Cast bronze DMS logo dimensions

Who modeled the DMS logo that we have subsequently lost-wax cast in bronze? I’d like to know the exact dimensions of the “square” (rectangular?) perimeter in the computer model that was 3D printed for the master.

I’m trying to guesstimate the amount of shrinkage between model and finished part. While I expect some variability, I figure that following the same process as the DMS logo would give me a rough benchmark as a starting point.

I have a cast one that I can measure - hence just need to know the starting dimensions of the model.

What alloy of bronze, do you know?

IDK, but I’m about to make a brass DMS square plaqque so I’m interested.
Also I have a fusion file where the logo is dynamically resizeable with one simple size variable if you want it.

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Hmmm. Nope. I have to ask @JBluJkt what bronze alloy we used …

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It looks like most shrinkage is between 5%-6%

End-to-end, or during just one stage of the process? Our process includes:

  1. 3D Printing the “master”
  2. A silicon rubber mold of the master.
  3. A wax model from the rubber mold
  4. A kiln-fired “plaster” investment of the wax model
  5. Centrifuge casting the bronze in the investment

I figured if I started with the dimensions of the model, and then measured the piece that has gone through all the steps that should yield an end-to-end shrinkage number.

(OK everyone - yes - I know steps 2 & 3 can be eliminated by printing directly to wax, but that isn’t what was done here and it’s not the process I’m going to replicate).

If you need some relative dimensions, I made an OpenSCAD model of the DMS logo several years about. There are poly-point coordinates for the outline in that file.

I also incorporated that into a quick-to-print keychain:

And a coin-op bottle opener with the logo (remixed from another bottle opener):

Good empirical method and shows how the mold reacts in terms of distortion. The reality is - you engineer your best guess, make a prototype, then tweak. Some of the CAD programs have features for castings: you design the as design part, then through it’s voodoo it changes the dimensions.

Generally, the shrunken size is after cooling, so the casting mold would be bigger.

Off topic, but about metal: If you watched Elon’s Mars event last evening, he explained why they made it out of 301 Stainless Steel. No reason is 301 SS gets stronger under cryogenic conditions that exist in space where other metals and composites become brittle. Also talked re-entry and heat tiles.

I believe this is the specific bronze we used, last time you and I cast. I’m sure Rio could give you some shrink factor on it, but my research for bronze is approx. 2%. The silicone mold material you used is said to have zero shrink. The pink injection wax we used is rated at low. So I’d estimate a total of 3 to 4 percent at most. However the best way to know for sure will be to just measure it.


Hobby grade silicone for molding can have 0.5%+ shrinkage. Since there’s multiple steps of error stacking, that should be factored. If a platinum cured silicone was used it should be near zero.

Kevin, it looks like the dimensions may be off. Here is the logo dimensions. image

This page discusses issues with shrinkage when casting PLA-printed parts.

On this page they recommend:

The hard part is conceptualizing how volumetric shrinkage occurs. Basically the part will shrink ~2-3% depending on the alloy, but holes will get bigger as metal contracts from the side walls of the plaster. This means that parts need to be scale up ~2% while holes need to shrink by 2%.

I think his are just using a factor of 0.8 instead of 1. I think they have the same ratios, but I don’t feel like checking them all. You could probably open his up and change that single 0.8 to a 1 and get the same thing.

FWIW, the image @apparently_weird linked is from here:

I can’t promise it’s truly “canonical”, but I think it has been used multiple times like that. Basically the pixels are all single units wide everywhere except the top of the bottom bit.

(FWIW, most of this is off topic as clearly @John_Marlow knows about that image since she was nice enough to add it to the wiki. She really just cares about a particular instance someone did to try and figure out shrinkage)

I can’t find where it’s off.
It’s a data driven version.
All the dimensions are formula based on a scale number
It’s at 80% right now.

Just multiply .8 by the length of the segments.
Should work.

This way it can easily be dynamically resized to match the size of the stock material its going on.

Since the cast piece I have measures 1.030", I’m reasonably certain it wasn’t printed at the scale listed above.

If you are referencing one of our casted logos. Several are copies of copies as well. The ABS were Gen 1 with Very Low Temp silicone listed at 0-1% shrinkage. Some of those models in bronze become the Gold Silicone models…

Do you have any of the wax printed parts that were used to make the mold? I could at least measure that since no one seems to know anything about the CAD model that was sliced for the printing.

Heres some models I made. Download in whatever format you’d like

We can make some new ones. The samples I leave out tend to go missing.