CNC Feeds And Speeds, Explained As A First-Timer

May 5, 2023 by Donald Papp 35 Comments

If you’ve ever looked into CNC cutting tools, you’ve probably heard the term “feeds and speeds”. It refers to choosing the speed at which to spin the cutting tool, and how fast to plow it into the material being cut. They’re important to get right, and some of the reasons aren’t obvious. This led [Callan Bryant] to share his learned insights as a first-timer. It turns out there are excellent (and somewhat non-intuitive) reasons not to simply guess at the correct values!

A table of variables and how they relate to one another (click to enlarge).

The image above shows a tool damaged by overheating. [Callan] points out that as a novice, one might be inclined to approach a first cutting jobs conservatively, with a low feed rate. But doing this can have an unexpected consequence: a tool that overheats due to spinning too quickly while removing too little material.

CNC cutting creates a lot of heat from friction, and one way to remove that heat is by having the tool produce shavings, which help carry heat away. If a tool is making dust instead of shavings — for example if the feed rate is too conservative — the removed pieces will be too small to carry significant energy, and the tool can overheat.

[Callan] makes a table of variables at work in a CNC system in order to better understand their relationship before getting into making a formula for calculating reasonable feed and speed rates. Of course, such calculations are a reasonable starting point only, and it’s up to the operator to ensure things are happening as they should for any given situation. As our own Elliot Williams observed, CNC milling is a much more manual process than one might think.

The $50 Pen Plotter

March 19, 2023 by Chris Lott 23 Comments

[Arca] sets out to build himself a low-cost pen plotter that doesn’t require access to a 3D printer. The plotter uses a coreXY arrangement, powered by 28BYJ-48 stepper motors, which he overdrives with +12 VDC to increase the torque. Pen up and down control is done using a stepper motor salvaged from a DVD reader. The frame is constructed using PVC electrical conduit and associated fittings, and [Arca] uses the hot glue gun quite liberally. Steppers were driven by A4988 modules with heatsinks, and motion control is provided by GRBL running on an Arduino UNO.

He has a few issues with glitches on the limit switches, and is continuing to tweak the design. There is no documentation yet, but you can discern the construction easily from the video if you want to try your hand at making one of these. This is a really cool DIY plotter, and many parts you probably have laying around your parts boxes. As [Arca] says, it’s not an AxiDraw, but the results are respectable. Keep a lookout for part 2 of this project on his YouTube channel.

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Powercore Aims To Bring The Power Of EDM To Any 3D Printer

March 7, 2023 by Dan Maloney 39 Comments

The desktop manufacturing revolution has been incredible, unleashing powerful technologies that once were strictly confined to industrial and institutional users. If you doubt that, just look at 3D printing; with a sub-$200 investment, you can start making parts that have never existed before.

Sadly, though, most of this revolution has been geared toward making stuff from one or another type of plastic. Wouldn’t it be great if you could quickly whip up an aluminum part as easily and as cheaply as you can print something in PLA? That day might be at hand thanks to Powercore, a Kickstarter project that aims to bring the power of electric discharge machining (EDM) to the home gamer. The principle of EDM is simple — electric arcs can easily erode metal from a workpiece. EDM machines put that fact to work by putting a tool under CNC control and moving a precisely controlled electric arc around a workpiece to machine complex shapes quickly and cleanly.

Compared to traditional subtractive manufacturing, EDM is a very gentle affair. That’s what makes EDM attractive to the home lab; where the typical metal-capable CNC mill requires huge castings to provide the stiffness needed to contain cutting forces, EDM can use light-duty structures and still turn out precision parts. In fact, Powercore is designed to replace the extruder of a bog-standard 3D printer, and consists almost entirely of parts printed on the very same machine. The video below shows a lot of detail on Powercore, including the very interesting approach to keeping costs down by creating power resistors from PCBs.

While we tend to shy away from flogging crowdfunded projects, this one really seems like it might make a difference to desktop manufacturing and be a real boon to the home lab. It’s also worth noting that this project has roots in the Hackaday community, being based as it is on [Dominik Meffert]’s sinker EDM machine.

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Will Carmakers Switch Clay For Computers?

March 3, 2023 by Al Williams 47 Comments

The 3D printing revolution has transformed a lot of industries, but according to [Insider Business] the car industry still uses clay modeling to make life-sized replicas of new cars. The video below shows a fascinating glimpse of the process of taking foam and clay and making it look like a real car. Unlike the old days, they do use a milling machine to do some rough work on the model, but there’s still a surprising amount of manual work involved. Some of the older film clips in the video show how hard it was to do before the CNC machines.

The cost of these models isn’t cheap. They claim that some of the models have cost $650,000 to create. We assume most of that is in salaries. Some models take four years to complete and a ton of clay.

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3 Ways To DIY Custom CNC Dust Covers

February 4, 2023 by Donald Papp 6 Comments

Home shop machinists know dust shields are important for keeping swarf out of expensive linear rails and ball screws. [Petteri Aimonen] demonstrates three inexpensive ways to DIY some bellows-style dust covers. Such things can of course be purchased, but they’re priced at a premium and not always available in the size one needs.

A bellows-style dust cover ideally maximizes extension length while minimizing side wall distortion. It should hold its shape without external support.

The first method is to fold a suitable flat plastic or paper sheet into a bellows pattern. This method is all about the fold pattern, and thankfully, there’s no need to reinvent the wheel. [Petteri] used a fellow enthusiast’s bellows folding pattern generator which is, believe it or not, itself inspired by a remarkably comprehensive US Patent Number 6,054,194.

The downside to this method is the thickness of the bellows when it is fully collapsed. The corners always contain the most material, because it is there that the material is folded upon itself, and this limits how close to the end of travel the CNC carriage can move with the bellows attached.

The second method is to cut a large number of C-shaped sections from fabric and sew them together to make bellows. This method collapses down well and holds its shape well, but the cutting and sewing it requires can be a barrier.

The final method — and the one [Petteri] found most useful — was to hack some IKEA window blinds. IKEA Schottis pleated blinds are inexpensive, with a slick finish on one side and polyester fabric. The polyester is perfect for gluing. By cutting the material at a 45-degree angle into three sections and gluing them into a U-shape, one can create a serviceable bellows-style cover for a minimum of work.

Any of the explored methods can do the job, but [Petteri] has formulas to determine the maximum extensions and folded thicknesses of each method just in case one would like to see for themselves before choosing. And if a bellows-style cover isn’t your cup of tea, check out this method for turning a plastic strip into a spring-like tube that does the same job.

DIY Fiber Laser Adds Metal Cutting To The Mix

January 13, 2023 by Dan Maloney 23 Comments

Sadly, the usual CO₂-powered suspects in the DIY laser cutter market are woefully incapable of cutting metal. Sure, they’ll cut the heck out of plywood and acrylic, and most will do a decent job at engraving metal. But cutting through a sheet of steel or aluminum requires a step up to much more powerful fiber laser cutters. True, the costs of such machines can be daunting, but not daunting enough for [Travis Mitchell], who has undertaken a DIY fiber laser cutter build that really caught our eye.

Right off the bat, a couple of things are worth noting here. First — and this should be obvious from the fountains of white-hot sparks in the video below — laser cutters are dangerous, and you should really know what you’re doing before tackling such a build. Second, just because [Travis] was able to cut costs considerably compared to a commercial fiber laser cutter doesn’t mean this build was cheap in absolute terms — he reports dropping about $15,000 so far, with considerable ongoing costs to operate the thing.

That said, there doesn’t appear to be anything about this build that anyone with some experience building CNC machines wouldn’t be able to tackle. The CNC side of this is pretty straightforward, although we note that the gantry, servos, and controller seem especially robust.

The laser itself is an off-the-shelf machine, a Raycus RFL-C1000 fiber laser and head that packs a 1,000-Watt punch. There’s also the required cooling system for the laser, and of course there’s an exhaust system to get rid of the nasty fumes.

All that stuff requires a considerable investment, but we were surprised to learn how much the consumables cost. [Travis] opted for bottled gas for the cutter’s gas assist system — low-pressure oxygen for carbon steel and high-pressure nitrogen for everything else. Refills are really pricey, in part because of the purity required, but since the proper compressor for the job is out of the budget for now, the tanks will have to do. And really, the thing cuts like a dream. Check out the cutting speed and precision in the video below.

This is but the first in a series of videos that will detail the build, and if [Travis] thought this would whet our appetites for more, he was right. We really haven’t seen many DIY fiber laser builds, but we have seen a teardown of a 200-kW fiber laser that might tickle your fancy.

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