Which one of these features is making my extruder a complete piece of uselessness???

OK, here are some pictures of my continuous blunder:

[www.avayan.com]

I have tried a gazillion different things and none of them work. Basically, I get the first layer printed (some times) and then I get a big blob of plastic somewhere in the barrel making any future progress an impossibility. I have cleaned this extruder at least 50 times and it always clogs the same regardless of what I have tried. Here is a list of what I have tried:

1. Short and longer PEEK
2. a long brass screw as shown in the pictures
3. a short brass screw with a longer PEEK barrel.
4. A shorter stainless steel connecting the PEEK to the hot end, and then brass connecting the hot end to the nozzle (in other words imagine the screw from the peek to the nozzle is actually two screws. One is stainless steel and the other is brass.
5. feed rates from 50 to 800 steps/mm in increments of 50 to 100. I have no idea how many millimeters I have as I have not thought how to measure this, but at the moment it does not matter as the plastic clogs pretty much the same.
6. temperatures from 200 to 240 in increments of 10C.
7. with and without PTFE sleeve.
8. have tried both ABS as well as PLA plastic filament.

Here is what I think is obvious:
1. the temperature is enough to melt the plastic as I see it extruding at the beginning before the plug forms.

Here are a few areas which I wonder anybody of you know are problematic:
1. Is it a problem for the barrel to be too long? I read somewhere it is best to keep the extruder as short as possible. I unfortunately designed the table too far away from the extruder so may need a complete redesign of the table if I need to keep the extruder short. The first cup cakes didn't have short extruders though and they seemed to work.
2. I made the internal holes 9/64" (0.140" or 3.55 mm) this hole is bigger than the filament. Could this be a cause for the jamming?
3. Do not have a fan. I guess I can try one real quick, but is this such a miraculous fix?
4. Could it be I am using too much heat?

What else can I be doing wrong??? I am puzzled! Have been working for two days straight and am about to throw the towel on this design and start from scratch. If there is an easy fixer upper I would truly welcome it. Thanks for any input!

JIQ

If we use elvated melt temperatures we camn make extruder a complete piece of uselessness.

I'm no hot end expert but 2 sounds dodgy. The diameter should stay the same until the molten zone.

add a heat sink to the SS and put a fan blowing across it

I had used temperatures 180-190 C with PLA and 205-215 with ABS, but it is filament specific

I have come to realize that hot ends are the one thing that is just not as easy as it looks.

All of your questions kind of point to the same thing. If the plastic gets melted too far up into the hot end, then it will be very difficult to push plastic out. Adding some thermal wrap to the bottom will help keep it hot, and then adding a fan to the entire operation will keep the heat from leaking vertically. Keep the threaded rod exposed above the resistor heaters, and possibly even put a heatsink on it.

I spent a lot of time and money trying to build my own. I finally realized that I should have just bought one, as I spent more money on a lot of things that didn't work.

avayan Wrote:
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> What else can I be doing wrong??? I am puzzled!
> Have been working for two days straight and am
> about to throw the towel on this design and start
> from scratch. If there is an easy fixer upper I
> would truly welcome it. Thanks for any input!

There needs to be a quite sharp transition, heat-wise, from the cold side, where the filament is solid, to the melt zone. If the bit in your design with the threads removed is supposed to be the heat break, it's not a very good heat break. You would need to have an enormous heat sink on the cold side prevent it from overheating and melting the filament prematurely.

Hi Group,

Just wanted to thank you for all of your pointers with these questions. I was able to improve on my design considerably and have been printing for a few days. The trick? There were a few fixes, actually. First, I changed from brass to all aluminum. Second, I enclosed the hot end in a ceramic cloth and Kapton tape. Third, I added a fan. Fourth, I stretched by belts to kingdom come and fifth, press PRINT!!!

You can see some of the results here:

[www.youtube.com]

I will be making more videos detailing the nightmare that it was to overcome all these nuisances, and the solutions that lead me to success.

Thanks all for taking the time to instruct me!

JIQ