Originally shared by Florian Ford
What is your preferred and SIMPLE 
way of aligning and adjusting a dual hotend. I am designing a dual hotend that has a threaded heatbreak barrel (the usual ones ) and the simplest way I have thought of is the following:
- screw and mount the both hptends in their plastic or alu mounts. Don’t overtighten.
- unscrew one of the barrels ~3-5mm and tighten a nut you have previously put on the barrel against the heatsink until it’s strongly locked
- level the bed against the first hotend until you have the desired gap (use a filler gauge)
- place the feeler gauge under the second hotend and unscrew it until it touches the feeler gauge (rests on it)
- use a needle-nose pliers to firmly tighten the nut against the heatsink
Here’s the sketch. What do you think?
Sounds like it would work - except for the needle - nose pliers. I would always use a wrench. You can’t get a consistently good grip with pliers because they don’t contact the flats on the nut properly. If clearance for the wrench is a problem, you can always buy a cheap wrench and grind it thinner as needed.
A thin steel wrench like those for bicycle repair would also work well. But one would also need the needle-nose pliers to grab one of the heatsink’s fins to be able to fasten the nut against something because you don’t want to disturb the heater block even a little.
Edit: I believe that even a 3D printed part would work. You don’t need to tighten it too much, just enough to prevent it to unscrew easily.
This method is nice, but it assumes that everything else in the system is perfectly aligned. Is there a backup plan for when that’s not true?
What other option is there? What can be wrong in the system? Tilt is the only thing that can affect this but that’s easily solvable by design. The only problem with dual hotends is getting them at the same level with micro-adjustments. This can be achieved due to the micro-adjustment inherent to screws, the fact that a whole turn can only advance by one step (=pitch) …
I don’t think that kind of hot end barrel system is good for dual. E3D Chimera uses set screws to adjust the height. Lower your system to the bed, let both nozzles touch the bed and tighten.
Should be the same process … this one just have a threaded barrel instead of a smooth barrel. The only unknown to me is if all these threaded barrels have the same standard in terms of metric nuts that can go on them. And I don’t have one at hand now as I am not at home for a few months… so I took the time to finish the design of the #SCOUTcorexy #3Dpriner.
@paul_wallich the hotend is already on the bed, it can’t go lower and tightening the nut against the heatsink only tries to pull it even more from inside the heatsink, which it has nowhere to go. So it will be locked when fastening the nut. At first glance it seems pretty fail-proof to me. But again I have to try it and I don’t have any parts on hand atm.
On a second thought I am assuming that the barrel still rests on the lower side of the threads inside the heatsink, which it would normally do due to gravity, but if I rest the nozzle on the bed it might just loose touch and move inside the “backlash/clearance” within the thread pitch and then tightening the nut will move it again towards the lower shoulder of the thread (pulling it from inside the heatsink), which would translate in a flex of the X rods as it pushes against the bed and has no place to go downwards and resulting in a lower position than the first nozzle as a consequence… tricky
Ok, thinking out loud here. The previous post’s concern can be easily overcome by having a spring always push the barrel-heating_block_nozzle assembly downwards so the barrel’s threads always rest on the lower side of the heatsink threads, just as the gravity alone would have it should it not touch the bed. I’m even more confident now that this can achieve with lower cost hotends perfect level.
But I am still thinking about other possible faults so keep the critic coming. Thanks.
