Diamond 3 in 1 out nozzel setup for multispool prints

fma

Why don't you just set the mixer to 1/3-1/3-1/3?

deckingman

@cncmodeller I guess you should take a look at my blog (see my signature).

You are correct in that PLA will hydrolyse (become less and less viscous) when left at print temperature for an extended period of time. This isn't so much of a problem with PET-G.

There are things you can do to mitigate this but before I get on to that, there is another issue that you might not have considered as well. That is, when using mixing nozzles such as the Diamond, you have to retract all the loaded filaments and not just the one that is actively being printed. So if one or more filaments are not always moving forward, then the same section of filament will be subjected to that retract/unretrcat cycle which can wear the filament down or even wear it so much that the hobbed bolts no longer grip the filament at all. Sprung loaded extruders like E3D Titans suffer from this phenomenon, but fixed tension extruders like Bondtech BMGs do not (at least that is what I found I my testing).

So the best way to mitigate both those effects is to keep all the filaments moving forward, even if that is very slowly. The way to acheive that is to use filament mixing so that the main filament is (say) 96% of the total and the other two make up 2% each.

In the case that you have outlined above, you could use 3 tools. The first defined to use 96% of extruder 0 and 2% of extruders 1 and 2. The second tool would use 96% of extruder 1 and 2% of extruder 0 and 2, and the third tool would use 96% of extruder 2 and 2% of extruders 0 and 1. Obviously there is a slight flaw in this approach in that you would need a "filament low" sensor rather than a "filament out" sensor because there needs to be roughly 4% of a spool left when changing from the first filament to the second, and roughly 2% of a spool left when changing from the second spool to the third. To switch between filaments you could use a macro which would simply change tools when the filament sensor indicates that it is time to do so. Changing tools in such a case can be done "on the fly" without pausing the print.

Another alternative would be to use 33.3% of each filament in a single tool. Then all 3 spools would be used at the same time (but at 1/3rd feed rate for each one) so no need to change spools. Of course, the down side of that is when it comes to changing filament, you would need to change all 3 at the same time.

A third alternative would be to set each tool to use 100% of each filament but then you have the problems of hydrolysing and filament grinding during the retract/unretract cycles. The first can be mitigated by incorporating a tool purge in the tool change macro. So you simply dump the first 50mm or so of filament into a "bucket". The second problem is likely mitigated if you use something like Bondtech BMG extruders. From this test that I did https://somei3deas.wordpress.com/2018/05/11/bondtech-bmg-vs-e3d-titan-extreme-retraction-torture-test/ the sprung loaded E3D Titans ground right through the filament at between 7,000 and 8,000 cycles but the BMGs were still working properly at 23,600 cycles. I can't be sure if they would continue for an entire reel worth of filament but I suspect they would. Of course this is entirely dependent on the number of retract/unrectract cycles that the printed object requires.

Yet a forth alternative, but one that I haven't tried, would be to use 100% mixing ratios and switch between inputs every nnn retract/unretract cycles or nnn metres of filament. You would need to employ some sort of post processing of the gcode files to accomplish this.

HTH

deckingman

@fma said in Diamond 3 in 1 out nozzel setup for multispool prints:

Why don't you just set the mixer to 1/3-1/3-1/3?

He could do that - it's one of the options I set out above. The downside is that all 3 spools would need to be changed at the same time and after the first print, one would need to "guestimate" if there is enough filament left on the 3 reels to complete the next print. By using each reel sequentially, one has the option of fitting a new reel whenever it runs out and while the printer is using a different reel.

fma

This can be solve by using a ratio r1-r2-r3 not too far from 1/3-1/3-1/3, so each spool will end at a different timing.

deckingman

@fma said in Diamond 3 in 1 out nozzel setup for multispool prints:

This can be solve by using a ratio r1-r2-r3 not too far from 1/3-1/3-1/3, so each spool will end at a different timing.

Yes that would work too. So we can add this to my other 4 alternative methods.

fma

BTW, is there a simple, manual, tool to fuse 2 filaments, like the Palette does?

CNCModeller

Thanks very much for all the info. Im going to read the blog next. Some initial thoughts below.

I'm planning on printing with ABS but I expect that'll degrade just like PLA if exposed to extended time at print temperature.

So I really like the idea of tracking filament length so I can print out each spool one at a time. I've been looking into a filament alarm that tracks consumed filament against extruder steps as a print quality metric, it'd only take a tweak to alarm out the filament with a small percentage left.

This all needs some more thought but I also like the idea of simultaneous equal printing from each spool as I imagine the combined melt paths would act like a high flow nozzle giving me a higher print speed.

Food for thought...

Many thanks again!
Barry M

CNCModeller

It's also worth saying that my print style is effectively a complex vase mode print so I have very few retracts in a print...

CNC Modeller: Spiral 3D Print with Integral Structure
https://youtu.be/MQ3f92hDAdY

Thanks again!

Phaedrux

@fma said in Diamond 3 in 1 out nozzel setup for multispool prints:

BTW, is there a simple, manual, tool to fuse 2 filaments, like the Palette does?

I've seen it done with a hair straightener and a piece of PTFE tube.

deckingman

@cncmodeller said in Diamond 3 in 1 out nozzel setup for multispool prints:

This all needs some more thought but I also like the idea of simultaneous equal printing from each spool as I imagine the combined melt paths would act like a high flow nozzle giving me a higher print speed.

Oh yes! You get 3 times the melt chamber volume but also, each filament moves at 1/3rd speed of a "normal" hot end. So the time in contact with the hot surface is also increased 3 fold. The net result is very high melt rates as I have demonstrated here https://somei3deas.wordpress.com/2018/10/14/real-3d-printing-at-high-speeds-and-even-higher-melt-rates-with-a-large-nozzle/

T3P3Tony

@fma said in Diamond 3 in 1 out nozzel setup for multispool prints:

BTW, is there a simple, manual, tool to fuse 2 filaments, like the Palette does?

Predating the palette is @RichRap3D's filament fusing design:
https://richrap.blogspot.com/2011_06_01_archive.html
This works well and is relatively easy to make.

(as an aside, 2011! almost 8 years ago, where does the time go!)

fma

Thanks for the link!