QU-BU Extruder Improvements

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Re: QU-BU Extruder Improvements

Postby brnrd » Mon Jan 28, 2013 4:59 pm

Two things to consider:

1. You can still go fast even if with 2 NEMA17 motors on the carriage. What you have to reduce are the jerk and acceleration settings in the firmware keep your printer from vibrating.

2. There are lighter motors around. http://trinitylabs.com/ sells light PG35 motors with gears.

3. I would also suggest getting some experience with 1 extruder first, before going for 2.
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Mon Jan 28, 2013 9:10 pm

Thanks for the feedback Bart. I take it you would be concerned with remote extrusion. Are you having problems with this on your Delta?

Point taken on dual extrusion. I was just going to make the mounting where it will accept dual when I feel up to it.
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Tue Jan 29, 2013 3:40 am

Front.jpg
Here is the concept I'm thinking of
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Tue Jan 29, 2013 3:42 am

Back.jpg
The Carriage will be replaced with a vertical plate with air flow hole.
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Tue Jan 29, 2013 3:44 am

Parts.jpg
These are the three parts. The bottom plate and clamp will be aluminum for the heat. The top will be plastic.
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Re: QU-BU Extruder Improvements

Postby brnrd » Tue Jan 29, 2013 4:35 am

The bottom aluminum piece is not needed and it would only draw heat away from the nozzle. It's best not to include it. You might also want the two nozzles to be at different temperature like if one of them is being used for support material.

Have you thought about how you would adjust the nozzles so that they're on the same plane? If not, the lower one will drag into the part being printed or the higher nozzle will be too high.

BTW, this is the second time that someone mistook me for bart. I'll take it as a compliment. :)
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Tue Jan 29, 2013 5:00 am

Thanks for the feedback.

There is about .080" clearance between the aluminum plate and the brass element. I was thinking that it might furthest help prevent the heat migrating up the tube. I guess the plastic doesn't conduct much heat anyway.

If I support only at the top, I'll need to connect into the groove somehow.

On adjustment, I was going to make one of the corner holes in the carriage close and the other three a bit oversize. This would allow you to rotate the assembly to get the nozzles at the same height. I was thinking you wouldn't do this real often. Is this a bad assumption?

Would you put the fan on it and if so, do I need to shield the airflow from the brass head?

I'm pretty slow at CAD. I really hate to make any improvements if it means re-drawing. : :lol:
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Re: QU-BU Extruder Improvements

Postby brnrd » Tue Jan 29, 2013 5:38 am

I didn't notice that you weren't using the slot at the top of the PEEK to support the hot end. If you look at hotends.com, he sells a mounting plate that has a slot where the slot in the PEEK slides into. You can use the same method or come up with another design to use that slot. Then you won't need the lower support anymore.

The fan on the insulator should only blow on the upper slotted (or "finned") section and not below that. The melt zone of the MK V J-head extends into the bottom of the PEEK were there are no slots. The fan is needed for PLA but not for ABS.

I'm not sure I understood your adjustment scheme. I haven't used two nozzles yet but I also expect that you don't need to adjust often. But that depends on how it's mounted. There is significant expansion in the hotend upon heating. I see a large change in bed clearance when I heat up the nozzle. Hopefully, they expand by the same amount. Anyway, you would want to make the adjustments after letting the nozzle sit at operating temperature for a while.
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Tue Jan 29, 2013 7:58 pm

Ahhhh, I continue to learn. This forum and open source development is new to me. I love it!

I had not considered thermal expansion of the extruders. Also, I had made the assumption you wanted to keep the entire black tube cool.

I can see two possible scenarios:

1. If mounted at the top you would definitely need to check z zero after heating. But, if you were only using one extruder, the cold one would stay "shorter" and out of the way.

2. Or, if you could mount them close to the bottom without sucking the desired heat out, the expansion and contraction would happen "upward" because the bottom would be fixed and the top free to move. Z zero would be more stable relative to temperature change.

Hmmm, wonder which is the best scenario.... Guess I won't be making parts today.
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Re: QU-BU Extruder Improvements

Postby tmccafferty » Wed Jan 30, 2013 3:43 am

front2.jpg
Designed for minimal thermal contact with the tube. Material = phenolic
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