Teaching A CNC New Tricks

February 16, 2016 by Will Sweatman 16 Comments

Computer Numeric Control technology has been around for a long time. It’s at the heart of our 3D printers, laser cutters / etchers and CNC milling machines. They all work the same way — you begin with a CAD program and make some type of design. Then the computer converts the file into a set of XYZ coordinates and moves a tool head accordingly. Now let us pose to ourselves a most interesting question. What if you reversed the process? What if you could take a CNC’d object and convert it into XYZ coordinates?

This is precisely what [dave] is attempting to do. He’s made a basic CNC outfit and installed encoders on the steppers. He then manually moves the tool head to trace out an object. At the same time, the encoders are feeding the coordinates to a computer for recording. The idea is to replay the coordinates to see if the CNC can replicate the object.

Judging from the video below, the project is a success!

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Brushed DC Servo Drive

February 13, 2016 by Anool Mahidharia 37 Comments

Brushless DC motors, and their associated drive electronics, tend to be expensive and complicated. [Ottoragam] was looking for a cheaper alternative and built this Brushed DC motor servo controller and the results look pretty promising. Check out the video after the break.

He needed a low cost, closed loop drive for his home-brew CNC. The servo drive is able to supply a brushed DC motor with up to 7 A continuous current at up to 36 V which works out to about 250 W or 1/3 HP. It does closed loop control with feedback from a quadrature encoder. The drive accepts simple STEP and DIRECTION signals making it easy to interface with micro controllers and use it as a replacement for stepper motors in positioning applications. All of the control is handled by an ATmega328P. It takes the input signals and encoder data, does PID control, and drives the motor via the DRV8701 full bridge MOSFET driver. There’s also some error detection for motor over-current and driver under-voltage. Four IRFH7545 MOSFETs in H-bridge configuration form the output power stage.

This is still work in progress, and [Ottoragam] has a few features pending in his wish list. The important ones include adding a serial interface to make it easy to adjust the PID parameters and creating a GUI to make the adjustment easier. The project is Open Source and all source files available at his Github repository. The board is mostly surface mount, but the passives are all 0805, so it ought to be easy to assemble. The QFN footprint for the micro controller could be the only tricky one. [Ottoragam] would love to have some beta testers for his boards, and maybe some helpful comments to improve his design.

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A Home CNC Built By Someone Who Knows Their Stuff

February 7, 2016 by Gerrit Coetzee 24 Comments

[thisoldtony] has a nice shop in need of a CNC. We’re not certain what he does exactly, but we think he might be a machinist or an engineer. Regardless, he sure does build a nice CNC. Many home-built CNCs are neat, but lacking. Even popular kits ignore fundamental machine design principles. This is alright for the kind of work they will typically be used for, but it’s nice to see one done right.

Most home-built machines are hard or impossible to square. That is, to make each axis move exactly perpendicular to the others. They also neglect to design for the loads the machine will see, or adjusting for deviation across the whole movement. There’s also bearing pre-loads, backlash, and more to worry about. [thisoldtony] has taken all these into consideration.

The series is a long one, but it is fun to watch and we picked up a few tricks along the way. The resulting CNC is very attractive, and performs well after some tuning. In the final video he builds a stunning rubber band gun for his son. You can also download a STEP file of the machine if you’d like. Videos after the break.

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Tinijet — Affordable Waterjet Cutting At Home

February 4, 2016 by James Hobson 63 Comments

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.

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Fully Printed CNC On An IKEA Table

February 2, 2016 by Gerrit Coetzee 15 Comments

It seems that many 3D printer owners just aren’t getting the same buzz they used to off their 3D printers, and are taking steps to procure heavier machines. And making them in their home laboratories with, you guessed it, their 3D printers.

Following the pattern, [Michael Reitter], designed a 3D printable CNC around a IKEA MALM table. In order to span the length of the table for his X axis, he came up with a very cool looking truss assembly. The linear rails rest on top of the truss, and a carriage with the Z axis rides on the assembly. The truss has enough space in the center of it to neatly house some of the wiring. The Y-xis mounts on the side of the table.

Overall the mechanical design looks pretty solid for what it is, with all the rails taking their moments in the right orientation. We also like the work-piece hold downs that slide along the edge of the table. It even has a vacuum attachment that comes in right at the milling bit.

We’re not certain how much plastic this build takes, but it looks to be a lot. Monetarily, it will probably weigh in at a bit more than some other options. As many in the 3D printing world are discovering, sometimes there’s no reason not to leverage more mature industrial processes for lower cost large gains in accuracy and strength. Though, it’s pretty clear that one of the design goals of this project was to see how much one can get away with just a 3D printer, and we certainly can’t deny the appealing aesthetic of this CNC.

Video of it in action after the break.

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Sub $300 CNC, If You Have A 3d Printer

January 25, 2016 by Gerrit Coetzee 37 Comments

[Allted] has designed a CNC machine that you can print yourself; adding conduit, bearings, and the standard vitamins to bring it to life. The CNC machine uses a mechanical design similar to an etch-a-sketch, though instead of the maze of pulleys and cable it uses four stepper motors to do the X and Y translation. The machine looks to be about as accurate as a Shapeoko, and is able to handle light cutting in aluminum.

The coolest part is the extensibility of the printer. For example, [Allted] needed to print a lot of parts to make orders of the kit. So, he built a 4 headed 3D printer by copying blocks of the design, and tying them all to the same belt. The design also seems to be a little more resistant to dust and debris than some homemade rigs. The CNC won the Boca Bearings design competition. If you’d like to build one yourself, [Allted] has all the instructions with print setting recommendations on his website.

Pack Your Plywood Cuts With Genetic Algortihms

January 22, 2016 by Elliot Williams 42 Comments

Reading (or writing!) Hackaday, we find that people are often solving problems for us that we didn’t even know that we had. Take [Jack Qiao]’s SVGnest for instance. If you’ve ever used a laser cutter, for instance, you’ve probably thought for a second or two about how to best pack the objects into a sheet, given it your best shot, and then moved on. But if you had a lot of parts, and their shapes were irregular, and you wanted to minimize materials cost, you’d think up something better.

SVGnest, which runs in a browser, takes a bunch of SVG shapes and a bounding box as an input, and then tries to pack them all as well as possible. Actually optimizing the placement is a computationally expensive proposition, and that’s considering the placement order to be fixed and allowing only 90 degree rotations of each piece.

Once you consider all the possible orders in which you place the pieces, it becomes ridiculously computationally expensive, so SVGnest cheats and uses a genetic algorithm, which essentially swaps a few pieces and tests for an improvement many, many times over. Doing this randomly would be silly, so the routine packs the biggest pieces first, and then back-fills the small ones wherever they fit, possibly moving the big ones around to accommodate.

That’s a lot of computational work, but the end result is amazing. SVGnest packs shapes better than we could ever hope to, and as well as some commercial nesting software. Kudos. And now that the software is written, as soon as you stumble upon this problem yourself, you have a means to get to the solution. Thanks [Jack]!