Making Funhouse Mirror Lenses

[Robb] has had a little experience making lenses from scratch. His first attempt was for a DIY projector, and while the lens was a little blurry, it did work rather well for something carved out of a block of acrylic. Now he’s taking his experiments with lenses even further with DIY optics that turn everything into a funhouse mirror.

There were two techniques tested while making these lenses. The first was the old standby, CNC milling. A piece of acrylic was put in a CNC and carved with a 1/2″ ball mill. The second technique was 3D printing on a very fancy and very expensive Objet Connex 500. Neither of these methods produce a ready to use lens; to get a finished lens out of the machined or printed objects, [Robb] had to wet sand with 240, 320, 400, 600, 1000, 1500, and 2000 grit sandpaper. After a few hours worth of sanding, the parts were polished with a scratch remover.

Making a lens like this isn’t really that novel – it’s basically the same way lenses have been made for 500 years. The real trick here is making funhouse mirror style lenses. These lenses were created by raytracing in Rhino and Neon. It’s tricky; the index of refraction for acrylic is a little lower than glass, and the refraction for 3D photoresin is a bit higher than glass.

With those models in hand, it’s a relatively simple matter of making some very cool and very strange lenses.

Wounded Soldier Gets Robotic Hand Replacement

[Neal Muzzy], a local member of the Cedar Valley Makers makerspace, just made news on Open Bionics for his robotic prosthetic hand called Dextrus v1.2 which he made for his friend, and wounded war veteran, [Taylor].

In just two months, [Neal] worked with his friend to make this robotic prosthetic with the goal of having it more functional and easier to use than [Taylor]’s current prosthetic. The very first prototype was made by using the open-source Dextrus design, to test fit, and control using EMG sensors. Once they determined it would work — onto customizing!

They call it Dextrus V1.2, and it works better for [Taylor] than the original — but that’s the whole point of the Open Hand project — starting with a base design, and making it better. If you’re not familiar with the Open Hand Project, it was originally crowd-funded on Indiegogo, and is now an organization to make robotic prosthetic hands more accessible to amputees. We wrote about it in Hacklet 41 – Prosthetic Projects.

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3D Printing Different Colors with a Single Extruder

Let’s be honest, multi-extruder 3D printers don’t work the greatest — even MakerBot decided to get rid of the feature in their latest line of printers. So what are you going to do when you want to print a multi-colored object with your trusty single extruder? Pause the print like a savage and exchange the filament? No, no, it’s much easier than that — well, you’re still going to have to switch the filament.

[Jan Henrik] has put together a simple script in OpenScad to split up 3D files into layers in order to facilitate printing in multiple colors (or even materials). You load in the file, tell it the print height you want to do, export, convert to G-Code, print, rinse, repeat. In between the layers you have time to purge the extruder, remove any excess skirt or support material, and then hit print again. Quite a bit easier than hitting pause and jogging the extruder out of the way (while avoiding plastic dribble coming out of your extruder!).

Meanwhile if your prints get interrupted — or fail a lot — you might be interested in this project by a group of MIT researchers. It’s an add-on for 3D printers that uses a laser scanner to evaluate how much of the part was printed, allowing you to restart a print that failed!

3D Printed Pogo Pin Programmer

The new hotness for Internet of Things hardware is the ESP8266. Alone it can connect to a WiFi network, but it doesn’t really have a lot of output options. Paired with an ATMega, and you really have something. That’s the philosophy behind the WIOT board, and when [Chris] was assembling these boards, he needed a way to flash firmware. The board has an unpopulated ISP header from the assembler, so pogo pins are the answer. How do you make a pogo pin jig? With a 3D printer, of course.

The ISP header wasn’t populated to give the board a slim profile, but this means a jig of sorts would be needed to program the WIOT. The first attempt was buying a few pogo pin adapters from Tindie, but this was terribly uncomfortable to hold while the board was being programmed.

To fix this problem, a small clip device was rigged up, printed out, and used for programming. Interestingly, this clip has a very deep throat, and a few holes used for bolting on a separate programmer. This shows a lot of forward thinking: the programmer can be reused for different boards with completely different layouts and programmers. If the next revision of the WIOT needs a JTAG header to program the micro, the problem of programming it is already covered.

Repurposing a Palm Portable Keyboard

Typing comfortably on a Smart Phone is best done using an external keyboard, especially if you spend a lot of time on IRC or use other chat apps. Obviously, the keyboard needs to be portable too. [cy384] felt the current crop of portable keyboards left a lot to be desired in terms of build quality and feel. That’s when the Palm Portable Keyboard (PPK) caught his eye. It’s small enough to fold up and fit in a pocket, yet unfolds to a size big enough to feel comfortable while typing. Unfortunately, the version he preferred to use did not have either a Bluetooth or a USB interface, so he built up this Palm keyboard adapter.

The portable keyboards have a serial interface and custom connectors depending on the Palm model they were designed to connect to. [cy384]’s goal was to adapt the PPK as a generic USB HID keyboard using an Arduino Pro Mini clone, with a 3D printed adapter for both of the keyboard types that he had. The keyboards  use inverted TTL logic at 9600 baud with no parity and one stop bit. Some handshaking needs to be taken care of and there’s a low power mode that needs to be managed via the Arduino code. He was lucky to get his hands on a reference document that provided the hardware and software details to help him crack all of this. His Github repository has the code and 3D printable files for the adapters.

More MRRF, This Time A Roundtable

Ah, you thought we were done with our coverage of the Midwest RepRap Festival, didn’t you? No, there’s still more, thanks to [Timothy Koscielny] sending in some digital assets that were required to put this post together. This time, it’s the RepRap roundtable with [Johnny Russell] from Ultimachine, [Shane Graber] from MakerJuice, [Lars Brubaker] from MatterHackers, [Sanjay Mortimer] from E3D-Online.

The first video covers the introductions for these very prominent 3D printer developers and their views on what future advances in 3D printers will be, the differences between Delta, Cartesian, and Polar bots (there aren’t many), and when resin printers will start to pick up.

In the Q&A session, the panel fielded a few questions from the audience. Questions included how to get people into 3D modeling, an amazing question dealing with what we should be making (with the implication that we’re only making stupid plastic trinkets), and what needs work to bring 3D printing to the masses.

Special thanks to [Casey Hendrickson] from ninety two point three WOWO for MC’ing the RepRap roundtable and to [Timothy Koscielny] for the audio work. This isn’t it, though: I still need to dump a bunch of pictures after the break.

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Automated Robotic Target Practice

Fan of shooting things? Jealous of proper shooting ranges? Why not build your own automated target practice rig with a few servos and an ATMega168?

[Cowboy Bob] of Making Stuff decided he needed a practice target, and wanted to make it a bit more interesting than throwing up some beer cans on a fence. He’s created a highly durable 10-target “Robo-Target” which can be remote controlled or automated.  A thick piece of 1/4″ angle steel makes up the main frame of it, so if you’re practicing with hand guns it’ll take the abuse. If you’re just using  an air soft or paintball gun you probably don’t need to make it this beefy.

Five servo motors swing paper five targets back and forth on 3D printed swing arms — and since each target has a front and a back side, it gives you 10 different things to shoot at. In challenge mode it’ll even show you two targets at a time which will require you to quickfire in order to get both!

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