My shredder doesn't like me anymore :'-(

[Rodast]

We have a shredder that always starts with the little check program by turning in both directions for a few seconds during startup. I guess it is a health check and also clears out any remains from previous use.

When I wanted to use our shredder this weekend it started making unfamiliar sounds.
Also it would not pull in paper automatically but would work using the manual buttons - at least for taking in paper.
I first sounded like a possibly broken gear or lose mount. So I took it apart for closer inspection.

That said I can manually turn the motor in both directions which then turns the gears just fine.
I also used a power drill with a rubber tip to turn the motor spindle with a bit more speed which still worked fine and smoothly in both directions.

When I powered the shredder it started acting up on the reverse cycle during the startup sequence.
As far as I understand the forward mode is working fine.
But it seems that the motor starts stuttering when it is supposed to turn in reverse.
I made a quick video showing the behavior: https://youtu.be/dGiQTuzxNKo

I tried to visually look around at the components but did not see anything unusual.
Thinking this could be a startup current issue in reverse I tested the the beefy Yuhchang capacitor with my multi meter but it is spot on with 12,3 microF.

Searching the internet I have seen similar motor issues but mostly with stepper motors - so not very comparable.

Not sure what else to check, any ideas?

[richnormand]

1)
one of the gears is loose at the motor shaft-gear. Have you try to block one side and twist the other?
2)
try to use a small tygon or rubber hose and carefully position one end around while listening at the other end like a stethoscope. You might be able to locate more precisely the exact location of the noise.
3)
motor has any type of centrifugal switch to start that reenguage when to speed drops down?
4)
if you rotate the motor by hand (unplugged of course) can you follow the whole assembly up to the cutters both in reverse and forward?
Maybe there a jammed part that prevents it from rotating in one direction only?
5)
difficult to tell from the video but it does look like both left and right (fan, gear) do rotate similarly.
6)
machine has some sort of paper/shredder jam sensor that cuts the motor power?

Ran out of idea at this point.

[Digorion]

Hello!
It looks and sounds lika a mechanical issue. Like motor fan scraping something in one direction or something else. Also, it could be the sound of gears slipping. Сarefully check the mechanical part (especially the gear transmission).
If one of the bearings or shafts on the gear side has a lot of wear, this can lead to slippage, including only in one direction (depending on the nature of the damage).

[Rodast]

Hello richnormand, digorion, all,

thank you for your input.

Here is what I can already clarify based on preview testing.

1) I have already tried to wiggle all gears but could not find anything loose or broken
2) I have a stethoscope like device and will try. From what I can currently say the noise comes directly from the stuttering of the motor.
3) I have three pictures with the motor details that i wanted to upload which should clarify this - but my images triggered the security check and I should contact the site admin. Are uploads currently blocked?
4) turning by hand is working fine and really easy. Also the shredder is eating paper once I get it past this start up testing and manually press the shred button. Pressing the reverse button results in the shredder acting up again.
5) *
6) The shredder has several sensors. i had to trick two of them which are usually pressed by the paper basket. Without pressing the shredder refuses to work for security reasons. The shredder lso has a jam led which is currently not active as part of this behavior.

To me it seems to be more motor control related.

It seems to be easy to unscrew the motor from the rest of the gear assembly. I will try that tomorrow and report if the motor on its own also shows the issue. * I wil then also try to get a better footage of the situation.

[Yansi]

Let me guess: Power supply issue to the electronics. (wouldn't be the first shredder)

Post a photo of the shredder control board, I'll tell ya what to check.

[Rodast]

The story continues.... :-)

https://youtu.be/fokAfAY4OaY

In general I checked all the gears. They show no sign of wear or damage.
All fixed axles seem to be firmly in place without any play. The same is true for the axles and barings of the shredder drums.
The axles of the two gears you see in the video are removeable and are clamped fast between the chassis and the bracket.
I really don't see any kind of mechanical issue here that would explain the stutter in reverse.
At all times things are nicely turning in both diretions when done manually - either turning one of the gears by hand or the motor fan/axle.

The issue only occurs when the system is powered and only in the reverse direction.

Below are the pictures of the board and components:


https://imagizer.imageshack.com/img924/9620/uG5lux.jpg
https://imagizer.imageshack.com/img924/2296/WEZNdI.jpg
https://imagizer.imageshack.com/img924/4057/XD8kV0.jpg
https://imagizer.imageshack.com/img922/4921/N1E60v.jpg

It is a Rexel 2105018EU Mercury RSX1834 still sold today. It has not seen much use/abuse.

[Yansi]

If nothing else, check the capacitance of the big brown-or-whatever color foil capacitor on the control board.

The board is powered directly from mains, through that capacitor, acting as a reactive voltage dropper.  These caps are usually both piece of cheap shit & under-rated voltage wise. They typically start losing capacitance, as the overvoltage (even continuous due to the caps being incorrectly sized) causes the internal foil's metalization to burn out.

Desolder the cap and measure capacitance, or just replace with a new one straight away.  Use an X2 safety rated for mains operation. If not possible, cap must be at least 630Vdc or 275Vac rated.

The loss of capacitance leads to unsufficient power to the control board, which may cause it to malfunction.

[richnormand]

Since the motor operates OK with no load that removes a lot of electronic issues but the cap could still be suspect as Yansi pointed out.

I note on your video that in forward you see the cutters turning in the slot but in reverse not.
Same with the big gear at the bottom. Looks like there is an issue at the worm gear at that point.

Is there a clutch or slack in the gear that translate from the spiral pattern on the shaft to drive the big gear? The white gear at the left? How does it enage the black one in the middle.

If the rotation direction of the motor actually changes (cannot tell from the video) look at the gear that engages the motor shaft for sideway slop as the force will push it inward/forward depending on the motor direction and there could be slippage between in one of the two direction.

If the motor rotation does not change then there should be a mechanism to insert an idler gear to change direction and a solenoid or something that does not engage it fully.

[Rodast]

Hello richnormand, yansi, all,

I will look into the cap topic but need to get parts first. Due to the upcoming christmas holidays and online orders currently flooding the delivery companies this might take some time ;-)

@richnormand: You can see gears and blades turning in both directions at 1:40 (fwd) and 1:49 (reverse) after I completed the gear examination and reassembled everything. So once the shredder is turning in either direction it is working as expected. At that point it is a fixed system meaning not clutch or slack whatsoever. The shredder has a jam warning which means if you put in more pages at a time then the shredder can handle it will shut off the motor but not disengage anything in the drive train.

Looking forward to the next time I have to take it apart  (its a really heavy block and very greasy).
But if that brown cap would do the trick that would be really super nice.

[richnormand]

The gears do move in both directions but not smoothly in reverse. Still the gear train is suspect in my mind.

"The shredder has a jam warning which means if you put in more pages at a time then the shredder can handle it will shut off the motor"
Did you have a close look at that sensor? Is it mechanical, opto interrupter... Any chance of loose paper in it? Slack in its mounting? Can you the voltage to it while in reverse at its connector?
Can you remove it out of the way?

Also noted of the pcb that two power devices did not have what looks like a heatsink (labeled on the pcb) present.
Possibly an issue if one overheated if each handled one direction of the motor?
If the gear power transmission in both direction is ironclad I am running out of idea here.

Can you monitor the voltage supplied to the motor  (white gray black wires) and see what happens in both directions with load?

Cheers

[Digorion]

I still think it might be a mechanical problem, in particular with the worm gear to the plastic gear. Although I cannot exclude the electrical nature of the problem.

I noticed something strange at 0:20 in your video (it could be a video artifact, though). When starting the engine in the opposite direction, it looks like the plastic gear, although jerky, rotates, but the metal gear of the shredder shaft drive is practically in place. Then, when the power supply to the motor is turned off, by inertia, all the gears rotate absolutely evenly (this is less than one second, but you can see).

Based on the circuit shown on the motor, this is a single-phase motor with a starting capacitor and two (presumably the same) windings. To reverse it, I believe, the order of connecting the phase-shifting capacitor to the windings (in one direction - to one winding, in the other direction - to the other) is changed by connecting the neutral to the gray or black wire. If something is wrong with the switching circuit or with the windings themselves, this can lead to insufficient starting torque (due to current limitation, for example) or something similar. Perhaps a high starting current at the initial moment causes a voltage drop in the circuit, then the winding turns off and the current drops, then turns on again, etc. Something like that, I cannot say for sure without more detailed information, I just assume.

On the other hand, rotation of the worm gear in different directions causes different axial forces on the mating gear. That is, in one direction, the engine and the mating gear tend to be attracted, and in the other - to push off each other (something like that). Alternatively, check if the bolts securing the motor to the frame are tight.

I can suggest as an option, in order to determine if the problem is caused by the control electronics, temporarily swap the gray and black wires according to the diagram on the motor. In this case, when the forward button is pressed, the motor will rotate in the opposite direction, connected through the commutation elements of the forward direction of rotation. But before doing this, MAKE SURE that my assumption about the reverse circuit of this motor is correct. There is a fuse on the white wire according to the diagram, so I assumed that this is a common wire.

[S. Petrukhin]

Haven't you tried turning the motor manually in different directions, for example, by the impeller?

[Muttley Snickers]

I still think it might be a mechanical problem, in particular with the worm gear to the plastic gear. Although I cannot exclude the electrical nature of the problem.

On a side note, our local council recycle centre always has a good supply of name brand paper shredders and a common failure that I have seen is where the metal worm gear chews out the teeth on the main nylon drive gear, this failure appears to occur when these units get overloaded and jammed up. I strongly suspect that this is an intended design flaw so they can flog you a new one when the one you have chews itself to bits. On some units the worm gears are as sharp and effective as any milling cutter I have in the workshop.