[Abhimanyu Kumar] was watching YouTube videos one day when he came across something called a Polariscope — After learning how it worked, he discovered you can make your own using household items!
First off, what is a Polariscope? Well, put simply, it is a device that can show you the photoelasticity of a clear specimen, which can reveal the stress distribution in the material! And it is actually really easy to make one.
All you need to build your own is:
- A polarized light source (any modern LCD monitor)
- A transparent specimen (plastic cutlery, glass statues, plastic you can bend, etc)
- A circular polarizing filter (the cheap 3D glasses you didn’t return at the theater)
Then just place the objects in the order shown in the diagram and start snapping some photos. This would be really cool for checking stress concentrations in a project — provided you are using some Lexan or acrylic!
[Wilywyrm] needed to come up with a final project for art class that commented on a social issue. Healthcare, schmealthcare, he said, and busted out this movie poster about the NSA spying scandal instead.
The circuit uses three extended-duty astable 555 timers to control the brightness of the 5050 RGB common-anode LED strips that run up the sides of the 24″ x 12″ x 1/4″ acrylic panels. Each of the three panels was laser-engraved at 600 DPI on an Epilog laser engraver and features a different aspect of the poster. There’s one for Snowden, one for Daniel Craig, and one for the text.
[Wilywyrm] tied the color channels together in the first panel to output white light. He used red for the second panel and blue for the third. A complete list of parts with build notes is available on his Google Drive. [Wilywyrm]’s notes include improvement ideas, like making all the RGB strips color-adjustable with more 555s or a microcontroller and timers.
Perhaps [Wilywyrm] could get into the clear whiteboard business after college.
We’re starting to become a repository for Arc Reactor replica projects. The one shown above uses mostly laser cut components. We missed it back in May when [Valentin Ameres] tipped us off the first time. But he sent it in again after seeing the 3D printed version earlier this month.
Our biggest gripe is that we don’t have our own laser cutter to try this out on. Everything has been cut from 2mm thick acrylic. The black, silver, and copper colored components were painted to achieve this look. Many of the clear parts also had a dot matrix etched into them to help with light diffusion.
Basic assembly just required the parts be glued together. The finishing touches include wire-wrapping the slots of the outer ring and adding LEDs and current limiting resistors.
The plans are not freely available, but the 3D printed version linked above doubles as a 123D tutorial. That should help get you up to speed designing your own if you are lucky enough to have time on laser cutter.
Continue reading “Laser cut Arc Reactor replica”
[Ben Krasnow] milled some lenses out of cast acrylic and needed a way to get an optical finish on the tool-marked surface. He tested several acrylic finishing methods to achieve a crystal clear finish. The tests were done using flat chunks. A regiment of sandpaper, from coarse to fine, was used as the first stage of the operation. From there [Ben] sought out the best finishing step, starting with hand polishing tests, flame polishing, and methylene chloride vapor polishing (which is something along the lines of acetone vapor polishing for 3D printed ABS parts).
Flame polishing and vapor polishing are not really exact sciences… at least in the tests he performed. It was difficult to know exactly how long to expose the acrylic. Too short or too long resulted in poor clarity. Watch his video to get a look at all results. We’d say the the easiest way to make milled acrylic clear without achieving an optical finish is to flame polish it as it doesn’t really require that you sand it ahead of time. But [Ben’s] tests prove that you can’t beat hand polishing with 600 then 2000 grit sandpaper before finishing up with a liquid plastic polish.
Continue reading “Polishing optics milled from acrylic”
Regular reader [RoadWarrior222] has watched as we’ve featured several projects that show how to bend acrylic. But so far he hasn’t seen us cover his favorite technique developed by [Dale A. Heatherington] which uses a hot wire forming tool to make precise bends. The tool is simple to use plus it’s cheap and easy to build. It’s a great choice if you don’t have a heat gun, and it may be possible to make cleaner bends than other techniques.
The business end of the bending tool is the red-hot Nichrome wire running through the aluminum channel. That channel is used to protect the MDF and act as a spacer so that the wire doesn’t touch the acrylic. On the near side the wire is anchored with a screw, but on the far end it is kept taught by including a spring. The wire heats up as it is connected to a 12V battery, but since the heating is cause by the wire’s resistance it will only get red-hot in between the alligator clips providing power. To make sure your bends will be perpendicular to the edge of the acrylic there’s an aluminum guide strip on one side of the MDF platform.
You can salvage Nichrome wire from an old hair dryer. If you have any left over it’s great for other projects like building a CNC hot-wire cutter.
Here’s a design that lets you make acrylic enclosures without using fasteners. The red outline in the diagram above is a bit hard to make out. But look closely and you’ll realize that there is very little material which has been removed to form the clip. This uses the rigidity/flexibility of the material to form a spring that will hold a couple of pieces tightly together.
In a links post last year we looked at [Patrick Fenner’s] fantastic analysis of the strength of using kerf-bending to form several sides of a case out of one piece of material. He’s used that same analytic expertise to take a look into this design. He even suggests that making the cut on the hook-side a bit deeper will help improve the resilience of the part. If you have a laser cutter on hand and want to give this a try he’s posted the plans on Thingiverse.
Yet another project that proves you need to acquire a laser cutter. This Airsoft turret rotates, tilts, and includes a hopper for ammo.
All of the pieces were cut from acrylic. The base includes a bracket which keeps the large rotating gear level by sandwiching it between the layers. That and the tilt mechanism are pretty straight forward. The module responsible for loading the BBs is pretty neat though. It uses a gear with round teeth the same diameter as the ammo. Once a BB is picked up it is forced upward into the tubing that feeds the gun. Get the full picture from the demo video after the break.
The one thing [The Liquider] is wondering about is how to provide feedback for the tilt and rotate functions. We can’t think of an easier way than to use simple rotary encoders. The Arduino Mega he wishes to use as a driver will have no problem interfacing with reflectance sensors and the acrylic makes it simple to mount this type of black and white encoder wheel.
Continue reading “Airsoft turret has turn, tilt, and auto-feed to keep those BBs flying”