Nurdle extruder collection spool.

I am currently very close to having a working Nurdle to filament extruder. So now some way of collecting the hot freshly extruded filament is required. My first thought was to automate an existing cable spindle so that it slowly rotates to take up the  filament as it comes out of the extruder.

A large cable spindle that the extruded filament could be coiled onto.

Right away there are a few problems with this idea. After extruding around 30cm of filament its own weight becomes enough to cause it to pull away (string) at the point where it just extruded and so still molten. So the tension caused by a slowly rotating spindle will also cause the filament to stretch and break at this hot point.

On possible solution to this could be to have a small 12v fan (image below) directed at start of the extruded filament so that it becomes cool enough to be handled. At this point, around 10cm beneath the extruder, two rotating shafts could gently grip the filament on its way to the spindle. This would take up any tension created by the spindle or the filament its self so that no force is applied onto where the filament exits the nozzle.

From bottom to top: The proposed feeder for the extruded filament, a 12v fan and a cylindrical blower fan.

In the image above I have two salvaged stainless steel shafts that could be placed together to grip the filament see between them. The rubber could be cut to shape so the filament doest lose its round profile. The filament would then be cooled further by a vertical mounted blower fan, also seen in the image above.

Here is a sketchup of the whole idea.

A sketchup depiction of the setup.

The top object is the drill press, the bottom is the spindle. The spindle and the board its mounted on is suspended by a weigh scale. This is so the amount of filament spooled can be known on the fly. A DC motor drives the spindle and a second motor drives the feed rods at the top. A fan is located with the feed rods and level with the spindle (the shaft looking thing).

Before investing hours in building this I’m interested to hear if anyone else has a better solution. So if you have any thoughts at all please let me know.

Advertisements

About Richard

I am a PhD candidate in Materials Engineering located in Melbourne, Australia.
This entry was posted in DIY Granular extruding and tagged , , , , . Bookmark the permalink.

15 Responses to Nurdle extruder collection spool.

  1. It isn’t a requirement, but it could be useful if you could, in a controlled fashion pull the filament with a stepper motor, to achieve exactly the right thickness (probably requires a measurement module). It would also help create the right amount of tension to avoid too much curling before it is spooled. It could be done with feed-forward or a feedback mechanism (when the thermoplast is still well above its Tg). Or you could just ‘roll it out to the right size by pinching it through two wheels (at least one idler) with a U-groove (or semi-O groove or whatever you’d like to call it).

    Strategically cooling it at some point could also prove useful for consistency’s sake.

    It’s not straightforward, but we could alleviate the dependence on high-tolerance filament by having measurements of its thickness. Therefor the ‘measurement module’ could create a meta-file that goes with your filament. Alternatively, every RepRap could be fitted with a measurement module. This reduces the need to calibrate it when changing materials and you can use slightly varying filaments because the machine adapts to the right “feed length in times surface” / “volume output” ratio.

    But I do urge you to start simple. Still, I wanted to just get the idea out.

    • Richard says:

      The ‘controlled stretching’ method you described is what some commercial extrudes use I believe. Another problem I have just come across is that as the spool of filament begins to fill, the amount of filament spooled for every rotation increases. A bit more information here. I hope I can get around this problem with some kind of simple tension switch, but thats a problem for another day.

      My hope is that if I can get the auger drill bit turning at a constant rate, and thus supplying a constant pressure, it will produce a constant filament diameter. Therefore I could avoid all the problems and complications that come with trying to measure and adjust stepper motor speeds. It might be wishful thinking on my part, but time will tell.

      All in all, the spooling of the filament is turning out to be a lot more complicated than the extruding of the filament.

      • Erik says:

        Couldn’t you just run a thread or rope along the axle and hang a big weight from a pulley. If you use a smaller radius pulley, you need a bigger weight but less rope. This will tension it by itself. Also, spooling horizontally might be something to think of, although somehow vertically seems more appropriate here…

      • Richard says:

        The rope and weight idea is simple but effective, perfect for what I need. Now why didnt I think of that?

        I will definitely give it a try.

        I could modify the extruder feed hopper to work horizontally if so required but I’m unsure how much it would help.

  2. Jon Katz says:

    Would it be possible to have the filament enter water right at the exit, it seems like the sooner it gets cooled the smaller the chances of distortion are

  3. As Eric S. Raymond famously coined as “Linus’ Law”: “Given enough eyeballs, all bugs are shallow.”
    I love how a varied audience can interact and produce better (and far more creative) results than a homogeneous team of ‘specialists’. Its what makes RepRap (and open source projects in general) innovate so fast.

    • Richard says:

      I couldn’t agree more.

      The last 3 years of my undergraduate degree have all been structured around varied ideas and diversity. My hope is that by having chosen units in a lot of different areas (physics, maths, food chemistry, environmental chemistry, astronomy, atmospheric science, geology, materials science, science communication and mandarin chinese) I will have a broad background of knowledge to draw ideas from when I finally move into a research based career.

      Only time will tell if it pays off.

  4. araspitfire says:

    Someone recently posted images on IRC of filament extrusion where there was a long tray of water below the multi-holed extrusion head.. they pulled the hard filament out of the tray, keeping a specific angle on the filament exiting the head, as it entered the water…

    Al…

  5. jean-paul says:

    Think of it!

    And if the filament is too hot, why not have a bit of the loop go threw a water filled fish can 😉 before going onto the spindle?

    • Richard says:

      I like the fishing reel feeder idea. I will need to eventually adapt something similar in order to feel the whole spindle correctly.

      As for a can of water idea there are a few problems that put me off it. Mainly that you would need a very big can of water to passively dissipate the constant flow of heat or some active way of removing it such as fans.

      So a form of water cooling will be a last resort at this stage.

      Thanks for the comment.

  6. Joel Clemens says:

    Its been over half a year since any news on this, have you made any progress? I want to suggest a way for constant tension spool/reel…. I’ve seen this done on toy helicopters, where the object to spin (blade of helicopter or spool to collect filament) is loosely connected to a motor, where you could stop it with your hand and the motor would keep going, let go and the spindle starts up again.
    Like try mounting an empty reel onto an axle with an idler or something, but yes does not spin freely (has friction) hook the idler up to a motor that spins fast and voila, you have constant tension. you could do something similar with an adjustable brake if you wanted adjustable tension.

    I’ll be getting a prusa mendel soon and after i get that going, my next project will be this extruder. (probably a while away from now)

    • Richard says:

      I’m afraid this project, along with many others, are on hold for the time being while i work on my university honours year thesis.

      A clutched based system is a good idea and I will be sure to give it a try if I ever get the time to finish my auger extruder. I have all the parts needed to copy the “Web4Deb extruder“, just not the time or interest at the moment to build it. I will be sure to post the results when I do build it though.

      best of luck with your prusa mendel!

  7. Bigman says:

    I think the fillament should cool down a while before spooling. I think you should extrude it onto a (long) conveyor belt until it hardens. After that you can put it on a spool. The conveyor belt should be driven by a stepper motor at a constant speed.

  8. Tony says:

    Could you have the filament drop onto a flat table and lay itself into a coil as it falls? Maybe have a guide mechanism to steer it to fall the right way.

  9. rob says:

    well if you cool it could you not just spin it slighty and create a coil on the floor
    look at a crab pot coiler or if you feed the cooled filament through a hoop and spun it
    slowly it would create a fairly even coil on the floor and like much filiment comes with out a spool

    but I am very interested in this project

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s