Openhand Combines 3D Printing with Urethane Casting

Yale University brings us quite a treat with their Openhand Project.

If you’ve ever operated a robotic arm, you know that one of the most cumbersome parts is always the end effector. It will quickly make you realize what an amazing work of engineering the human hand really is, and what a poor intimation a simple open-close gripper ends up being.

[Yale] is working to bring tendon-driven robotic hands to the masses with an interesting technique of combining 3D printing and resin/urethane casting. Known as Hybrid Deposition Manufacturing (HDM), it allows the team to 3D print robotic fingers that also contain the mold for finger pads and joints, all built right into the 3D part.  The tendon-driven fingers allow for a very simple design that are not only easy to make, but have a low parts count as well. Because of the human-like tendons, the fingers naturally curl around the object, distributing it’s force much more evenly and naturally, much like a human hand would. In the videos after the break, you can see the building process, as well as the hand in action.

Best news is that it’s all open source. They also include some python libraries so you can customize the CAD files fit your needs.

Continue reading “Openhand Combines 3D Printing with Urethane Casting”

TwinTeeth: The Delta Bot PCB Factory

There are a few all-in-one CNC/milling/plotting/3D printing/engraving bots out there that claim to be mini factories for hobbyists, prototypers, and other homebrew creators. The latest is Diyouware’s TwinTeeth, a bot obviously inspired by a few 3D printers, but something that has a few interesting features we hope will propagate through the open hardware ecosystem.

The design of the TwinTeeth is an inverse delta bot, kinematically similar to a large number of 3D printers out there. Instead of suspending the tool from a trio of arms, the TwinTeeth puts the work surface on the arms and suspends the tool from the top of the machine. There are a few neat bonuses for this setup – all the tools, from a BluRay laser diode, a Dremel, solder paste dispenser, and a plastic extruder for 3D printing can be mounted in easy to mount adapters. The TwinTooth design uses three locking pins to keep each toolhead in place, and after a little bit of software setup this machine can quickly switch between its various functions.

One very interesting feature of this bot is the ability to mask off PCBs for chemical etching with a BluRay laser diode. This actually works pretty well, as evidenced by the teams earlier work with a purpose-built PCB masker machine. The only problem with this technique is that presensitized boards must be used. If that’s an issue, no problem, just use the Dremel attachment with a v-bit cutter.

3D Printering: Hobbs Meters And 3D Printer Reliability

A direct link to Makerbot's  3-pack of Smart Extruders is very hard to find
A direct link to Makerbot’s 3-pack of Smart Extruders is very hard to find

It’s been a little over a year since Makerbot introduced their new line of printers, and since then there have been grumblings about the quality of the Smart Extruder that each one of these printers comes with. While there is no 3D printer extruder that will not eventually clog, wear down, or otherwise break, there are reports of the Makerbot Smart Extruder failing in only hundreds or even tens of hours of use. Considering that a single large print can take a dozen or so hours to complete, you can easily see the why the Smart Extruder is so despised and why even the availability of a three-pack of Smart Extruders is a joke in the 3D printing community.

Of course a cheap shot at Makerbot that plays right into your preconceived ideas and prejudices is far too easy. We’re here to solve problems, not just state them, so here’s what we’re working with: to quantify the long-term reliability of 3D printers we need a way to measure the mean time before failure of extruders. This is already a solved problem; it’s just not implemented.

On aircraft and some very expensive engines that power things like buildings and ships, there’s one gauge, tucked away in the control panel, that keeps track of how long the engine has been running. It’s called a hobbs meter, and the idea behind it is extremely simple – when there is power going to the Hobbs meter, it counts out hours on a small clockwork display. The resolution of the display is only tenths of an hour, usually, but that’s good enough for scheduling maintenance and to be mentioned in NTSB accident reports.

Spend enough time with a 3D printer, and you’ll quickly realize the ‘estimated print time’ is merely a ballpark, and with failed prints the ‘total print time for this object’ isn’t exactly a perfect measure of how many hours you’ve been using your extruder. Only by directly measuring how many hours are logged on a hot end or how many kilometers of filament have been sent through an extruder will you ever get an accurate idea of how long an extruder has been running, and how reliable a printer is.

Hobbs meters are available from Mouser, but you’ll be overpaying there. The better option is from a vendor in a different niche; $30 for a meter that can connect directly to the extruder heater. If enough people add this and keep proper logs, there’s a slight chance of improving the state of 3D printers with real data and not the prejudices of people trying to justify their own designs and purchases.

But perhaps that’s too hard; adding a $30 item to a printer’s BOM just for the sake of data is a bit much. Luckily, there’s an even simpler solution that won’t cost a dime. Just measure the time a heater has been on in the firmware, or save the total length of extruded filament in a microcontroller’s EEPROM. Every printer firmware out there, from Marlin to Repetier to Sprinter has in it a way to calculate both the length of time a heater has been on or how much filament has been pushed through a nozzle.

However, this is 3D printing we’re dealing with. An organized community is not a luxury we currently enjoy, and for this to work several things are needed. The first is somewhere to upload failure statistics. This would be a web site, naturally, with the ability to input the printer make, extruder and hot end model, and the time since last clogged nozzle. The website itself is just a database, some JavaScript, a bit of CSS, and some hosting costs; not hard until you consider tens of thousands of operators would have to know about this website and contribute.

Secondly, if we’re not going with mechanical Hobbs meters there would need to be a ‘total time heater on’ or ‘total length of extruded filament’ variable in the various firmwares. There would hopefully be standardized Gcodes or Mcodes to read and reset this variable.

Will this happen? Of course not. Organization isn’t a strong suit of the RepRap project, and any company that implements Hobbs meter functionality will probably lock that up in proprietary obfuscation. However, Makerbot isn’t dumb, and given they’re selling three-packs of extruders, I would bet they have some data on the MTBF of their extruders. A community-based measurement of the most common cause of broken printers is certainly possible, but like all problems it’s one of organization, not technology.

3D Printering is a semi-weekly column that digs deep into all things related to 3D Printing. If you have questions or ideas for future installments please sending us your thoughts.

Add Extra Storage to Your PS4 With Retro Flair

[Frank] came up with a clever way to extend the storage of his PS4. He’s managed to store his digital PS4 games inside of storage devices in the shape of classic NES cartridges. It’s a relatively simple hack on the technical side of things, but the result is a fun and interesting way to store your digital games.

He started out by designing his own 3D model of the NES cartridge. He then printed the cartridge on his Ultimaker 3D printer. The final print is a very good quality replica of the old style cartridge. The trick of this build is that each cartridge actually contains a 2.5″ hard drive. [Frank] can store each game on a separate drive, placing each one in a separate cartridge. He then prints his own 80’s style labels for these current generation games. You would have a hard time noticing that these games are not classic NES games at first glance.

Storing the game in cartridge form is one thing, but reading them into the PS4 is another. The trick is to use a SATA connector attached to the PS4’s motherboard. [Frank’s] project page makes it sound like he was able to plug the SATA cable in without opening the PS4, by attaching the connector to a Popsicle stick and then using that to reach in and plug the connector in place. The other end of the SATA cable goes into a custom 3D printed housing that fits the fake NES cartridges. This housing is attached to the side of the PS4 using machine screws.

Now [Frank] can just slide the cartridge of his choice into the slot and the PS4 instantly reads it. In an age where we try to cram more and more bits into smaller and smaller places, this may not be the most practical build. But sometimes hacking isn’t about being practical. Sometimes it’s simply about having fun. This project is a perfect example. Continue reading “Add Extra Storage to Your PS4 With Retro Flair”

Wait, a 3D Printed Lawn mower?

Well, we have to admit, we never saw this coming… A 3D printed lawn mower? What? Why? Huh? How? Those were at least a few of the thoughts running through our head when we saw this come in on the tips line.

[Hans Fouche] has a giant 3D printer that takes up most of the space in his garage, and after printing several large vases, a briefcase, bowls, and even a wind turbine blade — he decided to try printing a lawnmower. A freaking lawnmower.

To do so, he reverse engineered his old rusty lawn mower, and redesigned it to be printable. Apart from the steel axles, some fastening hardware, and of course the motor and blade, the entire thing is 3D printed. And it looks like it works pretty good too.

Continue reading “Wait, a 3D Printed Lawn mower?”

3D Printable LED Diffusors

While you can get an LED matrix in any size or shape, the really cool looking ones that are perfect for low-res displays all have diffusors. When they come from a nameless Chinese factory, these diffusors are thin sheets of plastic set into an extruded plastic frame. Since [Jan] has a 3D printer, he figured a custom diffusor was just a few bits of filament and a SCAD file away.

The basis for this custom LED diffusor was a LoL Shield given to [Jan] by the creator at the recent 31C3 conference. This shield is really only just 126 LEDs, multiplexed and in an Arduino form factor, and that many LEDs were just too bright and indistinct next to each other. The plan for a 3D printed diffusor was hatched.

After taking a few measurements, a pair of OpenSCAD files were whipped up and printed out. Assembly consisted of pressing 126 tiny little white diffusors into a frame, but once everything was attached to the matrix, the results were worth it.

Check out the video below for the before and after, demonstrating what a few bits of plastic can do to a LED matrix.

Continue reading “3D Printable LED Diffusors”

New 3D Printing Technique – Friction Welding

Even though 3D printers can fabricate complex shapes that would be nearly impossible to mill, they are not well suited to designs requiring bridging or with large empty spaces. To overcome this, [Scorch] has applied an easy plastic welding technique that works with both ABS and PLA. All you need is a rotary tool.

Friction welding” is the process of rubbing two surfaces together until the friction alone has created enough heat to join them. Industrially, the method is applied to joining large, metal workpieces that would otherwise require a time-consuming weld. In 2012, [Fran] reminded us of a toy from decades ago that allowed children to plastic weld styrene using friction. This modified method is similar to stick welding in that a consumable filler rod is added to the molten joint. Inspired by our coverage of [Fran], [Scorch] experimented and discovered that a stick of filament mounted into a Dremel works just as well for joining 3d prints.

That is all there is to it. Snip off a bit of filament, feed it into your rotary tool, and run a bead to join parts and shapes or do repairs. Friction welded plastic is shockingly strong, vastly superior to glued plastic for some joints. Another tool for the toolbox. See the videos below for [Scorch]’s demo.

Continue reading “New 3D Printing Technique – Friction Welding”