other inking. It is very hard to distinguish this from a dry screen/drum body—it can only really be determined by watching the squeegee roller fail to rotate while looking through the viewing portal (see § Portal access above). | In this case, it's most likely that the one-way bearing in the squeegee gear on roller has failed. If the gear itself has broken, there may be a distinct clicking sound as the drum rotates. Either way, it must be replaced (see replacing the squeegee gear for instructions). | ||
| See inking mechanism for more information on how the internal inking process works. If repeated problems seem to be occurring with the internal rollers, the squeegee gap may need to be calibrated. | |||
Ink leakage |
Ink is seeping out from underneath the clamp and/or to the left of it. | The adhesive seal on the ink blocking sheet (part of the ink recycling mechanism) has failed, and ink is leaking through it during printing. | Disassemble through removing the screen, then follow instructions for reattaching the ink blocking sheet. |
False empty ink tube error |
The riso is registering an ink tube as empty even when it still has ink—eventually it will refuse to print with this tube. | The riso tried to pull ink for a set period of time, but did not detect ink in the drum even after that time. This will throw a C01-512 error.
|
Remove the tube and click it back in. Optionally run test mode 887 (inking action) to try and re-ink the drum.It can be useful to increase the values of drum test modes |
The riso has permanently marked this tube as empty (on the tube's RFID sticker), throwing a C01-574. This is a common and known issue 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. drums—so long as the ink tube carries this RFID sticker, the riso will refuse to print with it.
|
Replace the RFID sticker on the tube with a "blank chip." This will generate an H01 error any time this drum is used, and the ink parameters will need to be put in by hand.
| ||
| If this is continually an issue with this drum, it's likely the ink pump is failing (either the motor has weakened, or the vacuum in the pump is poor, so not enough ink is being pulled). | Disassemble through separating the ink pump & motor, so that the "mechanical test of the ink pump" can be performed. | ||
| See false empty ink tube error for more information about this issue. | |||
| Issue | Behavior | Cause(s) | Procedure |
|---|---|---|---|
Dry/patchy drum |
A printed image is coming through, but it is very patchy. | If the drum has not been used for a while, it is likely that the screen or drum body is clogged. Three soft, three wide light bars running from side-to-side (parallel the axis of the paper feed), or a thin line corresponding to the bottom of the drum body in the resting position are the two areas most likely to dry first. | Remove the stencil manually, then wipe the surface of the screen with some solvent on a rag (following proper solvent safety). If this improves, but does not resolve the issue, disassemble through removing the screen, then clean both sides of the screen and the surface of the drum body with solvent. |
| If the front and rear edges of the printed image are patchy, on all drums (but perhaps some more than others) the most likely cause is the buildup of dry ink on the pressure roller, not an internal drum issue. | Clean the pressure roller. | ||
| See inking mechanism for more information on how the internal inking process works. | |||
Printing too light/dark |
The drum is printing consistently (not actively fading, or with patchy spots)—but the printed image is much lighter or darker than other drums. Sometimes a gradient light/dark from front to rear (or vice versa) is visible in the print. | The squeegee gap is set incorrectly. If it is too open, too much ink is getting deposited on the inside of the drum and too much ink is printed out. If it is too closed, not enough ink is making it out of the drum and the printing is lighter (and subsequent prints may be patchy). If it is closed at one end and open at the other, a gradient will appear in the print. | Disassemble through removing the drum body and then calibrate the squeegee gap. |
| The squeegee pressure is set incorrectly. Too much pressure will force too much ink out, and the printing will be wet and heavy. Too little pressure won't press enough ink out, the printing will be light and the drum may be dented by the pressure roller. Again, if the pressure is set different at the front and rear a gradient may occur. | Disassemble through removing the drum body and then calibrate the squeegee pressure. | ||
| If this effect is happening across multiple drums it's more likely that the pressure roller mounting position is incorrect or the TPH power is set incorrectly. In rare occasions, a drum can have a dry screen or drum body that results in a uniform lightness of the print (though usually this results in patchiness instead). | |||
Drum specific skew |
The printed image is skewed to the paper, differently or more so on this drum than on other drums. | There are many different causes of skew, but it is a known fact that even when the riso is fully tuned up, all drums will have slightly different skew from each other. | There are many ways of trying to address this (though they are not truly satisfactory), but they don't involve disassembly of the drum. |
| See skew for more information on causes for skew and tactics for correcting for it. | |||
Separator needle scratch |
An ink mark or scratch is appearing around the clamp/screen in the center of the drum. | The separator needle is running too close to the drum and scratching the surface of the drum. This can be a very dangerous issue—the drum may soon be punctured by the separator needle. |
If this is happening to only this drum, there is some issue in the installation of the clamp or tension in the screen. Disassemble through removing the screen then reassemble. If this is happening to all drums the separator needle needs to be recalibrated (see separator calibration for instructions). |
Dented drum body |
A small soft patch prints consistently lighter in the same spot every time, and the drum is otherwise clean. | A dent has been introduced to the drum body, and it is bent in slightly at this location—the pressure roller cannot press cleanly against it, so it doesn't ink or print fully. | Sometimes increasing the density while printing will slightly diminish the effect of the dent, but otherwise the only course of action is to replace the drum body (disassembling through removing the drum body). Large dents can be pressed out of the body with the back of a spoon once the body has been removed, but at best they can be made into smaller dents. |
Irregular drum body |
A thumping sound is happening while printing with this drum. When turning the drum by hand, a softer thump can be heard consistently at a specific angle of rotation. | The drum body was installed without proper tension and is raised up in some areas. This sound is the ink between the squeegee roller and the inside of the drum body separating and coming back together as the bumped out area passes the squeegee roller. A small sound will often be heard when the clamp passes the squeegee roller—this is expected behavior; this issue is specifically referring to a louder sound at any other angle. |
Disassemble through removing the drum body, then reinstall—making sure to get the drum body back on in proper tension. The drum can be rotated by hand after taping the drum body closed again, to check for how it sounds. |
Torn screen |
A small line prints too dark, always in the same place. | A tear or sharp crease in the screen is allowing ink to pool up along the length of it, which prints out too dark. | The only course of action is to replace the screen (disassembling through removing the screen). |
White line |
A sharp white line (wider than a single dead pixel runs along the length of the print (parallel to the axis of the paper feed), and is also visible running around the drum. | Some debris or corrosion is stuck between the squeegee and doctor rollers, so ink cannot reach that area. | Disassemble to accessing the rollers, then use a feeler gauge to scrape out the debris. Turn the back flange by hand afterwards to ensure the gap is now inking properly on the squeegee roller. |
Moire |
The printed image has a moire effect (often looks like a wood grain pattern), even when using graintouch. | The drum is using a generic replacement screen instead of an OEM screen. The original screens use two different layers of a metallic mesh, which are arranged so as not to introduce a moire; the generic replacements just use a fabric mesh doubled back on itself, so it always introduces a moire to the print. | Replace the screen with an OEM one (following instructions through removing the screen and referencing the appropriate parts manual to find the correct part number for the screen). Note that OEM screens are often ~5 times as expensive as generic ones, so often the solution is to trade screens around so that the generic screen is on a lighter color such as Yellow where the moire will be less visible. |
| Issue | Behavior | Cause(s) | Procedure |
|---|---|---|---|
Phantom stencil |
The riso continues to ask for a stencil to be removed from the drum, even though there is no stencil on the drum. It often also throws a A04-303 or A16-525 error.
|
The "light absorbing strip" (black rubber strip to the right of the clamp) is inky or damaged, so it is not properly absorbing the light from the reflective master-on-drum detection sensor; the riso cannot see that the stencil has been removed. | No disassembly is necessary, besides manually removing the stencil. Clean the light absorbing strip, and/or place a portion of a replacement strip on top of the old one (only ~2" are needed, the sensor position can be seen through the master disposal unit while the disposal box is removed. |
| The screen has been replaced with a generic replacement—the light absorbing strips on these are often too thin/flimsy to properly absorb the light from the sensor. | No disassembly is necessary, besides manually removing the stencil; color in the sensor area of the light absorbing strip with a black permanent marker. If this is not strong enough, the strip can be reinforced with a patch of a replacement strip, as described above. | ||
Stencil removal failure |
The riso only partially removes stencils from this drum, either tearing the stencil and leaving a portion on the drum, or not removing it at all and leaving a "bubble" of stencil to the right of the clamp. | The clamp is damaged (usually one of the two posts with the white wheels on the end is bent slightly) and is not opening fully when the riso is trying to remove stencils. | It is recommended that the clamp be replaced, referencing the appropriate parts manual for the correct part number for the clamp assembly. While it is possible to bend the clamp back into shape, this is a dangerous operation—if any part of the clamp is raised too high off the drum (deformed incorrectly when trying to bend it), the drum can get caught in the riso—totaling the drum and potentially damaging the riso.
|
| Too much stencil is being fed under the clamp, and it cannot be successfully released, often tearing partially. Note that this generally affects more than just a single drum. |
This issue does not require drum disassembly—the "clamp range adjustment" should be decreased (test mode 543) to decrease the amount of stencil fed under the clamp. This value should be changed as little as possible, if not enough stencil is fed under the clamp it will be more likely to wrinkle.Note that this will change the amount of stencil fed under all drums—and if only this drum has the issue this is probably just compensating for the slightly-damaged clamp described above. | ||
| Stencil removal issues are usually more of an issue with the riso than the drum. They are only a drum issue if only the one drum is affected. On single drum machines correcting an issue across all drums is usually a matter of: (A) replacing the disposal unit bands/o-rings (if broken the stencil will jam in the rollers of the disposal unit), or (B) calibrating the "clamp range adjustment." On two drum machines it may also require (C) the calibration of the MMU positioning. For more information see master making mechanism. | |||
Stencil wrinkling |
Stencils on this drum quite frequently wrinkle, more so than others. | The clamp reinforcement clips are in the wrong position (the wrong clamp has been installed on this drum), so the stencil is being pinched in the middle but not on the edges.
|
Replace the clamp for the correct model for this machine. Alternately try to increase the "clamp range adjustment" (test mode 543) to feed more stencil under the clamp (be careful though, as this will affect all drums, and too much stencil under the clamp will result in the master removal errors described above).
|
There are additional measures for dealing with wrinkled stencils in the technical bulletins, which should be reviewed to see if any are drum-specific (most seem to be about the MMU and master making process). Additionally the clip position on the clamps should be absolutely confirmed, especially in the case of standard (non "HD") drums of the two sizes—enough A3/tabloid drums with the smaller clip position have been found that they might have shipped with it at some point. | |||
| Issue | Behavior | Cause(s) | Procedure |
|---|---|---|---|
Misalignment on insertion |
The drum has a hard time clicking into the risograph, or cannot click into it at all. | The spindle (inside the riso, at the back) is not properly aligned at 12:00, so it cannot click into the center of the drum. This issue usually applies across multiple drums—it is caused by misalignment in whichever drum was previously in the riso. |
The "position-B" (home position) needs to be calibrated for all drums in the system (see home position calibration (Z+) for instructions). |
| The rotational lock lever is out of place or damaged. | The lever needs to be removed and repaired (see rotational lock repair for instructions). | ||
| If the drum was recently shipped it may need some issues corrected before use—these often occur in transit or as part of the packaging process. | Check for and remove packing foam underneath the front of the drum body and towards the back handle. Check the handle lock latch underneath the front of the drum body—the hooked bar should sit horizontally (sometimes it becomes dislodged in transit and hangs down)—compare this area to a working drum. | ||
| If this issue persists across all drums, especially on one-drum machines, it is likely that the main drive gear is worn down. For instructions of further testing and correction, see main drive gear repair. | |||
Misalignment on removal |
The drum sticks when coming out of the risograph—it has to be pulled hard, wiggled, or rotated slightly by hand. | The "position-B" (home position) for this drum is miscalibrated—this setting can be adjusted for each drum, so if this issue is only affecting the one drum, it may be a settings cause. | Recalibrate position-B for this drum (see home position calibration (Z+) for instructions). |
| The rotational lock lever is out of place or damaged. | The lever needs to be removed and repaired (see rotational lock repair for instructions). | ||
| If this issue persists across all drums, especially on one-drum machines, it is likely that the main drive gear is worn down. For instructions of further testing and correction, see main drive gear repair. | |||
Stuck drum |
The drum cannot be removed from the riso, even when using the manual drum removal trick. In extreme cases the riso will turn itself off (this is very harmful for it). | It's very likely something in the drum was damaged, and it has caught on a component inside the machine. This is one of the most harmful situations a riso can be in—it is recoverable, but extreme caution must be used.
| |
