Robot 3D Prints Giant Metal Parts With Induction Heat

March 29, 2023 by Bryan Cockfield 36 Comments

While our desktop machines are largely limited to various types of plastic, 3D printing in other materials offers unique benefits. For example, printing with concrete makes it possible to quickly build houses, and we’ve even seen things like sugar laid down layer by layer into edible prints. Metals are often challenging to print with due to its high melting temperatures, though, and while this has often been solved with lasers a new method uses induction heating to deposit the metals instead.

A company in Arizona called Rosotics has developed a large-scale printer based on this this method that they’re calling the Mantis. It uses three robotic arms to lay down metal prints of remarkable size, around eight meters wide and six meters tall. It can churn through about 50 kg of metal per hour, and can be run off of a standard 240 V outlet. The company is focusing on aerospace applications, with rendered rocket components that remind us of what Relativity Space is working on.

Nothing inspires confidence like a low-quality render.

The induction heating method for the feedstock not only means they can avoid using power-hungry and complex lasers to sinter powdered metal, a material expensive in its own right, but they can use more common metal wire feedstock instead. In addition to being cheaper and easier to work with, wire is also safer. Rosotics points out that some materials used in traditional laser sintering, such as powdered titanium, are actually explosive.

Of course, the elephant in the room is that Relativity recently launched a 33 meter (110 foot) tall 3D printed rocket over the Kármán line — while Rosotics hasn’t even provided a picture of what a component printed with their technology looks like. Rather than being open about their position in the market, the quotes from CEO Christian LaRosa make it seem like he’s blissfully unaware his fledgling company is already on the back foot.

If you’ve got some rocket propellant tanks you’d like printed, the company says they’ll start taking orders in October. Though you’ll need to come up with a $95,000 deposit before they’ll start the work. If you’re looking for something a little more affordable, it’s possible to convert a MIG welder into a rudimentary metal 3D printer instead.

Enormous Metal Sculpture Becomes An Antenna

March 23, 2023 by Bryan Cockfield 16 Comments

Those who have worked with high voltage know well enough that anything can be a conductor at high enough voltages. Similarly, amateur radio operators will jump at any chance to turn a random object into an antenna. Flag poles, gutters, and even streams of water can be turned into radiating elements for a transmitter, but the members of this amateur radio club were thinking a little bit bigger when they hooked up their transmitter to this giant sculpture.

For those who haven’t been to the Rochester Institute of Technology (RIT) in upstate New York, the enormous metal behemoth is not a subtle piece of artwork and sits right at the entrance to the university. It’s over 70 feet tall and made out of bronze and steel, a dream for any amateur radio operator. With the university’s permission and some help to ensure everyone’s safety during the operation, the group attached a feedline to the sculpture with a magnet, while the shield wire was attached to a ground rod nearby. A Yaesu FT-991 running on only 5 watts and transmitting in the 20-meter band was able to make contacts throughout much of the eastern United States with this setup.

This project actually started as an in-joke within the radio club, as reported by Reddit user [bbbbbthatsfivebees] who is a member. Eventually the joke became reality, as the sculpture is almost a perfect antenna for certain ham bands. Others in the comments noted that they might have better luck with lower frequency bands such as the 40-meter band or possibly the 60-meter band, due to the height of the structure. And, for those who are still wondering if you really can use a stream of water to transmit radio waves, it is indeed possible.

The Die Is Cast!

March 1, 2023 by Jenny List 31 Comments

We all know the basics of how metal casting works, a metal is heated up to melting point and the resulting liquid metal is poured into a mold. When the metal sets, it assumes the shape of the mold. It’s a straightforward way to reliably replicate a metal item many times over, and the basics are the same whether the metal is a low-temperature alloy in a silicone mould or a crucible of molten steel poured into a sand mould.

The mould is black sand in a cast iron box, and the pattern piece is half submerged in it — A sand mould being formed around a pattern. Lukas Stavek, CC BY-SA 3.0 .

What we all understood as casting in our conversation was sand casting. Sand is packed around a pattern of the piece to be cast, and then the pattern is removed leaving a cavity in its shape which becomes the mould. There are refinements to this process and the mould is frequently formed in two halves, but it’s something that’s even practical to do in a hackerspace level setting.

A refinement of sand casting is so-called lost-wax casting, in which a hollow wax model of the piece to be cast is packed around with sand, and ~~when the metal is poured onto the top of it the wax melts~~ and the wax is melted out before pouring the metal in to take its place. A variation on this appears here from time to time, so-called lost-PLA casting, where the wax model is replaced with a PLA 3D print.

Injection Molding For Metals

Diagram of a die casting machine — A die casting machine. Ahmed elbhje, Public domain.

Where our confusion crept in was with die casting. We could recognise a die-cast piece, but just what is die-casting, and how is a die-casting made? The answer there lies in mass-production, because a snag with sand casting is that a sand mould can be labour intensive to produce. Much better to come up with a quick-turnaround process that re-uses the same mould over and over, and save all that time!

Enter the die-casting, to metalwork what injection moulding is to polymers. The die is a mould made out of metal, usually with liquid cooling, and the casting is done not by pouring but by forcing the molten metal into the mould under pressure. The whole process becomes much quicker, meaning that it can become a piece of process machinery spitting out castings rather than a labour-intensive individual task. The metals used for die-casting are the lower temperature ones such as aluminium, zinc, and their alloys, but you will find die-castings in all conceivable places.

It’s obvious that Hackaday editors are not experienced foundrymen even if some of us grew up around metalwork, but we know that among our readers lie genuine experts in all sorts of fields. If that’s you and you operate a die-casting machine, please take a moment to tell us about it, we really would like to know more!

Header: Constantin Meunier, Public domain.

Casting Metal With A Microwave And Vacuum Cleaner

September 29, 2022 by Bryan Cockfield 38 Comments

Metalworking might conjure images of large furnaces powered by coal, wood, or electricity, with molten metal sloshing around and visible in its crucible. But metalworking from home doesn’t need to use anything more fancy than a microwave, at least according to [Denny] a.k.a. [Shake the Future]. He has a number of metalworking tools designed to melt metal using a microwave, and in this video he uses them to make a usable aluminum pencil with a graphite core.

Before getting to the microwave kiln, the pencil mold needs to be prepared. A 3D-printed pencil is first created with the graphite core, and then [Denny] uses a plaster of Paris mixture to create the mold for the pencil. The 3D printed plastic is left inside the mold and placed in the first microwave kiln, which is turned on just enough to melt the plastic out of the mold, leaving behind the graphite core. From there a second kiln goes into the microwave to melt the aluminum.

Once the molten aluminum is ready, it is removed from the kiln and poured in the still-warm pencil mold. This is where [Denny] has another trick up his sleeve. He’s using a household vacuum cleaner to suck the metal into place before it cools, creating a rudimentary but effective vacuum forming machine. The result is a working pencil, at least after he wears down a few razor blades attempting to sharpen the metal pencil. For more information about how [Denny] makes these microwave kilns, take a look at some of his earlier projects.

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Cutting Metals With A Diode Laser?

September 21, 2022 by Dave Rowntree 34 Comments

Hobbyist-grade laser cutters can be a little restrictive as to the types and thicknesses of materials that they can cut. We’re usually talking about CO₂ and diode-based machines here, and if you want to cut non-plastic sheets, you’re usually going to be looking towards natural materials such as leather, fabrics, and thin wood.

But what about metals? It’s a common beginner’s question, often asked with a resigned look, that they already know the answer is going to be a hard “no. ” However, YouTuber [Chad] decided to respond to some comments about the possibility of cutting metal sheets using a high-power diode laser, with a simple experiment to actually determine what the limits actually are.

Using an XTool D1 Pro 20W as a testbed, [Chad] tried a variety of materials including mild steel, stainless, aluminium, and brass sheets at a variety of thicknesses. Steel shim sheets in thicknesses from one to eight-thousandths of an inch appeared to be perfectly cuttable, with an appropriate air assist and speed settings, with thicker sheets needing a good few passes. You can definitely see the effect of excess heat in the workpiece, resulting in some discoloration and noticeable warping, but those issues can be mitigated. Copper and aluminium weren’t touched by the beam at all, likely due to the extra reflectivity, but we do have to wonder if appropriate surface treatments could improve matters.

Obviously, we’ve seen that diode lasers can have an impact on metals, simply smearing a little mustard on the workpiece seems to make marking a snap. Whilst we’re on the subject of diode lasers, you can get a lot of mileage from just strapping such a laser module onto a desktop CNC.

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This Stainless Steel Knife Build Starts With Raw Iron Ore

August 6, 2022 by Dan Maloney 11 Comments

Making knives at home has become a popular hobby, thanks partly to reality TV and the free time and idle hands afforded by lockdowns. Depending on how far you get into the hobby, builds can range from assembling and finishing a kit with pre-forged parts, to actual blacksmithing with a hammer and anvil. But pretty much every build includes steel from a commercial supplier.

Not this one. Rather than buy his metal from the usual sources, [Thoisoi]’s first stop was an iron mine in the Italian Alps, where he picked up a chunk of iron ore — magnetite, to be precise. Smelting one’s own iron from raw ore and alloying it into steel is generally not a backyard project thanks to the high temperatures needed, a problem [Thoisoi] solved with the magic of thermite. The iron oxide and aluminum in the thermite mix react in an exceptionally exothermic manner to generate elemental iron, which under controlled conditions can be captured as a more or less pure ingot, ready for forging.

After a test with commercially obtained iron oxide, [Thoisoi] tried his pulverized magnetite. And thanks to the addition of goodies like graphite, manganese, nickel, silicon, and chromium, he was eventually able to create a sizable lump of 402 stainless steel. He turned the metal over to an actual blacksmith for rough forging; it sure seemed to act like steel on the anvil. The finished knife looks good and performs well, and the blade has the characteristic look of stainless. Not a bad result, and all at the cost of a couple of clay flowerpots.

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Can You Build An Industrial Grade CNC With Only DIY Resources?

May 30, 2022 by Dave Rowntree 14 Comments

[FloweringElbow] aka [Bongo] on YouTube is certainly having a go at this, and we reckon he’s onto a winner! This epic flatbed CNC build (video, embedded below) starts with some second hand structural I-beam, with welded-on I-beam legs, DIY cast aluminium side plates and plenty of concrete to give a strong and importantly, heavy structure.

The ideal machine is as rigid as possible, and heavy, to dampen out vibrations caused by high-feed speed cutting, or the forces due to cutting harder materials, so bigger really is better. For construction of the frame, steel is pretty strong, and the mass of the structure gives it additional damping, but triangulation was needed to counteract additional twisting. He stitch-welded the pre-heated frame in inch-long sections to limit the heat transferred into the metal, minimizing the subsequent warpage. [Bongo] used hacky Vibratory stress relief (VSR) constructed from a washing machine motor and eccentric weight, clamped to the frame, with feedback from a mobile phone app to find the resonant frequencies. There are other videos on the channel devoted to that topic of such stress relief techniques.

Precise enough to cut sticky-backed vinyl at half thickness!

When it came time for adding even more mass, a priming coat was made from a mixture of bonding epoxy and sharp grit, intended for non-slip flooring. The concrete mix used Portland cement, pozzolan (Silica fume) polycarboxylate superplasticiser and 1/2″ glass fiber threads. A second mix added crushed stone for additional mass. A neat trick was to make a handheld vibratory compactor from a plate welded onto the end of old drill bit, mounted in an SDS hammer drill.

Once the frame was flipped the right way up (collapsing the overloaded hoist in the process) it was necessary to level the top surface to accept the linear rails. This was done using a super runny, self-leveling epoxy, and checked by flowing water over it. Once the epoxy surfaces were adequately flat and coplanar (and much scraping later) the linear rails were attached, after creating some epoxy shoulders for them to butt up against. End plates to attach the Y axis lead screws, were added by bolting into the frame with a grit-loaded epoxy bond in between.

The gantry design was skipped for this video (but you can see that here) and once mounted a quick test showed the machine was viable. One curious task was making their own cable-chain from ply, on the machine itself, rather than buying something expensive off-the-peg. Why not? Once the machine was working well enough to mill a flat sheet of steel to nice reflective surface, it was used to mount a DIY drag-knife to cut out shapes in some vinyl, so it has the precision. We did like seeing an XBox controller used to manually jog the machine around! So much to see in this build and other related videos, we reckon this channel is one to watch!

We’ve featured CNC builds many a time, there’s a build whatever your needs and budget, but here’s a good starting point to build a machine, just good enough to build the tools you need. If you don’t happen to have a source of structural I-beam to hand, you can do something quite capable with wood, and if you fancy a go at 3D printing a knee mill, we’ve got that covered as well.

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