The jet of pure water emerges from a 0.004″, or 100 micron, diameter sapphire orifice with a flow rate of around 2 milliliters per second giving a speed of 240 meters per second. It collides at 90° with a dielectric material where the plasma is produced as a toroid surrounding the collision point.
There’s been very little research into the phenomena but a proposal from one research paper which [Ben] found is that the plasma is a result of charging due to the triboelectric effect. This is the same effect which charges a balloon when you rub it against your hair, except that here there are water molecules running across a clear dielectric such as fused quartz. This effect results in a positively charged anode downstream of the collision while the water near the point of highest shear becomes conductive and conducts negative charge to the point of smallest curvature, producing a cathode. The electric field at the small-radius cathode acts like a short point with a high voltage on it, ionizing the air and forming the plasma. If this form of ionization sounds familiar, that’s because we’ve talked it occurring between the sharp wire and rounded foil skirt of a flying lifter.
[Ben] found support for the triboelectric theory when he substituted oil for the water. This didn’t produce any plasma, which is be expected since unlike water, oil is a non-polar molecule. However, while the researchers tried just a few dielectric materials, [Ben] had success with every transparent dielectric which he tried, including fused quartz, lithium niobate, glass, polycarbonate, and acrylic, some of which are very triboelectrically different from each other. So there’s room here for more theorizing. But check out his full video showing his equipment for producing the waterjet as well as his demonstrations and explanation.
The iPhone 8 was just released last week, and that means some people were standing in line in front of an Apple store for hours waiting to get their hands on the latest and greatest glowing rectangle. [Patrick Adair] had a better idea: he would stand in front of an Apple store for four hours, then do something productive with his new smartphone. With the help of a waterjet, some resin, a lathe, and some very fine grades of sandpaper, he created the Apple Ring.
Setting aside the whole process of actually acquiring an iPhone 8 on launch day, the process of turning an iPhone into a ring is more or less what you would expect. First, the iPhone was cut into ring-shaped pieces on a waterjet cutter. Special care was taken to avoid the battery, and in the end [Patrick] was able to get a nice chunk ‘o phone that included the camera lens.
This ring piece was then embedded in clear resin. For this, [Patrick] used Alumilite epoxy, a pressure pot, and a toaster oven to cure the resin. Once the phone parts were firmly encased for the rest of eternity, the ring blank moved over to the lathe. The center of the ring was bored out, and the process of sanding, polishing and gluing in all the tiny parts that fell out during the process commenced. The end result actually looks pretty great, and even though it’s probably a little too bulky, it is a remarkable demonstration of the craft of turning.
You can check out [Patrick]’s video below, along with a video from the Waterjet Channel showing the deconstruction of a glowing rectangle.
Most hobbyists don’t have waterjets in their garage, but they would if they could! A Waterjet (or Water Jet Cutter) is a marvelous tool. Simply mount a high-pressure stream of grit and water on an x-y gantry, and the pressure generates enough erosion to cut through just about any thin material. Unfortunately, claiming your own waterjet will erode away a nice big hole in your pocketbook too. Machines up to this point start at about $75K, not to mention that they’d claim the better part of your workspace in a two-car garage.
Most of us everyday hackers that want to play with the benefits of this tool send their parts out to a professional shop. Consequently, we don’t often hear about everyday hackers using waterjets, or waterjet-cut parts all that often, with one exception. Back in 2014, a crew of students from UPENN built a functional waterjet with a parts-list that could make it affordable for about $5000. Now that same team is back. This time, they’ve spun together not just a one-off, but a fully-featured product called Wazer, which just launched its Kickstarter campaign minutes ago and has already nearly quadrupled the $100k goal. How could it do that? The full package starts at modest $3599-$4499. This is crowd-funding, after all, but a 20x undercutting of price is a powerful motivator.
While laser cutting remains the dominant force for rapid prototyping anything made of plastic, MDF or wood, the real holy grail is the ability to cut metal — something most laser cutters are just not capable of.
In the industry, this is done using extremely high-powered laser cutters, plasma cutters, or water jet cutters. All of which are very pricey equipment for a hacker. Until now anyway. Introducing the Tinijet, the missing tool for affordable water jet cutting.
We first covered this project a few years ago when it was just a university research project called Hydro — it’s since evolved immensely, and will be available for sale very soon.
Waterjet cutters are generally huge machines, with equally large price tags. But what if there was a hobbyist level waterjet cutter that was actually affordable? Well, for their Senior Design Project at the University of Pennsylvania, [Adam Libert] and his team made one that could retail for less than $5000.
[Adam] was the lead mechanical designer on this amazing project, and he designed the fully waterproof XY gantry, capable of withstanding the water and abrasive from the cutter. The entire machine is only 2′ x 2′ by about 5′ tall, making it extremely portable and easy to move through doorways — and it runs off of plain old 120VAC and shop air. It is capable of cutting through up to 1/4″ aluminum and 1/8″ steel with a working area of 12″ x 14″ at a tolerance of 0.005″.
Not surprising, the project won the Mechanical Engineering Senior Design competition in 2012 with accolades for outstanding creativity. We weren’t able to find any information on the future plans for this project, but we hope they make it open-source, or even run a crowd-funding campaign for it.
The goal was to create the first ever low-cost, small scale, and easy to use waterjet cutter, and judging by the video, it looks like they did it — stick around after the break to see for yourself.