[Dt99jay] lives in a historic Victorian-era district in the UK. Most homes in the area have ornate exterior window dressings with stone consoles holding up heavy stone hood molding.
The window hood molding turned out to be wood — most likely the result of damage repaired after the blitzkrieg bombings of WWII. The 1940’s era work is now rotting away, so it was time for a repair. When the hood was pulled away from the window, disaster struck. One console completely crumbled, while the other lost large chunks of material. The They weren’t solid stone after all, but replacements most likely molded with Coade stone.
There are no ready replacements for consoles like this. [dt99jay] couldn’t just swap them out for modern looking replacements, so he set about replicating the consoles. The remaining console was much too delicate to remove from the building, so [dt99jay] glued the missing pieces back on. He then filled any missing parts and carefully scraped way all the loose paint. Then came the difficult part — making a mold while the console was still mounted on the house.
Room Temperature Vulcanizing (RTV) silicone rubber was carefully applied to the console. The RTV is thick enough to stay on while it dries. After several thick layers of RTV, the console was covered. [Dt99jay] then covered the mold with plaster of Paris bandages to support it. The finished mold was carefully removed from the house, and [dt99jay] filled all the low spots and air bubbles with RTV.
New castings were made using a mixture of cement and playground sand. Once painted, the results matched perfectly. The historic conservation committee was pleased, and the window was once again structurally sound.
Staking and potting are not often used in the hobby electronics world, not really entering to the common vernacular. However, everyone who’s ever busted out a glue-gun to convince that dang wire that keeps coming loose to stay has done it.
However, as [Sean Thomas] touches on, staking is not necessarily as easy as a dob of hot glue. There is a method to the madness. [Sean] gives some examples in pictures, but also directs people to the excellent NASA standard methods for staking. It’s surprising how many unintuitive caveats there are to the proper technique.
Potting, or covering everything in epoxy forever, is a great way to get a waterproof, unserviceable, and practically mechanically invincible circuit. The big challenge in potting is picking the right material. A soft silicone, for example, might transfer an unexpected force to an unexpected section of the circuit and cause a mechanical failure. A nice hard epoxy may be too insulating and cause a thermal failure. The standard RTV from the big box store has acetic acid that will eat your components.
These two techniques that come in handy when you need them and worth the bit of reading it takes to get familiar. Have you used either in your own workshop? Let us know the application and the material/techniques you have tried in the comments below.
This set of white RepRap parts were created in molds, instead of being printed by another RepRap. [Mark A. Ganter] of the University of Washington admits that this breaks the idea of a 3D printer that is self-replicating. But the molds – which were created by tweaking Prusa Mendel parts to be mold friendly – have the ability to produce every plastic part necessary to build your own RepRap and they can do it much faster. Once the molds were completed [Mark] and his students were able to produce a full set of parts in just 30 minutes, cutting as much as 14 hours off of the time it would have taken to print the parts. Still not convinced? How about this: the molds can be created by a 3D printer or by using a high-resolution power printing method like they have here.
The process starts by printing master parts, then creating a silicone RTV mold from them. Once the molds are ready, [Mark’s] team pours polyurethane into them and waits for it to harden. They plan to share the STL files in less than a week so that you can make your own molds to use to build your RepRap army.