Zebra S Series Printers: Ribbon Nightmare No More

Everyone knows laser and inkjet printers since they are ubiquitous in every office, SoHo and homes around the globe. They have some far cousins known as barcode printers or label printers and they basically specialize in using rolls (or stacks) of labels rather than sheets. The "ink" can be a ribbon of plastic film with carbon particles attached to one of its sides using a formulation of wax and/or resins (thermal transfer) or either the labels have some treatment to react to heat by turning black (Direct transfer). Zebra brand name manufactures great printers that are the workhorse of the industry. The S Series are heavy-duty, robust and generally with a worry-free performance, however there is a black cloud in the horizon...

Ladies and Gentlemen, please welcome: The FEED SPINDLE! or where you insert the ribbon when it is new. Please note the arrow in the background that clearly signals the orientation. It says in a graphic way that the ribbon should unwrap falling at the BACK and not the FRONT of the spindle. I wonder how many operators other than me have noticed it?

Anyway, the problem with this spindle is that if you happen to have your mind set in your facebook page rather than at the printer, you may end up loading the ribbon the wrong way. -"Sooooo???"- you may think, but the issue is:

1.- It won't print anything since the ink side of the ribbon is facing up towards the printhead instead of down towards the label (you just placed the ribbon upside down) and all that carbon/wax/resin intended to be on the label is being caked in the ever hot printhead, therefore your print quality is bad, probably leaving blank lines and scratches that will interfere with your barcodes and render them unreadable.

2.- There is a spring inside the spindle that keeps the ribbon properly tensioned to avoid wrinkles. Wrinkles in your ribbon means traveling blank lines in your labels, and by now, it spiraled out in such a way that chances are it is deformed, stuck, or both. You may not even be able to remove the ribbon because the spring is in your way.

Headache time! Now you cannot finish those labels that you needed yesterday to ship these boxes and on top of that, you need to find and call a technician to rescue you, and not likely for free.

This occurrence is worse on those places where there are diverse untrained personnel handling the machine. Looking grim so far, huh?

So let's analyze the issue here: In the first image, an explosive diagram of the spindle, you can see the spring that gets damaged. Its function is to provide drag to the ribbon so it remains flat, extended, thus preventing wrinkles from happening in your labels.Spun the right way it tends to spiral in. Spun the wrong way makes it to spiral out. When the torsion is excessive the felt washer is supposed to give in to protect this spring. In the real world, this is not often the case when spirals out and the spring simply gets deformed. I have personally seen places where the repair man is a staple and they could have bought dozen printers with the money spent. Yeah, stupidity is profitable for some.

The long end of the spring is attached to the end cap that adjust the right amount of drag to the ribbon; the short end is attached to a clutch assembly that doesn't work very well when the spindle turns the wrong way. Yeah, the part itself is cheap, but getting someone to fix it plus all the indirect cost of not having the printer going can be really high. I dunno why Zebra decided to go for this design even when some lower, budget models like its Stripe series (already discontinued) had a far superior feed spindle, one that is really one way, like the one in the last picture.

DISCLAIMER:
I am not in any proportion at all responsible or liable for any damage or lost incurred to you, your equipment or your activities by following these instructions. This instructable is offered in "as is" condition and is your solely responsibility to decide to do it or not.

Enough of mumbo jumbo, let get our hands dirty!

So before all Zebra's customer that suffer the direct or indirect consequences of this flawed design get together and call for a class-action suit against Zebra and force a massive recall, let me offer my solution to the issue:

What I wanted is this:
a.- Tension in the ribbon when loaded right, like it is supposed to do and
b.- Nothing, absolutely nothing happening if the ribbon was loaded the wrong way
c.- Mod should be able of being reproduced with a minimum of tools, supplies, time, training and effort
d.- Low cost

After few sleepless nights I decided that the turning point was on the Clutch disk. It has a small hole to house the spring but that spring actually wants to be homeless wherever it may roam. Instead of a hole I'll give it a notch to rest. One is more than enough, but it can have two, three.

It has to be done with some accuracy though:
1.- Starting in the center of the face of the rim
2.- Running perpendicular to its radius
3.- Straight as straight can be

There is little space so not a lot of room for mistakes, however in case something happens, you can fill it in with some epoxy putty and start in another location. Mark your starting points with a marker and let's move!

Now dust off your CNC plasma and... oh! How come you don't have one? okay, then what about a dremel? The cutting disk seems to have the required thickness. I think even a hacksaw, the ones with fine teeth, will do. Hold the clutch disk with a locking plier because it will get really hot. Get on a comfortable position, visualize your cut and most important: BE PATIENT!

If the piece gets hot enough the inner plastic tubing seems to come out (maybe piece is expanding), as soon as it gets loose remove it to prevent any damage, remember, it has to spin freely in the metal axis when put back together. (Mine got badly stuck as soon as it got on the axis. I had to sandpaper the inside of the plastic tubing until it spun freely again.)

Finish all sharp edges with sandpaper by trying to make edges and surfaces as smooth as you can so the spring doesn't get stuck and can be released freely..

Once your piece is modded, then we are ready to see if it works. I also recommend to apply a bit of sandpaper to smooth and round up the short end of the spring, after all, it is made of steel and will be charging against aluminum, so you want that steel edge smooth as a rose's petal.

Let's put everything back together into the spindle and cross your fingers. This time instead of getting the short end of the spring into the hole, just let it go on top of the rim. I guess at this point it doesn't really matter if you insert the short or long end, but let's abide by what the book says.

This is what the feed spindle is supposed to do when you load the ribbon properly: When the ribbon gets pulled forward there must be a little resistance, that tension keeps the film tense to prevent wrinkles on it. Too little tension and you may have wrinkles. Too much tension and you will notice some dragging of the ribbon's core over the spindle.

In all Zebra printers, the film should fall at the back of the spindle as indicated in the plate, the carbon coat is in the outside of the ribbon roll. I left the end cap of the spindle loose, but normally is adjusted to a proper tension attaching it with the socket set screws.

* UPDATE FEB 2017: I noticed my youtube account was deleted with all my content there, I have no backup of these videos, they were very illustratives. My apologies!

The video simply showed the short end of the spring latching into the gap on the clutch disk, therefore engaging into providing the spring with some drag (you can regulate how much) which resulted in a nicely tensioned, flat ribbon surface. No wrinkles!!

No worries! nothing happens! You may notice that your labels are blank, and there is a funny metallic noise you didn't hear before; you will be curious and see that the noise is coming from the spindle, but instead of panicking and running away wondering if someone saw you around the printer, now you can just take the ribbon out and load it the right way. No problem! You won't be fired!

Pat yourself in the back for few moments thinking in all the suffering you saved to your company with this little mod and... Get back to work!

* UPDATE FEB 2017: I noticed my youtube account was deleted with all
my content there, I have no backup of these videos, they were very illustrative. My apologies!

The video here showed how the short end of the spring was jumping thru the gaps you made in the clutch disk without engaging at all, saving your precious and delicate spring from harm. This video was the piece de resistance for my instructable but I no longer have access to a zebra printer to redo the videos. I really wish I could work repairing this little work horses.