Fail of the Week: Silicone Molding That Won’t Cure

fotw-uncured-silicone

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.


2013-09-05-Hackaday-Fail-tips-tileFail 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.

DIY Heatsinking PCBs

pcb heatsink

We have covered many do it yourself PCBs before, but this video guide adds an easy way to sink heat from high power devices, which we think you might find handy.

It is a very simple process that [CNLohr] uses to keep his small RGB LED projects from overheating. It starts by using a readily available silicone thermal sheet as the substrate by applying it to copper foil. He then applies a toner-transfer circuit pattern to the copper by running the pair through a modified laminator a few times. He makes note that you have to apply the plastic backing side of the silicone sheet to the copper foil to prevent the laminator from chewing it up.

After the typical ferric chloride etching process is complete, he then uses 220 grit sandpaper to remove the toner pattern. Often steel wool is used, but because of the sensitive nature of the silicone, sandpaper works better to avoid peeling up traces.

We have featured [CNLohr] before, as he does some top-notch tutorials in his workshop — which makes for both a fascinating and distracting backdrop for the videos. This one is a bit long (~20 minutes), but is very thorough and goes through the entire process from start to finish. Check it out after the break.

[Read more...]

Air-powered gripper design makes them easy to produce

air-powered-gripper

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.

[Read more...]

Molding rubber for a pre-production prototype using a 3D printed model

molding-rubber-for-production-models

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.

Ice record single needs six hours in the deep freeze before you can listen

ice-record

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!

[Read more...]

Reproduce 3D printed models by making your own molds

Need fifty copies of that 3D printed whirligig you’re so proud of? It might be faster to just cast copies by using the 3D printed model to make a mold. [Micah] found himself in this situation and managed to cast one copy every 10-12 minutes using the mold seen above.

With the object in hand, you need to find a container which will fit the mold without too much waste. The bottom half of the mold is then filled with modeling clay, a few uniquely shaped objects to act as keys, and the model itself. After getting a good coating of release agent the rest of the mold is filled with a silicone rubber product which is sold for mold making. This creates one half of the mold. After it cures the clay and key objects are removed, everything is sprayed with the release agent, and the other half of the mold is poured.

Now your 3D object can be copied by pouring two-part resins in the to shiny new mold.

Soft robots given veins the let them change their stripes

If it were alive this robot would be classified as an invertebrate. It lacks a backbone and interestingly enough, all other bones are missing as well. The Harvard researchers that developed it call it a soft robot. It’s made out of silicone and uses pathways built into the substance to move. By adding pressurized air to these pathways the appendages flex relative to each other. In fact, after the break you can see a video of a starfish-shaped soft robot picking up an egg.

Now they’ve gone one step further. By adding another layer to the top, or even embedding it in the body, the robot gains the ability to change color. Above you can see a soft robot that started without any color (other than the translucent white of the silicone) and is now being changed to red. As the dye is injected it is propagating from the right side to the left. The team believes this could be useful in a swarm robotics situation. If you have a slew of these things searching for something in the dark they could pump glowing dye through their skin when they’ve found it. The demo can be seen after the jump.

[Read more...]

Follow

Get every new post delivered to your Inbox.

Join 91,391 other followers