Using Statistics Instead Of Sensors

Statistics often gets a bad rap in mathematics circles for being less than concrete at best, and being downright misleading at worst. While these sentiments might ring true for things like political polling, it hides the fact that statistical methods can be put to good use in engineering systems with fantastic results. [Mark Smith], for example, has been working on an espresso machine which can make the perfect shot of coffee, and turned to one of the tools in the statistics toolbox in order to solve a problem rather than adding another sensor to his complex coffee-brewing machine.

To make espresso, steam is generated which is then forced through finely ground coffee. [Mark] found that his espresso machine was often pouring too much or too little coffee, and in order to improve his machine’s accuracy in this area he turned to the linear regression parameter R2, also known as the coefficient of determination. By using a machine learning algorithm tuned to this value, which assesses predictable variation in a data set, a computer can more easily tell when the coffee begins pouring out of the portafilter and into the espresso cup based on the pressure and water flow in the machine itself rather than using some other input such as the weight of the cup.

We have seen in the past how seriously [Mark] takes his coffee-making, and this is another step in a series of improvements he has made to his equipment. In this iteration, he has additionally produced a simulation in JupyterLab to better assist him in modeling the system and making even more accurate predictions. It’s quite a bit more effort than adding sensors, but since his espresso machine already included quite a bit of computing power it’s not too big a leap for him to make.

3D Printer Cuts Metal

Every now and then we’ll see a 3D printer that can print an entire house out of concrete or print an entire rocket out of metal. But usually, for our budget-friendly hobbyist needs, most of our 3D printers will be printing small plastic parts. If you have patience and a little bit of salt water, though, take a look at this 3D printer which has been modified to cut parts out of any type of metal, built by [Morlock] who has turned a printer into a 5-axis CNC machine.

Of course, this modification isn’t 3D printing metal. It convers a 3D printer’s CNC capabilities to turn it into a machining tool that uses electrochemical machining (ECM). This process removes metal from a work piece by passing an electrode over the metal in the presence of salt water to corrode the metal away rapidly. This is a remarkably precise way to cut metal without needing expensive or heavy machining tools which uses parts that can easily be 3D printed or are otherwise easy to obtain. By using the 3D printer axes and modifying the print bed to be saltwater-resistant, metal parts of up to 3 mm can be cut, regardless of the type of metal used. [Morlock] also added two extra axes to the cutting tool, allowing it to make cuts in the metal at odd angles.

Using a 3D printer to perform CNC machining like this is an excellent way to get the performance of a machine tool without needing to incur the expense of one. Of course, it takes some significant modification of a 3D printer but it doesn’t need the strength and ridigity that you would otherwise need for a standard CNC machine in order to get parts out of it with acceptable tolerances. If you’re interested in bootstraping one like that using more traditional means, though, we recently featured a CNC machine that can be made from common materials and put together for a minimum of cost.

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IBM Cheese Cutter Restoration

For a while now, Mac Pro towers have had the nickname “cheese grater” because of their superficial resemblance to this kitchen appliance. Apple has only been a company since the 70s, though, and is much newer than one of its historic rivals, IBM. In fact, IBM is old enough to have made actual cheese-related computers as far back as the 1910s, and [Hand Tool Rescue] recently obtained one of these antique machines for a complete restoration.

The tool arrived to the restoration workshop in a state so poor that it was difficult to tell what many of the parts on the machine did except for the large cleaver at the top. The build starts with a teardown to its individual parts, cleaning and restoring them to their original luster, machining new ones where needed, and then putting it all back together. The real mystery of this build was what the levers on the underside of the machine were supposed to do, but after the refurbishment it was discovered that these are the way that portions the cheese wheel would be accurately sized and priced before a cut was made.

By placing a section of a wheel of cheese on the machine and inputting its original weight with one of the levers, the second lever is adjusted to the weight of cheese that the customer requested, which rotates the wheel of cheese to the correct position before a cut is made. To us who are spoiled with a world full of electronic devices, a mechanical computer like this seems almost magical, especially with how accurate it is, but if your business in the 1910s involved cheese, this would have been quite normal. In fact, it would be 50 more years before IBM created the machines that they’re more commonly known for.

Thanks to [Jasper Jans] for the tip!

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Workshop Tools Are Available In First-Class

Most of dream of having a fully-stocked shop with all of the tools needed to build our projects, at least if we don’t already have such a shop. In the meantime, a lot of us are hacking together our own tools and working on whatever bench space might be available to us. While [Emiel] aka [The Practical Engineer] has an envious shop to work from, his latest project goes to show how repurposing some aircraft-grade equipment can result in a high-quality toolbox for himself, without shelling out for any consumer-level solution. (Video, embedded below.)

The core of his workshop cart build is actually a recycled food service cart from an airline. While the original probably only housed some soft drinks and ice, this one has been kitted out to be much more functional. Since [Emiel] is using this to wheel around his machine shop, he used a CNC machine to cut out slots in black MDF sheets which would hold his drill bits, taps, and other tools. Working with MDF on a CNC machine turned out to not be as simple as he thought, since the MDF would separate and break away unless the CNC tool heads were operated in a specific way.

The build also includes several buckets for other tools, and a custom enclosure for the top of the cart specifically built for his machine tools’ tools to sit while he is working. It’s certainly a more cost-effective solution to a wheeled shop toolbox than buying something off-the-shelf, and a clever repurposing of something which would have otherwise ended up in a landfill. [Emiel] is no stranger to building any tools that he might need, including this custom belt sander built completely from the ground up.

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Chainsaw Cuts More Than Timber

We often take electricity for granted, to the point of walking into a room during a power outage and still habitually flipping the light switch. On the other hand, there are plenty of places where electricity isn’t a given, either due to poor infrastructure or an otherwise remote location. To get common electric power tools to work in areas like these requires some ingenuity like that seen in this build which converts a chainsaw to a gas-driven grinder that can be used for cutting steel or concrete. (Video, embedded below.)

All of the parts needed for the conversion were built in the machine shop of [Workshop from scratch]. A non-cutting chain was fitted to it first to drive the cutting wheel rather than cut directly, so a new bar had to be fabricated. After that, the build shows the methods for attaching bearings and securing the entire assembly back to the gas-powered motor. Of course there is also a custom shield for the grinding wheel and also a protective housing for the chain to somewhat limit the danger of operating a device like this.

Even though some consideration was paid to safety in this build, we would like to reiterate that all the required safety gear should be worn. That being said, it’s not the first time we’ve seen a chainsaw modified to be more useful than its default timber-cutting configuration, like this build which turns a chainsaw into a metal cutting chop saw.

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Adjustable, Piston-Damped Hammer

When all you have is a hammer, every problem is a constant quest for an even better hammer, as the popular saying goes. At least, that seems to be [Ebenisterie Éloïse]’s situation. She wanted a deadblow hammer that not only had an aesthetically pleasing wood and brass construction, but also one that included adjustable dampers to make sure that each hammer swing is as efficient as possible.

For those unfamiliar with specialty hammers, dead blow hammers typically have some movable mass such as sand or lead shot within the hammer head. This mass shifts forward when the hammer strikes an object, reducing rebound of the hammer off of the object and transferring more energy into each strike. This hammer omits a passive mass in favor of four custom-machined brass tubes, each of which holds a weighted fluid, a spring, and brass weight. Each piston acts as a damper in a similar way to a shock absorber on a vehicle, and a screw and o-ring at the top of each one allows them to be adjustable by adding different weight fluids as needed. Some detailed testing of the pistons shows a marked improvement over any of the passive mass varieties as well.

Not only is this an incredible amount of detail and precision for a tool that is often wielded in a non-precise way (at least among those of us for who aren’t skilled craftspeople), but it is also made out of wood, leather, and brass which gives it an improved look and feel over a plastic and fiberglass hammer that is typical of most modern deadblow hammers. It even rivals this engineer’s hammer with its intricate custom engraving in craftsmanship alone.

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Balanced Design And How To Know When To Quit Optimizing

I got a relatively inexpensive 6040 CNC machine, and have been spending most weekends making the thing work, and then cutting stuff, learning the toolchain, and making subsequent improvements. Probably 90% of my machine time has been on making improvements. It’s not that the machine was bad — I got the version with ballscrews and a decently solid frame — but it’s that it somehow didn’t work together as a whole. It’s just an incredibly unbalanced design.

Let’s start with the spindle motor. It’s a 2.2 kW water-cooled beast that is capable of putting tons of work into a piece and spinning at very high speed. Yet to keep up with the high speed spindle, the motors that move it around would have to be capable of high speeds as well — it’s a feeds and speeds thing if you’re not a CNC geek. And they can’t. Instead, the stepper motors that came with the kit are designed for maximum force at low speeds. Which can make sense for some machines, but for one with a slightly flexible X-axis like this one, that’s wasted as well. The frame just can’t handle the low-end grunt that the motors are capable of, so it can’t take advantage of the spindle’s power either. The design is all over the place.

Over the last two months’ of weekends, I’ve been going through this iterative procedure of asking “what is my limiting factor right now?”, working on fixing that thing up, running it some, and then asking the question again. And it’s a good general procedure, and I believe that it’s getting me to the machine I want at the minimum cost of time, money, and effort.

At first, it was the driver hardware/software with its emulated USB parallel port, so I swapped out the controller for an Arduino running GRBL, soldered directly to the DB-25 that comes out of the back. At least it can put out pulses fast enough to order the motors around, but they would still stall out at high speeds. Swapping the stepper motors out for a high-speed pair only cost me €40, which makes you wonder why they didn’t just put the right motors on in the first place. The machine now travels fast enough to make use of the high-speed spindle, and I’m flying through plywood and plastics without leaving burn marks. It’s a huge win for not much money.

The final frontier is taking big bites out of aluminum. The spindle can do it, but I fear I’m up against the frame’s rigidity on the X-axis. For whatever reason, they went with unsupported rods on the X, which are significantly more flexible than an axis that’s backed up by more metal. And this is where the limiting factor may actually be my time and patience, rather than money. I just can’t bear to disassemble and reassemble the thing again. So for now, it’s going to be small nibbles, taking advantage of the machine’s speed, if not yet the spindle’s full horsepower.

But it’s odd, because this machine is a bundle of good parts. It’s just that they haven’t been chosen to work together optimally; the frame doesn’t work with the stepper motors, which don’t work with the spindle. If they went through my procedure of saying “what’s the limiting factor?” they could have saved themselves €100 by just shipping it with a wimpier spindle, which would have been a balanced, if anemic, machine. Or they could have built it with the right motors for more speed. Or supported rails for more grunt. Or both!

I’ll never know why they quit optimizing their design when they did. Maybe they never got past the slow USB/parallel port speed? But I’m near the end of my path, and I can tell because the limiting ingredient isn’t a simple upgrade, or even mere money anymore, but my own willpower.

How can you tell when you’re at the top of a mountain in a dense fog? A step you take in any direction would lead you downhill. How can you tell when you’re satisfied with a project’s state? When you don’t have the need, or desire, to undertake the next most obvious improvement.