CNC Drag Knife Upgrade with Off-the-Shelf Blades

Drag Knives seem to be the overshadowed awkward kid on the playground of CNC equipment, but they have a definitive niche making stencils, vinyl stickers, and paper cuts. Unfortunately, the drag knife blades for CNC routers are pricey — over $100 for a single blade. [Brian] at the Grunblau Design Studio took the price point as a challenge to build his own end-effector. A few iterations later, he’s created his very own drag knife blade tool that accepts replaceable steel blades for cutting.

From constraint-driven concept, to a 3D printed proof-of-concept, to a fully machined aluminum prototype, [Brian’s] efforts hit all the highlights of a well-engineered project. At the end of the day, dull blades can be swapped for a few dollars, rather than shelling out another $150 for the off-the-shelf variant. We’ve seen bootstrapped CNC vinyl cutters before, but nothing that takes an original re-envisioning of the tool itself.

FR4 Machine Shield Is A CNC Milling Machine From FR4 PCB

The people behind the PocketNC heard you like CNC PCB mills, so they milled you a PCB mill out of PCB. They announced their surprising new open source hardware product, a pocket sized 3-axis CNC machine entirely made out of FR4 PCB material, aptly named “FR4 Machine Shield”, at this year’s Bay Area Maker Faire.

UPDATE: The FR4 Machine Shield is now on Kickstarter

fr4_thumbWe know the concept from quadcopters, little robots, and generally things that are small enough to make use of their PCBs as a structural component. But an entire CNC machine, soldered together from a few dozen PCBs certainly takes it to the next level.

There is no doubt that 2mm thick fiber reinforced epoxy can be surprisingly rigid, although the Achilles heel of this method might be the solder joints. However, it looks like all load bearing, mechanical connections of the machine are supported by tightly interlocking “dovetail” finger-joints, which may help protecting all the solder connections from the strain hardening effects of continuous stress and spindle vibrations.

As you might expect, most of the wiring is embedded into the FR4 frame construction, and to squeeze the maximum value out of the PCB material, the motor driver boards interface via card edge connectors with the (currently Arduino based) controller board. In addition to the milling head, which features a brushless DC motor and a tool coupler, the team wants to develop heads for circuit printing, microscopy, pneumatic pick and place, hot air reflow, and 3D printing.

With all those cost-driven design choices, from the one-step manufacturing process of the frame and wiring to the dismissal of screws and nuts from the frame assembly, the “FR4 Machine Shield” could indeed become one of the cheapest CNC machine kits on the market. The team targets an introduction price of $400 during a Kickstarter campaign in June 2016. Can they deliver? [Gerrit] checked Pocket NC out at the Faire and ended up raving about how they run their business.

Enjoy their teaser video below!

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Mechaduino- Closed Loop Stepper Servos For Everyone

Is it something in the water, or have there been a lot of really cool servo projects lately? Mechaduino is a board that sits on a regular stepper motor and turns it into a servo with a closed loop control of 0.1degree.

Whenever we post something about using cheap brushless motors for precision control, someone comments that a stepper is just a brushless motor with a lot of poles, why not just control it like one. That’s exactly what the Mechaduino does. They also hint at doing something very clever with a magnetic encoder on the board which allows them, after a calibration routine, to get the accuracy they’ve promised.

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CNC Clock Mills Itself, Displays The Time

[Christian] wrote and sells some CAM/CNC controller software. We’re kinda sticklers for open source, and this software doesn’t seem to be, so “meh”. But what we do like is the Easter egg that comes included: the paths to mill out the base for a clock, and then the codes to move steel ball-bearings around to display the time.

Of course we’d like to see more info (more, MORE, MOAR!) but it looks easy enough to recreate. We could see redesigning this with marbles and a vacuum system, for instance. The seats for the ball bearings don’t even need to be milled out spheres. You could do this part with a drill press. Who’s going to rebuild this for their 3D printer? You just have to make sure that the machine is fast enough to move the balls around within one minute.

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Hackaday Prize Entry: Industrial Servo Control On The Cheap

[Oscar] wonders why hobby projects ignore all the powerful brushless motors available for far less than the equivalent stepper motors, especially with advanced techniques available to overcome their deficiencies.  He decided it must be because there is simply not a good, cheap, open source motor controller out there to drive them precisely. So, he made one.

Stepper motors are good for what they do, open-loop positioning along a grid, but as far as industrial motors go they’re really not the best technology available. Steppers win on the cost curve for being uncomplicated to manufacture and easy to control, but when it comes to higher-end automation it’s servo control all the way. The motors are more powerful and the closed-loop control can be more precise, but they require more control logic. [Oscar]’s board is designed to fill in this gap and take full advantage of this motor control technology.

The board can do some pretty impressive things for something with a price goal under $50 US dollars. It supports two motors at 24 volts with up to 150 amps peak current. It can take an encoder input for full closed loop control. It supports battery regeneration for braking. You can even augment a more modest power supply to allow for the occasional 1 KW peak movement with  the addition of a lithium battery. You can see the board showing off some of its features in the video after the break.

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Shaper Tools Will Blow Your Mind

Have you ever wanted to own a full-sized ShopBot? What if some geniuses somewhere made a tool the size of a coffee maker that had the same capabilities? Does an augmented reality, real-time feedback, interactive, handheld CNC router that can make objects ranging in size from a pillbox to an entire conference room table sound like a thing that even exists? It didn’t to me at first, but then I visited the Shaper Tools office in San Francisco and they blew my mind with their flagship tool, Shaper Origin.

This table and the spool holder sitting on it was made with a machine the size of a coffee maker.
This table and the spool holder sitting on it was made with a machine the size of a coffee maker.

It’s impossible for me not to sound like a fan boy. Using Shaper Origin was one of those experiences where you just don’t know what to say afterwards. This is what the future looks like.

I’ve used a lot of CNC tools in my life, from my first home-built CNC conversion, to 1980s monstrosities that ran off the floppy kind of floppy disks, and all the way over to brand new state-of-the-art vertical machining centers. I had to shake a lot of that knowledge off when they demoed the device to me.

Origin is a CNC router built into the form factor of a normal wood router. The router knows where it is on the work piece. You tell it where on the piece you would like to cut out a shape, drill a hole, or make a pocket. It tells you where to go, but as you move it keeps the cutting bit precisely on the path with its three axes of control.

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Converting Kids’ Hand-Drawings to G-Code

[Martin Raynsford] wrote a program that converts a black-and-white 2D image to G-code so that his laser printer could then etch the image. Not satisfied with just that, he used his laser printer to make a scanner that consists of a stand for his webcam and a tray below it for positioning the paper just right. The result was something he took to a recent Maker Faire where many kids drew pictures on paper which his system then scanned and laser etched.

Screenshot of Martin's scanning and G-code maker program
Martin’s scanning and G-code maker program

[Martin’s] program, written in C#, does the work of taking the image from the webcam using OpenGL and scanning it line by line looking for pixels that surpass a contrast threshold. For each suitable pixel the program then produces G-code that moves the laser to the corresponding coordinate and burns a hole. Looking at the source code (downloadable from his webpage) it’s clear from commented-out code that he did plenty of experimenting, including varying the laser burn time based on the pixel’s brightness.

While it’s a lot of fun writing this code as [Martin] did, after the break we talk about some off-the-shelf ways of accomplishing the same thing.

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