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pivoting extruder to relieve bowden tube tension experiment

Posted by Milton 
pivoting extruder to relieve bowden tube tension experiment
October 04, 2016 06:37PM
I am experimenting with this, it's working very well.

The effector movement pivots the extruder rather than bend the tube, releasing forces involved.

Sometimes with J head and other slot mounted hotends they pivot, I have been told (my hotend has screw mounts). This pivoting is from buildup of forces. The hotend pivots from the torque of something, I suspect the bowden tube is the culprit, along with the screw drive action of a coiled filament. The pivoting extruder mount allows less buildup of forces, if the pivot was not less opposing force on the effector than the tube, the tube would simply bend. This allows a closer extruder, shorter bowden tube, and less motion system unrelieved forces buildup.

Still experimental the setup in pictures was the ad hoc first try which works great, working on a more 'designed and engineered' version now. Tube can be quite a bit shorter Mount closer, as long as at higher layers the pivot of the extruder does not enter the range of movement of the effector. Thinking of incorporating side panels and controller and filament mounts to the pivot vertical axle, change axle from coarse thread cheap rod for test to nice anodized aluminum tube, which will be wire routing as well. Also maybe some angled brackets so the pivot mount vertical is also a good overall frame stiffener.

Suggest others with effector tilt or rotation issues consider this setup and developing something like it for their printers frame structure. It allows bowden to not push or pull as effector moves, extruder pivots instead. Can see obvious relief of strain as extruder moves instead of tube bending, seems to have made retraction more effective and less pressure issues. Its brand new only tested a day so lots of testing to do.

Filament coming off a spool is in the shape of a helix. When filament is pushed through the system this twist has be allowed to continue or it creates undesired forces in the extruder/bowden/effector system which can transfer to the ball joints. I suspect the forces cause the filament to work with or fight the bowden tubes natural curvature based on the physical setup. Left hand turn on bowden curvature from its being coiled at some point then the filament should be positioned to want to follow the same general twist with its own material memory. Not sure how much this matters, for my setup and retraction problems it seemed to help as well.
Re: pivoting extruder to relieve bowden tube tension experiment
October 04, 2016 07:02PM
Side note, I have some experience with cables hoses and lines of various kinds. Several years as a dive tender for commercial divers using surface supplied air, handled and maintained the air lines and compressor operations. Unloading fishing boats using small lifts and cranes both from a dock and at sea (were you really focus and learn how the drum size and cable diameter effect the twisting of suspended cargo). A few years installing network cable in industrial settings, probably thousands of miles of cable run through ceilings and floors of schools, hospitals and defense contractors back in the 90's when ethernet was new. Can sew a nice jacket, can fake being a tailor and make and cut patterns, use a sewing machine, just takes me twice the time to plan and execute a body fit design as it's not my focus (can make a pack or bag fairly quickly). Surfboard leashes, was dealing with the twist from badly packaged monofilaments in my teens in the 80's. Breakage being possible drowning in large surf it was a serious thought process at the time.

I find that filament is familiar to me in many ways, what it will do and how I might improve the handling of it as it is tensioned. I hope my experience can help but its experimental, no guarantees of anything other than good tinkering fun if you love tinkering with your printer.
Re: pivoting extruder to relieve bowden tube tension experiment
October 06, 2016 06:25AM
Nice idea and definitely worth doing if you choose to have a bowden setup.

However you can set things up to follow the hot end with the extruder much more closely, and reduce your bowden tube to just 10-15cm by using the flying extruder, which is essentially a more extreme (but highly successful) version of what you have done. Or even better, use a direct drive extruder mounted on the effector, in the form of a flexible drive extruder such as flex3drive or Zesty, which keeps the mass of the motor off the effector.

You are clearly a very innovative person, but I wonder if you have solved a problem that's already been solved. Have you got any thoughts on a self calibrating extruder i.e. an extruder that can monitor actual filament flow and feedback to the controller to ensure the volume of filament required is always delivered?

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Re: pivoting extruder to relieve bowden tube tension experiment
October 06, 2016 04:00PM
Multi materials, want to not be limited when I transfer to that after learning a bit more about single extrusion, since it appears to be the future. I can do 3-4 extruders on the pivot, or more. planning 3-4 to adapt the new Prusa system to a delta. Imagine 8 extruders on that setup... Like taht visual? I do.

On extrusion. I have some ideas based on current and near future sensing technology but they are way outside my budget and ability to prototype right now.

Not sure about sharing them as they are conceptual thoughts and I am sensitive to the naysayers dissuasion from exploring new paths, try to avoid them. they dont stop me but they make me feel less happy about humanity in general.

here is the 4 extruder setup I am working on, just a render of what I am still building. Not even sure what hotend to use, may machine my own, budget is super tight for messing about with 3d printing.

Edited 1 time(s). Last edit at 10/06/2016 06:15PM by Milton.
Re: pivoting extruder to relieve bowden tube tension experiment
October 06, 2016 06:29PM
Yeah I'd certainly agree flying extruder might work for 1/2 extruders but 4 would be pushing it. I think its Aussiephil who's flying 4 of them(ish) not sure how successful that is yet. Your proposed scheme would work well for that many extruders.

Keep it up, you've got some good ideas and a fresh way of thinking which is what something like reprap needs.

Apologies if I sounded negative, I'm not - just don't want you to spend a lot of time doing stuff that's already been done, when there's things that haven't been done waiting to be discovered.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Re: pivoting extruder to relieve bowden tube tension experiment
October 06, 2016 07:59PM

apology not needed. I am sensitive, yep. There are reasons, but to go into them all, ugh. one is that in a society where lack of emotion is considered maturity it leaves the psychotic people that do not feel emotions at a distinct advantage. They abuse others emotional nature to gain social dominance, fake emotions when necessary to retain control, and we have a society that is on the verge of species extinction to maintain a status quo and a capitalist lifestyle for 1% of the population. I have no intention of proceeding along that same path, so I display honest emotion. Partially hoping that if my display allows others to express any little amount I will 'take one for the team' and try to push boundaries so others have more room to breath.

insane species so I am a bit sensitive, as I try to help it survive long enough to mature by just trying to do things differently. not even sure I am right, I am not that crazy as to form a perception of my actions as any less fallible than anyone else, but things just cannot continue as they are or experts say and my own life experience seems to confirm that no one has any grand kids and some other species gets to try and reach the stars in a few million years. The abuse of emotions to control the average person, to make a society based on perception of status dictated by like 5 media outlets, the concept in the business world that emotion is bad, as they push us all towards massive environmental change so a very few can use all our shopping decisions as indicators of their social status? Emotion is bad for the selfish that would ruin us all, yes, for our species survival it is necessary and nature provided it for a reason.

My theory is that the situation of a totally dominant species developing a fatal flaw in its own social structure that causes its extinction makes sense as far as checks and balances in nature. I believe the situation where those devoid of emotion and empathy are at the greatest advantage is probably reflective of this.
Re: pivoting extruder to relieve bowden tube tension experiment
October 06, 2016 08:32PM
forgot to address one crucial thing, you cannot improve what has been done unless you experience it. this was taught to me by a former head of design for a major car manufacturer and his instructors in a design program at a university, all successful designers. I built a mini kossel to understand 3d printing better not to have a good 3d printer, but then my designer education and maker background took over and I had to redesign it. I have only had an FF printer for maybe 5 months now so I have a ton of stuff to repeat that others have done to understand it fully and then move forward. I am a quick study, I see the value in the thought process and the ability to conceptualize systems better by building disassembling and rebuilding repeatedly, do not worry about me repeating what others have done in any way. I view it as a valuable process towards innovation.
Re: pivoting extruder to relieve bowden tube tension experiment
October 07, 2016 02:38AM
Would you care to post a short video of this in motion? I am getting a hard time to understand the benefits of it based on your description smiling smiley. Just kidding smiling smiley
Re: pivoting extruder to relieve bowden tube tension experiment
October 07, 2016 01:27PM

Have you thought about pulley and counter weight system that elimate stepper motor and lead screw?
Re: pivoting extruder to relieve bowden tube tension experiment
October 10, 2016 04:46PM
First of all sorry for being so touchy, going through a tough time in life.

yes I have thought about pulleys and counterweights, but I dont think it will work that well versus controlling the extruder height through software.

This setup is having some issues with line thickness as extruder pivots in some configurations but not others. It's a bit complicated figuring out the best height for full print area, best length for relaxed curvature, and working out issues with the tube bending at the ends and staying straight through the middle which is not what I wanted. I am looking for a gentle progressive curvature maxing out at middle with the greatest radius for the setup. It may be the PTFE I have was on the inner part of a spool and is coiled to tight naturally. It might be that the movement slowly is making the bends at the ends and straightening the middle. I may need some printed clip on curvature guides to force the curve to the middle, or possibly stop the extruder rotating altogether and rethink it.

Experiments continue. Its working, retraction control and stringing much better but again some lines are narrow. It seems to be due to bending at the ends of the Bowden, it's not skipping but the tube ID and movement are causing slight under extrusion as the filament is allowed to fill space rather than push forward on certain movements, is what appears to be happening. It seems to be when moving away from extruder and straightening the tube. Just slightly thinner but enough to notice gap. But then it stops doing it and the same movement extrudes a full width line. Still in the stare at it and wonder 'whaaat?' stage tongue sticking out smiley

Sorry again being short tempered, will be posting only pics for a while, brief descriptions maybe, and not replying much, not that replies are not worthy of responses but I am just way too stressed over RL stuff to deal with the internet.

Thanks to everyone that replied, suggestions noted and appreciated.
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