Reliable dual extrusion
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Hi,
I saw this thread (https://forum.duet3d.com/topic/15905/nozzle-wipe)
and wanted to ask anybody who has a dual extruder system (that works and uses it)
To maybe share their setups.Starting off with what i believe is a must for reliable dual extrusion:
- A system which mechanically lifts or otherwise separates the support nozzle away from the build plane in order to not scar the surface of the print with ooze. In my opinion the best solution is either a lifter or an IDEX system.
Tool changers are hard to make work in a heated environment - A way to lower the temperature of the inactive nozzle and heat it back up before it is selected (Cura works wonderful)
- A way to clean the nozzles reliably on every tool change, where the material that has been sitting and degrading is purged. In my mind a purge tower is unreliable (can fail) and also does not clean the nozzles.
Here is my implementation:
I mounted the support extruder on a linear rail that toggles it up and down similarly to an ulitmaker 3 with the help of a bistable mechanism. The model extruder is an ultra direct drive with similar drive distance to a hemera, but using bondtech gears. The support extruder is a bowden.
My wipe assembly consists of a 0.5mm silicone sheet and behind that a row of brushes.
The most important part is a sort of purge ledge that the extruder purges on to bunch the purge material up. I then stop it for 2 sec to cool off and then drive over the silicone sheet which flicks the ball away, and the brushes clean the nozzle. It is important that the purged material is bunched up because otherwise it can get stuck on the nozzle or heat block and or trap itself in the brush. There are two brushes for the two nozzles because of the different Z height. If you had an IDEX or tool changer, you could probably get away with a single.
!Here is a print example.
I use ABS with SR-30 support material. It is available from different resellers, and now even from makerbot.
I use this combination in a 90°C chamber environment.
IMG_8559.JPG
I can get this combination to work with PC-PBT in a 110°C chamber, but the adhesion is a bit less.
For nylon i use the AquaSys 120 filament, they claim it works with almost anything but in reality it only works with nylon reliably enough to call it a working combination.
Since my printer can handle 220°C chamber i want to get it working with stuff like ULTEM, PPSU and PEEK, but i still have not found a good way to protect the heat block from debris sticking to it at the 400-ish temperatures.
If anybody has also managed to do dual extrusion reliably, please post up! I´m eager to see solutions
- A system which mechanically lifts or otherwise separates the support nozzle away from the build plane in order to not scar the surface of the print with ooze. In my opinion the best solution is either a lifter or an IDEX system.
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@NitroFreak Just to clarify. When you say dual extrusion what you actually mean is dual nozzle or dual hot end yes? Because there are other ways (I currently have 6 extruders feeding a mixing hot end).
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I think in general you did a great job of describing the challenges. Many people experimenting with how to wipe, etc. No widespread perfect solutions yet.
There seems to be a lot of focus on toolchangers lately. I don't see why they are fundamentally incompatible with high chamber temps. Water cooled motors are hot ends work great. I say this because I tried every kind of dual out there, fixed, elevating, tipping, you name it. I gave up on all of them fairly quickly. Lately, I've built a "Jubilee" and it is producing good prints. To be clear, I am NOT heating it, but I believe it could be done with a bit of thought and meticulous work.
@NitroFreak said in Reliable dual extrusion:
A way to lower the temperature of the inactive nozzle and heat it back up before it is selected (Cura works wonderful)
Duet does this with no help from the slicer (or can do, if you put the commands in the toolchange macros).
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@deckingman said in Reliable dual extrusion:
@NitroFreak Just to clarify. When you say dual extrusion what you actually mean is dual nozzle or dual hot end yes? Because there are other ways (I currently have 6 extruders feeding a mixing hot end).
Yes that is what i mean. The problem with mixing hotends (in my mind) is that they need a large amount of purge, and even then they cross contaminate which can severely weaken the part, especially when a soluble material is used.
Also, you would always need to alter the temperature for the different materials which takes a long time, plus the extended time for purging, it probably easily adds a whole minute per layer to the print time.If you have two nozzles, the changeover and purge time is probably closer to 8 seconds for me.
So, for engineering purposes a dual nozzle setup is best.@Danal said in Reliable dual extrusion:
I think in general you did a great job of describing the challenges. Many people experimenting with how to wipe, etc. No widespread perfect solutions yet.
There seems to be a lot of focus on toolchangers lately. I don't see why they are fundamentally incompatible with high chamber temps. Water cooled motors are hot ends work great. I say this because I tried every kind of dual out there, fixed, elevating, tipping, you name it. I gave up on all of them fairly quickly. Lately, I've built a "Jubilee" and it is producing good prints. To be clear, I am NOT heating it, but I believe it could be done with a bit of thought and meticulous work.
@NitroFreak said in Reliable dual extrusion:
A way to lower the temperature of the inactive nozzle and heat it back up before it is selected (Cura works wonderful)
Duet does this with no help from the slicer (or can do, if you put the commands in the toolchange macros).
You are correct, however I think the Cura version works a little better because it can pre-warm the second nozzle while the first is still printing, based on a warm-up time (for me, 2.0°C per sec).
Also, it can say, if the nozzle is inactive for a period shorter than , let´s say, 45 seconds, the nozzle will not be cooled down. The Duet board would need a massive look ahead i think.The problem i have with toolchangers is that they don´t work with the bellow system that separates the motion components and cold end from the heat. It is an elegant solution. The patent runs out this year.
I´m not a fan of watercooling because of the added complexity that can also fail, and even then it can´t cool all the linear rails which would suffer a reduced lifespan.
Even if you could, you wouldnever achieve an even chamber temperature which is crucial for warp free printing, if you have all sorts of (cooler) components with a temperature differential inside the chamber. It will produce temperature gradients that will produce cold drafts of air. -
@NitroFreak said in Reliable dual extrusion:
You are correct, however I think the Cura version works a little better because it can pre-warm the second nozzle while the first is still printing, based on a warm-up time (for me, 2.0°C per sec).
Also, it can say, if the nozzle is inactive for a period shorter than , let´s say, 45 seconds, the nozzle will not be cooled down. The Duet board would need a massive look ahead i think.That is quite nice. I will take a look, thanks!
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@Danal said in Reliable dual extrusion:
@NitroFreak said in Reliable dual extrusion:
You are correct, however I think the Cura version works a little better because it can pre-warm the second nozzle while the first is still printing, based on a warm-up time (for me, 2.0°C per sec).
Also, it can say, if the nozzle is inactive for a period shorter than , let´s say, 45 seconds, the nozzle will not be cooled down. The Duet board would need a massive look ahead i think.That is quite nice. I will take a look, thanks!
Its awesome - look specifically at the "Heat Up Speed" and "Cool Down Speed" (if you have the Printer Settings plugin installed). Effectively the slicer is performing the look ahead, rather than the Duet board.
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@sebkritikel said in Reliable dual extrusion:
@Danal said in Reliable dual extrusion:
@NitroFreak said in Reliable dual extrusion:
You are correct, however I think the Cura version works a little better because it can pre-warm the second nozzle while the first is still printing, based on a warm-up time (for me, 2.0°C per sec).
Also, it can say, if the nozzle is inactive for a period shorter than , let´s say, 45 seconds, the nozzle will not be cooled down. The Duet board would need a massive look ahead i think.That is quite nice. I will take a look, thanks!
Its awesome - look specifically at the "Heat Up Speed" and "Cool Down Speed" (if you have the Printer Settings plugin installed)
Exactly, it works like magic
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@NitroFreak said in Reliable dual extrusion:
@deckingman said in Reliable dual extrusion:
@NitroFreak Just to clarify. When you say dual extrusion what you actually mean is dual nozzle or dual hot end yes? Because there are other ways (I currently have 6 extruders feeding a mixing hot end).
Yes that is what i mean. The problem with mixing hotends (in my mind) is that they need a large amount of purge, and even then they cross contaminate which can severely weaken the part, especially when a soluble material is used.
Also, you would always need to alter the temperature for the different materials which takes a long time, plus the extended time for purging, it probably easily adds a whole minute per layer to the print time.If you have two nozzles, the changeover and purge time is probably closer to 8 seconds for me.
So, for engineering purposes a dual nozzle setup is best.I think for further clarification what you really mean is dual extrusion with different materials. In which case I agree with your comments and that multiple hot ends are probably the best approach for using different materials. For multiple colours of the same filament, or multi filaments which have similar temperature requirements, then the purge requirement for a mixing hot end can be minimal and it is often possible to accomplish any purging during the infill where it won't be visible (which of course has zero waste in both filament and print time).
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Nice!
How the nozzle lifting mechanism work ?
