Saturday, October 30, 2010

I printed a whale tooth I found on Thingiverse: (Whale Tooth) because I thought it looked cool and would really test the capabilities of my machine and software tools. (Which is great for working out the kinks.) I'm happy to report success! The RepRap java tool couldn't handle the STL file, so I used Skeinforge. to create the GCode. I had to customize Skeinforge a bit before it worked right. It wanted to send Z moves in the same line as an X-Y move, and that clashed with the different speeds required. It still doesn't do acceleration right, which messed up a few layers when the X stepper skipped a few steps.

Tuesday, October 26, 2010

The secret to my success

Here you can see my extruder's hot-end. The bottom part is a standard welding tip, which already had a 0.6mm hole in it. I drilled it out to 3mm (well, 1/8" really.) almost to the tip, so there's maybe 1-2mm left for the nozzle. Around that is wrapped the nichrome wire for heating, with a thermistor near the tip. Kapton tape surrounds it all for insulation and to keep it all in place. The welding tip goes through a fender washer and into a nut which keeps it in the washer. The washer has 3 holes drilled for the long bolts (black thread in photo) that attach it to the extruder. The white PTFE insulator sits between the washer and the extruder. I carved out a hex nut-shaped hollow in the PTFE so everything stays centered, and in a pinch I could unscrew the nut using the insulator. Leakage between the insulator and the nut is minimal. (Only noticeable when disassembled.)
The latest change to get things working is I added a bunch of Kapton tape around the washer so it stops acting like a heatsink. I found that the PLA was cooling too much, (especially when it stopped while moving between layers after the extruder was warm,) and creating a plug in the top half of the welding tip. If I pulled out the filament, the portion between the pinch wheel and in the PTFE was a little stringy (it would stretch as I pulled) but the part below that, in the area of the nut and washer, was a perfect 3mm cylinder, which terminated in the really melted part.

And here's my first success with PLA! It's a small stand for my Droid phone, which holds it in portrait position. It fits a bit tight, but that's because I haven't had a chance to calibrate the extruder settings.

Monday, October 25, 2010

Print complete!

It finished, with only a little help here and there. Success! Now on to fine-tuning. But first, some sleep.

Printing! (crosses fingers)

As I write, I'm printing layer 7 of my best print so far.. Here's hoping!
I added Kapton tape to insulate the big washer that mounts the heater to the extruder, so it doesn't cool down so much. I'm extruding at 200C, with some minor back slipping of the stepper, but it's extruding pretty well.

Saturday, October 16, 2010

or so I thought

I can't get consistent feed from PLA. There were a few times it would feed perfectly for a few minutes, but now I can't even duplicate that much. Eventually, it gets jammed up in the extruder barrel. Frustrating. I can get it to squirt a foot or two of extruded plastic before it starts jamming. Then I have to either push it out with extreme pressure, or drill it out. If I'm really careful, and a bit lucky, I can pull a plug out and then squeeze out the remainder with a metal rod. I even re-built the hot end twice, with no improvement. :-(

Friday, October 8, 2010

A few months off

After a few months off this project, spending my time doing work and summer stuff, I'm back to my RepStrap project. I ended up ordering a custom extruder part from Shapeways that cut a big headache out of my design. It's a bit of a cheat, perhaps, but it solved my chicken and egg problem.
I just ran the first few layers of PLA, and it's looking good. still have some feed issues I'll have to work on, but there is no warp at all. I should be able to make good progress, and perhaps some full prints, this week.