Posted by: @therippa

Does anyone else having problems with blobs on the purge tower happening with these settings?  They completely fixed the stringing issues I had, but now there are blobs that the hotend are ramming into.  I've tried adjusting the filament parking position and extra loading distance settings but I can't even tell what effect they might be having.  Any idea where to start debugging?

I have the same issue with the settings of Eric T. But the tips are better than ever now. 
Did you solve it already? I guess Extra loading distance is the one which need to be changed. 

Posted by: @therippa

Does anyone else having problems with blobs on the purge tower happening with these settings?  They completely fixed the stringing issues I had, but now there are blobs that the hotend are ramming into.  I've tried adjusting the filament parking position and extra loading distance settings but I can't even tell what effect they might be having.  Any idea where to start debugging?

I've seen it too. But it hasn't caused any problems so far.

my setup MK3.5, REVO hotend, MMU3

But I think the values I retrieved from here are incorrect.

I reloaded the filament, and the MMU3 started with crazy errors on the MMU3 (e.g. unable to home, filament not detected...) but then it was able to recover and I tried to continue the print.

Unfortunately it did not print. I heard only click, crack from the extruder but no plastic was extruded. Even if the temperature was ok, I lost the print. 😑 

I dismounted the extruder to bypass the grinder, set 198° and noticed that when I tried to push manually filament it was like blocked: it could not fit. Almost nothing come out.

So I decided to use "Mister Scloggo". I  removed my test PLA piece of filament and inserted the metal filament, an then pushed hard with the metal filament, and suddenly with a pop I eject all the plastic from inside the nozzle.

Basically with my surprise the clog was gone (I though that I had to throw away the Revo, that now is expansive compared to the old cheap nozzles).

I could hear probing with the metal filament inside the nozzle that probably the ramming attached some plastic on the high part of the nozzle, shrinking the space for the filament to enter. I scratched all the walls inside until I felt them smooth, always at 198°.

This happened suddenly when I rearranged the buffer and the filament tubes moving them from a temporary straight behind position to the right of the printer. With the tubes at 90° bent I think the friction is too high. 

After cleaning the nozzle and slightly rearrange the position of the buffer only bending it 30° on the table, I reprinted the queue and all worked successfully.

- Was this just a temporary issue of the filament or bending to 90° the tubes with the buffer and spools on the right of the printer causes friction ?

- Or may be it was just the REVO that may clog often 😯 

Regards

Then I have tested it with the PRUSA filament stock values,using Prusament PLA, and the filament tips were  disappointing 😑 

I have always a failed print because:

• The initial black plate was done correctly, no issue on load and unload.
• Then on subsequent white/orange changes I got bad tips and strings, and at a certain change, one filament that could not be extracted any more (e.g. brute force removal and extruder dismount)
• The failing filament was worn and scraped at the MMU or EXTRUDER level by the gear.
• The sensors stopped to work with lots of strings inside.
• The force nm required to pull the filament was however too high. 😯 
• Probably to long tubes between the buffer and the spools
• Surely the PTFE tubes are not PTFE but probably are in cheap flex policarbonate plastic.

So I have done the following:

1. I removed ALL the tubes between the spools and the buffer, leaving two short 10 cm tubes.
2. The filament is exposed to the air until it goes on the buffer, but it has zero friction.
3. I moved the buffer behind the printer so that the PTFE tubes from MMU3 to the buffer are straight, and not curved as they were when it was on the side.
4. I tight the screw of the extruder to increase the pressure between the gear and the filament. I suspected it was just shifting grinding the filament.
5. I applied your MMU3 full settings, since I had replaced also the MMU tube when I upgraded.

Result:  almost perfect print, perfect tips, not issue in load/unload. 🤩 

There is only a little under-extrusion. I will check how is tuned.

All the results with your settings were exceptional at level of tips. Now I will check with more changes how reliable is.

Best Regards

I guess with all Revo nozzles I have - will be going to my Minis that I plan to upgrade it to Revo. 

During my Mk3.5 update, I had to dismount the REVO, and when I reassembled it I was unsure if I had to screw it correctly.

I realized that I was too soft with the touch, and the nozzle silicon cover was just shifting on the copper and I had not really screwed it to the end. This could have caused change on the nozzle position and potential air print.

Remember that after any nozzle change you have to retune the fist layer height.

Regards

Posted by: @chrisg

I have also a Prusa MK3.5 and MMU3. Every time when I have a big colour print after one cm it starts to print in the free air.

It looks as the revo is failing. Jammed or wat ever. Would the settings above fix this too?