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aehM_Key wrote: Here you go: http://vimeo.com/68489641 .
Ask Kisslicer why it's producing such crazy moves
You can see the extruder not only moving, but also tilting, which requires also less force.

(BTW: I changed the tube fittings.)

Wow that's crazy! I can't argue with the tiny bowden tube. You must have retraction dialed in now.

No, I didn't mean shorter bands attached at the top of the frame. I was talking about attaching them to the carriages just above where the arms are attached. Not so much force difference there, because the carriages move along with the platform, and with the extruder.

Looking at the video, I see it does a great job of damping the smaller fast motions, but the extruder sure bobs around a lot. Have you ever seen it hit one of the arms during a long horizontal move?

- dan

I call it the bobble head extruder. better yet the "bobble-struder" or "bob-n-strude"

dbarrans wrote:No, I didn't mean shorter bands attached at the top of the frame. I was talking about attaching them to the carriages just above where the arms are attached. Not so much force difference there, because the carriages move along with the platform, and with the extruder.

Ah, sorry, I got you wrong.
I was thinking about this, but then the steppers would have to carry the whole mass.

dbarrans wrote:Have you ever seen it hit one of the arms during a long horizontal move?

No, but this is one of the things I have to monitor. Especially when I try to print at the outside of the heat bed. I can make the tube a bit longer if this happens.

cambo3d wrote:I call it the bobble head extruder.

Whatever makes you happy

Try print a stretchlet at high speed - I'm curious to see if it sets up an ugly resonance...

g.

It would take a bit of work to implement, but I'd think a separate set of arms with separate steppers to drive them would work out better. That would remove the possibility of resonances causing problems with the elastic interface between the extruder and the hot end. The idea is to move the extruder along with the hot end platform while filtering out the high-frequency movements of the hot end. Of course, it would also take a bit of programming to make it work.

I wonder if much of the benefit of this setup might be had by using the simpler approach of a fixed extruder mounting that would place it as low as possible in the center, just above the hot end in home position. This would allow a shorter Bowden tube, but not nearly as short as the flying extruder.

I guess I'm trying to solve theoretical problems that haven't been observed yet with the flying extruder. Maybe I should wait and see whether these are real problems first.

- dan

Of course, it would also be simpler to use more powerful steppers along with a stronger framework that can handle the acceleration with more weight on the platform. That's the brute force method, but might save a lot of trouble in the long run. Just don't get in the way while it's running.

- dan

I have to wonder if it wouldn't be better to use counter weights rather than elastic. If they were mounted inside a tube, they might even function as a damper to the "bobbling".

This might not belong here whatsoever and may already have been suggested - but going back to the problem that's trying to be solved - the imprecision of using the tube.

What if there were two cold extruders?

One with a very small stepper motor sitting directly on the head and another - the existing extruder sitting stationary.

The original would push the filament through and do most of the work. The second would work in tandem relieving the stress from the tube, evening out the feed and removing the variability that the tube introduces.

Questions: Could they work synchronously? Would the tube still introduce issues that the second would only exacerbate?

If you're using an extruder on the end effector, would you need a bowden tube at all? Maybe a feed device to ensure that there was always some slack in the filament leading to the direct drive extruder.

The problem with the stepper is the weight/speed relationship. The selling point of the delta is speed at hopefully +25mm/sec.

Can you use three spring attached to the top which could act the same. This would free the space to remove parts from bed.

I like the idea of getting a small stepper motor with as many steps per degree as I can find, and then printing up some mounting hardware to put it on various hot-ends. That should do the trick. A lot of the mass in this mod is done away with if you start with an EZStruder rather than the "Steve's" extruder. I've seen videos of someone printing at decent speed with a QUBD head, which is a stepper motor and hot-end in one. He has some info and video here: http://www.kronosrobotics.com/3d/rostock/

626Pilot wrote:I like the idea of getting a small stepper motor with as many steps per degree as I can find, and then printing up some mounting hardware to put it on various hot-ends. That should do the trick. A lot of the mass in this mod is done away with if you start with an EZStruder rather than the "Steve's" extruder. I've seen videos of someone printing at decent speed with a QUBD head, which is a stepper motor and hot-end in one. He has some info and video here: http://www.kronosrobotics.com/3d/rostock/

Why does the number of steps matter? It seems that what you want is a good torque to weight ratio.

Industrial robots have similar mechanisms to keep the wires hoses suspended lightly above the robot.

Something like this could be used as it "might" have costant pull for most of the travel range.
http://m.banggood.com/Stainless-Steel-T ... 24361.html

I am considering doing something similar, but instead of rubber bands, did you try doing it using just counterweights ?

If you need some elasticity, maybe the counterweights could be attached using a spring ?

Does it make sense ?

Totally!

The rubber band solution was working great at the beginning, but they wore out over time, so I upgraded to the counterweight solution.
A plastic coated metal string is running over two ball bearing down to a moving weight.

The extruder is now really "flying" - negligible force influences to the end effector no matter at what position!

(In comparison to the "very new" Fly-n-Strude.)

MK

Lovely

Is that a space blanket heated build chamber?

Yes, it is. Get it above 40deg Celsius now.

It looks a little bit like a plant growing box.