Cable MMU3 to MK4  

RE: Cable MMU3 to MK4

MMU3 with MK4

I was able to print this piece this morning. The only glitch was that the shaft in the #5 wheel of the idler came partially out. I reinserted it and the print continued. I'm going to try a amore complicated print this afternoon.

RE: Cable MMU3 to MK4

Can you specify, perhaps using a picture from the assembly instructions, which shaft is that in wheel #5 of the idler pulley? I found a difference in one position in the part of the tension pulley compared to other positions and I would like to make sure that I was not mistaken. Thanks.

RE: Cable MMU3 to MK4

Sure, here's the picture. The wheel has fallen out twice and the shaft has partially come out and stopped the idler from turning all the way.

RE: Cable MMU3 to MK4

Posted by: @tim-10

Sure, here's the picture. The wheel has fallen out twice and the shaft has partially come out and stopped the idler from turning all the way.

 8c49b707-loose-idler-shaft.jpg

Really push down the wheel it takes quite a bit of force bit they do click in and the shaft can be inserted into the middle of the wheel also the shaft has to be pushed by an Allen key to go in all the way

RE: Cable MMU3 to MK4

I've had no problem getting the wheel in place and I have pushed the shaft as far as it will go with an allen key. When the shaft is first inserted it is fully seated in the hole. The hole is just too big for the shaft. I saw a post from one other person who had the shaft and wheel fall out. I'll figure out a way to keep the shaft in place. Thanks.

RE: Cable MMU3 to MK4

Thanks for the picture, it's exactly what I think. This hole has an inexplicable increase in diameter at the beginning of 0.4 mm in a length of 3.85 mm, which no other shaft hole has. This reduces the frictional surface to hold the shaft in place. I have not yet measured whether this hole also has a different diameter than the other holes. The image comes from Fusion 360 in which I will try to repair the part, or rather I have it repaired, but I haven't printed it yet, I'm waiting to see if it will appear among the printed parts for MMU3 for MK4.

RE: Cable MMU3 to MK4

Posted by: @miroslav-h4

Thanks for the picture, it's exactly what I think. This hole has an inexplicable increase in diameter at the beginning of 0.4 mm in a length of 3.85 mm, which no other shaft hole has. This reduces the frictional surface to hold the shaft in place. I have not yet measured whether this hole also has a different diameter than the other holes. The image comes from Fusion 360 in which I will try to repair the part, or rather I have it repaired, but I haven't printed it yet, I'm waiting to see if it will appear among the printed parts for MMU3 for MK4.

 589f7bb2-idler.jpg

Srange I don't have this for my mmu3 prusa printed my parts. Did you print your own or did prusa print theme

RE: Cable MMU3 to MK4

Thanks.

RE: Cable MMU3 to MK4

Printed my own from Prusa download.

RE:

One more addition: This increase in diameter is also clearly visible in the printable parts viewer for MMU3. I don't know why they are there. I only believe that it is a mistake in the design of the idler, when this increase in the diameter was intended as a bevel at the beginning of the hole, but due to some oversight, it moved 3.85 mm to the depth. This is the result of "programmer modeling" in OpenScad, when most of the printable parts of Prusa are designed in this program.

RE: Cable MMU3 to MK4

HEUREKA!
First I was messing around with creating a MK4 - MMU3 configuration. Always had loading problems or purge failure. Then I got encouraged using the MK3 compatibility mode. I created a MK3 - MMU3 configuration with all MK4 inputshaper values. In the MK3 printer profile I added some start-gcode:

M708 A0x0b X10 ; pushing the filament a bit further after filment senor activated

M593 X T2 F42

M593 Y T2 F41.2 ; my input shaper values

I printed the planetary gear with 3 colors:

Print time was 5h30 min (vs 8h with the regular MK3 profile). 200 tool changes. No trouble.

Configuration will follow.
With this result I'm really wondering why Prusa is keeping the MMU3 for the MK4.

RE: Cable MMU3 to MK4

My configuration files. I copied all mechanical data from the MK4 Input shaping to the MK3.

I'm using very short ramming (2s) with slightly higher volume. The tips are just fine.

RE: Cable MMU3 to MK4

Great work. Where do these files go? Do they replace the custom gcode for each printer?

RE: Cable MMU3 to MK4

Go in PrusaSlicer in "Help" and "show configuration folder". There you'l find some subfolders where you can put the *.ini. After restart the configuration should be available.

RE: Cable MMU3 to MK4

Ha . . . excellent work, I knew you guys would find a way if I posted the wiring diagram and cut you loose 😉

ty -mp

RE: Cable MMU3 to MK4

😀

RE: Cable MMU3 to MK4

Thanks very much.

RE:

Once again to drop out the bearing shaft at position #5. By exact measurement, it was found that the cause is the too large diameter of the rear part of the hole for the shaft compared to the other holes. Therefore, I modified the model so that the opening is the same as in position #4. If you want to print the modified idler, the modified stl files are attached. The mmu3-idler-R3 (3).stl file is modified as described, the mmu3-idler-R3 (4).stl file has the hole even tighter by 0.05 mm. Print with the slicer settings as for the original idler. Please give feedback if this modification helped. Thanks.

Posted by: @miroslav-h4

Thanks for the picture, it's exactly what I think. This hole has an inexplicable increase in diameter at the beginning of 0.4 mm in a length of 3.85 mm, which no other shaft hole has. This reduces the frictional surface to hold the shaft in place. I have not yet measured whether this hole also has a different diameter than the other holes.

RE: Cable MMU3 to MK4

Thank you. I'll give it a try. The Prusa help guy said mine was a unique problem and referred me to an troubleshooting article that had nothing to do with the roller falling out. Prusa should pay you.

RE: Cable MMU3 to MK4

And an addendum to the falling shaft #5. It turns out that position #1 on the other side suffers from the same problem. But it doesn't matter so much here. Alternatively, the extended shaft stops against the edge of the metal coupling and does not fall out completely as in position #5. If there is interest, I can insert an idler here, which also has this defect fixed.