Elysium Max Exoskeleton

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01binary

Member
It's still very early in the game, but after reading & following some advice I got the next jump in quality:

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- Keep metal cooler. The hotter the metal is at the time of pouring, the more it will bind with air & water in the atmosphere to create hydrogen inclusions, which results in a horrible looking surface.
- Keep metal from getting too cool. Wrap the crucible and/or the ceramic mold into a ceramic blanket to curb heat loss on transfer.
- Pour slowly (just like with wax) to let gasses escape from the vents while metal is going into the sprues.
- Maintain a large thermal mass of metal just above the mold, to increase the force pushing the metal inside the mold. This is a low-tech alternative to vacuum casting or spinning centrifuge. The result is improved fills on thin and intricate mold cavities.
- Carefully degass with tablets just before the pour
- Fire ceramic molds as long as possible (but not higher than 500 F) to remove all water. Any remaining water will convert into hydrogen upon contact with molten metal and result in gas entrapment.


Wax casts prepared for box molding:

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Another batch: parts attached inside respective boxes for pouring UltraVest investment:

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Removing from boxes after investment solidified overnight:

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Wax burnt out and investment de-watered:

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joberg

Master Member
The pour is such a science...one of my friend uses a "vibrating table" to make sure that the metal (mind you it's lead into plaster molds) goes into every details inside the mold. So yes, the mold is kept warm and while pouring, that table is vibrating it, which in turn, makes it easy for the metal to hit the details.
You're right when you're saying that keeping a good "metal puddle" on top will help with gravity and filing all of those details. I don't know what kind of metals you've studied and the feasibility of pouring those without a more sophisticated type of tooling...I'm sure you've already made up your mind. Keep on pouring and good luck with the rest of the project.:)
 

01binary

Member
I have a tumbler I use for vibrating the table when pouring silicone and investment, but haven't tried it with metal. Maybe that's (one of) the magic bullets to getting better results in my context as well. I think one of my worst issues is going to be temperature control, so I am getting a laser meter that goes to 1500 F first and spending some time on profiling my kiln, forge and the pouring process for temperature vs. time to generate a graph in Excel with volume multiplier. For this volume, you have to do this step this long and at this temperature, then drop/increase and do this long, and ensure temp. doesn't go down or up during control checks.
 

01binary

Member
Whoever did this, please note that this work was shared for the benefit of industrial design, movie prop and cosplay communities and for the purposes of education (Inventor files contain a complete record of their creation, which makes the project valuable for learning industrial design & computer aided drafting). Continued attempts to sell will likely result in all files being taken offline (not by me).

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01binary

Member
I got some advice on a metal casting forum to try vacuum casting as a way to improve fill & surface. I got marked improvements on fill but the surface quality is still lacking.

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The surface defects are probably temp-related. The thermocouple probe I put together wasn't working, so I calculated using time after last ingot melts:

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I also got some thin parts laser cut that wouldn't make much sense to cast:

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joberg

Master Member
Yep, sometimes I think that machined alu and laser cut pieces make more sense. As you have experienced, casting is a complicated process (more miss than hit). True that it's a personal satisfaction to do it and hit it right;)
 

01binary

Member
After what felt like a very long year of experimenting with metal casting techniques, I finally got perfect casts using the vacuum process. Now it's a matter of shotgunning all 300 parts of the exosuit using the same method, and then a few more months of finishing and painting.


The last problem turned out to be a lack of control over the mold burnout and baking process which is very crucial to obtaining quality. Ultravest instructions need to be followed to a T, especially the part where you hold it at 1350 F for two hours to ensure there is no water left in the mold, which otherwise turns into steam and destroys the metal surface. I had to sit by the kiln for 8 hours and get up every 10 minutes to measure the temperature and adjust the controls. Once that was done, the casts become 100% repeatable, and every one comes out perfect.

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01binary

Member
Looks like there are still a few issues with repeatability left to solve but I got pointed to new tools and processes which might help. I also had a lengthy discussion with a Rio Grande dealer about how I am doing my investing, so I think I have a good chance of increasing the number of good casts out of each batch.

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Some interesting things that came up:

- When putting sprues on, both the sprues and the model have to be very clean (i.e. trim all imperfections with hot knife and exacto knife). Investment will get in those and then break off during burn-out, fall on cosmetic surfaces as dust and jagged particles and get imprinted in the casting.
- Fewer sprues is actually better, because that will create less turbulence of streams of metal mixing together and possibly destroying more investment on the inside.
- More investment & less water for heavy pieces.
- Instead of doing the complete burn out inside a kiln (which so far has cost me $300/month due to having to replace burnt out coils, not to speak of black smoke that gets everywhere), flasks can be boiled in a pressure cooker/canner, which gets most of the wax out in a very clean way. It can then be collected from the bottom of the cooker in one piece and thrown away
- Jewelers use flex-shaft tools for chasing and finishing work, which are stronger than dremels - got one to try it out
- Got sticky wax and a wax warming pot (that looks like a little food tray with sections and a built-in hot plate). Apparently sticky wax, besides helping to put the sprues on quicker, is a much stronger bond after cooling (not flexible). Got a hot knife also (waxer pen with tips and a wire going to the power supply with potentiometer).
- Got more pre-made sprue sizes
- Longer burnouts are necessary both for larger flasks and for detailed parts. The longer burnout will harden investment more and not let metal destroy small details when swirling inside.
- It's good that I've been using risers, that still helps even with vacuum casting
 

Lunajammer

Active Member
This is such a jaw dropping project. I can't say I've seen one so technically, financially and emotionally involved. My concern for you is that most people I've seen get this involved in a project over such a long time eventually burn out on it or grow out of their interest. The end is in sight and since taking minor shortcuts doesn't seem to be your style, I hope you persevere to the finish. This is going to be a trophy piece, an heirloom. All the best my friend.
 

joberg

Master Member
Yep, the learning curve on that project is hovering high for sure. Beautiful casts!! The light is getting brighter:cool
 

01binary

Member
I love new tools, especially ones that improve the process. After consulting with a jewelry teacher, I got a pressure cooker for steaming wax out of invested flasks:

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The steamer collects the wax on the bottom as a large disc that looks like a vinyl and you throw the disk away (or re-melt) after a 2-3 hour steam cycle on hi. Flasks go in the kiln with wax already removed, and the only thing left to do is get the water out of investment so there is no scary fire or heavy black smoke.

I also contracted a welder to make two tall 4" flasks out of four short ones. This takes care of all the long parts in the suit, mostly arm bones. I will still need custom box flasks welded for the chest piece and the hips because those are tall and wide at the same time.

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Since the major reason I still have defects are internal mold fractures, I got jewelry waxing tools to perform detailed cleanup on the wax parts before they are invested:

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...another reason was that water still left in the investment if not completely evaporated during the 300 F step will start boiling at 700F and generate steam that will push its way out of investment pores and take pieces of surface detail with it, destroying cosmetic surfaces. For larger parts, 300 F has to be held longer.

This weekend we did some seriously heavy lifting to fire-proof the kiln room at the hackerspace and installed 5/8" sheetrock on the ceiling as the first step (after stapling fireproof insulation to the rafters). When the job is done, the newest member of the family, Rio 14" programmable oven, can start cooking my flasks overnight so all I have to do is come in and do the casting. Theoretically that could allow me to double the production from 6-part batches to 12-part batches:

https://www.riogrande.com/Product/RioLargeProgrammableOven/703022

Lastly, a moment of silence for the AI vacuum oven. It worked very hard pulling gas out of my wax positives since January and now must be taken to service because it stopped pulling vacuum. They didn't provide a shipping crate so I built my own... not even Robison Crusoe would be proud of such a job.

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joberg

Master Member
Wow...this build is, in term of investment (dollars/time) incredible!! I'm pretty sure when I say that you've beaten us all with that build. Always a pleasure to read your trial/error and tuto when it's all said and done:cool
 

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01binary

Member
This week I got the vacuum oven back from service and went to a trucking company warehouse with an axe and a crowbar to retrieve my new burnout kiln (they failed to deliver 3 times). I broke down the box in their parking lot and dragged it into my car, finally making it to the hackerspace to place both on the new fireproof desk that once belonged to National Guard.

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The extra-long flask fits inside the programmable kiln! Now I need to complete a custom VAC duct system and we have to put in a new electrical system for power requirements of the burnout kiln.
 

joberg

Master Member
Love those desk! Well, that`s the way to do it (as far as dealing with a company and their snail way of not delivering goods to their customers:D).
Eager to see the next update with that whole set-up!
 

01binary

Member
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The new burnout kiln has finally been hooked up to 30 A / 240 V outlet, which I routed to a fusible safety switch, which then goes across the wall and the ceiling to the breaker box. After so much time spent routing EMT (electrical metallic tubing) conduits, my brain is randomly focusing on them everywhere I go and naming the components. I also had to cut off the kiln's power plug and replace it with another, NEMA 10-50.


The homebrew ventilation visible here was a result of intense labor to make a 3D model of the duct in Inventor, unfold it using sheetmetal functionality, export the sketch to Illustrator, and finally print it at 5% size. I projected the print using a tracer projector and got it to a focus state where 1" on Inventor drawing was equal to 1" on the wall, then traced on sheet metal and cut the patterns out with sheet metal scissors. Common sheet metal screws were used to assemble the final patterns after re-folding them with clamps.


Finally the switch was pulled and nothing exploded. The kiln emitted a long beep and the Sentry controller came online, burning with a demonic red glow. Today I am starting the first over-night (13-hour) burnout.
 

01binary

Member
In this one I get to use my new automatic kiln and extra-tall vacuum flask welded out of two smaller flasks. I made too many mistakes because I haven't done casting for some time while improving my tools, but I am seeing small improvements from process control.

 
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