Mold making is a hacking skill we see pop up around here from time to time. But rarely do we hear about problems in the process, and they must happen. Here’s proof. This Fail of the Week focuses on [Michael’s] unfortunate experience with failed mold making due to uncured silicone around the master mold. It’s worse than it may sound, since he lost about a pound of silicone to the fail, and we’re unsure of whether he can even use the master again (how do you clean uncured silicone off of something?). Not to mention the time lost from setting up the pour and waiting 20 hours for it to cure.
Soon after the issue presented itself [Michael] started researching to see what had gone awry and noticed that the master should have been sealed with acrylic lacquer. This gave him the opportunity to test several different finishes before making a run at the full mold once again. He picked up a variety of the paint products he could find locally, used them to coat some scraps, and globbed on some silicone to see which worked the best. He found a couple of different primers worked well, as did both glossy and matte acrylic coatings.
If you’ve never had a reason for mold making before, keep it in mind. You’d be surprised what kind of factory-production-type things can be pulled off by 3D printing a master, and casting a silicone mold of it.
Fail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.
We see more and more projects that use custom molds and casting materials. The latest is this custom seven segment display which [Ray74] put together. The idea of making your own LED displays couldn’t be much easier than this — everything but the LEDs and wire is available at the craft store.
He started by making models of each segment out of pink erasers. The lower left image of the vignette above shows the eraser segments super glued to some poster board. The decimal is a pencil eraser, with a fence of wood to contain the molding material. Amazing Mold Putty was mixed and pressed into place resulting in the mold shown in the upper right.
From there, [Ray] cast the clear epoxy three times. Once dried the clear pieces were sanded, which will shape them up physically but also serves to diffuse the light. They were then placed inside of another mold form and an epoxy pour — this time doped with black enamel paint — finishes the 7-segment module. The final step is to glue the LEDs on the back side and wire them up.
This definitely trumps the build which Hackaday Alum [Kevin Dady] pulled off using hot glue sticks as light pipes.
This invertebrate gripper uses air pressure to grab onto objects. The secret is all in the design. But you don’t have to reinvent the wheel. If you’ve got a 3D printer you can follow this guide to make your own.
The gripper is made of silicone. The trick is in designing an inner structure that deforms in one direction when pressurized. To make one or one hundred, simply download the design files and 3D print a mold. The process from there is much like the silicone band prototyping process we looked at back in March. The two-part silicone is mixed and poured in the mold. You also need to pour some on a flat surface. We were under the impression that uncured silicone would not stick to cured silicone but we were wrong. The two parts are glued together with a fresh batch of the mix. After everything has set up you can pierce the bladder with a hose in order to inject air.
Below you can see the star-shaped version being tested. There’s also a Harvard research video which shows a similar design lifting an egg.
Continue reading “Air-powered gripper design makes them easy to produce”
For those unfamiliar with it, Bocce Ball is an outdoor game played with a set of heavy grapefruit-sized balls. We’ve never really thought of making our own set, but as you can see above, it can be done. These are six Bocce balls produced at home by [Horvitz444].
It seems the commercially available balls have a cement or clay core covered in a layer of high-impact epoxy. [Horvitz444] was able to recreate this starting with some vacuum forming. He built his own former out of peg board and a shop vac. The plastic stock he used was a light panel from the home store. After heating it up in the oven he formed a mold using what looks like two halves of Bocce balls. The mold halves were melted together using a soldering iron. After pouring in the secret concoction of cement ingredients and letting them harden, he removed the orbs from the molds and ground down the seams until smooth. They were covered in epoxy and painted. Most of these details were gleaned from his comments in the Reddit thread.
When you’re getting close to a production run the prototypes really need to hit the mark before pulling the trigger. [Bob’s] still hard at work getting his scoreboard off the ground and his most recent endeavor was to find a way to prototype the rubber gasket without blowing his shoestring budget. His solution was to harness the power of 3D printing to generate a model from which he could create the mold from which he cast the rubber part.
To make things a bit more difficult, the band isn’t just decorative, it doubles as the tactile part of the scoreboard buttons. You can see all six of them (before being painted to make them stand out) in the inset image above. Just above that image is a picture of the mold making process. The toothpicks are suspending the 3D printed model of the rubber band while the lower half of the silicone mold sets up. Once that had happened [Bob] sprayed release agent to ensure the top half of the mold wouldn’t stick while it cured.
The results turned out just great. Sure, this isn’t the way to go if you’re making a lot of these things. But we’re impressed at the quality he achieve for a one-off item.
If the finished product on the left looks familiar it’s because we looked in on the project last June. [Bob] continues with improvements and plans to launch a crowd funding campaign this week.
This delightful marketing ploy requires the listener to fabricate their own record out of ice. The band Shout Out Louds wanted to make a splash with their newest single. So they figured out how to make a playable record out of ice. The main problem with this is the grooves start to degrade immediately when the ice begins to melt. So they shipped a mold of the record and a bottle of water to a select few listeners (just ten in all). Hear the result in the video after the break.
Now if you want to make something like this for yourself we can help you out just a bit. The mold is made of silicone and it wasn’t so long ago that we saw a guide for those new to mold making. The raw material isn’t that hard to find either. The project above tried several different approaches and found the best results can be attained with plain old distilled water. No, the one hard part is figuring out how to make your own master. If you’ve got a way of doing this in the home lab, please tells us about it!
Continue reading “Ice record single needs six hours in the deep freeze before you can listen”
Soft robots are a peculiar wing of technology. They don’t use frames and motors for locomotion, but as the name implies they are made of soft materials. They move by pumping fluid — it could be air or liquid — in and out of bladders that push or pull against the body itself. [Matthew] points out that fabricating soft robots has traditionally been a time-consuming and difficult task. He’s trying to make it easier by 3D printing molds into which soft robots can be cast. This way the parts can be designed in CAD, converted to a mold design, and pushed to a 3D printer.
The object with which he’s been testing the technique functions like an octopus tentacle. The image at the bottom left illustrates the internal structure, with rings separated to allow the appendage to flex, and tubes running parallel to the appendage to provide the force needed to bend it. Above that image you can see one of the molds that was used, and the final product is on the right. The video after the break shows a demonstration of this bending left and right as air is pumped in using the bulb of a blood pressure cuff (or Sphygmomanometer for those paying attention).
Continue reading “Simplifying fabrication of soft robots”