Repbox "Cereal Box" MMU Buffer
I have tried out every possible buffer variation I can think of, and time my MMU would act up, it was almost always related to feed issues, almost every time being the buffer causing too much drag or friction.
I had a really good run using auto-rewind spools in the Repbox. But it was frustrating to load and once they started acting up it was a reporting to fix any issues.
I'm happy to report I'm 90% to a fully baked solution at this point that never seems to cause feed issues and is super easy to load. I present to you, the Cereal Box Buffer System.
Using the Repbox rollers along with some mostly accurately cut up cereal boxes, everything is contained in the Repbox and it amazingly easy to load. The rolls feed directly into the MMU in the printer below.
My plan is to design something I can print to replace the cereal boxes. It's a bit big for a MK4 print bed. But, I'm betting I actually don't need to extend all the way to the bottom (since the filament would back feed upwards around the top of the roll).
RE: Repbox "Cereal Box" MMU Buffer
I was planning to use the auto-rewind spools in the [un]original drybox solution - what is the issue with using these?
--> MK4 - MK4S - MINI+ - MMU3 - Accelerometer Guide - BambuLab A1 Combo <--
RE:
I want to add here that I did have a good amount of success with the auto-rewinders. They do work a lot of the time. But, for me, it became a tinkerers maintenance problem. All of this is my experience. I'm sure others will have their own experiences and opinions and that's fine. This is just what I have found for myself.
My first beef with them was the loading. I found it awkward to get it onto the spool and then inside the tiny window of the Repbox, then be able to get it onto the supports for it. All while ensuring they're properly oriented and without accidentally unspooling the filament.
But the real problem I found was the inconsistency in it. If a spool was brand new (1kg), it was often too heavy to rewind quickly enough. If there were a number of small prints from that colour in succession, it would eventually unwind the spool inside the repbox. Best I could describe it is, it was pulling in more than it was rewinding on every filament change. Eventually leading to a mess in the repbox that would likely get snagged or tangled.
On the lighter side of things, if there wasn't a lot of filament left on a spool, it wasn't always heavy enough to actually wind the rewinder. So, similar to with the full spools, it would eventually unwind the spool inside the Repbox. Cardboard spools helped with this because of the friction, likewise roughing up the spool or covering it with plastidip could also help, but not always. However cardboard spools in the enclosed area against the plastic of the rewinder can cause a non-trivial amount of dust in the box. I tried using the inner facing rotini designs, but they just result in the earlier problems of "when they're too heavy or too light".
For me, I found that the whole auto-rewinder is such a complicated solution for what should be a simple problem to solve. In my career, the more pieces you ad to a solution, the more things can go wrong. Thus the troubleshooting becomes incredibly time consuming and frustrating. The best quality prints I've had when using the MMUs have been when using air buffers and TUSH rollers. But they have their own problems of getting tangled if you don't keep them separate.
This felt like a decent middle of the road solution. Easy to load, limited set of components to cause problems, and minimal friction when feeding. (It doesn't hurt that pre-loading to MMU is so easy now)
RE: Repbox "Cereal Box" MMU Buffer
I like the simplicity. I also like there is no buffer outside in the open. Eliminating the drag of a buffer also. Let us know how it works over the long run. It may need 2 walls between spools to adjust the fit next to each spool.
You have given me something to think about in my solution with a bigger box. Adjustable walls around the spools.
RE: Repbox "Cereal Box" MMU Buffer
This was the first thing that got me thinking about it
He made some dry boxes and mentioned that he had no problem with the buffering system. Each spool is in it's own box.
So, I started wondering... could I do that in the Repbox somehow.
If this doesn't work out, I'm going to try this one next.
A small insert that clips onto a rod installed. This would force the back-fed filament to stay "within the borders of the spool" in theory.
https://forum.prusa3d.com/forum/postid/632886/
RE: Repbox "Cereal Box" MMU Buffer
This looks pretty cool, I have tried several auto rewinders and have had the same experience, some work sorta ok, some are just junk, and all of them need to be tweaked every time you print. Not found one that works the same way with a full spool vs a quarter full spool, etc. I have given up and use Joanna Stern's solution, mount above, feed downwards, spools are on hangars, no issues so far