Revo 6 nozzle changes and z-height  

RE: Revo 6 nozzle changes and z-height

My Revo is still sitting in the drawer until they come out with tungsten carbide nozzles so I can't speak to this particular case. But it's certainly not uncommon, in fact more likely than not, that a nozzle change requires adjusting Live Z. And even though the mechanism in which the nozzle gets connected to the hotend is different for the Revo, I have no reason to believe that their method is any less likely to have small variations in nozzle height than the good old V6 hotend. Re larger vs smaller nozzles, I never noticed any difference. 

RE: Revo 6 nozzle changes and z-height

on my Revo Six, I notice that the 0.25 nozzle is slightly longer than the 0.4 and first layer Z needs to be raised slightly, about 0.03mm for a 0.25 print to avoid slight "Elephant Footing".  For those afflicted with antiquated Imperial measurement units, 0.03mm is about .001", a fairly small distance.

This is similar to swapping standard v6 nozzles on the Mosquito, which I did frequently.  It would be nice if all nozzles were made so that Z would always be "just right" for the particular nozzle diameter after a nozzle swap, but that's not the case.... yet!    

What we have  is actually very good for a system where the Z height is set by an inductive (or even a contact) probe separate from the nozzle.   I'll bet that Prusa is working on or at least considering a nozzle touch system where the nozzle itself is the probe.

RE: Revo 6 nozzle changes and z-height

The Prusa XL has auto first layer calibration using a force sensor in the nozzle. It would be nice to see that come to the MK3 eventually although that might be a hefty upgrade. 

RE: Revo 6 nozzle changes and z-height

I have just installed the Revo 6 and done a couple of nozzle changes and have also observed that Live Z has to be adjusted even when going back to the 1st nozzle .  I have a hunch that the top of the nozzle might be touching the PTFE tube and may give variation to tightness when you screw it in, additionally I may have also made the mistake of tapering the end of the  PTFE tube that goes into the heatsink like on the old V6 when it may be  meant to be a straight cut for the Revo.  The instructions are not clear and I am getting clarification from E3D. I also set my top of the PTFE at 11mm rather than the nominated 10mm as it better matched the original V6 setup.... don't know if this will be critical or not to stop jams....

RE: Revo 6 nozzle changes and z-height

Posted by: @bazzalight

I have just installed the Revo 6 and done a couple of nozzle changes and have also observed that Live Z has to be adjusted even when going back to the 1st nozzle .  I have a hunch that the top of the nozzle might be touching the PTFE tube and may give variation to tightness when you screw it in, additionally I may have also made the mistake of tapering the end of the  PTFE tube that goes into the heatsink like on the old V6 when it may be  meant to be a straight cut for the Revo.  The instructions are not clear and I am getting clarification from E3D. I also set my top of the PTFE at 11mm rather than the nominated 10mm as it better matched the original V6 setup.... don't know if this will be critical or not to stop jams....

Please let us know what they reply. 
Thanks. 

RE: Revo 6 nozzle changes and z-height

Had a 1st reply back from E3d that didn't quite satisfy me (I probably need to go up another level at the help desk and I have asked a followup with more info ). Their initial reply was " As you are modifying the existing PTFE tube during the installation, yes the other end needs to be shaped according to the Prusa standard for that printer." and referred me to the standard Prusa links on the V6 tube.  Later today I will get my Vernier callipers out and double check the nozzle dimensions to check for variations and check against their drawing for the Revo heatsink.  Will further update...

RE: Revo 6 nozzle changes and z-height

I used the extra tubes that Prusa included (pre tapered) and just cut it down to length using a jig that was posted on the Prusa model site.

My 0.6mm nozzle had a perfect first layer when I switched to the 0.4mm, it was too low. Switching back to the 0.6mm today and going back to good height seemed to produce a good first layer again. If that's the case, I guess using Sheet Profiles to add a nozzle size could be a workaround, although I'm not sure how many you can have.

The other thing that worries me is how you grip the nozzle. The silicon ring around the nozzle isn't just for heating purposes, it's the way you grip and torque the nozzle to turn it. However, is this ring glued to the nozzle or something? Can it loosen and turn on its own, making it much harder to grip and turn the nozzle?

I guess we will see as we go along. Overall, I would still say it's much easier than changing nozzles the old way especially not having to worry about breaking wires.

RE: Revo 6 nozzle changes and z-height

The Silicon rings are not glued and can be carefully pealed/eased off the nozzle if you really need to.  There are serrations on the brass nozzle which aid the grip on the silicon sock.  I expect these will deteriorate with heat cycles like the V6 socks and  that replacement (revo) socks are going to become an orderable item  ( https://e3d-online.com/products/revo-sockpack ) .  I think you would get enough finger grip on the nozzle without the sock anyway.

Totally agree that the Revo is far easier to nozzle change (even if the z adjust is a feature of each change)

RE: Revo 6 nozzle changes and z-height

This is the advice from E3D on my enquiry:-

" It is recommended to check you z offset after a nozzle swap even with all the nozzles being the same length. There are other variations in the system as a whole that can result in a small difference each time a nozzle is installed. We've made the nozzles the same length to help minimize the change but there are still imperfections in the system that for accuracy you'll want to z offset after each swap.  The idea being that a single z calibration is all that's needed on a swap and not a bunch because of a large variation in length. "

I have been using the Live Z adjust feature for the 1st print after the nozzle change which is quicker than the z calibration print option in the console and I can get it close enough as the print area skirt (and waste block in MMU mode) is being done without compromising the 1st layer plate adhesion. Of course I am sure at some stage I will forget to do it and end up with a failed print....

E3D has also assured me that the Prusa spec taper on PTFE going into the heatsink is not an issue.

RE: Revo 6 nozzle changes and z-height

Thank you for the update. 

RE: Revo 6 nozzle changes and z-height

You can also set a z-offset in Prusa Slicer in printer settings. So do a first layer calibration for each nozzle and notice the z-offset.

Set z-offset for 0.4 mm nozzle in the printer and z-offset-difference in the printer profiles for the other nozzles.

RE: Revo 6 nozzle changes and z-height

Posted by: @oliver-andre

You can also set a z-offset in Prusa Slicer in printer settings. So do a first layer calibration for each nozzle and notice the z-offset.

Set z-offset for 0.4 mm nozzle in the printer and z-offset-difference in the printer profiles for the other nozzles.

This is interesting, has anyone had a chance to try setting up different profiles for their Revo nozzles with preset offsets? I have two Revo kits I have not had the chance to install on my printers, I print extremely detailed high quantity small prints with the .25 nozzle and I am afraid of what is going to change.

Easily swapping out for larger nozzles on other prints that do not require such detail sold me. Having to deal with adjusting live Z for each swap kind of takes away 50% of the "easy".

RE: Revo 6 nozzle changes and z-height

I have not gone with separate profiles as I see a little bit of variation of the Live Z number on the same Nozzle when I come back to it after using a different size.  What I have observed is that you need to be attentive and consistent on how finger tight you put the nozzle in (which is hard to assess as it is a bit awkward with the Nozzle fan shroud and the slipping heatsock ... Have found it best to raise the head to at least 100mm Z to get the fingers in).  I have changed about 10 times so far and the variation between the nozzles is not that much different the the z differences on the same nozzle and I am able to assess the live z adjust on the perimeter rings (I set to about 3 anyway) or the MMU waste block.  Of course the 0.25mm nozzle is the most sensitive to 1st later height to get the bed stick as you normally using 0.15 or less layer height but the Revo's imo have only taken about 15% of the expected "easy".  Still more than happy the the convenience of the Revo.

The other thing I have found is that I get a lot more ooze out of the nozzle before the print starts as the head gets to temp even more quickly than the bed and if it is a sensitive print I try to tweezer away the "drip" to stop it getting dragged around bed and onto  the print.

I still nearly always forget to do is to change the nozzle size setting in the printer console till I get the gcode warning  😐 

RE: Revo 6 nozzle changes and z-height

Circling back to comment with my input after spending many hours on this issue.

I spent crazy time creating printer profiles in my slicer with live Z modified for each extruder diameter. I experienced the same problem. Even after mapping the necessary adjustments to Z for each extruder, there would be slight adjustments necessary every time they were changed.

in my mind the major culprit variable is the fact that the nozzles are being tightened by hand. I'm pretty sure by the feel of the threads when tightening/changing extruders that there is inconsistency in the final position once tightened. This inconsistency leads to the need for minor adjustments each time a nozzle is changed regardless of the previous settings.  Tightening an extruder by hand does not exactly result in inconsistent torque values.

I've learned to live with having to print a test pattern to make minor Z adjustments each time I change sizes, there is just no easy way to consistently automate the process via settings that i can think of.  To be honest it's kind of a bummer, not exactly the superfast extruder size changing experience I was hoping for but at the end of the day I am happy that it's worth the price paid in my opinion.

Regarding your comment on accessing the extruder, I highly recommend you install this modification, it makes it much easier to access the extruder for finger tightening - https://www.printables.com/model/155387-remix-x2-delta-p-duct-v2r22-for-the-mk3s-new-flow-

RE: Revo 6 nozzle changes and z-height

oriddlero,

thanks for the suggestion for the alternate fan duct.  It is on my list to do. I am getting better at judging the tightness of the nozzle and find I only need a minor tweak on the live z after a change.

Other observations with the revo

1. I run a MMU2 and have found no problems with filament changing. Prior to the revo I installed a titanium heat break which was a big step forward from the standard Prusa modded heat break, The Revo is performing better than the titanium even with 0.25mm printing, I suspect there is less heat softening of the incoming filament.

2. The revo nozzles do get a bit contaminated with stray filament build up (particularly PETG strings) on the flat part just below the silicon sock but I find it far easier to clean up than the old nozzles by just using a brass bristle brush when nozzle is hot.