Sharpies and Glue Sticks Fight the Gummy Metal Machining Blues

“Gummy” might not be an adjective that springs to mind when describing metals, but anyone who has had the flutes of a drill bit or end mill jammed with aluminum will tell you that certain metals do indeed behave in unhelpful ways. But a new research paper seeks to shed light on the gummy metal phenomenon, and may just have machinists stocking up on office supplies.

It’s a bit counterintuitive that harder metals like steel are often easier to cut than softer metals; especially aluminum but also copper, nickel alloys, and some stainless steel alloys. But it happens, and [Srinivasan Chandrasekar] and his colleagues at Purdue University wanted to find out why, and what can be done about it. So the first job was to get up close and personal with the interface between a cutting tool and metal stock, to observe the dynamics of cutting. In a fascinating bit of video, they saw that softer metals tend to fold in sinuous patterns rather than breaking on defined shear planes.

Source: American Physical Society.

Having previously noted that cutting through Dykem, a common machinist’s marking fluid, changes chip formation in soft metals, the researchers tested everything from Sharpies to adhesive tape and even correction fluid, and found that they all helped to reduce the gumming action to some degree. Under their microscope they can clearly see that chips form differently once the cutting edge hits the treated surface, tending to act more brittle and ejecting rather than folding. They also noted a marked decrease in cutting force for the treated metal, and much-improved surface finish to boot.

Will Sharpies and glue sticks enter the book of old machinist’s tricks like gauge-block wringing? Only time will tell. But for now, this is a pretty fascinating bit of research that you might be able to put to the test in your shop. Let us know what you find in the comments.

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TrackRobot Sports Welded Steel, Not Plastic

Don’t let the knee-high size of [Hrastovc]’s creation fool you. TrackRobot weighs in at a monstrous 60 kg (130 lbs) of steel, motors, and battery. It sports two 48V motors in a body and frame made from pieces of finger-jointed sheet steel, and can reach speeds of up to four meters per second with a runtime of up to an hour. The project’s link has more pictures as well as DXF files of the pieces used for the body.

Currently TrackRobot is remote-controlled, but one goal is to turn it into a semi-autonomous snow plow. You can see TrackRobot going through its first steps as well as testing out a plow prototype in the videos embedded below.

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Military Surplus Repurposed for High Energy Physics

Performing high-energy physics experiments can get very expensive, a fact that attracts debate on public funding for scientific research. But the reality is that scientists often work very hard to stretch their funding as far as they can. This is why we need informative and entertaining stories like Gizmodo’s How Physicists Recycled WWII Ships and Artillery to Unlock the Mysteries of the Universe.

The military have specific demands on components for their equipment. Hackers are well aware MIL-SPEC parts typically command higher prices. That quality is useful beyond their military service, which lead to how CERN obtained large quantities of a specific type of brass from obsolete Russian naval ordnance.

The remainder of the article shared many anecdotes around Fermilab’s use of armor plate from decommissioned US Navy warships. They obtained a mind-boggling amount – thousands of tons – just for the cost of transport. Dropping the cost of high quality steel to “only” $53 per ton (1975 dollars, ~$250 today) and far more economical than buying new. Not all of the steel acquired by Fermilab went to science experiments, though. They also put a little bit towards sculptures on the Fermilab campus. (One of the few contexts where 21 tons of steel can be considered “a little bit”.)

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Opening the Door to Functional Prints

If you are going to do something as a joke, there is nothing to say that you can’t do a nice job of it. If you’re like [Michael], a whimsical statement like “Wouldn’t it be funny to put Gründerzeit-style doors on the server cabinet?” might lead down a slippery slope. True to his word, [Michael] not only installed the promised doors, but he did a darn nice job of it.

Buying new doors was the easy part because the door frame and hinges were not standardized back then, so there was nothing on the server cabinet to his mount doors. He walks us through all the steps but the most interesting point was the 3D printed door hinges which [Michael] modeled himself and printed in steel. His new hinges feature his personal flair, with some Voronoi patterning while matching the shape of the originals. We love seeing 3D printed parts used as functional hardware, and hinges are certainly a piece of hardware meant to hold up under pressure.

This is not the first 3D printed door hardware we’ve seen. Check out this innovative latch printed as a single piece and here’s the skinny on making flexible objects yourself.

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Engineering and Artistry Meet an Untimely End at Burning Man

Burning Man is so many different things to so many people, that it defies neat description. For those who attend, it always seems to be a life-changing experience, for good or for ill. The story of one man’s Burning Man exhibition is a lesson in true craftsmanship and mind-boggling engineering, as well as how some events can bring out the worst in people.

For [Malcolm Tibbets], aka [the tahoeturner], Burning Man 2017 was a new experience. Having visited last year’s desert saturnalia to see his son [Andy]’s exhibition, the studio artist decided to undertake a massive display in his medium of choice — segmented woodturning. Not content to display a bamboo Death Star, [Malcolm] went big– really big. He cut and glued 31,000 pieces of redwood into rings of various shapes and sizes and built sculptures of amazing complexity, including endless tubes that knot and loop around and back into each other. Many of the sculpture were suspended from a huge steel tripod fabricated by [Andy], forming an interactive mobile and kinetic sculpture.

Alas, Burning Man isn’t all mellowness in the desert. People tried to climb the tripod, and overnight someone destroyed some of the bigger elements of the installation. [Malcolm] made a follow-up video about the vandalism, but you’ll want to watch the build video below first to truly appreciate the scale of the piece and the loss. Here’s hoping that [Malcolm]’s next display is treated with a little more respect, like this interactive oasis from BM 2016 apparently was.

Thanks to [Keith Olson] for the tip.

Low Background Steel — So Hot Right Now

The nuclear age changed steel, and for decades we had to pay the price for it. The first tests of the atomic bomb were a milestone in many ways, and have left a mark in history and in the surface of the Earth. The level of background radiation in the air increased, and this had an effect on the production of steel, so that steel produced since 1945 has had elevated levels of radioactivity. This can be a problem for sensitive instruments, so there was a demand for steel called low background steel, which was made before the trinity tests.

The Bessemer process pumps air through the iron to remove impurities. shropshirehistory.com

The production of steel is done with the Bessemer process, which takes the molten pig iron and blasts air through it. By pumping air through the steel, the oxygen reacts with impurities and oxidizes, and the impurities are drawn out either as gas or slag, which is then skimmed off. The problem is that the atmospheric air has radioactive impurities of its own, which are deposited into the steel, yielding a slightly radioactive material. Since the late 1960s steel production uses a slightly modified technique called the BOS, or Basic Oxygen Steelmaking, in which pure oxygen is pumped through the iron. This is better, but radioactive material can still slip through. In particular, we’re interested in cobalt, which dissolves very easily in steel, so it isn’t as affected by the Bessemer or BOS methods. Sometimes cobalt is intentionally added to steel, though not the radioactive isotope, and only for very specialized purposes.

Recycling is another reason that modern steel stays radioactive. We’ve been great about recycling steel, but the downside is that some of those impurities stick around.

Why Do We Need Low Background Steel?

Imagine you have a sensor that needs to be extremely sensitive to low levels of radiation. This could be Geiger counters, medical devices, or vehicles destined for space exploration. If they have a container that is slightly radioactive it creates an unacceptable noise floor. That’s where Low Background Steel comes in.

A person is placed into a low background steel container with sensitive equipment to measure the radioactivity of the body, which may be near the background level. Photo from orau.org

So where do you get steel, which is a man-made material, that was made before 1945? Primarily from the ocean, in sunken ships from WWII. They weren’t exposed to the atomic age air when they were made, and haven’t been recycled and mixed with newer radioactive steel. We literally cut the ships apart underwater, scrape off the barnacles, and reuse the steel.

Fortunately, this is a problem that’s going away on its own, so the headline is really only appropriate as a great reference to a popular movie. After 1975, testing moved underground, reducing, but not eliminating, the amount of radiation pumped into the air. Since various treaties ending the testing of nuclear weapons, and thanks to the short half-life of some of the radioactive isotopes, the background radiation in the air has been decreasing. Cobalt-60 has a half-life of 5.26 years, which means that steel is getting less and less radioactive on its own (Cobalt-60 from 1945 would now be at .008% of original levels). The newer BOS technique exposes the steel to fewer impurities from the air, too. Eventually the need for special low background steel will be just a memory.

Oddly enough, steel isn’t the only thing that we’ve dragged from the bottom of the ocean. Ancient Roman lead has also had a part in modern sensing.

Innovating A Better Printing Platform

Just because you have a fancy new 3D printer doesn’t mean that innovation should stop there. Almost everyone has had a print go foul if the first layer doesn’t properly adhere to the printing platform — to say nothing of difficulty in dislodging the piece once it’s finished. Facing mixed results with some established tricks meant to combat these issues, [D. Scott Williamson] — a regular at Chicago’s Workshop 88 makerspace — has documented his trials to find a better printer platform.3D Printer Steel Print Plate 1

For what he had (a printer without a heated plate), painter’s tape and hairspray wasn’t cutting it, especially when it came time to remove the print as the tape wouldn’t completely come off the part. How then, to kill two birds with one stone? Eureka! A flexible metal covering for the printing plate.

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