Milling Dies And Injection Moulding Some Acrylic Lenses

[Zach] over at his channel Breaking Taps has put up an extraordinary account on manufacturing some homemade acrylic lenses. In the end, not only does he produce some beautiful concave lenses, he also covers the complete manufacturing process, from milling the aluminium die used for injection moulding to tweaking the parameters associated with injecting the actual acrylic, he even goes over the limitations of optics produced in this fashion.

What caught our eye in particular, was how [Zach] used the finished product to practically demonstrate photoelasticity originating from the stress induced by the moulding process. You might be familiar with describing the optical properties of a material by a single number, i.e its permittivity. But what happens if in addition to altering speed, the material also alters the polarisation and direction of light depending on the stress distribution within the material? Whilst a quantitative answer gets a bit complicated you can check out [Zach’s] additional videos to visualise the answer in a pretty and colourful way, without resorting to fancy computer simulations! If however, you really want to persist with the simulation route, check out our article on stress analysis in a totally different setting using Finite Element Analysis.

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A Behind The Scenes Look At Small Scale Production

Back in 2013, [Karl Lautman] successfully got his kinetic sculpture Primer funded on Kickstarter. As the name implies, you press the big red button on the front of the device, and the mechanical counter at the top will click over to a new prime number for your viewing pleasure. Not exactly a practical gadget, but it does look pretty slick.

These days you can still by your very own Primer from [Karl], but he tells us that the sales aren’t exactly putting food on the table. At this point, he considers it more of a self-financing hobby. To illustrate just what goes into the creation of one of these beauties, he’s put together a time-lapse video of how one gets built from start to finish, which you can see after the break.

Even if you’re not interested in adding a mathematics appliance to your home, we think you’ll agree that the video is a fascinating look at the effort that goes into manufacturing a product that’s only slightly north of a one-off creation.

The biggest takeaway is that you really need to be a jack of all trades to pull something like this off. From milling and polishing the metal components to hand-placing the SMD parts and reflowing the board, [Karl] demonstrates the sort of multi-disciplinary mastery you need to have when there’s only one person on the assembly line.

Small scale manufacturing isn’t cheap, and is rarely easy. But stories like this one prove it’s certainly possible if you’re willing to put in the effort.

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Bend Some Bars With A Flywheel

The ability to look at a pile of trash, and see the for treasure is a skill we hold in high regard around here. [Meanwhile in the Garage] apparently has this skill in spades and built himself a metal bar bending machine using an old flywheel and starter pinion gear.

To bend metal using muscle power alone requires some sort of mechanical advantage. Usually this involves a bending tool with a long lever, but [Meanwhile in the Garage] decided to make use of the large gear ratio between a car’s starter motor and the flywheel it drives. This does away with the need for a long lever and allows bending to almost 270° with a larger radius. Lathe and milling work features quite prominently, including to make the bend formers, drive shaft and bushings and to modify the flywheel to include a clamp. The belt sander that is used to finish a number of the parts is also his creation. While the machine tools definitely helped, a large amount of creativity and thinking outside the box made this project possible and worth the watch.

We’ve featured a number of scrap-built tools including a milling machine, sheet metal hole punch and a hydraulic bench vice. Keep them coming!

CNC Machine Rolls Up An Axis To Machine PVC Pipe

Whether it’s wood, metal, plastic, or otherwise, when it comes to obtaining materials for your builds, you have two choices: buy new stock, or scrounge what you can. Fresh virgin materials are often easier to work with, but it’s satisfying to get useful stock from unexpected sources.

This CNC router for PVC pipe is a great example of harvesting materials from an unusual source. [Christophe Machet] undertook his “Pipeline Project” specifically to explore what can be made from large-diameter PVC pipe, of the type commonly used for sewers and other drains. It’s basically a standard – albeit large-format – three-axis CNC router with one axis wrapped into a cylinder. The pipe is slipped around a sacrificial mandrel and loaded into the machine, where it rotates under what looks like a piece of truss from an antenna tower. The spindle seems a bit small, but it obviously gets the job done; luckily the truss has the strength and stiffness to carry a much bigger spindle if that becomes necessary in the future.

The video below shows the machine carving up parts for some lovely chairs. [Christophe] tells us that some manual post-forming with a heat gun is required for features like the arms of the chairs, but we could see automating that step too. We like the look of the pieces that come off this machine, and how [Christophe] saw a way to adapt one axis for cylindrical work. He submitted this project for the 2019 Hackaday Prize; have you submitted your entry yet?

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Vintage Fairchild IC Proves Tough To Decap

You’d think that something called “white fuming nitric acid” would be more than corrosive enough to dissolve just about anything. Heck, it’s rocket fuel – OK, rocket fuel oxidizer – and even so it still it wasn’t enough to pop the top on this vintage Fairchild μL914 integrated circuit, at least not without special measures.

As [John McMaster], part of the team that analyzed the classic dual 2-input NOR gate RTL chip from the 1960s, explains it, decapping modern chips is a straightforward if noxious process. Generally a divot is milled into the epoxy, providing both a reservoir for the WFNA and a roughened surface for it to attack. But the Fairchild chip, chosen for dissection for the Maker Faire Bay Area last week specifically because the features on the die are enormous by modern standards, was housed in an eight-lead TO-99 case with epoxy that proved nigh invulnerable to WFNA. [John] tried every chemical and mechanical trick in the book, going so far as to ablate epoxy with a Nd:YAG laser. He eventually got the die exposed, only to discover that it was covered with silicone rather than the silicon dioxide passivation layer of modern chips. Silicone can be tough stuff to remove, and [John] resorted to using lighter fluid as a solvent and a brush with a single bristle to clean up the die.

We applaud the effort that this took, which only proves that decapping is more art than science sometimes. And the results were fabulous; as Hackaday editor-in-chief [Mike Szczys] notes, the decapping led to his first real “a-ha moment” about how chips really work.

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CNC Your Own PCBs With A 3D Printed Mill

Yes, you can whip up a design for a printed circuit board, send it out to one of the many fab houses, and receive a finished, completed board in a week or two. There are quick-turn assembly houses that will manufacture a circuit board and populate it for you. But sometimes you need a board now, and that’s when we get into home PCB fabrication. You can do this with either etching or milling, but [Renzo] has a great solution. He built a 3D printed milling machine that will make a printed circuit board.

The design of this tiny micro mill is based on a handheld rotary tool, also called a Dremel, but that’s like Kleenex, so just buy a Proxxon. This mill is designed with 3D printed T-track and constructed with linear bearings on smooth rods with standard NEMA 17 stepper motors and herringbone gears for little to no backlash. There is quite a bit going on here, but lucky for us [Renzo] has a video tutorial of the entire build process available for viewing below.

We’ve previously seen some of [Renzo]’s previous efforts in homemade PCB fabrication, up to and including applying green soldermask with the help of Fritzing. This is good, very good, and the only thing that really separates this from manufactured PCBs is the lack of plated through holes. That’s just a bit of graphite and electroplating away, and we’re looking forward to [Renzo]’s further adventures in making PCBs at home.

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CNC Your Own PCB With This Tutorial

It is getting so easy to order a finished printed circuit board that it is tough to justify building your own. But sometimes you really need a board right now. Or maybe you need a lot of fast iterations so you can’t wait for the postal service. [Thomas Sanladerer] shows how he makes PCBs with a CNC machine and has a lot of good advice in the video below.

He starts with Eagle, although, you could use any creation package. He shows what parameters he changes to make sure the traces don’t get eaten away and how to do the CAM job to get the files required to make the boards. If you don’t use Eagle, you’ll need to infer how to do similar changes and get the same kind of output.

We’ve only heard a few people pronounce Gerber (as in Gerber file) with a soft G sound, but we still knew what he meant. We have the same problem with GIF files. However, once you have Gebers, you can join the video’s workflow about 5 minutes in.

At that point, he uses FlatCAM to convert the Gerbers to a single G-code file that integrates the paths and drill files. There were a few tricks he used to make sure all the tracks are picked up. Other tricks include leveling a spoil board by just milling it down and mounting different size bits. He also has ideas on aligning the Z axis.

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