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.

Thursday, 5 April 2018

How To Digitally Push a Button

If you ever need to interface to an existing piece of hardware, for example because you're modifying or otherwise tampering with something, then sooner or later you'll find yourself wanting to simulate pressing a button with a digital signal.

The foolproof way to do this is to use a small relay, which is literally a switch closed by an electrical signal. However, there's another way that's cheaper and simpler. If the switch you're wanting to "press" connects an input to ground (which is very common), then you're in luck. You can do it with a single NPN BJT transistor (like a 2N3904 or 2N2222) and a resistor.

I have used this method many times in the past, and most recently used it when I modified a cheap USB mouse so that I could click the buttons with an Arduino. When mixing and matching different hardware, sooner or later you'll want to just simulate a button press and this way is smaller and cheaper than using relays and isn't fussy about voltage levels.

The transistor is used in saturation mode, meaning that it works much like a switch. When a digital signal is applied (through the resistor) to the base of the NPN, the collector is essentially connected to ground. By connecting the collector to the switch's input we can simulate the button being pressed, with no need to replace the actual switch.

Thursday, 15 March 2018

3D Printing Tools I Can't Do Without

There are few tools that I have found are absolutely necessary in 3D printing; these items are kept in easy reach and each do a slightly different job.

Starting from the bottom upwards:

  • The Scotty Peeler (specifically the SP-2 metal peeler). It's intended for peeling pesky labels but it's absolutely wonderful for getting a print separated from the build surface of a filament-based 3D printer. For larger prints where the Scotty Peeler isn't long enough to reach underneath, once an edge gets lifted with the Scotty Peeler a larger scraper can be used to lever the rest of the print. Invaluable, inexpensive, and available off Amazon.
  • Illuminated Magnifying Glass. Bought this at the dollar store. The plastic lens isn't the greatest, but the bright LED illumination makes up for it. Two AAA cells go into the handle and a switch turns on bright LEDs. I used to have a flashlight and magnifying glass together to illuminate and examine prints -- often while they were being printed. This all-in-one does the same job in a much handier package.
  • Tweezers are mainly useful for grabbing small bits and removing stray extrusions, like the bit of plastic from the nozzle after priming the hot end.
  • Deburring Tool. This item has a specialized use but well worth having. I use it for cleaning up prints. Ever have an edge that needs trimming, for example the inside of a hole or the outside edge of a print, and you can't or don't want to sand it? A cheap deburring tool from your favorite offshore discount place is what you need. If you have never seen one it might look a little strange, but it's a knife that you pull instead of push. You stick the metal curved part into the hole or lay it onto the edge, and drag it along. The sharpened side will cut off a tiny amount of material while it pivots around as needed. It's great for quick and easy cleanup of edges.
Lots of tools are useful but these have all found a niche for me. Especially the Scotty Peeler, that is absolutely #1 for me. If you 3D print and don't have anything like it, give it a shot!