Help for developt Pellets Extruder for Anthropomorphic Arm

Hello Everyone, The project we have in mind is to use Anthropomorphic arm as a huge 3D Printer. we have been thinking to adapt a Lyman Filament Extruder (http://www.thingiverse.com/thing:380987) modifying the nozzle to 1 cm. however that have arise many questions, that he hope we can pick your brain up :

* Is form for controlling the process of extrusion itself when you are using a single screw, which is the volume of plastic extrude ?

* Is possible to have retractions in the extruder ? The people who have done something similar (http://3dprint.com/52978/robotic-arm-3d-printer/ [youtu.be]) usually make continues geometries (spiral vase). make me wondering if is difficult to have a retraction in a system like this one.

* How to recalculate the Geometry of the Screw?, because I must be required much mire pressure for extrude 1 cm of material.

* As the size of the nozzle is quite high does the heating pipe has to be longer ?

Thanks in advance

I have build a heavily modified lyman so maybe could answer some questions based on my own ideas and experiences :-)

- extrusion volume can be controlled by controlling the extruder motor speed
- retraction might maybe be possible but will create problems with the plastic as it would introduce air into the melt. If working on this scale (10mm) and if I would build it I would go for installing a cutter at the nozzle end controlled by the retract code.

Imho I think that printing speed will be the most important component in this as it will determine how big the extruder motor must be and how much heat is needed. And from there on all other components will be selected/designed based on that.

The lyman is already using a 4.5mm nozzle so one easy modifications can get you to 10mm. However it's a horizontal model and I would think that for a robot arm you need a vertical model?

Have you considered running the pellet extruder in a fixed location and simply feed the fresh filament that it makes to a more traditional print head on the arm?

Hello Feing, I am open to any suggestion, the extruder for me seems to be the most important and difficult part a that is the one is using jasper-manger:

[www.3ders.org]

the problem is how to maintain a flux of plastic, even thought the pipes must bes hot as well. do you know this kind of pipes ?

@Frans@France, thanks for sharing your experience. i will do the test with the robot on Monday, I will try to deter the maximum speed. the how I can calculate the size of the extruder?

yes you are right my intention is to mount the extruder in the tip of the robot, so the new of the leyman's extruder needs to be horizontal is not so good.

The base design of the lyman makes it easier to move to full vertical model then the designs where the barrel has been cut for the entry of pellets. You only need to rotate\redesign the pellet hopper to make it a vertical version.

I have no idea how to calculate the extruder size but I would guess that from max speed and the needed 10mm filament you can get to total weight per time needed from the extruder via the materials specific gravity. I can get my extruder to do ~700grm/hour @4.5mm, stronger motor or a bit more heat would get it to 1000grm/hour. main issue at higher speeds is the consistency of the width but that is an issue of the wood auger used. "Real" extruder screw ($$) might solve that.

Hope this helps

Edited 1 time(s). Last edit at 11/12/2015 05:24AM by Frans@France.