i have an idea for my dual extruder setup to make it really compact. But i want to know first that it is really possible to configure in klipper before i continue with the design.
the extruding stepper needs to switch direction when extruder is being changed and the Switch_Extruder needs to complete a certain amount of turns and keep ON after it has turned to make sure that the filament can be pushed through.
i haven’t counted the gear ratio yet.
is it possible to configure this and if it is, how hard will it be?
I had a printer that had a hot end that did basically what you’re proposing - the Zortrax Inventure.
One stepper was used for extruding on each of the two nozzles while the other was used for moving one nozzle up and down as well as selecting the gear path for the extruder.
When it worked, it was quite good but after about 1,000 hours it became a nightmare with the dual path extruder ended up having the filament getting wrapped around it and clogging the system. The first time I repaired it it took about two hours but after a while I got it down to forty five minutes. I just did a search on “Zortrax Inventure problems” and I see that I was no alone.
Zortrax did replace the hot end BUT that did not fix the problem, the filament paths within the printer were worn which caused damage to the filament which caused them to catch and get wound around the extruder gears.
If you’re looking at the best two nozzle solution, I would recommend going with a traditional IDEX architecture.
but after about 1,000 hours it became a nightmare with the dual path extruder ended up having the filament getting wrapped around it
personally i dont see how this can happen when you contain your filament in PETF tubes as much as possible and make the entire system as strong and closed of as possible.
In the Inventure, there were no PTFE tubes in the hot end. They were used to bring the filament to the mechanical pieces of the toolhead which were largely brass. The overall printer mechanism was very complex - as originally designed, the filament was stored in cassettes from which the filament was drawn using extruder like hardware.
Thinking about it, there were basically two levels of extruders, one to bring the filament from the cassettes to the hot end and then the one in the toolhead which provided precise delivery of the material to it’s hot end/nozzle.
The hot end extruder handled both filaments (one typically being a support material) and which was selected was done by moving the toolhead to the left or right which would force one nozzle up or down and move the toolhead extruder hardware to clamp on one of the filaments so it wouldn’t move and unclamped the other to work with the extruder.
Would going with PTFE tubes as much as possible helped? I can’t really say as it’s not my area of expertise. The only comment I would make is that the printer was very mechanically complex with filament going a number of different ways as well as going through a very circuitous path.
Looking back at your original drawing, I’m not sure why you would use one stepper as the extruder drive with the other one selecting the operation - If you’re looking to save space, I would rotate the steppers about 30 degrees and offset them so the flanges don’t make the overall toolhead wider and you have one stepper for each hot end/nozzle with a slight offset/distance difference.
I want to amend my previous answer to this as saying “I don’t know” if having as much PTFE tubes as possible to “I don’t think it would make a difference”.
I’m not sure, but I think a big part of the issue was that the extruder drive teeth engaged with the filament, then were withdrawn and then engaged again.
I have to think that doing that would affect the mechanical properties of the filament, maybe breaking it and causing it to hold onto the teeth (resulting in the wrapping around the toothed extruder gear. I’m also wondering if the material on the other side of the extruder would affect things (as I said, in the Inventure, it used a water soluble support material) and maybe cause the filament to stick (I don’t think I ever saw the support material get wrapped around the toothed extruder gear - but don’t hold me to that).
I should point out that Zortrax did use quality materials in the two printers of theirs that I owed and, mechanically, they were very robust.
So, based on what I observed and after some time thinking about it, having more PTFE tube would NOT have improved the situation.
I repeat my recommendation of using only one extruder for each filament in your prospective toolhead.
Please don’t get me wrong Myke. I was just commenting, but my thoughts were on the extruder from @Jasper. What do you think about my last edit above?
Your lower drawing (showing the moving tension wheels coming down to be in contact with the stationary one) is how I envisioned things and why I’m talking about the need to lock the unused filament or else you don’t know exactly where it is.
Longer/more PTFE would definitely increase the friction but I don’t think it would be good enough to keep the position of the unused filament (especially if the toolhead is moving around). If I remember correctly, the Inventure had a brass piece that locked the unused filament in place as it switched over to the other filament.
I thought you were asking what happens when you switch which filament is being driven and how do you know exactly where the unused filament is and how to keep it from moving so that nothing oozes out of the nozzle and the filament hasn’t moved back so you’re extruding air when you switch over.
Looking back I’m guessing that you’re asking how do you set the extruder teeth force on the active filament?
The middle gear is the main drive for the filament, the 2 gears on the outside also have gears on the back and connect to those of the middle one onces brought in place. Then it becomes a dual-gear drive.
to keep keep force on my filament i am (currently) hoping that the gear ratio and stepper locking would be enough paired with the right angle at wich the switcher is put. so that it is not loose and also no too tight.
i am also looking if i can use a wormgear that way there will be no way that the filament can get loose when it is being extruder.
for keeping the secondary filament i place i haven’t got that may ideas for it yet…
but i wanted to ask first if this type of design was programmable into klipper before i continued my designing.
if you want, i can continue my initial design so that everything become more clear.
an idea of mine is to maybe lock the secondary filament using the switcher, but that is an idea…
Based on my experience, I think you have an uphill climb to get something working well and long term.
I just searched my email and found a few pictures I took showing the problems I had. Here’s one with the filament wrapped around the toothed extruder gear (you can see the different filament paths):
Here’s one with the filament wrapped around the toothed extruder gear
i see what you mean.
Sorry about being negative about your project - I do wish you good luck on it.
I understand your point of view. You experienced this before and are just trying to put me on a path that will be easier and more efficient, and i respect that. But as a young engineer that is trying to achieve something that is clearly hard (i like that, it means i will learn a lot) i will take on the challenge and throw myself in the deep once again.
i already have an individual dual-extruder design standing but that had some issues here and there and is relatively wide so i am not able to use the outer parts of my head bed.
if this really does not work out i can still return to the old design and make that more efficient. or do that first and then make this new design.
