Spool Holders  

Re: Spool Holders

FWIW, the beta-testers are concentrating on testing the printing, not the spool placement.

But there are already alternative methods in use, however, you have to get the thing up and running, understand what is happening and then think about what you can do to fit it into your particular environment.

Peter

Re: Spool Holders

On the photo you posted, there is quite some filament that appears to have been pushed back (on the holder, between where it enters the guide when it leaves the roll and where it enters the tube. The amount of filament there, is it equal to the length of the tube that connects the MMU with the printer? Or is there more (e.g. is there given extra slack) ?

One thing that surprised me of the MMU2 is how far back it sits from the vertical support of the printer; I did not anticipate that much. If you consider the XY plane on which the printer sits, does it stick out (and if so how much)? Extra space is needed for the tubes, but it would be interesting to know the dimensions (e.g. how much higher does it make the total construction)?

Re: Spool Holders

I would have thought the purpose of "Beta" testing is to exercise the whole experience of the product, not just the end result. I am not pointing fingers at beta testers, I am curious why these specifications or requirements were not published (until two days prior to shipping buried in the manual) as a warning to potential buyers so they could make an informed decision on what the end product needed to function properly. Does 15 inches actually translate into almost 22 inches when you factor in the diameter of the spool? Additionally, this is not a knock on the product either; there are plenty of things in life people want but don't purchase because it will not work for them in their scenario/setup. I am not pulling the plug on my order yet, I will wait and see for a few weeks.

Re: Spool Holders

To answer the recent queries:

The amount of retracted filament during a tool change is around 500mm. That's about 100mm (extruder) + 360mm (PTFE) + 40mm (selector).

The additional height above the frame is going to be about 80mm (MMU2) + 180mm (half the length of the PTFE - actually a little less)) when the extruder is at full height.

The rear of my spool holders are around 32" from the rear of the printer, with the bed at the front. There was nothing mentioned about this anywhere; if your assumption was incorrect, then it really is not fair blaming others 😉 In any event, this is only a starting point from which you can do whatever you wish. And as has been pointed out previously, there will be many alternative put forward as users receive their kits.

For me the spool placement is a temporary inconvenience; I will find my own solution in the near future. I do actually consider the filament feed tubes both too long and too low. And I have never liked these spool holders; I have a preference for larger bearings at the spool centre which allows the spool to turn more freely and even take up the slack on unload.

Peter

Re: Spool Holders

Thanks for your answers!

The amount of retracted filament during a tool change is around 500mm. That's about 100mm (extruder) + 360mm (PTFE) + 40mm (selector).

I thought it would be less, I can understand why positioning becomes critical with such a large piece of unguided filament. 🙂

The additional height above the frame is going to be about 80mm (MMU2) + 180mm (half the length of the PTFE - actually a little less)) when the extruder is at full height.

Does the MMU stick out of the back of the printer (when the bed is at the farthest position)?

The rear of my spool holders are around 32" from the rear of the printer, with the bed at the front. There was nothing mentioned about this anywhere; if your assumption was incorrect, then it really is not fair blaming others 😉 In any event, this is only a starting point from which you can do whatever you wish. And as has been pointed out previously, there will be many alternative put forward as users receive their kits.

For me the spool placement is a temporary inconvenience; I will find my own solution in the near future. I do actually consider the filament feed tubes both too long and too low. And I have never liked these spool holders; I have a preference for larger bearings at the spool centre which allows the spool to turn more freely and even take up the slack on unload.

In all fairness, it is a bit of a surprising requirement, which more than doubles and even triples footprint, so comments could be expected. Particularly as most people won't have space on the back (or it won't be easy to reach). I think your statement

When you receive the kit follow the instructions, get some prints completed and then try other positions (most of which will cause problems 🙁 ).

and particularly the part in bold may come over more strongly than you intended and that is what people followed up on. 😉 I suspect once more MMUs appear in the wild and more people try configuration we will get a better idea on which positioning works and which will cause issues.

Re: Spool Holders

The rear of the MMU is about an inch further back than the frame of the printer, but then there's the PTFE feeder tubes to consider.

Likewise, I was somewhat surprised when I received the kit. I had to move 2 printers, re-stack my filament stock and then build a shelf. But that is what was necessary at the time to properly test the kit. I really haven't had the time to try alternatives; the printer has been running almost continuously.

Peter

Re: Spool Holders

I would have thought the purpose of "Beta" testing is to exercise the whole experience of the product, not just the end result.
+1

I am curious why these specifications or requirements were not published (until two days prior to shipping buried in the manual) as a warning to potential buyers so they could make an informed decision on what the end product needed to function properly.

...and +1

In any event, this is only a starting point from which you can do whatever you wish. And as has been pointed out previously, there will be many alternative put forward as users receive their kits.

And as has also been pointed out previously:
most of which will cause problems 🙁

IMO, it's the optics of Prusa not being straightforward about this issue, and the uncertainty of solutions/resolution that are most disconcerting. YMMV.

I suspect the Prusa selection of "on the table behind the printer" was simply the lowest common denominator. PR [k]new that everybody would have access to a table of some kind and could make this approach work. They could not depend on everyone having a shelf over the printer or under the table, as most would not.

❓ __ 😕 __ ❓
I'm sorry--I had to read that a few times.
I take it you mean a second table(?) I think chances of finding/building a shelf above or below a LACK-sized table are greater than having a single table 48" (1.22 m) deep.

For some of us, the issue is less "behind the printer" and more how far behind, and accessing the bottom rear of the MMU to load/unload filament.

Re: Spool Holders

I suspect the Prusa selection of "on the table behind the printer" was simply the lowest common denominator. PR [k]new that everybody would have access to a table of some kind and could make this approach work. They could not depend on everyone having a shelf over the printer or under the table, as most would not.

❓ __ 😕 __ ❓
I'm sorry--I had to read that a few times.
I take it you mean a second table(?) I think chances of finding/building a shelf above or below a LACK-sized table are greater than having a single table 48" (1.22 m) deep.

For some of us, the issue is less "behind the printer" and more how far behind, and accessing the bottom rear of the MMU to load/unload filament.

I suspect what Paul means is that everybody can install it on a big table or even the ground so for testing purposes. Suppose that the recommended way would be to put the spools on a shelf above the printer: not everybody can just do that. So in that sense it is logical that Prusa recommends a setup that everybody can do: in case of problems, such an easy setup is good as a fall back to check that there is no other issue. Of course for a more permanent installation, it is problematic, but I still think Peter may have phrased it too strongly. We have to wait how people manage: the first MMU have just been sent out, but so far none of the users have posted first prints or problems, and we are right at the location where such thing will be posted.

Re: Spool Holders

the first MMU have just been sent out, but so far none of the users have posted first prints or problems, and we are right at the location where such thing will be posted.

The first ones were sent out to the Beta testers around (I gather) the beginning of July, and we haven't heard from any of them that I'm aware of (but I'm not monitoring GitHub, Reddit, or social media).

Re: Spool Holders

The first ones were sent out to the Beta testers around (I gather) the beginning of July, and we haven't heard from any of them that I'm aware of (but I'm not monitoring GitHub, Reddit, or social media).

Yes, but beta testers may be under an NDA, in which case they are not allowed to post anything about it (usually, one is not even allowed to disclose if he/she is or even was a beta tester). It should have been lifted by now (the MMU became available), but that is not always the case (sometimes no disclosure about beta devices is allowed). But there may be other reasons why nothing was posted yet. So I would rather expect non-beta tester users to post things. 🙂

Re: Spool Holders

I am working on a stacking set up it gives so much more room will post pics when done

Re: Spool Holders

we haven't heard from any of them that I'm aware of (but I'm not monitoring GitHub, Reddit, or social media).

And what do you think I have been doing for the past month or so? Did you have a look at my "Troubleshooting" post ( https://shop.prusa3d.com/forum/hardware-firmware-and-software-help-f56/mmu2-troubleshooting-t24123.html )? There's a link to some of my MMU2 prints in that!

Peter

Re: Spool Holders

Yes, but beta testers may be under an NDA

No, as with the MMU1, only asked not to post anything until shipping was announced.

Peter

Re: Spool Holders

And what do you think I have been doing for the past month or so?

I have no idea--the surveillance equipment broke down around that same time. Spoze it had anything to do with the MMU? 😆

I did say, "that I'm aware of". I had no idea you were a Beta tester, and I hadn't got to that sub-forum yet.
Thanks for the 411--I will be checking it out. First I need to figure out where to put--and how to set up--the printer & MMU now that our previous plan is kaput. ...Or if we need to make other arrangements. :geek:

Re: Spool Holders

I have no idea--the surveillance equipment broke down around that same time. Spoze it had anything to do with the MMU? 😆

😀

Just test printing with BVOH as I write 😉

Peter

Re: Spool Holders

Ignore the spanners 😉

Peter

Re: Spool Holders

I suspect what Paul means is that everybody can install it on a big table or even the ground so for testing purposes. Suppose that the recommended way would be to put the spools on a shelf above the printer: not everybody can just do that. So in that sense it is logical that Prusa recommends a setup that everybody can do: in case of problems, such an easy setup is good as a fall back to check that there is no other issue. Of course for a more permanent installation, it is problematic, but I still think Peter may have phrased it too strongly. We have to wait how people manage: the first MMU have just been sent out, but so far none of the users have posted first prints or problems, and we are right at the location where such thing will be posted.

Yes, that is what I meant, I realize I was unclear. Almost all people will be able to do the initial build on a big bench, a kitchen table, a floor, or a piece of plywood on two saw horses. They can then get things set up and working. They can then adapt to their specific geometry knowing the main printer works, and with a good idea of how the filament feed/return works.

Re: Spool Holders

They can then get things set up and working. They can then adapt to their specific geometry knowing the main printer works, and with a good idea of how the filament feed/return works.

It does take a while to figure out exactly what is happening, and that is why I think that most ideas will fail (at the start). Problems is that there only needs to be one very small thing to go wrong, and a whole print is ruined.

I did a 56 hour print; it ended up with 3 load failures which I didn't notice due to the orientation of the model on the bed. I was a little peeved when I removed the model from the bed, thinking it was good 🙁

Peter

Re: Spool Holders

Ignore the spanners 😉

Should we also ignore the stacked rolls on the left? 😯

It does take a while to figure out exactly what is happening, and that is why I think that most ideas will fail (at the start). Problems is that there only needs to be one very small thing to go wrong, and a whole print is ruined.

A downside is perhaps that most of the dryboxes (Polymaker, eSun, or even the Ikea boxes) might be incompatible.
50cm is quite a lot of filament to have hanging loose unguided. But at least the spool holders shows that solutions are possible; maybe people will come up with even more stable constructions.

I did a 56 hour print; it ended up with 3 load failures which I didn't notice due to the orientation of the model on the bed. I was a little peeved when I removed the model from the bed, thinking it was good 🙁

How come the filament sensor on the printer did not notice this?
Was it the same filament that failed to load 3 times? And if so, was it due to the type of filament itself, a roll issue or something else?

Re: Spool Holders

How come the filament sensor on the printer did not notice this?
Was it the same filament that failed to load 3 times? And if so, was it due to the type of filament itself, a roll issue or something else?

The extruder filament sensor is disabled. Even with it enabled, it would only detect that filament is present and not that there is a feed problem. The FINDA sensor is much more reliable, as long as there is no stringing.

If the unload strategy is not right or there is higher friction in the feed path, then filament can string on the tip. This is then has a potential for a load fail, where the filament loads, but not all the way into the Bondtech gears. You then get one or two layers which are unprinted. In addition, this can then cause the filament to be ground down in the MMU, which can cause poor feeding from the MMU or Bondtech.

Failed prints, understanding the cause of failure and knowing how to fix it is all part of the learning curve.

Peter