Dock fixing bolt - Becoming loose
I was getting collisions during print with no apparent reason. TBH the printer sounded like it was about to strip the belt whilst recovering which is not comforting. Anyway, a little further along I noticed that the toolhead was getting extra rough at parking and collisions more frequent.
I went to recalibrate the tool parking and noticed the first toolhead dock was loose (Wobble on the fixing to the alu. extrusion). This requires removing the nozzle seal to tighten…. Yup, loose. This single bolt does not really feel to me like it will endure the vibration etc. I recall it’s just the threaded plate spacer for the heads in the extrusion. I could use a threadlock but it feels flimsy compared to the balance of the printer.
Curious if anyone else is having an issue with this?
(Dual tool)
RE: Dock fixing bolt - Becoming loose
I also thought it was odd when assembling to only have one screw holding the entire nextruder assembly to the frame.
RE: Dock fixing bolt - Becoming loose
I’m having the same problem - loose docks over short periods of time exacerbated by some collisions which I blame on an issue not mentioned in the assembly guide 😒
RE: Dock fixing bolt - Becoming loose
I'm thinking my only option with this is to remove the heads, thoroughly clean the bolts and threaded spacer plate and reassemble with Loctite thread locker to stop this repeating. If i had access to tooling I would redesign this as an inverted T with two fixings visible either side from the rear but this requires drilling and tapping the spacer plate. Aside from this and a mulititde of other issues I'm seeing with erattic print quality across the threads and also experiencing, confident my XL it will be a great machine.... oneday. Don't think I've seen any comment on the shipping box design, exceptional in my opinion - might want to lend their skills to other departments... Dock mount and nextruder covers a good start
RE: Dock fixing bolt - Becoming loose
So the solution I've employed thus far was I actually redid the set up pushing the dock against the bar as I installed it. I then have shimmed under the dock as there is just enough gap for it to wiggle if the dock isn't set up just PERFECTLY.
I've noticed two things since then:
1) more consistent tool changes (no errors).
2) it's quieter, indicating that it's not rattling loose.
If it comes lose again, I'm definitely putting some spacers behind the dock then as well. I agree, one two threaded holes should have been part of this design, as one allows for rocking (which the shimming has seemed to minimize).
My current issue now is seeing that it wasn't built with PETG in mind it feels like; I'm getting very stringy prints using any of the default settings and nozzles, despite having dried the filament. This annoys me as the reason I bought prusa equipment in the past was because of no fuss PETG, ASA, and PC.
RE: Dock fixing bolt - Becoming loose
Check your retractionsettings and check if you are maybe printing too hot. Also bigger nozzles means more stringing and oozing. IMHO for mechanical parts it isn't a big problem, but for Parts that need to look good a 0.4mm nozzle work just sooo much better.
RE: Dock fixing bolt - Becoming loose
Can I clarify with you guys, is this screw present on your XLs? The one on the top left corner?
I assume this is to try and stabilise the plate somewhat - I didn't have it and used a spare to replace it. I also ended up using loctite on the single dock screws, recalibrated 100 times and finally have the toolhead changing working smoothly. Even if I sometimes feel my heart skip everytime I visually see it change tools.
RE:
you might need to actually seat the metal piece into the frame (same as the vertical extrusions during assembly). the tolerances on these parts seem more press-fit than loose.
tighten the screw, then rock the part back and forth axially to the extrusion to help it slip into the extrusion slot, then tighten the screw more. makes ugly grinding sounds but you'll feel the screw coming to a proper stop.
RE: Dock fixing bolt - Becoming loose
I actually had to file mine down a bit for them to fit flush up against the metal.
They really need to rethink how the docks are attached to the frame. This was a frustrating step.
RE: Dock fixing bolt - Becoming loose
yeah the fits are extremely tight....but this way you can re-mount them without recalibrating, which is nice.
when the screw gets tight, rock the metal part back and forth along the axis of the extrusion so it slips into the slot easier, then tighten the screw more.
RE: Dock fixing bolt - Becoming loose
you might need to actually seat the metal piece into the frame (same as the vertical extrusions during assembly). the tolerances on these parts seem more press-fit than loose.
tighten the screw, then rock the part back and forth axially to the extrusion to help it slip into the extrusion slot, then tighten the screw more. makes ugly grinding sounds but you'll feel the screw coming to a proper stop.
That's precisely this, I had the same issue and the same strategy fixed it.
I'm pretty sure this thing is supposed to be a very tight fit it's just the assembly instructions that make no mention of it.
You just shake it back and forth while you tighten the screw slowly and it scratches enough paint to fit in perfectly. No need to file anything.
This is going to get a lot of people if they don't improve the assembly instructions for this.
Here is another post with the same issue -> https://forum.prusa3d.com/forum/original-prusa-assembly-and-first-prints-troubleshooting/extruder-cable-holder-rubbing-against-back-belts/
RE: Dock fixing bolt - Becoming loose
Interesting, I see that they have changed the nozzle seal screw fixing positions. Looks like the primary seal fixing has rotated 90deg and i assume as it notes in the manual that the seal is pre-installed on the dock that it no longer obstructs the dock fixing bolt. Still the single bolt but definatly an improvment. Unfortunaly I don't see this in the printable parts, nor my version for that matter - TBH i'm not sure how this is fixed to the alu dock plate. Investigation required..
RE:
Correction. The new version and old are available but in missleading folder [Nextruder single tool]?
dock-cablerouter.stl (version A) and the new (version B) as discribed above. Looks like the nozzle cap might be in the [Tool Changer] folder... but doesn't look like it aligns with the B version either.... i might make that myself if cannot find
RE:
wait what, this is a huge change, is there a photo of this?
actually I can see the files you are talking about in the next post. Yes. this is quite a big revision!
RE: Dock fixing bolt - Becoming loose
I printed the newer version of the dock and as I could not locate the compatible nozzle seal I made my own to match Prusa's. The design feels better as the seal can be adjusted whilst the head is in the dock + the dock fixing bolt... that little guy can be checked anytime without having to remove the nozzle seal completely first!
I did modify the back of the dock slightly with a fine bevel near the belts to try enhance the clearance... after reinstalling I can see the lower bolt of two fixing the plastic strop for the filament/cable loop actually rubs on the belt as well for both so ended up leaving the lower bolt out for now.... V. annoying
My dock is snug to the alu extrusion so there is no question this is too tight a tolerance in my mind. The little machine screw holding this is doing a lot of work and tbh think would be easy to strip the thread on this if tried to wind it too hard - for now I think this will resolve + threadlock. Hopefully Prusa issue a new STL for the dock with better clearance in mind... incrementally better for now.
I'll put the nozzle seal bits I made on printibles if anyone wants to use
RE: Dock fixing bolt - Becoming loose
good stuff,
hopefully Prusa will upload the seal part as it's pictured in their manual changelog already, but yes would really appreciate it if you uploaded yours.
Was it hard to reassemble the dock parts?
RE: Dock fixing bolt - Becoming loose
It was really easy to switch. One done and now working on the second.... once printed.
Just make sure you have some cable ties to replace the two per head and small enough to fit the part.
I'm thinking the dock part's body could be just 2mm shorter and all the interferrance at the belts would be resolved. Was hoping that the B version was shorter but nope, the same
RE: Dock fixing bolt - Becoming loose
I have run into the same dock fit issue discussed above. I have already removed the metal part from the printed parts and am trying to attach that on it own, but not combination of rocking and tightening is getting the job done. I measured the parts as the protrusion on the dock piece is 8.15mm wide and the opening in the extrusion is only 7.95mm. I suspect that they might have a manufacturing tolerance issue and some of these parts are coming out in sizes that just don't quite fit. I am currently waiting on an email reply back from support to find out if the 8.15mm measurement on the dock part is actually within spec or not.
RE: Dock fixing bolt - Becoming loose
I also removed the metal part from the dock, tightened it just to fit snugly with the screw, then proceeded by pushing the part forward and pulling backward, tightening the screw a little bit after each move.
RE: Dock fixing bolt - Becoming loose
Anyone having issues with the screws themselves being short?
Working on building mine and took notice that one of the docks just won't install.
Turns out the screw is less than half the standard length