Monday, 7 January 2019

How To Make a Small DIY Ultrasonic Knife

Some time ago I made a DIY ultrasonic knife. It's a small tool for fine detail work, and I use it for removing tricky supports from SLA 3D prints. I wrote an article about it that you can review for details.

The tool was made from a cheap ultrasonic dental scaling tool I bought from China. I sharpened one of the tips into a sharp chisel point. This knife edge vibrates a tiny amount at a high frequency, which gives the knife edge some mild superpowers. It's able to cut through hard plastic (like the supports of 3D prints from my Formlabs Form 2 SLA printer) with ease, without putting stress on the part being cut.

In the animation below, you can see my tool slice through the supports on a tiny piece that would not normally survive being cut by a utility knife or side cutters. The supports on Boba Fett's helmet-mounted rangefinger (I printed it at 25% size so it's much smaller than usual) are larger than the piece itself and would normally be too delicate to reliably remove supports, let alone leave a good surface finish.

One potential application that I have been made aware of for a tool like this is to post-process prints that are intended for casting jewelry. They often have fine details that must be preserved.

DIY Ultrasonic cutter removing supports from SLA 3D print. Note the puff of particles and water vapor when cutting.
The liquid droplets are water; I used a small spray bottle to help control the dust.
Note: the rangefinder is a separate piece in the original 3D model. I attached it for the express purpose of printing it as one piece and seeing if my ultrasonic cutter could handle removing the supports from such a small and delicate part, and it worked great!

If you'd like to know more, there's a video and additional details on The device turned out to be a handy addition to my toolbox, and wasn't particularly expensive. About $125 in parts and a bit of work to modify one of the steel tips, and I had what I needed.

If you'd like to try making your own, search eBay for "dental scaler" and "EMS Woodpecker" in the description. Buy one that has the correct plug for your country and you should be set for trying your own experiments.

Thursday, 30 August 2018

Get MUSICAL for the Final Round of The 2018 Hackaday Prize

The Hackaday Prize is in its fifth year, and the final round of entries is currently underway: the Musical Instrument Challenge. It runs until October 8th. Twenty finalists will receive $1000 each and go on to the final round where a $50,000 cash prize (and more!) are waiting.

What's the money for? It's cash, for you to use to develop your open-sourced idea or concept. Make something, and make the design and details open and available to others; that's it. 

The 2018 Hackaday Prize consists of multiple challenges (of which an entry can enter more than one) which run in sequence one after the other. Twenty finalists from each will receive $1000 cash, and will go on to the final round where the following prizes are up for grabs:

  • Grand Prize:​ $50,000
  • Second Prize:​ $20,000
  • Third Prize:​ $15,000
  • Fourth Prize:​ $10,000
  • Fifth Prize:​ $5,000

All you really need to get started and entered is an idea and some documentation. So if you have an idea rattling that has been on the back burner waiting for an opportunity, this is it. 

Monday, 30 July 2018

3D Printing Used to Manufacture Rifle Compensators

Who says 3D printing isn't a viable manufacturing process? The Salen Compensator (named for Kenneth Salen, competitive Norwegian IPSC shooter) shows it can be done. Tonrud Engineering manufactures the Salen Compensator and a write up about the compensators themselves is on The Firearm Blog.
A build platform of Salen Compensators (Image source: The Firearm Blog)
Note the flat support structure visible through the side holes on each compensator. These are required as part of the manufacturing process, but will be removed with post-processing.

When printing in plastic, support structures are normally only for supporting the geometry of the part. But with printing in metal, support is often used to provide stability across the parts of the entire model; otherwise some warping can occur as smaller and thinner parts cool faster than larger areas, leading to deformation.

3D printing can be used not only for manufacturing, but for cheaper and faster prototyping and to open new doors. For example, 3D printing in metal can be used to create suppressors in strange, nontraditional shapes like those shown below. These are shapes that would be impractical or impossible to create using any other method. In the image shown, the barrel of the gun goes into the hole on the left. The bullet exits from a hole inside the "wedge" on the right.
Unusual design firearms suppressors 3D Printed in metal. The top is a centerfire suppressor, the bottom for rimfire. (Image: The Firearm Blog)

Tuesday, 17 July 2018

Adding Color to FormLabs SLA 3D Prints

I use a FormLabs Form 2 printer whenever I need detailed, high-quality, smooth prints. The results are fantastic, but recently I needed to change the color of some small parts. The parts were so small and finely-detailed that I wanted to avoid paint if possible. FormLabs sells a color kit where you can make a batch of resin into any color you want, but I didn't need or want to buy a whole separate batch of resin; I just needed to do a few small pieces. I decided to try dyeing the parts, and the results were fantastic.

I purchased some liquid Rit Dye ("Chocolate" color for synthetics in my case) from Amazon; it's intended to change the color of synthetic fabrics. Since synthetic fabrics are basically plastic, I figured it might work out okay to dye my 3D prints, which are also plastic. This kind of simpleminded reasoning was all I needed to give things a shot.

Testing consisted of simply filling a plastic cup part way with very hot (but not boiling) water. Then I poured in a small amount of the liquid dye; I didn't measure anything, but it was probably a couple of teaspoons.

Then I dropped in a test piece, which was a scrap base and support structure. I stirred it a few times over five minutes, then removed and rinsed it. The result is shown below on the right.

Plain Grey FormLabs resin on the left. On the right is also Grey resin, but after five minutes of dyeing.
The results were impressive! I was expecting only to get a rough idea of whether this might work, and what direction to go in next. Instead, it worked beautifully on the first try! The color was even and smooth.

I decided to do a production piece. Five minutes seemed plenty so I did four minutes. The results are below. On the left are regular prints, on the right are the dyed pieces.

Left: undyed Grey FormLabs resin results. Right: results from four minutes in dye solution.
I honestly hadn't expected the results to be so good and so easily done. There is more to be learned, but if you're looking to dye a small 3D print out of a FormLabs printer, it's awfully easy and fast to do so with the liquid Rit-Dye and some hot water. Probably this is feasible for other 3D prints and other resins; I haven't tested any, but the results here were so readily done that it certainly looks to be worth trying out.

Thursday, 24 May 2018

Free Machine Learning Crash Course by Google

I was really impressed by this introductory course for machine learning by Google. Not only is it well designed and put together, but as someone who is extremely hard of hearing, I took special interest in the subtitles for the video section.

The closed captioning is incredibly well done. It's more than just subtitles, it shows a time-stamped list of the spoken part that scrolls automatically. This is much better than subtitles for learning material, since the viewer can see not only what is currently being spoken, but quickly review what was just said as well as what's coming next.

They're even clickable so that one can skip ahead to salient parts of the video. Oh my god -- a way to skim and basically page-flip in a video. I'm on cloud nine.

I'd be happy just with subtitles, but this interface knocks it out of the park. Videos in place of documentation is more and more common, but even simple subtitles are a luxury for most learning material. Autodesk's Fusion 360 training materials, for example, are almost entirely video based and have no subtitles whatsoever.

Millions of people in North America suffer from some level of hearing loss, and half of them are still in the workforce. If your documentation is all on video where the subject matter is unfamiliar to the viewer and the speaker (and their mouth) is not visible, it makes learning far, far harder than it needs to be.

Anyway, not only is the video and captioning done extremely well in the course I linked, the course itself is really well done. If you have any interest in this area at all, give it a look.

Wednesday, 16 May 2018

What to do when STL files aren't quite right

My latest article at Hackaday is all about When an STL File Isn't Quite Right and deals with some of the shortcomings of STL files, which are used to share 3D printable designs.

STL files aren't really a CAD format, they're not intended to be edited. This is troublesome when a file needs tweaking. The thing is that 3D CAD formats like STEP (which are non-proprietary) might be a good solution, but they're not even readable by most 3D printing applications. I wonder why this is?

Sunday, 22 April 2018

Understanding Costs for Individuals and Makers

My latest column about working as a technical or engineering contractor (or freelancer) is called Lowering Your Cost Without Dropping Your Price and is part of a series called Life on Contract.

I could probably have titled it HOW A KICKSTARTER RUNS OUT OF MONEY AND LEAVES THE CREATOR A BURNED OUT HUSK and that would have been a pretty good summary of the content!

While the article mainly describes a way to lower costs without making things "cheaper" in quality, the article is also useful as a way to understand costs better.

People who are getting into making things or services -- either in business for themselves or for launching a crowdsourcing campaign -- will benefit from understanding how much something really costs in the end, and there's much more to it than the Bill of Materials.