Mill Warped PCB Blanks On An Uneven Bed

Milling a PCB at home is a great way to save some time and money if you are making one-off circuit boards. There is a downside though, it’s a little tough. Sure, just export your Eagle design to CNC-Machine-understandable g-code and fire up your mill…. well, it’s not that easy.

The copper on a PCB blank can be anywhere from about 0.001 to 0.006 inches thick. When milling a board the ideal situation is to mill just deep enough to get through the copper but not cut too deep into the fiberglass backer board. Cutting too deep can weaken the board, break a bit, or in an extreme case, cut through the entire board.

Shallow cuts can result in another problem, inconsistent cut depth over the surface of the board. Check out the left photo above. The traces on the left side of the board appears to have just faded away. This happened because the circuit board was not flat. The side where the traces are missing from is lower than the other so the tool bit is not able to reach that part of the board. Since an ideal depth of cut is about 0.010 inches, even a very small amount of waviness or out of flatness can cause a serious problem in the milling process. If you have a hard time picturing what 0.010 inches is, think the thickness of two pieces of paper, it’s not a lot. There are two main contributors to the flatness problem; the PCB board and/or the machine’s bed. If the bed is not flat, the PCB won’t be. Even if the bed is flat, the PCB may be warped or bent.

PCB fabrication enthusiast [daedelus] had this exact problem, and in true hacker fashion, decided to do something about it. He created a software program called AutoLeveller that takes a g-code file and adds a probing section to the beginning before the milling operation. When the modified g-code file is run on the CNC Machine, it first probes the surface of the PCB in a grid pattern and maps the flatness variation of the PCB’s surface. Then, when running the program, it adjusts the height of the tool bit on the fly so that the actual depth of cut is consistent over the entire board, regardless of how flat or not it is. The result is a clean and usable PCB on the first try.

There is one catch: the Machine Control Software has to be set up to accept a probe. This is easy to do if communicating to the CNC Machine via a computers parallel port. An input pin on the parallel port is pulled high with a resistor and connected electrically to the PCB board. The tool spindle is grounded with a clip lead. When the tool touches the board, the input pin is pulled low and the Machine Control Software records the tool height for that specific XY position.

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The Tumblemill: Homemade CNC Milling

[Jens] aka [Tumblebeer] has compiled an impressive overview of the Tumblemill, his homemade CNC mill. It warms our hearts to learn that [Tumblebeer] was inspired to pursue electronics by projects featured here on Hackaday, even if it means he dropped out of med school to pursue electrical engineering. We’re glad he’s following his passion, though, and reading through his blog reveals just how far he’s come: from fiery disaster in his first projects to a gradual obsession with making a CNC device, [Tumblebeer] has made plenty of mistakes along the way, but that’s how it should be.

His first iteration was a CNC router that used rubber wheels as linear bearings. It worked…barely. His latest build grew out of meticulous Solidworks modelling, with a moving gantry design constructed largely from aluminum, and upgraded linear motion: this time a bit overkill, using HIWIN HGH20CA blocks. Rather than sourcing a traditional spindle mount, [Tumblebeer] opted for the housing from a LM50UU bearing, which provided both the perfect fit and a sturdier housing for his 2.2kw spindle.

Visit his project blog for the details behind the mill’s construction, including a lengthy installment of upgrades, and hang around for a demo video below, along with the obligatory (and always appreciated) inclusion of the Jolly Wrencher via defacing an Arduino.

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DIY Plotter Strives For Cheapest CNC Machine Title

Arguably, taking the plunge into the CNC hobby does indeed have potential to end up costing more than expected. But that should be no reason to deter anyone from doing it! [msassa11] shows us how to do it in full effect with his definitely unique and extremely inexpensive homemade plotter.

The design goal was to keep this machine as low-cost as possible while at the same time using materials that can be found around any tinkerer’s shop or at least purchased locally. First of all, you’ll notice that there is only one linear rail, yes, one rail for two axes of movement. The single rail was removed from an inkjet printer along with the mating bushing that originally allowed the print head to move freely back and forth. A threaded rod lead screw does double duty here, keeping the X axis carriage from rotating around the linear rail and also transmitting the force to move the carriage back and forth. Both the lead nut and bushings are held in place with cast-epoxy mounts.

uniquecnc-closeupAs unique as the X axis is, the Y sure gives it a run for its money. No linear rails are used, two lead screws are the only things that maintain the gantry’s position. To prevent gravity from pulling the gantry down and bending the Y axis lead screws, there are a couple of bearings on either side that ride along the bed of the machine. The frame material also hits the cheap target, it’s made from blank PCB board. A PIC16F877 microcontroller and a handful of mosfets control the motors. [msassa11] built this control circuit but admits it’s performance is not that great, it’s noisy and loses torque at high speed.

[msassa11] certainly proves that he is extremely resourceful with the outcome of this project. He met his goal of building an extremely inexpensive CNC machine. Check out his project page to see a ton of photos and find out what other unconventional ideas he used to build his machine.

Turning the Raspberry into a CAD Workstation

Inventables has been working hard on a successor to the extremely popular Shapeoko CNC milling machine, and to bring digital fabrication to the masses, they’ve created Easel, possibly the easiest 3D design software you’ll ever use. [Sacha] was trying out the beta version of Easel and mentioned to the dev mailing list he was running his installation on a Raspberry Pi. One of the developers chimed in, and after a bit of back and forth we now have a workflow to use Easel with the Raspberry Pi.

Easel is a web app, but since the graphics, design, and g-code generation are handled locally, even the most rudimentary CAD suite would choke the decidedly low power Raspi. Instead, [Sacha] is using the Raspberry to grab 2D and 3D files, turn that into g-code for a machine, and send it off to a Shapeoko router.

Easel doesn’t yet have local sender support that works on Linux, so a separate piece of software is used to shoot the g-code over a serial port to the machine. That’s something that will probably be added in a later version of Easel, making a Raspberry Pi a great way to control router or milling machine.

Carvey, the CNC Machine for Everyone

Over the past few years, [Bart Dring] has contributed immensely to the homebrew CNC machine scene, with the creation of MakerSlide linear rail, the buildlog.net open source laser cutters and CNC machines, and a host of other builds that have brought the power of digital fabrication to garages and workshops the world over. After a year of work, he, along with Inventables, is releasing Carvey, the CNC machine for everyone else.

Carvey is heavily inspired by Inventables other CNC machine, the Shapeoko, but built to be the Makerbot to the Shapeoko’s RepRap, without all the baggage that goes along with that analogy, of course. The machine has a 300W spindle capable of cutting wood, plastic, foam, carbon fiber, and linoleum, as well as aluminum and brass. There are a few interesting features like a color-coded bit system, and this time the machine has an enclosure for containing MDF dust.

CiebwEA13yxYp576g_7HRNUx06KmzO3QEqGCLfs4kRoCAD programs might be a little too foreboding for someone just getting into the world of CNC, so Inventables has created their own design program called Easel. It’s a web app that allows you to design all your parts for the Carvey and send them all to the machine without worrying about speeds, feeds and all the other intimidating machinist terminology. You can, of course, output GCode from Easel, so those of us with slightly more complex toolchains can still use the Carvey.

Inventables is Kickstarting their production, with the non-early bird Carveys going for $2400. That’s a bit cheaper than some extremely similar machines we’ve seen on Kickstarter before.

4 Axis CNC Foam Cutter Sports A Unistrut Frame

CNC Foam Cutters are capable of cutting out some pretty cool shapes that would otherwise be extremely difficult to do. They do this by pulling a heated metal wire though a block of foam. Electrical current passing through the wire heats it up causing the foam to melt away, there is no dust and no mess to clean up. [batchelc] decided to make his own large-scale CNC Foam Cutter and took a lot of photos along the way.

Since machine is 4 axis, meaning both sides can move forward/back and up/down independently of each other, tapered shapes are possible. One example where this would be helpful is cutting wings that are swept or have different profiles at each end.

DIY foam cutter made from Uni-Strut.

The main frame of the machine is made from Unistrut and measures a whopping 60 by 60 inches. Subtract the size of the mechanical components and the cutting area ends up being 48 by 42 and 22 inches high. The foam sits on an MDF bed, gravity is the only method of holding the foam down during cutting. The wire doesn’t actually touch the foam so there is no force applied to cause it to move. The hot wire moves slowly and melts the foam just a few thousands of an inch in front of the wire resulting in no contact between the two.

Both axes on each side are driven by 1/2-10″ lead screws supported by bearing blocks on both sides. The longitudinal axes smoothly traverse the length of the machine by means of skate bearings that ride on the Unistrut channel itself. The vertical axes have a plastic bushing that slides along a round shaft.

The control portion of the machine is a HobbyCC FoamPro kit that came with the 4 axis stepper motor control board and 4 NEMA 23 stepper motors. GMFC software is used to both generate the g-code and send the commands to the stepper motor control board.

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Add CNC to your…Propane Tank??!?

It’s starting to be that time of year again; the Halloween-themed hacks are rolling in.

[John Lauer] needed a propane-powered flame effect for his backyard ICBM “crash site”. Rather than pony up for an expensive, electronically-controlled propane
valve, he made a custom bracket to connect a stepper motor to the propane burner’s existing valve.

With the stepper motor connected up, a TinyG stepper motor controller and [John’s] own graphical interface, ChiliPeppr, take care of the rest.

The hack is almost certainly a case of “everything looks like a nail when you have a hammer” but you have to admit that it works well and probably didn’t take [John] all that much time to whip up. Maybe everyone should have a couple spare stepper motors with driver circuitry just lying around ready to go? You know, just in case.

All the details of the build are in the video. If you’re done watching the flames, skip to around 2:50 where we see the adapter in action and then [John] steps us through its construction.

You may have seen coverage of the TinyG motor controller here before.

Additional thanks to [Alden Hart] for the tip.