A Robot For Everything: Now Even Zippers

Sometimes we see projects that are so clever while being remarkably simple, that we can’t help thinking: Why didn’t I think of that! Take [Haresh Karnan]’s zipper robot, for example. It’s a well-designed 3D-printed shell with two geared motors for traction, that can both undo and do up zippers. Behind that seemingly simple design probably lies a huge iterative design process to arrive at a shape perfect for the job, but the end result is so elegant that even [Haresh]’s write-up and Hackaday.io page for the project are short and to the point. Download the STL file, snap in the motors, apply to a zipper, and away you go. He suggests rubber bands as a traction aid, but that’s pretty much it.

The results can be seen in the video below the break. While we might be tempted to make jokes about the terminally lazy using this device to save unnecessary labour after a toilet break, we can see that it might have a real application. If you have any friends with restricted dexterity you will understand how having an automated helper with such a fiddly task as a zipper could be an extremely useful accessibility aid.

While we’re on the subject of zippers, if you missed it a few weeks ago here’s our in-depth look at their story.

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3D-Printed Parts Torture-Tested in Nitro Engine — Briefly

Additive manufacturing has come a long way in a short time, and the parts you can turn out with some high-end 3D-printers rival machined metal in terms of durability. But consumer-grade technology generally lags the good stuff, so there’s no way you can 3D-print internal combustion engine parts on a run of the mill printer yet, right?

As it turns out, you can at least 3D-print connecting rods, if both the engine and your expectations are scaled appropriately. [JohnnyQ90] loves his miniature nitro engines, which we’ve seen him use to power both a rotary tool and a hand drill before. So taking apart a perfectly good engine and replacing the aluminum connecting rod with a PETG print was a little surprising. The design process was dead easy with such a simple part, and the print seemed like a reasonable facsimile of the original when laid side-by-side. But there were obvious differences, like the press-fit bronze bearings and oil ports in the crank and wrist ends of the original part, not to mention the even thickness along the plastic part instead of the relief along the shaft in the prototype.

Nonetheless, the rod was fitted into an engine with a clear plastic cover that lets us observe the spinning bits right up to the inevitable moment of failure, which you can see in the video below. To us it looks like failing to neck down the shaft of the rod was probably not a great idea, but the main failure mode was the bearings, or lack thereof. Still, we were surprised how long the part lasted, and we can’t help but wonder how a composite connecting rod would perform.

Still in the mood to see how plastic performs in two-stroke engines? Break out the JB Weld.

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Scan Your Film The 3D Printed Way

Everyone has a box or two at home somewhere full of family photographs and slides from decades past. That holiday with Uncle Joe in Florida perhaps, or an unwelcome reminder of 1987’s Christmas jumper. It’s fair to say that some memories deserve to be left to gather dust, but what about the others in a world of digital images?

You could of course buy a film scanner to digitize Uncle Joe on the beach, but aside from the dubious quality of so many of them where’s the fun in that? Instead, how about 3D printing one? That’s what [Alexander Gee] did, in the form of an adapter to fit the lens mount of his Sony camera that contains both a 50mm enlarger lens and a mount for the slide. It’s a simple enough print, but he’s made enough parts parametric for users to be able to adjust it to their own camera’s mount.

Sometimes builds do not have to be complex, push boundaries, or contain more computing power than took us to the Moon. This one is simple and well-executed, and for anyone prepared to experiment could deliver results with a variety of cameras and lenses. Of course, you have to have some film to scan before you can use it, so perhaps you’d like to try a bit of home developing.

Repairs You Can Print: Nintendo DS Lite With New Battery And Case

The problem with hanging on to old consumer products is that the original batteries no longer hold a charge. To make matters worse, replacement batteries ordered online have likely been sitting on a warehouse shelf for years and are no better. [Larry G] faced this issue with his old Nintendo DS Lite. Luckily he remembered a hack from his youth where a friend’s Dad had duct-taped a massive alkaline D-cell battery pack to the back of a Gameboy to give it a longer life. And so [Larry] gave new life to his Nintendo DS Lite by designing and 3D printing a case for a battery with an even larger capacity than the original.

He first obtained a 2400 mAh 18650 lithium-ion cell, one with over voltage and under voltage protection. With that as a guide, he designed and 3D printed a case for it made up of four printed parts. The case was needed because the 18650 doesn’t fit in the NDS Lite’s battery compartment. Instead, one of the parts, which he calls the fake battery, fits in the compartment and has copper strips glued to it for connecting to the NDS Lite. From there, wires go to another part wherein sits the 18650. The remaining parts secure it all in place.  Charging is done using the NDS Lite’s built-in charger. Even though the new case adds significant bulk, it actually fits well in the hand.

No doubt many of you have your own old NDS Lite sitting around that can benefit from this repair. The project details and STL files can be found on his Hackaday.io page using the above link.

This is also [Larry]’s entry for our Repairs You Can Print contest which puts him in the running for one of two Prusa i3 Mk3s plus the multi-material upgrade.

Repairs You Can Print: A Turn Signal Switch For A Chevy Corvair

Running a classic car is often an easier prospect than a more recent model, as the mechanical parts have a tendency towards commonality between models, simplicity, and maintenance using basic tools. However assuming some level of parts availability for your model it is not usually the running gear that causes headaches. Instead, it is the smaller and less durable parts, the little plastic pieces that formed vital components but have not been manufactured for decades. These are the parts for which the advent of accessible 3D printing has been a revelation, suddenly the owner of a wreck need only to have basic CAD skills to deliver the goods.

A Chevy Corvair (not [Ken]'s one). Greg Gjerdingen [CC BY 2.0].
A Chevy Corvair like [Ken’s]. Greg Gjerdingen [CC BY 2.0].
[Ken] has a ’63 Chevy Corvair, an attractively-styled motor notable for its rear-engined layout and air-cooled engine. And it seems his car is plagued by the same issue as all other early models, a failure of its turn signal mechanism. The version fitted to later cars is a vastly superior replacement, but required some modification to fit his ’63 model. Even after modifcation, the updated part had a plastic component that was too long for his steering wheel. Would he grind down the later part to fit, or go with a later wheel? No, he turned to Google Sketchup, and 3D printed a replacement of the correct size. He does admit that it’s not perfect as the signals cancel at a slightly different point from where they should, but since he’s been using it for four years it appears to have done the job.

We wish [Ken] every success with his Corvair, and indeed can’t help envying him a little for owning it. Some of us have been known to dabble in older metal, too.

This is an entry in Hackaday’s

Repairs You Can Print contest

The twenty best projects will receive $100 in Tindie credit, and for the best projects by a Student or Organization, we’ve got two brand-new Prusa i3 MK3 printers. With a printer like that, you’ll be breaking stuff around the house just to have an excuse to make replacement parts.


Repairs You Can Print: Better Cable Splicing With 3D Printed Parts

A while back, [Marius] was faced with a problem. A friend of his lives in the middle of a rainforest, and a microphone was attacked by a dirty, greasy rat. The cable was gnawed in half, and with it went a vital means of communication with the outside world. The usual way of fixing a five- or six-conductor cable is with heat shrink, lineman’s splices, insulating tape, and luck. [Marius] needed something better than that, so he turned to his 3D printer and crafted his own wire splice enclosure.

The microphone in question is a fancy Jenal jobbie with a half-dozen or so conductors in the cable. A junction box was the obvious solution to this problem, and a few prototypes, ranging from rectangular to fancy oval boxes embossed with a logo were spat out on a 3D printer. These junction boxes have holes on either end, and when the cable ends are threaded through these holes, the wires can be spliced, soldered, and insulated from each other.

This microphone had to hold up to the rigors of the rainforest and rats, so [Marius] had to include some provisions for waterproofing. This came in the form of a hot glue gun; just fill the junction box with melted hot glue, pop the cover on, and just wait for it to cool. Like all good repairs, it works, and by the time this repair finally gives out, something else in the microphone is sure to go bad.

It’s a great repair, and an excellent example of how a 3D printer can make repairs easy, simple, cheap, and almost as good as the stock part. You can check out a few videos of the repair below.

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Student 3D Prints Eyes

[Ondřej Vocílka] is a student at the Brno University of Technology in the Czech Republic.  In addition, the 23-year-old lost his vision in his left eye. While attending a lecture on 3D printing, he wondered if he could 3D print an ophthalmic prosthesis — an artificial eye. Turns out, he could. If you don’t speak Czech, you’ll need to call on a translation service like we did.

Unlike conventional glass or plastic eyes, it is trivial to change parameters like color when 3D printing the prosthetic. This is especially important with the iris and the finished product takes about 90 minutes to print. There is additional time required to coat the product with an acrylic layer to mimic the gloss of a natural eye.

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