Well, then. The semester is over.
To recap: My group was a bunch of losers who never showed up or did anything. On Sunday after my last update, I got an email from one group member asking if I had made the presentation yet. The last time I talked to (or saw) this guy was 2 months prior, so I responded telling him that we all decided I was to be in my own group, and yes.. I already made my presentation. He replied saying that he wants to have a meeting with me, the professor, and the department chair.
I agreed, suspiciously. I figured it would be in my best effort to document all our interactions, so I made a 2-page spreadsheet consisting of times/dates/topics/actions/etc of everything everyone in the group had done. During the meeting, he started crying out that I never let him do any work, and that I kept him from succeeding and that he sent email after email to me and I ignored them all. I whipped out my sheet, and from that point on, it was all over for that lying scumbag.
Let's see, he showed up TWICE out of 16 weeks in the lab, and almost as many times in the lecture, and it's my fault?!
To recap the design:
First one sucked.
Had porosity and surface roughness.
Second one did not suck, but did have a lot of flash.. and a sand problem at two of the gates (not at the parting line). The one guy who meows to himself in the corner (did I mention he does that?) came up and was standing so close to me, I could feel his long hair on my neck as I was packing the sand. JUST A BIT distracting. Everything went fine during the pour, and the casting came out great. A sledge hammer broke off everything easily enough; light swings on the risers while it was laying on the floor, then a drop of the hammer on the gates.
..and she looked damn good. No real surface roughness or porosity.
On both designs, I incorporated a simulated "washburn core" on the risers. That is, a design such that the riser doesn't have full diameter where it meets the casting. A short, small cylinder (or tapered square) is in between the riser and casting for ease of removal. That's why on the second design (without having to wait on zero input from WORTHLESS group members), I incorporated something similar in the gating. (Finishing is part of the design! It isn't supposed to take 5 hours to removed the gating and risers.) Studies show that the small volume in between the riser and casting has no detrimental effects (in terms of feeding the casting liquid metal on solidification). A real washburn core is a donut of sand placed in between the casting and riser, instead of a small piece of foam with sand packed around it.
Anyways, here's what the bottoms of the risers looked like after hammered off.
I wrote up the report (19 pages) and gave a 31-slide presentation by myself.
Then, when I turned in my take-home final for the lecture class, my teacher and I got to talking.. and I scored some scrap gray iron for my brother for a cylinder on a miniature engine he is machining.
I could go into a lot more detail, but.. I'll save it unless anyone has questions/comments.
Next semester is CNC!