[WIP] another direct dual extruder

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dognotdog
Posts: 181
Joined: Tue Sep 04, 2012 9:22 pm

[WIP] another direct dual extruder

Post by dognotdog »

While temporarily abandoning the bowden approach, I did build a direct dual extruder: (yea, can't see much, and it's messy, I'll post the parts when I have the time)
Image

It's nice in that it's only a total of four printed parts for the whole X carriage. Not so nice is that everything's hidden away a bit, and it's harder to see what's going on when there are jams. One thing it's missing is a holder for the additional fan to cool the extrusion, but I haven't wired up the electronics for it, either, so far.

Well, prints look like so:
Image

I've done a hilbert cube as the first thing, but I can't find it.

There's some oozing, not sure how to really combat it, except with a close and full-height skirt. Also, one of the extruders keeps getting jammed, but I don't really know why. I have some funny air routing around the cold-ends, but hooked up the fan to the 12V line instead of 5V, initially to combat plugs forming when the filament didn't move for too long.

Also, software wise, slic3r as of 0.9.4 does the right thing, and can generate gcode for dual extrusion, it's what I used.

Speaking of slic3r, it doesn't do any optimization of the polygons, and thus the gcode often overwhelms the marlin firmware with filling the path planner with ridiculously small line segments, thus slowing everything to a mere grind. I've written a simple optimizer that cut's the gcode by 50% when there's lots of small curvy stuff, and results in much nicer prints.

Kjetilei
Posts: 334
Joined: Fri Mar 16, 2012 8:26 pm
Location: Stavanger, Norway

Post by Kjetilei »

Nice to see that you have gotten dual extrusion to work too :) Thumbs up!

You beat me with one less needed printed part ;)

I would really love to see a detailed view of the printed extruder parts.

Does the middle fan blow downwards to cool the cold ends? Do you need the fan on the stepper or is it just in case?
Would you be able to move the hot ends even closer together? Mine are practically touching each other without a problem.

Have you tried slicing with Cura instead of Slic3r?

dognotdog
Posts: 181
Joined: Tue Sep 04, 2012 9:22 pm

Post by dognotdog »

I have tried Cura, but I failed to set it up properly. It kept outputting too much material, and I wasn't able to figure out why.

The parts look like so:
Image
Image

These are the "old" parts, the ones I have mounted now have better tuned air ducts for the cold ends. Also, you obviously need two of the tension arms, while the photo only shows one.

The fan on the stepper is just the 2nd fan still dangling there, it has no function. I just couldn't be bothered to get the cable out of the sleeve. The fan in the middle is indeed blowing onto the cold end, which have a more or less spiral duct going around it, and then blowing out the bottom. Kjetilei's design is more open, which is maybe better. I basically designed the tensioning mechanism first, and everything else came from that and the space constraints.

The distance between the nozzles is 25mm, and I could not move them much closer. Due to the oozing, I don't think that would be very good.

Kjetilei
Posts: 334
Joined: Fri Mar 16, 2012 8:26 pm
Location: Stavanger, Norway

Post by Kjetilei »

Thanks for the info and sharing the photos!

I love the way you have approached it quite differently from me but at the same time there are many tiny similarities between our (and Guillaume's) designs :)

Is it easy to adjust the height of the hot ends to ensure equal distance from the hot bed?

Did you include or omit the bearings to support the stepper shafts?

Did you upgrade to the Hiwin linear bearing guides (the four holes in your extruder base part)?

dognotdog
Posts: 181
Joined: Tue Sep 04, 2012 9:22 pm

Post by dognotdog »

Here's some sectioned renderings. There is a support bearing for the stepper shaft. I am not sure if it's necessary. If I would remove it, it'd result in much better ducting for the airflow towards the cold end. The fan is blowing air towards the cold end, which is guided around it in a full circle, then blown out downwards through the carriage.

There is no easy adjustment for the extruder heights. Mine happen to have the same height to within a few tenths, so I didn't bother. Not sure how I would solve it with this design, if I needed to really adjust it. I could print some shims and just stick it under one of the extruders, I guess.

Image
Image

And yes, I do have the new hiwin rails update, which really does quite improve backlash and general play.

I am starting to wonder if dual extrusion is really worth pursuing. For dual color prints, at least, it seems a bit too messy because of all the oozing. However, for soluble supports, it could work great. Now I only have to find some PVA :)

Kjetilei
Posts: 334
Joined: Fri Mar 16, 2012 8:26 pm
Location: Stavanger, Norway

Post by Kjetilei »

Great renderings! What application did you use?

I love the Hiwin update! It converted my printer from unusable for tiny details like small bolts and gears to a champ! (disclaimer: I was never able to fine tune the Igus bearings) No more frustrating backlash!

I think dual extrusion is worth pursuing but do agree that it would be better with soluble supports than dual colors. And it could also be useful for mixing hard plastic details with more rubber like details in one print (if the two materials bond good enough together).

But then I don't know of any affordable 3D printer that is anywhere near the level of details and color fidelity/flexibility that I really want ;)

Trnquill
Posts: 66
Joined: Fri Oct 05, 2012 10:01 am

Post by Trnquill »

Kjetilei wrote:I think dual extrusion is worth pursuing but do agree that it would be better with soluble supports than dual colors.
Speaking of which, has anyone tried PVA? http://wiki.makerbot.com/pva
http://store.makerbot.com/makerbotr-wat ... -75mm.html
It's kinda high on price but offers amazing possibilities combined with a dual extrusion head!

Another thought: has anyone tried using a single motor to drive two extruders? I'm thinking of some kind of (servo driven?) clutch mechanism to activate one or the other extruder. This would help keep the weight down.

Kjetilei
Posts: 334
Joined: Fri Mar 16, 2012 8:26 pm
Location: Stavanger, Norway

Post by Kjetilei »

It has been mentioned but I doubt it has been looked seriously into. It could most likely be done with a servo or actuator but would require firmware support. If one took that step I believe it would be an idea to look into solutions to avoid spilling from oozing too.

satoer
Posts: 436
Joined: Mon Oct 01, 2012 8:00 pm
Location: Netherlands

Post by satoer »

I think the best way to avoid oozing is a single head extruder with two feeds.
My Felix 1.5 printed designs on Thingiverse
E3D V6 Hot end upgrade for your Felix
Tweezer bracket for your Felix
Led bar upgrade for your Felix

dognotdog
Posts: 181
Joined: Tue Sep 04, 2012 9:22 pm

Post by dognotdog »

satoer wrote:I think the best way to avoid oozing is a single head extruder with two feeds.
Very probably, there are quite a few people running experiments with that. With that, though you run into the problem of differently colored filament requiring different temperatures. Ditto for PVA, which also needs slightly different temperatures from PLA.

Speaking of materials, there was some talk about rubber-like stuff? Is this the soft-PLA that I see occasionally, or are there other materials worth trying out?

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