RE: Dock fixing bolt - Becoming loose
So, would a modification to add a locking nut keep these from loosening? Just a nylon nut somewhere in the path to keep it from turning? I thought that all 5 of mine were pretty tight. Two were not as tight as I would have thought after just 8-10 print hours.
RE: Dock fixing bolt - Becoming loose
What about just using some locktite?
RE: Dock fixing bolt - Becoming loose
If I was building mine now, I’d definitely use some Loctite.
What about just using some locktite?
RE: Dock fixing bolt - Becoming loose
Is this problem (dock screw coming lose) happening maybe only by people who did not fully tighten the screw to the point where the two metal parts meet nice and flush (without filing, don't do that!).
I think you are suppose to get a nice grindy sound of the metal part pressing into (and deforming) the aluminium extrusions and a very clear sudden stop when the metal part fully meets with the aluminium extrusion. To me that feels like a decent rigid construction for the type of work it needs to do.
Creative Engineer and 3D printing @ AcEcraft.eu
RE: Dock fixing bolt - Becoming loose
Some guidance from Prusa on this part would be useful. Seems a critical step
RE:
I expect we are going to hear of cases if not already of people needing to dissasemble the back frame to remove a damaged dock/machine screw if overtighened.... it's a delicate balance for a very small machine screw. Prusa have definatly improved from the origional dock mount by rotating the nozzle seal adjustement bolt so it is no longer obstructing the dock thru fixing. I printed the new parts for this and at this stage I'm just keeping an eye on it to make sure not coming loose again.
The extrusion is anodised alu. Thus hard finish on a soft metal. The grinding people keep referring to is the brittle anodised finish deforming. I don't see this as a mechanical joint that can be relied on with constant vibration. I sort of expect they will modify this at some stage to improve the longevity here.
Suggest:
1. If you have the interferrence version of the dock fixing. Replace it with the new version Prusa released. See back in posts for details (easy then to check regularly)
2. Clean the plate thread & machine screw thread with a cottonbud and degreaser before installing dock again with a threadlocker
3. Await a new design. It works but it could definatly be improved with a nyloc nut or the plate with stud poking back for nyloc externally
RE: Dock fixing bolt - Becoming loose
Well, just ran into this issue today after making it 75% through a 21 hour print. I'll be working on my printer tomorrow and we'll see what's wrong, I'm assuming right now it's a loose screw (and probably made worse by my filing the part down).
RE: Dock fixing bolt - Becoming loose
I ended up using loctite and have not had any docking/undocking issues since.
I haven't done a heap of very long multitool prints on my 2 toolhead printer, but I have done a fair few smaller prints with tool changing.
RE: Dock fixing bolt - Becoming loose
Plus the single screw holding the dock(s) was very difficult to tighten properly through the long hole. I even made a tool for that:
https://www.printables.com/model/915686-prusa-xl-assembly-helper
I also thought it was odd when assembling to only have one screw holding the entire nextruder assembly to the frame.