YAPP (Yet Anothr Polymer Pump)

Hello to all again,

Just wanted to show you what way I'm going with the pump parts. Even though I came quite close I think with making them from polymorph, but couldn't get them quite right. I ended up making a PVC version as well, which seems to work well from the first moment it was switched on.

I made the polymorph version by sticking a printed version of the screw holder on the bottom of a piece of transparant plastic. Then I used a small round file and filed away the bit that i wanted the screw to protrude. Wound some sticky tape around the screw to make it somewhat thicker so it would have room to turn. Made the halfwasher bearings (top bearing is half a washer, bottom one is 'C' shaped washer). Then i put the two on the transparant plastic and made a wall around the outer shape made up of pieces of PVC again. Filled the lot with polymorph and drilled the holes afterwards (not very straight as you can see :-). I could use the same mold for the filament holder as well, by winding some sticky tape around my filament rod and turning one piece of PVC over. They both move quite smoothly but I couldn't get proper alignment.

The axle with the little copper pully that's more or less hidden in the PVC version comes complete with bearings from a motor I took out of an old printer

But seeing the nice transparant parts that Dr. Bower blogged yesterday in the 'Tons of RepRaps' article, I'll probably be ordering some as them as well when they become available :-)


Ron.

Looks great!

Ron,
Does this work in a different way, i.e. have you replaced the screw thread with the small gear wheel? If so, how fast does it extrude?

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[www.hydraraptor.blogspot.com]

Yes, it is a little gear wheel. This way I didn't need a lathe or any alien technology. On this little video clip you can see it connected directly to 5V. It goes much too fast, but I hope to compensate that in software. 4mm/sec is the aim if i'm right. (I haven't done the extruder tests with it yet and I'm not at home at the moment). The diameter of the filament I found in a local shop (HDPE) is not 3 but 4mm, so I guess thats another thing to compensate for.

Nice videoclip.

Do you think that that gear arrangement is going to give you enough thrust for the filament into the extruder barrel?

4mm/s would be in the range of outputs speeds yes, but the input into the extruder will be around 25 times less if you have a 0.5mm orifice yielding a 0.8mm filament. I hate to disappoint you but I don't think the gearing of the motor will be low enough to exert enough force for extrusion.

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[www.hydraraptor.blogspot.com]

I don't know much about extruder design, but I should think that you would want another gear or bearing on the other side of the filament, instead of just a pvc or polymorph wall. It would cut down on friction, though I suppose that since the real choke point is at the nozzle, it may not matter much.

-Samuel

great progress! keep us posted, hopefully with a video of it extruding through an nozzle. you have a very nice, repstrap style design going there. i hope it works out for you!

Well, back to square one (or two).

Even if I pull the 'Extruder Speed' slider to its lowest it still moves way too fast. It's still quite powerfull and I think it has a much better grip on the filament than the screw,but if it is too fast its no good.
So for now I hooked up the polymorph screwholder with the PVC filament holder and I can see at which speed it is supposed to be moving.

Here is one i dont have an answer for: I use the thermistor that Zach sells in the store, but at room temperature it says its 91 degrees C. Can anyone tell me which settings should change from their defaults in the preferences screen? My C2 is a 1uF electrolytic capacitor.

Zach, a video of something coming out of the nozzle - As soon as I have it :-)

Ron.

so far i havent looked at the video but from the discription it sounds something like what Im making. rather than using a screw drive im using pressure rollers like on a Mig welder wire feeder. so far im not running but have most of the frame constructed and just ordered the electronics that i was needing.

ive been realy obsessed with this project ever since i found out about it.

thanx for all the work yall have already put into this.