Sunday, November 21, 2010

RepRap: RepRap is reproducing!...

I finally finished my first set of parts for someone other than myself this week! My extruder has been relatively consistent and I had a reason to put in deliberate effort as they were willing to pay for the parts. The following are a few finished product images of a complete set of Mendel parts with an Adrian extruder. The quality that I'm getting on my Mendel is really encouraging.

Wednesday, November 17, 2010

RepRap: update: aluminum extruder perfection!

I was able to use the extruder I made in the previous entry for 10 hours before it jammed. The jam was due to the PTFE expanding with the pressure of the hot plastic and causing a bubble right before the transition zone. I cut the PTFE open to show this.

I find at times like these, when you've failed after many tries, it helps to talk with another mind. I talked things out over coffee with a friend and we came up with a solution. If you follow Nophead at all you will be familiar with his plumstruder, and you will see where the inspiration came from.

I'm now surrounding the PTFE with an aluminium heat sink that does not make contact with the hot end. This keeps the PTFE cool enough to not expand, and to keep the transition zone short. I'm also using a block of wood to further insulate the hot end from the heat sink.

I've been able to run this setup for over 30 hours without fail.

Sunday, November 7, 2010

RepRap: aluminum extruder perfection!

I made a few design decisions since the last OpenSCAD renders. I decided to stick with the vanilla x-carriage so that others can benefit from the design without having to purchase linear bearings. I also increased the size of the heater block at the suggestion of an engineer friend. The other design changes are a result of trying stuff until I got something working. I am not a mechanical engineer by education, nor do I remember much from thermodynamics, so there was a lot of trial and error before the design matured into the following.

The second to last picture shows me tightening up the whole rig with a 3mm rod used to align it. This is critical. I tightened a few designs without the alignment rod and the filament was really hard to push.

One element of the design that is very exciting is the fact that the top most plate of aluminum is cool to the touch! I think this is a result of three plates.

Finally, the PTFE is inside the hot tip, instead of the other way around. This really does make all the difference.

I have printed for about 4 hours without it failing. I'll leave it running for the rest of the weekend and report back on how it is holding together.