3D Printing Belts for Vintage Hardware

It may be hard for some of the younger readers to believe, but there was a time when hardware was full of little rubber belts. Tape decks, VCRs, even some computers: they all had rotating parts that needed to transfer power to other components, and belts were a cheap and quiet way to do it. Unfortunately, now decades later we realize that these little belts are often the Achilles heel of classic hardware, getting brittle and breaking long before the rest of the components are ready to give up the fight.

Which is exactly what [FozzTexx] found when trying to revive his newly purchased Commodore PET 2001. The belt inside of the cassette drive had become hard and fallen to pieces, and rather than hunt around for a replacement, [FozzTexx] reasoned he might be able to print one out of a flexible 3D printer filament like NinjaFlex. Besides, this wasn’t the only piece of vintage tech in his house that needed a belt replacement, so he figured it would be a worthwhile experiment.

As the original belt was little more than dust, [FozzTexx] had to design his replacement from scratch. He started by cleverly replicating the path the belt would need to take with string, and then measuring the inside diameter of the string circle with his calipers. [FozzTexx] then reduced the diameter by 5% to take into account the stretching of the new belt.

The profile of the belt was square, which made modeling and 3D printing much easier. [FozzTexx] just subtracted a smaller circle from a larger one in 2D, and then extruded that circle into the third dimension by 1.18 mm to match the height of the original part. Careful measurement paid off, and the newly printed NinjaFlex belt had his Commodore loading and saving programs on the first try.

We’ve covered the difficulty in sourcing replacement belts for old hardware previously, so it will be interesting to see if others are able to make use of the research [FozzTexx] has done here. Of course, longevity concerns are always brought up when NinjaFlex is used, so hopefully [FozzTexx] keeps us updated.

Print A Flexible Keypad

[Micah Elizabeth Scott] needed a custom USB keyboard that wrapped around a post. She couldn’t find exactly what she wanted so she designed and printed it using flexible Nijaflex filament. You can see the design process and the result in the video below.

The electronics rely on a Teensy, which can emulate a USB keyboard easily. The keys themselves use the old resistor divider trick to allow one analog input on the Teensy to read multiple buttons. This was handy, but also minimized the wiring on the flexible PCB.

The board itself used Pyralux that was milled instead of etched. Most of the PCB artwork was done in KiCAD, other than the outline which was done in a more conventional CAD program.

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Three Thumbs, Way, Way Up!

At least one in their lives — or several times a day — everyone has wished they had a third hand to help them with a given task. Adding a mechanical extra arm to one’s outfit is a big step, so it might make sense to smart small, and first add an extra thumb to your hand.

This is not a prosthetic in the traditional sense, but a wearable human augmentation envisioned by [Dani Clode], a master’s student at London’s Royal College of Art. The thumb is 3D-printed out of Ninjaflex and mounted to a printed brace which slides over the hand. One servo rotates the thumb, and a second pulls it closed using a bowden cable system — not unlike that of a bicycle brake. Control of the thumb is achieved by pressure sensors in the wearer’s shoes, linked via Bluetooth to a wristband hosting the servos and the electronics. We already use our hands and feet in conjunction, so why not capitalize on this intuitive link?

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Print Flexible PCBs with a 3D Printer

Let’s get it out of the way right up front: you still need to etch the boards. However, [Mikey77] found that flexible plastic (Ninjaflex) will adhere to a bare copper board if the initial layer height is set just right. By printing on a thin piece of copper or conductive fabric, a resist layer forms. After that, it is just simple etching to create a PCB. [Mikey77] used ferric chloride, but other etchants ought to work, as well.

Sound simple, but as usual, the devil is in the details. [Mikey77] found that for some reason white Ninjaflex stuck best. The PCB has to be stuck totally flat to the bed, and he uses spray adhesive to do that. Just printing with flexible filament can be a challenge. You need a totally constrained filament path, for one thing.

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3D Printed Door Latch has One Moving Part – Itself!

A group at the Hasso-Plattner Institute in Germany explored a curious idea: using 3D printed material not just as a material – but as a machine in itself. What does this mean? The clearest example is the one-piece door handle and latch, 3D printed on an Ultimaker 2 with pink Ninjaflex. It is fully functional but has no moving parts (besides itself) and has no assemblies. In other words, the material itself is also the mechanism.

The video (embedded below) showcases some similar concept pieces: door hinges, a pair of pliers, a pair of walker legs, and a pantograph round out the bunch. Clearly the objects aren’t designed with durability or practicality in mind – the “pliers” in particular seem a little absurd – but they do demonstrate different takes on the idea of using a one-piece item’s material properties as a functional machine in itself.

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Zizzy The Personal Robot Uses 3D Printed Artificial Muscles Instead of Hobby Servos

Zizzy is a personal robot designed to help those with limited mobility. Rather than being assisted by a nightmare creature, Zizzy would offer a more appealing and friendly option.

The coolest part about Zizzy is the 3D printable pneumatic artificial muscles. Project creator, [Michael Roybal] said it took over a year of development to arrive at the design.

The muscles are hollow bellows printed out of Ninjaflex with carefully calibrated settings. A lot of work must have gone into the design to make sure that they were printable. After printing the muscles are painted with a mixture of fabric glue and MEK solvent. If all is done correctly the bellows should be able to hold 20 PSI without any problem.

This results in a robot with very smooth and precise movement. It has none of the gear noise and can also give when it collides with a user, a feature typically found only in very expensive motor systems. If [Michael] can find a quiet compressor system the robot will be nearly silent.

3D Printed Kinetic Art

Artificial muscles and soft robotics don’t get the respect they deserve, but [mikey77] is doing some very interesting work with artificial muscles that can be made on just about any 3D printer.

Like other artificial muscles and soft robotic actuators we’ve seen – like this walking sea slug and this eerie tentacle – [mikey77]’s muscles are powered by air. Instead of the usual casting method, he’s printing these muscles from Ninjaflex, a flexible plastic that is compatible with most 3D printers.

As they come off the printer, these 3D printed pneumatic muscles leak, and that means [mikey77] has to seal them. For that, he created a sealant out of Loctite fabric glue thinned with MEK. The addition of MEK dissolves the outer layer of Ninjaflex, allowing the glue to bond very, very well to the printed muscle.

So far, [mikey77] has created a pneumatic flower that blooms when air is added. He’s also created a muscle that can lift more than four pounds of weight with the help of a 3D printed skeleton. It’s a great way to experiment with flexible robots and pneumatic muscles, and we can’t wait to see what weird creatures can be created with these actuators.

Thanks [Lloyd] for sending this one in.