Previously on Ten Tries.
Look at that glow! I don't have the money for that. I'm not cheap, I'm recycling! And I made a
pretty dumb mistake. Since i'm cheap, and I like a challenge, I'm going to replicate it! Seems
straightforward enough, are you ready to watch me fail... repeatedly? Because this is Ten Tries!
It appears there may not be enough pressure in the sprue to fill the voids with molten aluminum.
That should be easy enough to fix. I simply lengthened the sprue
and tightened the spacing of the parts to fit in the cup.
I must have pushed the strength of the plaster beyond its limits,
because the cracking in the mold was clearly extensive. You can tell there are blocky
chunks of plaster that broke off and shifted inside the cavity where the aluminum should be.
The good news is that all the other issues up to this point have been all but resolved.
It seems the plaster is breaking apart because of thermal stress. Basically some parts of the
plaster are expanding as they get hotter and other parts are taking a little longer
to heat up and expand. If you recall, I have been increasing the temperature of my furnace in steps.
This is because the temperature controller I am using increases the temperature to a setpoint
and holds it. To reduce the thermal stress, I increased the temperature in smaller,
quicker steps. That should significantly reduce the temperature differences and thermal stresses
inside the plaster. I also added a small amount of Portland Cement to my formula.
Wow, that is so much better. There was still one part that broke off, but if I’m being honest,
expecting that narrow, unsupported part to stay connected is a little ambitious.
Looking back on previous tries, I’m seeing that my plaster density has been very inconsistent.
In the last try, my density was only about
.3 g/mL. That’s one third the density of water and one sixth the density of pure plaster. I’m
altering the proportions to achieve an investment that is about 50% more dense than last try.
The water and soap seems to determine the final volume, so all I should have to do is keep the
water and soap constant while increasing the other ingredients by 50%. This should
reduce the large bubbles in the plaster and significantly increase plaster strength.
Alright! Now those are nice.
While I was pouring, I overdid it a little bit. I over poured, and some of my vents
got covered by aluminum. You can see here that air was trapped and formed a bubble
underneath the aluminum. That prevented this wheel looking part from fully forming.
Changing the temperature of my furnace every 15 minutes was very time consuming.
So, I automated that process a bit with a little soldering
and a bit of python code. Plus, it logs the actual temperature.
If you'd like to see more, you can visit my website TenTries.com.
I had some technical difficulties on this one. My furnace heating element burned up right before
the metal was hot enough to pour. Then after I rebuilt my furnace, I was ready to pour again.
There are some defects, but considering the trouble I ran into, it isn’t too bad.
I’m pretty happy with how these parts turned out. I have a feeling they’ll work well.
If you’d like to know what these parts are used
for… the video for that project will be available next Sunday (09.06.2020)
If I had an 11th try, what would you do differently? Post it in the comments below!