Precision adjusting dual nozzle height - solved

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
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JohnSays
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Precision adjusting dual nozzle height - solved

Postby JohnSays » Mon Aug 08, 2016 4:48 am

The problem with getting the two nozzles at the exact same height is that the very screw used to tighten the nozzle into place is moving the nozzle unpredictably. To solve this problem would be to solve not being able to tighten the nozzle right where you want it. What is needed is something between the nozzle body and the end of the screw. In that way, the action of the screw to tighen would be preserved but the unwanted vertical movement would be nullified.

I considered placing a bb into the hole, but discarded the idea as it could leave a dimple in the nozzle body. Instead I opted for a short (2mm) cylinder that slides into the threaded hole. I used the 1/8" shaft of a Dremal bit by simply cutting off about 2mm of the bottom of the bit with a hacksaw and then filing it flat and chamfering the edges. - so exit one bit and hello one spacer. The shaft fits perfectly and is soft enough to work with workbench tools. When placing the spacer in the hole, I place the flat end into the hole first and leave the slightly rounded end for the screw to press on (see picture below). Thus even less chance of this spacer moving.

So how did it work? In a word: perfectly. I use a gauge block on the bed placed under both nozzles and that gives a nice flat and smooth surface to slide a feeler gauge on. I use the one-finger-slide method: Keeping the feeler gauge flat on the gauge block, I use one finger to slide it under each nozzle and feel the very slight resistance of the feeler rubbing the bottom of the nozzle while being careful not to put any pressure down onto the block as that can cause the bed to move down slightly.

Note that I only had to mod the one nozzle fixing hole. Just leave the other nozzle where ever it is and adjust this one (in my case the right nozzle) to match it. I was able to move it into place and tighten the screw on the right (the one under the fan) without the nozzle moving. It took a little time moving the nozzle slightly, re-tightening the right screw, and then using the feeler to inspect the height. When I had it right I just tightened the front 3mm screw and the nozzle stayed right where I had placed it. Botta-bing botta-boom!

Caution: If you do this, there will now be about 1/3 less threads to tighten into. So tighten accordingly.

(Note: The fan is still attached in the photos below because I took them before I did the actual adjusting.)

P1020190.jpg
The 2mm spacer. Note the rounded end that mates with the screw end.

P1020191.jpg
The spacer in the nozzle fixing hole.

P1020192.jpg

P1020193.jpg
Gauge block and feeler in use. Note: Do not use feeler while it is attached to the feeler gauge pack.
- John
2 Raise3D N2 Duals, V2 nozzles, Bondtech BMGs, and adjustable table

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walshlg
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Re: Precision adjusting dual nozzle height - solved

Postby walshlg » Mon Aug 08, 2016 3:16 pm

Funny, I was just pondering this yesterday - had to remove the isolation tube to clear a bad jam, and now I'll have to realign the heads. I worry about the situation of having to take out the isolation tube, then having the load bushing slide partway into the hole, blocking re-insertion of the isolation tube.

I wonder if just sanding the end of the clamping screw would be enough to take off that raised rim?

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JohnSays
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Re: Precision adjusting dual nozzle height - solved

Postby JohnSays » Mon Aug 08, 2016 3:38 pm

I did this because I have had experience as a prototype machinist and had seen this solution in the past. It won't make any difference how flat the end of the screw is. It will still put movement pressure on the nozzle body. Even the smaller screw does it, but I believe it is small enough not to matter. Again, rounding the end of the screw would do it, BUT would most likely indent the surface of the nozzle body.

Ideally what I would like to see is an adjustment screw to move the heads up and down and that can be locked into place with a lock nut -- like the depth screw on a drill press.
- John
2 Raise3D N2 Duals, V2 nozzles, Bondtech BMGs, and adjustable table

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dhylands
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Re: Precision adjusting dual nozzle height - solved

Postby dhylands » Mon Aug 08, 2016 6:07 pm

Having a concave surface in the end of the plug (to match the curvature of the isolation tube would be ideal.

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rlballard
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Re: Precision adjusting dual nozzle height - solved

Postby rlballard » Mon Aug 08, 2016 7:49 pm

Nice work Johnsays, a great solution to a nagging is that makes you not want to touch the hot ends when you think you have them close enough...
BB

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JohnSays
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Re: Precision adjusting dual nozzle height - solved

Postby JohnSays » Mon Aug 08, 2016 8:03 pm

Yes rlballard, that's exactly how I was feeling!

Dave, as far as it being concave, I'm going to disagree as the screw will have a better opportunity to now grab the spacer and turn it. Most ideal of all would be to have a convex end for the screw to hit, but that takes more space and the depth of threads will be even more compromised.
- John
2 Raise3D N2 Duals, V2 nozzles, Bondtech BMGs, and adjustable table

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dhylands
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Re: Precision adjusting dual nozzle height - solved

Postby dhylands » Mon Aug 08, 2016 8:23 pm

JohnSays wrote:Yes rlballard, that's exactly how I was feeling!

Dave, as far as it being concave, I'm going to disagree as the screw will have a better opportunity to now grab the spacer and turn it. Most ideal of all would be to have a convex end for the screw to hit, but that takes more space and the depth of threads will be even more compromised.
I meant and have the concave surface against the throat tube. This would give more contact surface between the spacer and the tube which would distribute the load (less likely to mar the tube).

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walshlg
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Re: Precision adjusting dual nozzle height - solved

Postby walshlg » Mon Aug 08, 2016 9:05 pm

dhylands wrote:
JohnSays wrote:Yes rlballard, that's exactly how I was feeling!

Dave, as far as it being concave, I'm going to disagree as the screw will have a better opportunity to now grab the spacer and turn it. Most ideal of all would be to have a convex end for the screw to hit, but that takes more space and the depth of threads will be even more compromised.
I meant and have the concave surface against the throat tube. This would give more contact surface between the spacer and the tube which would distribute the load (less likely to mar the tube).


No, the isolation tube has a flat spot on its head where the set screws clamp.

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dhylands
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Re: Precision adjusting dual nozzle height - solved

Postby dhylands » Mon Aug 08, 2016 9:09 pm

Ahh - I hadn't realized that (I've not taken mine apart).

I had similar issues with my MendelMax3 which uses e3d hotends and had a setscrew clamping on the curved surface.

AR_LA
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Re: Precision adjusting dual nozzle height - solved

Postby AR_LA » Wed Aug 10, 2016 1:45 pm

You basically created your own swivel tip set screw. Nice. I'll have to get some to add in there.

Do you know the threads by any chance? M4 and M3 would be my guess.

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walshlg
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Re: Precision adjusting dual nozzle height - solved

Postby walshlg » Wed Aug 10, 2016 2:45 pm

I'm tempted to add a set screw down through the top of the plastic where the isolation tube sits. THen I can re-set the head heighth exactly by holding it up against the screw as I tighten it .

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JohnSays
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Re: Precision adjusting dual nozzle height - solved

Postby JohnSays » Wed Aug 10, 2016 11:20 pm

i don't know the threads 'cause I'm not metric literate<g>.

Walshlg, you are braver than me!
- John
2 Raise3D N2 Duals, V2 nozzles, Bondtech BMGs, and adjustable table

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walshlg
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Re: Precision adjusting dual nozzle height - solved

Postby walshlg » Thu Aug 11, 2016 4:45 pm

JohnSays wrote:i don't know the threads 'cause I'm not metric literate<g>.

Walshlg, you are braver than me!


so far I am long ideas but short on the bravery part. But the sleep on it for a week test is positive so I may just do that, will have to completely disassemble extruder, that is holding me back for a while.

M3 screws are typically 50 pitch

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JohnSays
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Re: Precision adjusting dual nozzle height - solved

Postby JohnSays » Thu Aug 11, 2016 6:19 pm

My two cents: I have not taken it all the way apart so I don't know exactly how it is made. I have the idea that an adjustment screw would need to put even pressure straight down and also be able to lift the nozzle. So that would be more of an ideal solution that probably is not attainable with this nozzle head in that a new one would need to be designed and manufactured.
- John
2 Raise3D N2 Duals, V2 nozzles, Bondtech BMGs, and adjustable table

AR_LA
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Re: Precision adjusting dual nozzle height - solved

Postby AR_LA » Thu Aug 11, 2016 9:40 pm

You'd want to index at least 3 points if you're hoping for a sort of "fire and forget" solution. And even then I think you'll still want to use a calibration block or similarly flat object under the nozzles.

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walshlg
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Re: Precision adjusting dual nozzle height - solved

Postby walshlg » Fri Aug 12, 2016 3:33 pm

My thought was just have a screw with a locking nut straight down to serve as a simple end stop: you raise the isolation tube up against it and hold it up against it tightly while you lock the head in place with the existing system.

Its not perfect but its simple and "good enough"

"perfection is the enemy of good"

AR_LA
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Re: Precision adjusting dual nozzle height - solved

Postby AR_LA » Fri Aug 12, 2016 3:58 pm

But the only time you're taking out the hot end, you'll be taking it apart, which means when you reassemble it, the OAL length will be different, so indexing at the isolation tube will lead to a nozzle height imbalance.
Unless I'm missing something?

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walshlg
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Re: Precision adjusting dual nozzle height - solved

Postby walshlg » Mon Aug 15, 2016 1:52 am

Yeh that's right, and the biggest problem is it moves when screwing it down. That is helped by my idea of a set screw, you hold it against it as an end stop so you can adjust with some reproducibility. Looking at it today, its a tough mod.

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JohnSays
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Re: Precision adjusting dual nozzle height - solved

Postby JohnSays » Tue Aug 16, 2016 2:36 pm

I am reporting back on the results of being able to easily and precisely adjust the dual nozzle height (alignment). I just printed a dual extrusion print with layer height of 0.2mm and neither nozzle dragged in the print.
- John
2 Raise3D N2 Duals, V2 nozzles, Bondtech BMGs, and adjustable table

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walshlg
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Re: Precision adjusting dual nozzle height - solved

Postby walshlg » Tue Aug 16, 2016 5:37 pm

OK well I'm going with the sawed off 1/8" insert next time I tear it down then.


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