Making Rubber Stamps With OpenSCAD

December 10, 2017 by Tom Nardi 21 Comments

There’s an old saying that goes “If you can’t beat ’em, join ’em”, but around these parts a better version might be “If you can’t buy ’em, make ’em”. A rather large portion of the projects that have graced these pages have been the product of a hacker or maker not being able to find a commercial product to fit their needs. Or at the very least, not being able to find one that fit their budget.

GitHub user [harout] was in the market for some rubber stamps to help children learn the Armenian alphabet, but couldn’t track down a commercially available set. With a 3D printer and some OpenSCAD code, [harout] was able to turn this commercial shortcoming into a DIY success story.

Rather than having to manually render each stamp, he was able to come up with a simple Bash script that calls OpenSCAD with the “-D” option. When this option is passed to OpenSCAD, it allows you to override a particular variable in the .scad file. A single OpenSCAD file is therefore able to create a stamp of any letter passed to it on the command line. The Bash script uses this option to change the variable holding the letter, renders the STL to a unique file name, and then moves on to the next letter and repeats the process.

This procedural generation of STLs is a fantastic use of OpenSCAD, and is certainly not limited to simple children’s stamps. With some improvements to the code, the script could take any given string and font and spit out a ready to print mold.

With a full set of letter molds generated, they could then be printed out and sealed with a spray acrylic lacquer. A mold release was applied to each sealed mold, and finally they were filled with approximately 200ml of Simpact urethane rubber from Smooth-On. Once the rubber cures, he popped them out of the molds and glued them onto wooden blocks. The end result looks just as good as anything you’d get from an arts and crafts store.

The process used here is very similar to the 3D printed cookie molds we’ve covered recently, though we have to assume these little morsels would not be nearly as tasty. Of course, if you had access to a small CNC machine you could cut the stamps out of the rubber directly and skip the mold step entirely.

MIT Is Building A Better 3D Printer

December 9, 2017 by Tom Nardi 79 Comments

Traditional desktop 3D printing technology has effectively hit a wall. The line between a $200 and a $1000 printer is blurrier now than ever before, and there’s a fairly prevalent argument in the community that you’d be better off upgrading two cheap printers and pocketing the change than buying a single high-end printer if the final results are going to be so similar.

The reason for this is simple: physics. Current printers have essentially hit the limits of how fast the gantry can move, how fast plastic filament can pushed through the extruder, and how fast that plastic can be melted. To move forward, we’re going to need to come up with something altogether different. Recently a team from MIT has taken the first steps down that path by unveiling a fundamental rethinking of 3D printing that specifically addresses the issues currently holding all our machines back, with a claimed 10-fold increase in performance over traditional printing methods.

MIT’s revolutionary laser-assisted hot end.

As anyone who’s pushed their 3D printer a bit too hard can tell you, the first thing that usually happens is the extruder begins to slip and grind the filament down. As the filament is ground down it starts depositing plastic on the hobbed gear, further reducing grip in the extruder and ultimately leading to under-extrusion or a complete print failure. To address this issue, MIT’s printer completely does away with the “pinch wheel” extruder design and replaces it with a screw mechanism that pulls special threaded filament down into the hot end. The vastly increased surface area between the filament and the extruder allows for much higher extrusion pressure.

An improved extruder doesn’t do any good if you can’t melt the incoming plastic fast enough to keep up with it, and to that end MIT has pulled out the really big guns. Between the extruder and traditional heater block, the filament passes through a gold-lined optical cavity where it is blasted with a pulse modulated 50 W laser. By closely matching the laser wavelength to the optical properties of the plastic, the beam is able to penetrate the filament and evenly bring it up to nearly the melting point. All without physically touching the filament and incurring frictional losses.

There are still technical challenges to face, but this research may well represent the shape of things to come for high-end printers. In other words, don’t expect a drop-in laser hot end replacement for your $200 printer anytime soon; the line is about to get blurry again.

Speeding up 3D printing is a popular topic lately, and for good reason. While 3D printing is still a long way off from challenging traditional manufacturing in most cases, it’s an outstanding tool for use during development and prototyping. The faster you can print, the faster you can iterate your design.

Thanks to [Maave] for the tip.

Continue reading “MIT Is Building A Better 3D Printer” →

Coin Cell Challenge: Jump Starting A Car

December 8, 2017 by Tom Nardi 80 Comments

Clearly a believer in the old adage, “Go Big or Go Home”, [Ted Yapo] has decided to do something that seems impossible at first glance: starting his car with a CR2477 battery. He’s done the math and it looks promising, though it’s yet to be seen if the real world will be as accommodating. At the very least, [Ted] found a video by [ElectroBOOM] claiming to have started a car with a super capacitor, so it isn’t completely without precedent.

Doing some research, [Ted] found it takes approximately 2,000 W to 3,000 W at 14 V to start the average car engine. This is obviously far in excess of what a coin cell can put out instantaneously, but the key is in the surprising amount of potential energy stored in one of these batteries. If the cell is rated for 1000 mAh at 3 V, [Ted] shows the math to find the stored energy in Joules:

According to the video by [ElectroBOOM], he was able to start his car with only 6,527 J, and [Ted] calculates it should only take about 9,000 J on the high side from his research. So as long as he can come up with a boost converter that can charge a capacitor with high enough efficiency, this one should be in the bag.

[Ted] has started putting together some early hardware, and has even posted the source code he’s using on a PIC12LF1571 to drive the converter. He notes the current charge efficiency is around half of what’s needed according to his calculations, but he does mention it was an early test and improvements can be made. Will it start? If it does, this is some awesome Heavy Lifting.

Curbside Mower Gets Electric Transplant

December 8, 2017 by Tom Nardi 28 Comments

There’s few things more exciting to a hacker or maker than seeing a piece of hardware on the curb. An old computer, an appliance, maybe if you’re really lucky some power tools. So we can only imagine the rush that known lawn equipment aficionado [AmpEater] had when he saw a seemingly intact push mower in the trash. The pull start was broken on the gas engine, but where this mower was going, it wouldn’t need a gas engine.

When he got the mower back to his garage, he started on the process of converting it over to electric. Of course this means basically everything but the wheels, handle, and deck would get tossed. But starting with a trashed gas mower still sounds a lot easier compared to trying to figure out how to make or source a wheeled mower deck.

Step one in this conversion was stripping all the paint off the deck and welding a plate over where the original gas engine was. [AmpEater] then 3D printed some mounts to hold the DeWalt tool batteries he would be using as a power source, taking the extra time to align everything so it would have the look of an old flathead gasoline engine. A tongue-in-cheek reference to the mower’s old gasoline gulping days, and an awesome little detail that gives the final product a great look.

The controller is a commercial model intended for electric bikes, and the heart of this new mower is a brushless direct-drive motor capable of 3,000 RPM at 40 A. [AmpEater] reports a respectable one hour run time with the six DeWalt batteries, and more power than his store-bought Ryobi electric mower.

If the name [AmpEater] looks familiar, it’s because this isn’t the first time he’s graced us with a mower conversion: back in 2013 he impressed us with his solar-electric Cub Cadet zero-turn. This build isn’t quite as slick as the Cub Cadet, but the much lower cost and difficulty level means that you may be able to follow in his footsteps even if you don’t have his Zeus-level mastery of the electric motor.

As electric mowers have gotten more popular, we’ve seen an increasing flow of hacks and mods for them. Everything from replacing the batteries to turning them into something else completely.

Biometric Authentication With A Cheap USB Hub

December 7, 2017 by Tom Nardi 26 Comments

It’s fair to say that fingerprints aren’t necessarily the best idea for device authentication, after all, they’re kind of everywhere. But in some cases, such as a device that never leaves your home, fingerprints are an appealing way to speed up repetitive logins. Unfortunately, fingerprint scanners aren’t exactly ubiquitous pieces of hardware yet. We wouldn’t hold out much hope for seeing a future Raspberry Pi with a fingerprint scanner sitting on top, for example.

Looking for a cheap way to add fingerprint scanning capabilities to his devices, [Nicholas] came up with a clever solution that is not only inexpensive, but multi-functional. By combining a cheap USB hub with a fingerprint scanner that was intended as a replacement part of a Thinkpad laptop, he was able to put together a biometric USB hub for around $5 USD.

After buying the Thinkpad fingerprint scanner, he wanted to make sure it would be detected by his computer as a standard USB device. The connector and pinout on the scanner aren’t standard, so he had to scrape off the plastic coating of the ribbon cable and do some probing with his multimeter to figure out what went where. Luckily, once he found the ground wire, the order of the rest of the connections were unchanged from normal USB.

When connected to up his Ubuntu machine, the Thinkpad scanner came up as a “STMicroelectronics Fingerprint Reader”, and could be configured with libpam-fprintd.

With the pintout and software configuration now known, all that was left was getting it integrated into the USB hub. One of the hub’s ports was removed and filled in with hot glue, and the fingerprint scanner connected in its place. A hole was then cut in the case of the hub for the scanner to peak out of. [Nicholas] mentions his Dremel is on loan to somebody else at the moment, and says he’ll probably try to clean the case and opening up a bit when he gets it back.

[Nicholas] was actually inspired to tackle this project based on a Hackaday post he read awhile back, so this one has truly come full circle. If you’d like to learn more about fingerprint scanning and the techniques being developed to improve it, we’ve got some excellent articles to get you started.

My Kingdom For A Capacitor

December 7, 2017 by Tom Nardi 148 Comments

While working on a project recently, I required a capacitor of around 1000 μF and went rummaging through my collection of parts. No luck there. At that point I’d usually go through my collection of junk electronics and computer motherboards, but I had recently gone through and tossed the stuff that had been laying around for as long as I could remember. No matter, I thought. I’ll just head over to RadioShack and…

Now, I have been accused of many things over the years, but “deep” is certainly not one of them. Yet, at this moment I had what could only be described as an existential crisis. There is no RadioShack, not in my state at least. I don’t live in an area that’s blessed with a maker “scene”, so no independent shop or even a hackerspace within reasonable driving distance of me either. I could order it online of course, but everyone’s trying to sell them in bulk and shipping will take a few days at least. A few days? Who knows where my interests will be in a few days. How can I get anything done under these conditions?

Desperate times call for desperate measures, so I got in the car and took a ride to the only place I knew where I could by electronic components for cheap: Goodwill. Continue reading “My Kingdom For A Capacitor” →

Junkyard RC Conversion Looks Like Mad Max Extra

December 7, 2017 by Tom Nardi 13 Comments

Over the years we’ve noticed that there is a subset of hackers out there who like to turn real life vehicles into remote controlled cars. These vehicles are generally destroyed in short order, either by taking ridiculous jumps, or just smashing them into stuff until there’s nothing left. In truth that’s probably what most of us would do if we had access to a full size RC car, so no complaints there.

As a rule, the donor vehicles for these conversions are usually older and cheap. That only makes sense, why spend a lot of money on a vehicle you intend on destroying? But even still, the RC conversion [William Foster] has recently completed may take the cake. We don’t know how much of the “antiquing” of his donor vehicle was intentionally done, but on the whole, the thing looks like it got dragged from the bottom of a lake somewhere. Presumably, he got a great deal on it.

The video posted to YouTube is primarily about [William] driving his creation around (sometimes from the back seat, no less), but towards the second half of the video there’s a quick rundown on the hardware used to make this pile of rust move.

A standard RC transmitter and receiver combination are used to control a pair of Arduinos mounted in the center console, which are in turn hooked up to external stepper drivers. The wheel is turned via a chain and sprocket arrangement, and the pedals are pushed with homebrew contraptions that look like they are made from lead screws intended for 3D printers.

All in all, it appears [William] has cooked up a fairly responsive control system with commodity hardware you could get on Amazon or eBay. Not sure we’d be backseat driving this thing personally, but to each their own.

We recently covered a Jeep that got a similar remote control upgrade, but these super-sized remote controlled vehicle builds are not just limited to the ground either.

Continue reading “Junkyard RC Conversion Looks Like Mad Max Extra” →