Chapter 1 Beginning of the journey:
Here is the last post of the semester. We worked together on this final project, and it sure was an adventure getting to the end. We started off with just a picture of Rice Academic Seal and our objective was to create a mold of the seal using the CNC machine, and then cast a seal with plaster or 300Q (which is like a super fast curing plaster that can cure within 3 minutes).
(http://ecx.images-amazon.com/images/I/51Qtm4KVE7L._SY300_.jpg)
We first tried approaching the project in a same way that other groups in the class did – we prepped the CAM file on easel.com to cut the negative of the seal (making it a mirror image and cutting along the dark lines) so that when we made our 300Q mold, it would come out as the actual seal.
Chapter 2 “Owl Test“ & Characters:
Before we tried cutting the entire seal, though, we decided it would be a good idea to just cut a small portion of our seal to make sure it would work as intended. We decided to cut an owl to make sure it worked. We chose to use the owl to test as we believe the eyes of the owl should be the most complicated part. The test would save hours of cutting in case the owl ended up not working.
Actually, what we were afraid turned out to be true. The eyes of the owls were messed up by the CNC as there were too many cuts in a small area. As a result, the material can stand the force no more and would easily break. So, our first owl tester turns out to be “eyeless”.
To solve the problem and optimize our cutting, we decided to make an ”Owl Test”. Basically, we tried 8 different combinations of strokes(1pt and 2.5pt), and the tool path location (fill, on path, inside, outside). After cutting out and comparing the owls, we find our best owls!
(Owl Test Candidates)
The next step is to work on the ribbons and the characters. Due to the size of the drill bit, some part of the characters could not be carved as the line was too thin. To solve the problem, we went back to the illustrator, made the shape of the characters and made the strokes thicker. This was a long try&fix process as thin lines could not be cut while thick ones lost the original details. In the end, we found a perfect balance of the two!
(Owl and character trials)
Chapter 3 The Cut of Whole Seal
With everything ready, we set off to cut the whole seal.
Spending some time experimenting with different sizes and materials, we found that a 10×10 inch seal on a piece of plywood worked best. We cut the seal, and after taking some time to sand it down we had a very nice looking reverse-Rice seal!
Final cut of wood seal
(Final cut of wood seal!)
Chapter 4 The New Adventure: Positive cut and Oomoo
It seemed at this point that our project was almost complete, all we had to do was throw some casting material in the seal and take it out later. Unfortunately, though, after doing some test casts of individual owls in wood we realized that we would never be able to get the 300Q out of the wood mold after it cured. There were multiple reasons why this problem was happening and how we tried to solve the problem:
- We did not have a traditional “mold release,” which is a spray on substance that helps get casts out of molds. We tried using soapy water, graphite spray,linseed oil, and a spray on enamel, but none of them worked.
- Probably a more likely cause was the nature of the material we were using. Carlos and Danny were both pretty skeptical of our seal because it was made out of wood, which is very porous. As Carlos put it, the casting material would just soak into the pores of the wood, and once it cured it would be almost impossible to separate the two. This issue could be mitigated by carefully applying enamel or mold release, but missing just a small portion could ruin the whole thing.
- Probably the most likely cause was that the 300Q solutions that we were using were quite old and probably expired. After trying out the stuff that Dr. Wettergreen had just ordered we saw an incredible difference in how it cured and its general appearance. Yet it is still incompatible with our wood cut.
Though frustrated, we managed to calm ourselves down, jumped out of the box and sought other approaches. With the suggestion by Dr. Wettergreen, we chose to try making a positive cut. Making a positive cut of the seal (aka CNCing it the way we want the mold to look) would let us make a negative mold using Oomoo and then make another positive cast by pouring 300Q into the Oomoo. This would let us get around the issue of using casting materials in wood.
The downside of this technique was that the CNC cut took about 2.5 times as long as the negative. However, the upside was that cutting the positive gave us much finer detail than when we cut the negative (as you are no longer affected by the size of the drill bit).
（Our first positive cut trial）
For our second try, we used MDF board to cut our positive, since it was a homogeneous material (as opposed to plywood) and some of the finer details came out better on it.
(The MDF before sanding)
After cutting and sanding our positive, all we had to do was mix the Oomoo together and make that mold. After we clean the Oomoo mode with water blast, we made a 300Q cast in the Oomoo!
（Oomoo just took our from the mold）
（Wash the Oomoo）
(Mixing 300Q)
(300Q curing on Oomoo)
(Mold and Cast)
To get a better version of mold, we also launched another cut with the plastic. The plastic is a stronger material than MDF and is uniform. However, it has downside that it has many plastic shavings which are hard to clean from the mold.
(Plastic cut before sanding)
(The plastic mold after cleaning with sand-blaster, carving knife and sand paper)
Unfortunately, due to the plastic shaving problem, we didn’t get a perfect Oomoo mold out of our plastic cutting. So we decided to go back to our old molds and based our final work on it. We made a plaster seal and spray painted it blue and grey, which is the color of Rice!
We also made a Oomoo mold of our great wood cut, so in the future we can use make this mold to make rice university stamps.
The project took a lot of time to get right, but the rewarding feeling that we go once we finally got the mold right was definitely worth it.
This is the end of this adventure, but we know, there are more fantastic adventures awaiting us , both in OEDK and real life! Hope y’all enjoy our stories and hope it can be helpful for later OEDK adventurers.
Casey & Clark
