Tuesday, July 10, 2012

Next Stop: A BOAT!

This is it! Seafair is this Saturday. After yesterday I'm positive we will make it (if only just barely). Yesterday was a "roller coaster day". You know, one of those days filled with emotion: discouragement, hope, despair, and triumph. The best part is that it ended on the triumphant note.

Being unsatisfied with our test pieces up to this point the day started out with us in the process of reconfiguring our extruder. We were encountering problems with what we believe was a back pressure issue. Our paranoia about getting the HDPE to stick to the build surface caused us to mash down on the first layer which would lead to pressure building up in the tip with nowhere to go except backwards. I've lost count of how many times we've had to change that thing but it's near a dozen by now. The good news is I think we got it this time. Making changes to the auger and barrel seems to have made our extrusion reliable which has always been the goal (elusive as that goal has been).

Our new motor mount
The first tragedy of the day struck during a test of the new extruder when the z-axis motor coupling failed. It simply gave up. As disheartening as that was, we got rid of the old coupling assembly and built our own with some aluminum stock, a couple of hacksaws, and the hope that we could make it work. While the new design looks slapped together (it sorta is) it gives us access to the coupling if needed with the added bonus of being extremely quiet.

Using Brandon as a size reference
 With the machine now able to print something, we decided we needed to do a test print. Cubes, buckets, or anything else unboatlike were things of the past. We needed a quick small-scale test to prove to ourselves we could get the machine to do what it needed to do then move on to an actual boat. We pulled out some chalk and started drawing our what our final design would roughly look like. Who says sidewalk chalk is only for little kids?

We quickly modeled a small canoe, set up Big Red, plugged in three ventilation fans, ran a dry run, and prepped the surface. This was it: the moment of truth. Could we press go and let Big Red take over? The answer was no. Of course not. During our print of the base raft the extruder's drill motor began surging so Adam had to sit there with his finger on the trigger the entire time to deliver the appropriate amount of plastic while the computer operator tried to adjust the print speed on the fly. The sudden change in behavior of the drill motor was baffling. It was Adam though that suggested we reconfigure our extension cords so that the motor was not sharing an outlet with the ventilation fans. That did just the trick.

Our test when we finished
Without boring you with the nitty-gritty details, we tested a few variations of the G-code, layer thickness, and overall printing process. Looking at the layers tells a story of the individual lessons we learned as we were testing.

The fruit of our endeavors is a small-scale canoe which shows us that we can go large scale. What we will likely do during the big print is print the raft alone then feed the printer a separate set of G-code for the layers. 

The pretty side
This will be a long print and it will take constant baby-sitting. During our test we had Brandon on the computer, Adam working the extruder, and me cleaning up any slop/refilling the hopper. Theoretically one person could run the print but it should have at least two. This "automated system" is not automated in the least!

The less pretty side
Seafair is in 4 days. We have a verified process and about 70 pounds of HDPE. Stop on in sometime and check out what's going on. If you'd like to help during the printing process even better. Either catch up with us in MEB 252 or leave a reply to this post. We will utilize anyone who wants to lend a hand at this point.

I won't count my proverbial eggs before they hatch, but I think we got this. Let's show Seattle what UW students can accomplish in 2 months worth of free time and some recycled milk jugs.
Brandon thinking about his idea for "concrete skates". Just a little too small.

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