CNC Hot-Wire Cutter Gives Form To Foam

February 1, 2020 by Dan Maloney 12 Comments

Rapid prototyping tools are sometimes the difference between a project getting off the ground and one that stays strictly on paper. A lightweight, easy-to-form material is often all that’s needed to visualize a design and make a quick judgment on how to proceed. Polymeric foams excel in such applications, and a CNC hot-wire foam cutter is a tool that makes dealing with them quick and easy.

We’re used to seeing CNC machines where a lot of time and expense are put into making the frame as strong and rigid as possible. But [HowToMechatronics] knew that the polystyrene foam blocks he’d be using would easily yield to a hot nichrome wire, minimizing the cutting forces and the need for a stout frame. But the aluminum extrusions, 3D-printed connectors. and linear bearings he used still make for a frame stiff enough to give clean, accurate cuts. The addition of a turntable to the bed is a nice touch, turning the tool into a 2.5D machine. The video below details the construction and goes into depth on the toolchain [HowToMechatronics] used to go from design to G-code, including the tricks he used for making a continuous path, as well as integrating the turntable to make three-dimensional designs.

Plenty of hot-wire foam cutters have graced our pages before, everything from tiny hand-held cutters to a hot-wire “table saw” for foam. We like the effort put into this one, though, and the possibilities it opens up.

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A Ploopy Pick And Place

January 23, 2020 by Dan Maloney 11 Comments

A fair number of hackers reach that awkward age in their careers – too old for manual pick and place, but too young for a full-fledged PnP machine. The obvious solution is to build your own PnP, which can be as simple as putting a suction cup on the Z-axis of an old 3D-printer. Feeding parts into the pick and place, though, can be a thorny problem.

Or not, if you think your way through it like [Phil Lam] did and build these semi-automated SMD tape feeders. Built for 8-mm plastic or paper tapes, the feeders are 3D-printed assemblies that fit into a rack that’s just inside the work envelope of a pick and place machine. Each feeder has a slot in the top for the tape, which is advanced by using the Z-axis of the PnP to depress a lever on the front of the case. A long tongue in the tape slot gradually peels back the tape’s cover to expose a part, which is then picked up by the PnP suction cup. Any machine should work; [Phil] uses his with a LitePlacer. We like the idea that parts stay protected until they’re needed; the satisfyingly clicky lever action is pretty cool too. See it briefly in action in the video below.

It looks like [Phil] built this in support of his popular Ploopy trackball, which is available both as a kit and fully assembled. We think the feeder design is great whether you’re using PnP or not, although here’s a simpler cassette design for purely manual SMD work.

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RasterCarve Converts Images To CNC

January 19, 2020 by Richard Baguley 11 Comments

CNC machines are an essential part of the hacker’s toolset. These computer-controlled cutters of wood, metal and other materials can translate a design into a prototype in short order, making the process of iterating a project much easier. However, the software to create these designs can be expensive, so [Franklin Wei] decided to write his own. In particular, he decided to write his own program to engrave images, converting a photo into a toolpath that can be cut. The result is RasterCarve, a web app that converts an image into a GCode that can be fed into a CNC machine.

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Analyzing CNC Tool Chatter With Audacity

January 16, 2020 by Dan Maloney 32 Comments

When you’re operating a machine that’s powerful enough to tear a solid metal block to shards, it pays to be attentive to details. The angular momentum of the spindle of a modern CNC machine can be trouble if it gets unleashed the wrong way, which is why generations of machinists have developed an ear for the telltale sign of impending doom: chatter.

To help develop that ear, [Zachary Tong] did a spectral analysis of the sounds of his new CNC machine during its “first chip” outing. The benchtop machine is no slouch – an Avid Pro 2436 with a 3 hp S30C tool-changing spindle. But like any benchtop machine, it lacks the sheer mass needed to reduce vibration, and tool chatter can be a problem.

The analysis begins at about the 5:13 mark in the video below, where [Zach] fed the soundtrack of his video into Audacity. Switching from waveform to spectrogram mode, he was able to identify a strong signal at about 5,000 Hz, corresponding to the spindle coming up to speed. The white noise of the mist cooling system was clearly visible too, as were harmonic vibrations up and down the spectrum. Most interesting, though, was the slight dip in frequency during the cut, indicating loading on the spindle. [Zach] then analyzed the data from the cut in the frequency domain and found the expected spindle harmonics, as well the harmonics from the three flutes on the tool. Mixed in among these were spikes indicating chatter – nothing major, but still enough to measure.

Audacity has turned out to be an incredibly useful tool with a broad range of applications. Whether it be finding bats, dumping ROMs, detecting lightning strikes, or cloning remote controls, Audacity is often the hacker’s tool of choice.

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Stacks Of Spring Washers Power The Drawbar On This CNC Mill Conversion

January 11, 2020 by Dan Maloney 25 Comments

With Tormach and Haas capturing a lot of the entry-level professional market for CNC machines, we don’t see too many CNC conversions of manual mills anymore. And so this power drawbar conversion for a Precision Matthews mill really caught our eye.

What’s that, you say? Didn’t [Physics Anonymous] already build a power drawbar for a mill? They did, and it was quite successful. But that was based on a pneumatic impact wrench, and while it worked fine on a manual mill, the same approach would be a bit slow and cumbersome on a CNC mill. For this build, they chose a completely different approach to providing the necessary upward force to draw the collet into the collet holder and clamp down on the tool: springs. Specifically, Belleville spring washers, which are shaped like shallow cups and can exert tremendous axial force over a very short distance.

[PA] calculated that they’d need to exert 2,700 pounds (12,000 Newtons) of force over a length of a couple of inches, which seems outside the Belleville washer’s specs. Luckily, the springs can be stacked, either nested together in “series” to increase the load force, or alternating in “parallel” to apply the rated force over a greater distance. To compress their stack, they used a nifty multi-stage pneumatic cylinder to squash down the springs and release the collet. They also had to come up with a mechanism to engage to machine’s spindle only when a tool change is called for. The video below details the design and shows the build; skip to 11:32 to see the drawbar in action.

We’re looking forward to the rest of [Physics Anonymous]’ conversion. They’re no strangers to modifying off-the-shelf machines to do their bidding, after all – witness their improvements to an SLA printer.

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Universal Interface Board Comes To The Rescue Of Bigger Projects

December 19, 2019 by Donald Papp 31 Comments

As soon as a project involves other assemblies, parts, or modules, things get more complicated. Devices like fans, cooling units, probes, pumps, or lighting might have simple electrical requirements, but they are rarely identical. As a result, one’s tidy project ends up having to deal with, for example, a pump that is controlled with 5 V active high logic, a sensor that outputs 5 V active low, lights that expect to be switched with 24 VDC, and a fan that needs a relay right now. But that might change in the future.

That’s exactly what led [Lukas Fässler] to design and build the Universal Interface, a board intended to be a kind of universal translator and interface for all such devices. The idea is to have one Universal Interface board for every external device. For each board, a wide variety of input combinations controls a single output. The boards are “hardware programmable” in the sense that jumpers (zero-ohm resistors) are used to spell out in black and white exactly what combinations of inputs result in which output state. In this way, some standardization and clarity of control can be enforced while still being flexible enough to accommodate changes.

Jumper-configured logic table defining with utter clarity which combination of inputs results in an OFF or ON.

Each Universal Interface board has three inputs and an enable line, each with their own indicator LED visually confirming its state. The inputs are 24 V tolerant and each can be configured with a pull-up, a pull-down, and as an active high or active low. There is one output, but it takes several forms: a sturdy relay, a powerful open-collector output, a 5 V logic output, and a 24 V logic output. Configuring which output state corresponds to what combination of inputs is set by jumpers, so the board is very much WYSIWYG.

[Lukas] is currently using four of these devices with his CNC mill project, all in different configurations, and they’re working reliably. Interested? The GitHub repository for the project has all the board design files.

Steel Tubes And Ground Plates Form The Skeleton Of This DIY Vertical CNC Mill

November 27, 2019 by Dan Maloney 29 Comments

If you’re going to do it yourself, you might as well outdo yourself. That seems to be the thinking behind this scratch-built CNC mill, and it’s only just getting started.

According to [Kris Temmerman], the build will cost about $10,000 by the time he’s done. So it’s not cheap, and a personal CNC from Tormach can be had for less, but that’s missing the point entirely. [Kris] built most of the structural elements for the vertical mill from cheap, readily available steel tubing, of the kind used for support columns in commercial buildings. Mounted to those are thick, precision-ground steel plates, which eat up a fair fraction of the budget. Those in turn hold 35 mm linear bearings and ball screws for the three axes, each powered by a beefy servo. The spindle is a BT30 with a power drawbar, belt-driven by an external motor that [Kris] doesn’t share the specs on, but judging from the way it flings chips during the test cut in the video below, we’d say it’s pretty powerful.

There’s still plenty to do, not least of which is stiffening the column; perhaps filling it with epoxy granite would do the trick? But it sure looks like [Kris] is building a winner here, and if he keeps the level of craftsmanship up going forward, he’ll have a top-quality machine on his hands.

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