Extruder torque transfer - is it worth trying

[Dinesh Kantheti]

By now all of you you might have known how much I hate my bowden extruder :)

Just as a thought, I want to explore the option of removing the the extruder motor and replacing it with a flexible shaft that transfer the rotary power from a stationary base to the moving extruder.  By this we may avoid a chunk of moving mass and also create more space for multi extrusions.  The filament tube can be tied to the flexi cable 
Question time:

1. Do you think it is a good idea to test?  
2. What torque do we require for pushing a 3mm filament.  
4. Can we have the reduction mechanism also away form the carraige and and have a direct drive on the moving carriage with hobbed bolt.
5.  Just trying to get some specifications of these shafts (example link).  Any further sources can be of help.

[Bogdan Bednarczyk]

I think you will and up with similar problems ....flex of the shaft, small maybe, but so is the filament compression
but could be wrong
Bogdan

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Cheers
Bogdan

[Dinesh]

Yes, what u said is technically possible, but looking @ the specs it should not be a big problem. Some one with a engg background may understand well. Also not sure if they work clockwise and counter clockwise. 

Dinesh

[Dinesh Kantheti]

Greg,

Welcome to 3D printer community. 

My experience states that it is more sensitive to any spec variations.  Precision of the entire mechanism is very critical.  I am not discounting the Bowden idea in totality. Please dont discard the idea of testing it. It has some advantages that traditional on-board extrusion will never achieve.  Once we go to dual or triple extrusions bowden should be the way to go.

Not sure about the "inner core" from a tig welding gun/lea".  Could you post some more info about it (link or photos). 
Having a two steppers is definitely a good idea.  A small stepper could do the trick.  and least will reduce the weight to 1/4th.  It may add another point of failure, but worth trying.

Feel free to post more about your work.  

On Tue, Apr 16, 2013 at 12:18 AM, Greg Richens <greg.r...@gmail.com> wrote:

Hi Dinesh

I'm very new to this topic and looking to build a 3D printer. I have been considering the lighter faster bowden extruder idea over the more "traditional" extruders but could see these problems coming  One thought was to use the  "inner core" from a tig welding gun/lead these come in different inner diameters for different wire sizes and have a strong sidewall and still remain reasonably flexible. 

I also question the amount of control over feed-rate with this system since the filament must have some compression and cause some lag. (or can the lag be cancelled out by timing  meaning slight feed control before the event)

One thought was to use two motors. meaning a smaller motor above the extruder to provide better feed control. This would increase the mass but be less than the "traditional" heads.

Please take my comments as from a beginner! 

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[Hurgh]

"One thought was to use the  "inner core" from a tig welding gun/lead"

You could also look at using simple break cable from a bike shop, something like:

http://www.bicyclepartswholesale.com.au/contents/en-us/d81_bicycle_cable_housings.html

It will do the same thing, although the inner diameter may be too large.

Allan

On Tue, Apr 16, 2013 at 12:18 AM, Greg Richens <greg.r...@gmail.com> wrote:

Hi Dinesh

I'm very new to this topic and looking to build a 3D printer. I have been considering the lighter faster bowden extruder idea over the more "traditional" extruders but could see these problems coming  One thought was to use the  "inner core" from a tig welding gun/lead these come in different inner diameters for different wire sizes and have a strong sidewall and still remain reasonably flexible. 

I also question the amount of control over feed-rate with this system since the filament must have some compression and cause some lag. (or can the lag be cancelled out by timing  meaning slight feed control before the event)

One thought was to use two motors. meaning a smaller motor above the extruder to provide better feed control. This would increase the mass but be less than the "traditional" heads.

Please take my comments as from a beginner! 

On Wednesday, 21 November 2012 23:32:41 UTC-8, Dinesh Kantheti wrote:

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[Rob Gannon]

These cables won’t work because the extruder needs considerable force and needs to be able to turn forwards and backwards quickly. The cables would have a loss of motion at the other end while tension is built up.  It is the required action of both extruding and then retracting the filament on moves to avoid blobbing that makes Bowden extruders trickier, which would also be an issue with the welder or brake cable setup.

 

Maybe some sort of splined telescopic shaft with CV joints at each end might work better.

 

There are many ways to improve printing performance and quality before trying experimental extruders like this. I would suggest using a standard direct drive extruder to start with, then get the printer performing as well as you possibly can. When you reach a barrier that can only be overcome with a Bowden or other style of extruder then take that step.

[Dinesh Kantheti]

Also the internal friction due to spirals inside these cables will not work for a Bowden.  This should be minimum i.e. just enough to hold the filament

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[Gmail]

 

Here is a site that sells MIG torch inner liners.  These run the length of the cord to the welding torch.

For Aluminium welding a Plastic style is used. In most MIG system the wire is pushed through the liner to the torch. The inner itself is reasonably flexible and the diameter can be matched to the wire (Should)

I haven’t looked into this much but there could still be some merit in this with correct diameter & material choice.

http://www.weldingandgasestoday.org/index.php/2012/06/line-them-up/

 

Greg