MRRF: Hot Ends, Extruders, Extremely Posh Brits, and Stoic Swedes

As far as locations for the Midwest RepRap Festival go, it’s not exactly ideal. This is a feature, not a bug, and it means only the cool people come out to the event. There were a few people travelling thousands of miles across an ocean, just to show off some cool things they built.

Two Colors, One Nozzle

[Sanjay] and [Josh] from E3D came all the way from merry olde England to show off a few of their wares. The star of their show was the Cyclops extruder, a dual-extrusion hot end that’s two input, one output. Yes, two colors can come out of one nozzle.

cyclops

If you see a printer advertised as being dual extrusion, what you’re going to get is two extruders and two hot ends. This is the kludgy way to do things – the elegant solution is to make two colors come out of one nozzle.

The guys from E3D were showing off a few prints from their Cyclops nozzle that does just that, including a black and red poison dart frog, and a blue and white octopus. The prints looked amazing, and exactly what you would expect from a two-color print.

Rumor has it the development of the Cyclops involved extruding two colors, freezing the nozzle, and putting it in the mill just to see how the colors mixed. I didn’t see those pictures, but there’s a lot of work that went into this hot end.

The Power of Two Extruders

[Martin] of bondtech.se came to MRRF all the way from Sweden. He was there showing off his new extruder.

The extruder uses a normal stepper motor, but instead of the usual knurled or threaded feed wheel and bearing to push filament though, he’s using two counter-rotating feed wheels attached to a planetary gear system. That’s a lot of torque that doesn’t distort or strip the filament. When you consider all the weird filaments that are coming out – ninjaflex, and even 3D printable machinable wax filament, this is extremely interesting.

Even if your filament isn’t exactly 1.75 or 3mm in diameter, this setup will still reliably push plastic; there is a bolt that will move one of the feed wheels in and out 0.4mm.

[Martin] had a pair of his extruders hooked up to a strain gauge, and it’s strong enough to lift your printer off the table without stripping the filament. Here’s a video of that demo from the bondtech page.

Adding Recycling Codes To 3D Prints

Every little plastic bauble you interact with has some sort of recycling code on it somewhere. Now that we’re producing plastic 3D printed parts at home, it would be a good idea to agree on how to recycle all those parts, and [Joshua Pearce]’s lab at Michigan Tech has the answer; since we’re printing these objects, we can just print the recycling code right in the object.

The US system of plastic recycling codes is particularly ill-suited for identifying what kind of plastic the object in question is made of; there are only seven codes, while China’s system of plastic identification uses 140 identification codes. This system for labeling 3D printed parts borrows heavily from the Chinese system, assigning ABS as ‘9’, PLA as ’92’, and HIPS as ‘108’.

With agreed upon recycling codes, the only thing left to do is to label every print with the correct recycling code. That’s an easy task with a few OpenSCAD scripts – the paper shows off a wrench made out of HIPS labeled with the correct code, and an ABS drill bit handle sporting a number nine. 3D printing opens up a few interesting manufacturing techniques, and the research team shows this off with a PLA vase with a recycle code lithophane embedded in the first few layers.

Optimized Molds With 3D Printing

[Florian] has a few arcade games and MAME machines, and recently he’s been trying to embed objects in those hard plastic spheres on the end of joysticks. A common suggestion is to 3D print some molds, but even though that’s a great idea in theory the reality is much different: you’re going to get layer lines on the casting, and a mirror finish is impossible.

No, a silicone mold is the way to do this, but here 3D printing can be used to create the mold for the silicone. Instead of a few pieces of hot glued cardboard or a styrofoam cup, [Florian] is 3D printing a a container to hold the liquid silicone around the master part.

After printing a two-piece part to hold both halves of a silicon mold, [Florian] put the master part in, filled it up with silicone, and took everything apart. There were minimal seam lines, but the end result looks great.

In addition to making a 3D printed mold container, [Florian] is also experimenting with putting 3D printed parts inside these joystick balls. The first experiment was a small 3D printed barrel emblazoned with the Donkey Kong logo. This turned out great, but there’s a fair bit of refraction that blows out all the proportions. Further experiments will include a Pac-Man, a skull, and a rose, to be completed whenever [Florian] gets a vacuum chamber.

DIY Thermal Insert Press

You might not know what a threaded insert is, but chances are you’ve seen one before. Threaded inserts are small metal (typically brass) inserts that are pressed into plastic to give a strong point of attachment for bolts and screws. These inserts are a huge step up from screwing or bolting directly into tapped plastic holes since the brass threads are very strong compared to the plastic. The only major downside to these inserts is that the press to install them is incredibly expensive. Thankfully, [Alex Rich] came up with a cheap solution: a modified soldering iron mounted to an Arbor press.

Commercial threaded insert presses typically use ultrasonic welding or heat welding to fuse inserts with plastic. [Alex] chose the simple route and went with heat welding, which (as you might imagine) is way simpler than ultrasonic welding. To provide the heat, [Alex] mounted a 100W Weller soldering iron to the press, which he says handles the impact with no problem. Unfortunately the copper tips of the Weller just wouldn’t hold up to the impact, so [Alex] made his own tips out of some brass he turned on a lathe.

If, like most people, you don’t have the capability of making injection-molded cases, let alone an Arbor press on hand, you’re not out of luck! Using this same technique people have successfully added thermal inserts to 3d-printed parts using a soldering iron and much smaller DIY presses. Have any ideas on how you could use thermal inserts in your 3d prints? Let us know in the comments.

Midwest RepRap Festival, March 20-22nd

Right now there are two emails in my inbox inviting me to 3D printer conventions. If you’re not familiar with how these cons go, here’s a quick recap: a bunch of 3D printer manufacturers set up their booths the day before, put a printer behind an acrylic enclosure, start a very complex print, and come back the next day. This printer finally completes the print sometime Sunday afternoon, a bunch of people walk by the booths, and the entire venue is filled with enough morose faces as to be comparable to one of the higher circles of hell.

The Midwest RepRap Festival is not this con. It is, to the best of my knowledge, the only 3D printing convention that isn’t a trade show. It’s a blast, it’s March 20th through the 22nd, and we’re going to be there.

This will be our second expedition to the MRRF. Last year we saw 3D printed resin molds, and a strange Core XZ printer from [Nicholas Seward], the mind that brought you the odd Reprap Wally and Simpson. The most interesting man in the universe was there with a Smoothieboard. There were talks on 3D Bioprinting by [Jordan Miller] from Rice University, and everyone ate 3D printed waffles. If you’re looking for the possibilities 3D printing offers, this is the con to go to. If you’re looking for people to sell you stuff, look elsewhere.

This event is organized by the folks at SeeMeCNC, and it will be held on their home turf of Goshen, Indiana. Yes, you will be passing Amish buggies on the way to the event. Even though the MRRF is being held in the middle of nowhere, it was absolutely shocking how many people turned up last year and how good the con was. To put this in perspective, I’m driving nine hours to MRRF, and going to Maker Faire NYC takes me four hours. If I had to choose one 3D printing event to go to, this would be the one. That’s not just because I’m told there will be a t-shirt cannon at MRRF.

The event is free and open to everybody. You can just show up, although it would be a good idea to register. You’ll see the World’s Largest 3D Printed Trash Can. Yes, I’m serious. Call Guinness.

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.