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Plastic will not come out of extruder

Posted by avh.on1 
Plastic will not come out of extruder
March 22, 2013 12:06AM
Hello. I have just finished building my first 3d printer, a Prusa (first iteration). It seems to work correctly in all regards except that plastic will not come out of the extruder nozzel in any decent quantity.

I use pronterface to set the temperature to 230 degrees celsius, then wait 10 minutes for the entire nozzel to warm up.
Then, I insert 1.75mm abs plastic into my extruder and command it to force plastic into the nozzel. I can get several centimeters of plastic in before it becomes obvious that something is wrong. When I sent further "extrude" commands, either:
1: The motor and gears will turn, but no plastic will come out of the nozzel, OR
2. The motor will buzz/hum, but not turn
I have gotten one 1-cm extrusion from the nozzel.

Extruder: Wade's geared, laser cut
Hot End: TechZone, 1.75mm, 0.5mm nozzel
Plastic: ABS, blue, 1.75mm

How can I make my printer properly extrude plastic?
-Am I doing something wrong that is preventing the extruder from working properly?
-Is fault in the hot end? If so,
...can I fix it? Should I?
Or should I buy a new one. If so which one, and from where?

If you need more information or clarification, I will gladly provide it. Thank you for your help!
Re: Plastic will not come out of extruder
March 22, 2013 03:02AM
Can you manually push plastic and make it extrude? Sounds like your nozzle is blocked,
Re: Plastic will not come out of extruder
March 22, 2013 09:53AM
I can't think of a reason to bring the nozzle to temp before inserting filament. My extruder is always loaded with filament before turning on the hot end, that is the norm.

If your Techzone hot end is like the one on the Wiki page with an oak insulator(what?) there is not a PTFE liner in the nozzle so you are instantly fighting a bad hot end design because the filament with melt to the inside of the brass and jam.

Pics? I can't find a page for Techzone other than the Wiki.

Edited 1 time(s). Last edit at 03/22/2013 09:58AM by Dirty Steve.
Re: Plastic will not come out of extruder
March 22, 2013 10:22AM
lazzymonk Wrote:
-------------------------------------------------------
> Can you manually push plastic and make it extrude?
> Sounds like your nozzle is blocked,


No, I can't manually extrude plastic. I pulled the (hot) hot end off and tried to push filament through. The plastic melted, I got in a longer length of plastic than the hot end is long. However, no matter how hard I pushed, I could not get any out the nozzel.

However, the nozzel was not blocked when I first turned the printer on, because I was able to extrude plastic through it then. After that brief test, I turned the heater off and set about calibrating all of the axis. A few hours later, when I tried actually printing (as I described in the first post), nothing would come out. If my nozzel got clogged during use, how can I unclog it, and how can I prevent it from clogging?

Edited 1 time(s). Last edit at 03/22/2013 10:23AM by avh.on1.
Re: Plastic will not come out of extruder
March 22, 2013 10:31AM
Is there a PTFE liner in your hotend?
Re: Plastic will not come out of extruder
March 22, 2013 10:36AM
Dirty Steve Wrote:
-------------------------------------------------------
> Is there a PTFE liner in your hotend?


Yes, there is a PTFE tube that goes in to the hot end. I will upload pictures in a few minutes.
Re: Plastic will not come out of extruder
March 22, 2013 11:02AM
Here is the hot end.

The electrical tape is just holding the thermistor and heater wires out of the way, and the screw is what holds the hot end to the cold end.

Edited 1 time(s). Last edit at 03/22/2013 11:04AM by avh.on1.
Re: Plastic will not come out of extruder
March 22, 2013 11:28AM
Does the PTFE extend down inside the brass or just butt up against it in the wood block?

If not, you've got a BAD hot end design and will have to source another. That looks more like some homebrew repstrap hot end design. My hot end has PTFE liner clear down to about 5 mm from the nozzle exit hole, creating a short melt zone, which is what you want. If the melt zone is the length of the whole threaded barrel, that is way too much of a melt zone to work correctly.

Am I correct in that you have never been able to print with it?

I don't see a website for Techzone, and haven't seen any GOOD posts in the forum about Techzone.

Edited 1 time(s). Last edit at 03/22/2013 11:37AM by Dirty Steve.
Re: Plastic will not come out of extruder
March 22, 2013 11:57AM
Correct, I have never been able to print with it. All I have gotten from it is one 1-cm test extrusion. All subsequent attempts failed to yield anything.

When I ordered the kit (it was dirt cheap, 20 USD), the wooden block already had the PTFE tube in it. It was impossible to twist or slide the tube by hand. The brass nozzel extends about 1 or 2 cm into the wood block. It is slightly threaded so that you could just screw it into the block. I twisted it until I found that it met resistance, which *should* be the PTFE tube. The only way there would be a gap betwen the nozzel and the tube is if the nozzel has since been rotated the opposite direction.

There is probably a very large "melt zone" (I've never hear that term before) in the nozzel. In the picture, you can see that about 1 cm of the nozzel is wrapped in nicrome wire. The nozzel extends up into the wooden block about another 1 or 2 cm. It also has an interior diameter substantially larger than the filament.
Re: Plastic will not come out of extruder
March 22, 2013 12:32PM
I unscrewed the nozzel from the wooden block. Here is what I saw.

The nozzel is, obviously, clogged with a lot of plastic.
I peeled off the Kaptom tape, nicrome wire, and thermistor, and pulled hard with a pair of pliers. This removed most of the plastic.

There is a little plastic left, stuck in the bottom. Is it worth it to get this out?
-If yes, then how should I prevent this from hapening again?
-If no, then
--what hot end do you reccomend. (Price is a factor here.)
--will I have to do anything different to make sure that the next hot end doesn't end up the same way?

Also, I was very annoyed to see that the nozzel and PTFE tube have internal diameters of 3mm, even though I ordered the 1.75mm kit. I happen to have some 3mm plastic (thanks for the free gift, mixshop!). Should I try to use the hot end with this plastic, or is the design so flawed that it is not worth using?

Edited 2 time(s). Last edit at 03/22/2013 12:51PM by avh.on1.
Re: Plastic will not come out of extruder
March 22, 2013 01:07PM
For 1.75mm filament, the interior hole should be 2mm. If the hole is 3mm I don't know that 3mm filament will feed thru it either. maybe worth a try, but that is still a much too long melt zone. The PTFE liner I use is 4mm o.d. with 2mm i.d. You might be able to find 3mm o.d. to line it with or get some 4mm and drill the hole larger in your hot end.

Edited 2 time(s). Last edit at 03/22/2013 01:13PM by Dirty Steve.
Re: Plastic will not come out of extruder
March 24, 2013 04:17PM
This problem has been solved.

It turns out that I was shipped the 3mm hot end, rather than the 1.75mm hot end that I ordered. Fortunately, I had some 3mm filament to test, and the printer worked fine. I have finally constructed a 3D printer!

Thanks to Dirty Steve and Iazzymonk for your help!
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