New to extruders and wondering about results..

I've just built my first extruder, and i'm wondering if the results i'm getting are typical.

I'm using 3mm ABS white filament, and when I push the filament through I get a semi melted solid string. My heated length is about 1/2" and i'm wondering if that's not enough. I can take the nozzle head temp. well past 300c, but when i run it that hot, the plastic appears to burn, as the resulting string has a brownish tint to it.

It also seems like i need quite a bit of force to push the filament through, which would tell me that my nozzle isn't hot enough.

any thoughts or suggestions anyone has would be greatly appreciated.

thanks

That sounds about right. It does take several kilograms of force to extrude ABS and it never becomes a true liquid.

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[www.hydraraptor.blogspot.com]

Be careful. I clogged a couple of nozzles running the temperature that high. Beyond 260C, ABS starts to decompose. When it does, won't melt anymore and it's also insoluble to solvents. You'll have to drill it out or burn the residue off with a blow torch.

Thanks for the reply, and the advice guys. I've begun rebuilding my extruder (with gear reduction) as my current design doesn't have enough umph to push the abs out.

it would seem that with the abs not really turning into a liquid that it wouldn't make good parts... but it's obvious that people do. Hopefully i'll have it up and running by the weekend.

I generally do not post to other people threads as I do not feel qualified to answer questions and do not like to hijack other peoples threads.

But I have been wondering about extruding other materials than nylon(the only material I have experience with), and wonder about weather my extruder will not be able to extrude ABS.

I saw some information quoted from : [www.faqs.org]

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LEGO brick are made out of ABS (acrylonitrile butadiene styrene), it is heated to 450 degrees Fahrenheit (232 C), then injected into a mold which is kept at 85 degrees. The pressure used to mold the bricks varies from 24 to 150 tons. The molds are kept within one degree of the 85 degree specification. ABS absorbs moisture, so the entire molding hall is kept at 50% humidity. The allowable tolerance for a brick is two-hundredths of a millimeter, or about eight ten-thousands of an inch.

Above nophead says:

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nophead
It does take several kilograms of force to extrude ABS and it never becomes a true liquid.

I always imagined that materials had to become liquid to coalesce and bond together, is this not the case?

From my experiments nylon seems to become quite liquid and seems to flow quite well once heated to the right temperature, is ABS vastly different to nylon?.

Sorry that this does not help answer your problems rk396, I hope my questions do not take this thread too far off topic, but your questions seemed similar to ones I have been asking myself.

It sticks very well when really liquid - but for a reprap it would fail, we need it to build up a layer, not to spread in all directions. That's why we tend to use just the lower temperature to get it viscous enough to extrude, but not more.

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I always imagined that materials had to become liquid to coalesce and bond together, is this not the case?

Material can be partly liquid and partly solid at the same time. Think of crushed ice filled up with water. The liquid part bonds, the solid part fills and makes the material a paste.

While a water/ice solution (all exactly identical molecules) can exist at exactly one temperature only, compositions of different molecules (lengths), i.e. alloys, plastics, have a temperature range where this happens. The warmer the material gets, the higher the percentage of liquid. Excemptions exist, of course.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Mung, No problem at all. your questions is kinda like a second part to what i was wondering so it works out fine.