[Closed] MMU 2.0 video from MRRF  

Re: MMU 2.0 video from MRRF

How does this new MMU 2.0 get powered? We have been told it can be easily swapped from printer to printer - and since it can both be used for MK2 (12V) and MK3 (24V) - and due to that I don't belive som 5V can deliver power to the steppers - I looks like it will have it's own AC/DC power adapter?

Re: MMU 2.0 video from MRRF

How does this new MMU 2.0 get powered? We have been told it can be easily swapped from printer to printer - and since it can both be used for MK2 (12V) and MK3 (24V) - and due to that I don't belive som 5V can deliver power to the steppers - I looks like it will have it's own AC/DC power adapter?

Re: MMU 2.0 video from MRRF

They say it comes with it's own Arduino-powered board. My guess is that has a voltage converter.

Re: MMU 2.0 video from MRRF

it just needs a voltage regulator for the arduino chip and logic for the drivers. the motor voltage input on the drivers takes a voltage range it uses to drive them with.

Re: MMU 2.0 video from MRRF

But how will they connect it to the printer power if it should be easily swapable between you printers?

Re: MMU 2.0 video from MRRF

Also I think you can get away with a lot less purging, which should more than compensate.

And then there's the problem of the different gearing. The MMU2 uses a different pulley which will impress on the filament; there may be a situation where the filament will move in an attempt to match the impressions with the Bondtech gears.

That is a point, but i guess for feed the filament from the MMUv2 to the direct drive bondtech gears will not need that much force as we need now on our MK2/ses, MK3 or MMUv1.

Here what i imagine how a filament change during the print may look like:

0. As long a filament is loaded to the direct drive gears the MMUv2 bearings are in Idle position, which means no pressure on the filament.

Filament change initiated:
1. The direct drive bondtech gears pull out the filament out of the hotend. Need some force to get it out, so these are normal tight.
2. Few mm later (filament just passed the bondtech gears) the MMUv2 goes from Idle (no pressure on the filament) to engage the used filament.
3. The MMUv2 gears starts to pull filament back. Bondtech gear marks are just at the 1st few mm of the end. The MMUv2 marks should be much smaller as there is no need to have too much pressure to pull it though the PTFE tube.
4. As the filament end is close to the MMUv2 it will be cut by moving to next position. Part of the Bondtech gear marked filament is gone and it doesn't reach the MMUv2 gears.
5. MMUv2 switches to 2nd filament and engages the bearing to gear.
6. MMUv2 gear pushes the (nice cut) filament with gentle force though the PTFE tube.
7. As soon the direct drive filament senors detects filament coming in it initiates the direct drive load process.
8. MMUv2 goes in Idle mode. That is the tricky moment to get the MMUv2 in Idle mode so the bondtech gears aren't pulling the filament too fast and the filament get reals bad marks. Or they have to be in sync as mentioned.

The filament could well be driven through the MMU gears many times (not just 3 or 4), depending on the model extrusion and purge required - just think of the situation where you are extruding a few millimetres with a black filament (purge = 25mm); the path between MMU and extruder will be maybe 400mm, so that could well be 14 times through the upper gears.

Let's hope that this traveling through the PTFE tube doesn't need that much force on the bearings so the imprint is minimal and that the soft filament end will not get stuck in the PTFE tubes as it happens in the steel tubes of the MMUv1 quite often i hear.

Yes, I do have some concerns about MMU2 but I do believe it will work better than the first version. My biggest concern is that it will be released too early. MMU1 underwent 6 months of beta testing and still didn't work for many users.

Peter

I agree it should be better than the MMUv1 but will bring some new issues to be solved.

But i am exited to get my MMUv2

Re: MMU 2.0 video from MRRF

But how will they connect it to the printer power if it should be easily swapable between you printers?

I don't remember seeing this. All I remember seeing is that it was "easily removable" which could mean anything.

Re: MMU 2.0 video from MRRF

A little question:

Can't you control the given hardware in a way no filament is in the need of a pull out?

Like so:
0. Filament 1 is loaded.
1. Filament-changer-cutter unit moves to the next filament 2. Filament 1 needs to be cutted first. The right time to cut must be calculated from gcode.
2. Filament 2 is getting loaded right until it hits filament 1 in the Bowden tube.

I know, there are some inconsistencies in this description. But the feature I think can be guessed... . Dont focus on the description, focus on the question. Suggestions?

Re: MMU 2.0 video from MRRF

A little question:

Can't you control the given hardware in a way no filament is in the need of a pull out?

Like so:
0. Filament 1 is loaded.
1. Filament-changer-cutter unit moves to the next filament 2. Filament 1 needs to be cutted first. The right time to cut must be calculated from gcode.
2. Filament 2 is getting loaded right until it hits filament 1 in the Bowden tube.

I know, there are some inconsistencies in this description. But the feature I think can be guessed... . Dont focus on the description, focus on the question. Suggestions?

bit like poor man Palette plus without welding together...nice idea, as you don't have to think about pullout and molten end can stick the ptfe tube...purge will be the same
With the filament sensors you even should know when filament1 'runs out' at the direct drive and when filament2 arrives, so you could prevent collisions in the ptfe tube between filament1 and filament2.
UPDATE:
There is an issue with this idea when the filament changes are happening every few mm (small prints with lot of changes) then you would have small pieces in the ptfe tube and this could make the push/pull quite difficult/impossible.

Re: MMU 2.0 video from MRRF

I think 2 motors can be reused in the mmu 2.0. One motor has an integrated lead srew attached, so we probably cannot use an existing mmu 1.0 motor for that. The upgrade set will pobably include that motor. Bondtech gears are 50 euro's each, so you can imagine this solution is cheaper overall.

So Prusa probably will look at all mmu's 1.0 sold, because some of them are probably only with two motors only, in which case they will have to send an extra motor.

Re: MMU 2.0 video from MRRF

After thinking about it some more, I would like to modify my previous analysis about how much filament would be run through the transfer tube multiple times. One thing I didn't consider carefully is how much material needs to be purged. I'm not going attempt to quantify it because there are too many unknowns, but I would make a couple of observations.

First, the purpose of withdrawing filament is to make the transfer tube available for the next material. The purpose of inserting filament is to make it available to the extruder. Given that, I think you can assume that every filament insertion will be followed by a purge of the extruder. I wouldn't hazard a guess as to what percentage of the transfer tube contents would be extruded during this process, but I suspect it would, at least, purge any filament that had been previously chewed up previously by the extruder pulley. That's essentially what happens now when changing filament with a single material printer.

Assuming the roller/pulley system at the input end of the transfer tube is low pressure and doesn't chew up filament then I think chewed up filament really isn't a concern.

Re: MMU 2.0 video from MRRF

Might I add that I have trouble imagining they'll cut the filament on every change, as some apparently think. Simple question: Where would you put the cutoffs? You need some kind of chute to get them away from the build plate (not seen in video) or a little retainer that catches them. Otherwise, at some point it will pile up and drop on the print. I think they'll try to detect blockage and cut only then.

Re: MMU 2.0 video from MRRF

If I understand correctly, Joe said in the video that the "cutting" would be used only in case the first attempt to load the filament failed

Re: MMU 2.0 video from MRRF

After thinking about it some more, I would like to modify my previous analysis about how much filament would be run through the transfer tube multiple times. One thing I didn't consider carefully is how much material needs to be purged. I'm not going attempt to quantify it because there are too many unknowns, but I would make a couple of observations.

From my experience with the Palette+, you need to purge a minimum of 20-30mm to ensure a clean color transition. The Palette purges more because it can't be certain of exactly where the splice is.

You might be able to get away with less purge when changing to a strong color to a weak one (white to black, for example). But then you need more purge when going the other way--trust me, changing from black to white needs a ton of purge to prevent really obvious color bleed.

To be honest, I'm not sure how much of a problem the tooth marks on the filament will really be in practice. My Palette leaves tooth marks all over the filament and it doesn't seem to cause any issues at all. This might be a case where it's better to test how it works first before worrying about elaborate solutions to something that might not be a problem.

Re: MMU 2.0 video from MRRF

Is there a video anywhere showing the MMU2 actually running or is the MMU2 still in development stage?

Re: MMU 2.0 video from MRRF

Saw this video last night and it took me a couple minutes before I figured out how this all works. Showed it to a co-worker who also does a lot of 3D printing and his reaction at first was "What the hell?" and then "Whoa! I get it now. That's AWESOME!"

Hoping it works out in practice. I put in my orders for both the MK3 and the MM2 on Sunday. This is going to be my 2nd printer (First is a HEAVILY modified Cobblebot which I basically redesigned and built custom myself). The Cobblebot works, and can print some really big items (12" each axis!) but the quality just never has been all that fantastic, even when I set it to .1mm layers and slow it way down. I couldn't even consider printing any sort of mechanical interfacing parts with it, and with all the hassles getting it working with 1 extruder I never even bothered with setting up the 2nd.