Castaldo®’s VLT

We are looking for some help and suggestions.

The 3D/RM Taskforcegroup of the BeneluxSpoor.Net Foundation is still looking for the best 3D and Rapid manufacturing methods and technics for developing and fabrication of trainmodels and maquettes.

Regarding to the services of Shapeways, already several items were develops and tried. You can find them here in the galleries or shops. We tried all the available materials of Shapeways, and even more, also some new technics and methods not already supplied by Shapeways. e.g. MCor paper LOM and the Solido LOM.
Our foundation communicate with several producers and laboratories all over the world (e.g. TNO Science and Industry).

Now we want to share our knowledge and experiences with other users of the services of Shapeways, especially the jewellers (or students e.g. ROC Zadkine Schoonhoven, the Netherlands).

Well, we want to start with experiments regarding to the lost wax methods and the possibility to make molds with 3D printing.

Objet, makers of the Polyjet line of 3D printers, now has introduced "Castaldo®’s VLT™ [Very Low Temperature] molding rubber", which should greatly simplify the making of jewelery prototypes. The new material should permit the creation of jewelry molds in "as little as one hour".

https://www.beneluxspoor.org/bnls/objet_rubber.jpg

The advantage of the rubber would be that it cures at a low temperature that does not damage the pattern, and thus jewelers can bypass several of the traditional steps to produce prototypes.

More information:Objet

It seemed a possible way to develop trainmodels of nice and smoothy material with a very high resolution, similar to the SLA methods, but much cheaper. And probably also a way to use different materials as zamac or brass.

See also: theme page BeneluxSpoor.Net Foundation

kind regards,

Hans van de Burgt

I've been making molds for a while and casting polyurethane and what they call white metal.
One of the silicone rubbers that i use is transparent and can handle up to 220 degrees celcius (i use it to bake polymer clay) and there are plenty silicone rubbers that can handle even higher temperatures.

For a simple limited series I just take my part (3d printed) and glue some pins to it that will make my pouring channels in the mold and then pour rubber arround it.
then i cut the mold open and remove the pins and part.
Frankly I cannot see any easier or cheaper way to make molds.
For more complex shapes i make multiple part molds which takes more work, but still i cannot imagine a easier or cheaper way to make molds.
The lost wax method usualy involves a one-off piece where the mold is destroyed to free the endproduct.
I think for the stainless steel prints they use that method.

You can use the same method you use for polyurethane to make metal parts in woods metal (that is a compound with metal particles that cures at low temperature) which conducts electricity and is as strong as alluminium.
It can be used to pour circuitry inside a plastic part for instance and you can solder it.
There are some interesting articles about that stuff published by the university of Bath (UK)
Have a look at the RepRap site, there you can find the links in the Darwin version 2 articles.
Those guys are looking into 3dprinting electronic circuitry inside plastic parts in 1 run for their next version of the Reprap.
i believe that stuff cures at 70 degrees celcius or thereabouts.
Might be usefull for casting metal parts for your trainsets at low temperature.

Any silicone rubber can handle those temperatures since many plastics are hardned by heating them at those temperatures, for instance epoxy is post cured at those temperatures for extra strength.
And the mixing is not realy an argument anyone can weigh one part of the compound then weigh the other.
as far as airbubbles are concerned, If you mix it carefully (not to fast to prevent mixing in air) you get hardly any bubbles with modern RTV's.
For a fast mold i usualy find it sufficient to just burst airbubbles on the surface with a toothpick for 10 minutes after pouring the rubber, i rarely find bubbles pressed against the master, because i first apply a thin layer of rubber with a brush and let it cure first., then fill the moldframe
It's not fast, but it eliminates the need for a vaccuumchamber.
But then again i doubt there is any need for speed in the model train hobby

I've done quite a bit of casting using various RTV materials, and let me just speak for a second about bubbles in the RTV.

I went for a couple of years using the "mix carefully and pop the bubbles you can" method, and had some decent results. A while back, however, I put together a vacuum chamber and it made all the difference in the world. I went from succeeding most of the time to succeeding ALL of the time, and now I use an electric drill with a paint stirrer to mix up the RTV. It's quicker and much more thorough.

I mix the RTV, put it in the chamber and pull a vacuum for a couple of minutes. Then, I pour the mold and place the whole thing (frame, master and wet RTV) into the chamber, and pull a vacuum for another couple of minutes. When I open the chamber the RTV is bubble-free every time.

If you are pouring wax into the RTV this probably isn't as critical, but if you are pouring pewter directly into RTV molds a bubble near the surface can spell disaster. The heat from the pewter will cause the gasses to expand, deforming the mold and ruining the casting.

I spent a couple hundred dollars on the parts and vacuum pump, and it is some of the best money I ever spent.