My 6 input (5+1) mixing hot end
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Hi Ian,
I am keeping track of your blog for quite a while, but remaining quiet up to now. It is a pleasure to see what you have achieved with your printer.
I am also using a multi color printer with 2 e3d cyclops+, so 2 nozzles with 2 color mixing each. From this, I have a rough idea on what might make sense to consider in your full color hotend/coldend design.
Some ideas:
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Heat conduction. A 6 color hotend does not necessarily dissipate 6 times the heat, but each of your heatbreaks need to stay cool on the coldend side. And as there are 2 colors sandwiched in between, they do get less airflow. The mosquito heatbreaks help, but I am not sure this is enough.
Consider water-cooling. I sandwiched a water-cooled aluminum block with my 2 cyclops coldends and that really made a big improvement. Especially when swapping filaments completely - when pulling back the filament, the cold side is cleanly separated from the hot(melted) portion and it does not lead to jams. -
Heat radiation. Make a silicone sock for the hotend. It is huge and it radiates a lot of heat to the outside. I would guess this contributes a lot to not being able to reach high temperatures with your 40W heater. Design a cast and get some silicone to do it. Did the same for the cyclops, should put the design online for the community...
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The 6th color input. I think this is the most important part of your hotend. What I really miss from the Cyclops is an effective way to retract. Doing a lot of retracts may kill the input which is not printing currently.
Your idea to use transparent filament is a good shot a mitigating the issue (maybe the best), or you use an approach that does not involve any filament at all. E.g. use a rod of aluminum that you pull back within a channel close to the nozzle. But for this you need to somehow seal the construction and have tight tolerances. Don't know if that's feasible...
The hotend is very long (like a volcano) and I am guessing this is to make the colors mix nicely, which is fine. For the 6th color, however, you should not attach the input to the top of the hotend. I am guessing that you have a separate channel to the nozzle only for this color, but this is not as effective as it could be for retraction. Consider putting a side entry (or mill a part of the block down) and attach a heatbreak as close as possible to the nozzle. Of course, this decreases the throughput of that input, but it improves retraction due to the reduced friction between filament and channel.
This became a pretty long post, but maybe you find some useful input.
All the best!
Tommy -
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Hi Tommy,
Thanks for the kind words and I'm always open to hearing other people's ideas. Ref points 1 and 2 - keep an eye on my blog. I think the next post (part 3) which is due to be published shortly will have some interesting data which might surprise you (it did me).
The silicone sock is something that I have always planned - I made one to fit the Diamond 3 colour back in June 2017 - details here https://somei3deas.wordpress.com/2017/06/15/making-an-insulating-sock-for-the-diamond-hot-end/. The reason that I haven't yet made one for this hot end is that I might need to modify the mixing chamber which in turn, might mean that the outer size and/or shape might change. So if I made a silicone sock now, I might have to repeat that exercise at a later date.
Your point 3 may be valid. But then again, it might not be. It's an idea but without any data, it can only be speculative. The 6th filament does indeed have a straight, vertical path to the nozzle so it might work well. The Diamond hot end works well with respect to retraction (one of the few things about it that does work well) and all the filament inputs have that straight path to the nozzle. So I'll test this design and see what happens. The 6th filament may also prove to have a secondary use for single colour, high speed printing (due to it's long melt chamber). So I prefer to stick with this design for now. Only by doing tests will I know if there is a problem that needs to be solved.
Ian
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@Wurstkarton With regard to your pair of cyclops hot ends, are you using firmware retraction? It's important that you do when using hot ends with multiple inlets and a single nozzle because retracting just one filament simply pulls filament from the other input, rather than the nozzle tip. And what extruders are you using? If they are the spring loaded tensioner design such as E3D Titans, they tend to wear away any filament that isn't moving forward for part or all of a print but still needs to be retracted. The fixed tension type such as Bondtech BMGs don't suffer from this problem. https://somei3deas.wordpress.com/2018/05/11/bondtech-bmg-vs-e3d-titan-extreme-retraction-torture-test/
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Your explanation makes sense. Start off with your approach and check the result before going for something else.
Yes, I use firmware retraction for it. 4 BMGs doing the labour. It still grinds through the filament sometimes, but mainly with some soft wood pla filament. Well, I guess I could revisit the topic and try a retraction torture test like you did to find out the limits.
I am generally a big friend of letting the firmware do the work. Firmware retraction, setting temperatures for all tools in firmware (not in the slicer, slicer just says T3, T2, etc., Duet does the actual work), extrusion multipliers, etc. Not only can you print the same gcode on arbitrary tools (if it is a single color print), but also do testing for many different settings without reslicing.
For me, the whole multicolor printing topic is kind of bottomless, meaning that it is not ready for the final consumer. Especially your shot at fullcolor is challenging - both hardware and software(slicer) side. I am wondering if there is a slicer that lets you put full color on your object (like a bitmap)?
Quality wise you somewhat degrade by having to use a Bowden setup, which you countered by using a second xy axis. This is something that I am not willing to do and hence I am thinking if it might not have made more sense to use a prusa MMU with direct drive extrusion in my case.
But I have invested a lot in the current setup and it's working and so I think I should stick with it. In the other hand knowing you may perform better is nagging.
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@Wurstkarton said in My 6 input (5+1) mixing hot end:
For me, the whole multicolor printing topic is kind of bottomless,
That just about sums it up - having masochistic tendencies helps too
I am wondering if there is a slicer that lets you put full color on your object (like a bitmap)?
Not that I know of but this https://hackaday.com/2019/08/20/lithophanes-ditch-the-monochrome-with-a-color-layer/ is on my list of things to investigate
Quality wise you somewhat degrade by having to use a Bowden setup, which you countered by using a second xy axis.
This new hot end doesn't have the huge great cooling fan mounted on the top like the Diamond, which makes it quite a bit shorter. So maybe I will be able to drop the height of the upper "UV" gantry which will reduce the length of my Bowden tubes even more. I might be able to get them down to 100 - 150mm or so - we'll see.... The other thing is that the Bowden tubes on the Diamond exit the heat sinks at an angle of about 20 degrees, which means that they have to be curved to line up with the extruders. With my new hot end, the tubes should be very much straighter which should also help.
This is something that I am not willing to do
Have you considered using "remote" flex drive extruders like the Zesty Nimble ?
and hence I am thinking if it might not have made more sense to use a prusa MMU with direct drive extrusion in my case.
AFAIK, the Prusa MMU does not mix. It just allows you to automatically load different filaments but you can only print one at a time. And have you seen the size of the purge tower it produces?
But I have invested a lot in the current setup and it's working and so I think I should stick with it. In the other hand knowing you may perform better is nagging.
Which brings us back to your first sentence "..... the whole multicolor printing topic is kind of bottomless". -
@deckingman Kiss slicer supports applying colour via a bitmap image now and supports unto 12 extruders now
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@Dougal1957 interesting. I was originally on slic3r&cura, but now switched to iceSL for having the possibility of coding parts of the slicing myself easily in lua.
How about kisslicer in this regard?
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@Dougal1957 said in My 6 input (5+1) mixing hot end:
@deckingman Kiss slicer supports applying colour via a bitmap image now and supports unto 12 extruders now
Wow, that's interesting! I really must try to find the time to start playing with it.
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Part 3 is out now for anyone who might be interested https://somei3deas.wordpress.com/2020/03/09/my-6-input-mixing-hot-end-v2-part-3/
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......and now part is out https://somei3deas.wordpress.com/2020/03/12/my-6-input-mixing-hot-end-part-4/
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Not much comment, but still reading!
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Just had a look at your new posts.
Congrats! Looks good!Strangly, the sealing issue did not come to my mind during your previous articles. I also had issues with the Cyclops in this regard... Depending on how you want to tackle this, there is always the option of making a high temperature gasket - even though I do not really like this (you may destroy the gasket if you disassemble your parts and need to create a new one every time).
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@Wurstkarton I had thought that it might be necessary to use some sort of sealant between the plates which make up the mixing chamber which I simply assembled "dry". But now that I've been able to remove the hot end and inspect it, the problem was as I thought. Simply that the upper plate which the heat breaks screw into had distorted at the (unclamped) edges. There were no leaks from the area around the central heat breaks which are surrounded by screws. Nor were there any signs of leakage anywhere else - including the joints between the mixing chamber plates. I've taken those plates apart completely and can see that there is filament in all the slots and holes, but no seepage whatsoever. So I'm fairly confident that lapping the plates perfectly flat is a technique that works without the need for any sealant - (providing that the plate is clamped in such a way that there are no unsupported edges). But for sure, rtv silicone is always a possibility if all else fails. I also have some Boron Nitride paste that I could try if needs be.
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I'm up to part 7 of my journey now https://somei3deas.wordpress.com/2020/04/18/my-6-input-mixing-hot-end-part-7/.
I haven't been posting updates here, but this latest post might be of interest to some, as it contains details of how I use the nozzle as a Z probe/homing switch. This is an extract...
"I now have a Z probe / homing switch that is arguably as precise and repeatable as they come, has zero offset between the physical nozzle position and the switch trigger point in X, Y and Z, has no hysteresis, does not need any deployment mechanism, does not need any signal conditioning, and is self compensating in that the physical end stop is intrinsically linked to the electrical trigger point. Oh, and it was cheap"................
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I've just published part 8 of my journey https://somei3deas.wordpress.com/2020/04/28/my-6-input-mixing-hot-end-part-8/. There is a little YouTube video embedded in that post which shows my "nozzle as Z probe" (that I gave details of in part 7) in operation. I'm quite chuffed with the way that turned out.
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I'm now up to part 12 of this particular journey but I've moved over to doing updates via my YouTube channel rather than my blog. Link here if anyone is interested. https://www.youtube.com/watch?v=Sl4DMXJHvnU
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@deckingman Does that signal the end of the written form entirely for you? No more blog posts?
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@Phaedrux said in My 6 input (5+1) mixing hot end:
@deckingman Does that signal the end of the written form entirely for you? No more blog posts?
Undecided but probably yes. There is a chance that I could make a small amount of money from YouTube. It would never be much as it's a bit of a niche market and I don't do reviews which is what drives a lot of traffic. But if I could get some income, however small that might be, it would help towards my development costs (although knowing me I'd likely spend it on photography gear).
There are two criteria one has to meet. The first is to get 1,000 subscribers and I've recently made that target. The second is to accumulate 4,000 public viewing hours in a 12 month period. I only have 1,600 or thereabouts. So I have some way to go with that.
But I'm always open to feedback. Which format do you prefer?
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I like both. Youtube more for entertainment/edutainment. It's good to see things in motion sometimes, but it's also nice to be able to read a long form description with technical details and study a still high quality photo.
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