Spindle Upgrade Makes PocketNC Faster And Smoother

June 27, 2023 by Dan Maloney 21 Comments

Conventional wisdom says that rigidity is the name of the game when it comes to machine tool performance. After all, there’s got to be a reason for CNC machines that need specialized rigging companies just to deliver them. But is there perhaps a way for the hobby machinist to cheat a little on that?

From the look of [Ryan]’s PocketNC spindle upgrade, it seems like the answer just might be yes. The PocketNC, a much-coveted five-axis CNC mill sized for the home shop, has a lot going for it, but as with most things, there are trade-offs. Chief among these is a lack of the usual huge, heavy castings used for CNC machines, which results in the tendency for the cutting tool to chatter or even stall out if you push the speeds and feeds too far. After a good intro to some of the important metrics of machining, such as “material removal rate,” the video below delves into how MRR affects chip load which in turn results in chatter.

The easy fix for chatter, of course, is to take smaller cuts. But [Ryan] decided to increase the spindle speed to take lighter cuts, but to do it really fast. The hardware for this includes a 3,500 KV high-torque brushless DC motor and a custom spindle attachment. The motor is connected to the spindle shaft using pulleys and a drive belt, and the shaft is supported with stout bearings that can be pre-loaded to fight backlash. The end result is three times the stock 10,000 RPM spindle speed, which lets [Ryan] see a 300% increase in cycle time on his PocketNC. And as a bonus, the whole thing requires no permanent modification to the machine and can be easily removed.

We think [Ryan] did a great job breaking this problem down to the essentials and hacking up a low-cost solution to the problem. Continue reading “Spindle Upgrade Makes PocketNC Faster And Smoother” →

Automate Away The Drudgery Of CNC Manufacturing

June 25, 2023 by Dan Maloney 39 Comments

One of the keys to making money with manufacturing is to find something that you can make a lot of. Most small manufacturers have one or two “bread and butter” items that can be cranked out in quantity, which of course has a quality all its own. The problem with that approach, though, is that it runs the risk of being boring. And what better way to avoid that than by automating your high-volume job, with something like this automated CNC work cell?

[Maher Lagha] doesn’t offer too much in the way of build details, but the video below pretty much tells the tale. The high-volume items in this case are customized wooden coasters, the kind a restaurant would buy for their bar or a business would give away as swag. The small 3-axis CNC router at the center of the work cell is the perfect choice for making these — one at a time. With no desire to be tied to the machine all day to load raw stock and unload completed coasters, [Maher] came up with automated towers that hold stacks of pallets. Each pallet, which acts as a fixture for the workpiece through multiple operations, moves from the input stack into the router’s work envelope and to the output stack using a combination of servos and pneumatics. The entire work cell is about a meter on a side and contains everything needed for all the operations, including air for the pneumatics and dust extraction.

Each coaster requires two tools to complete — one for surfacing and one for lettering — and [Maher] has two ways to tackle that. The first is to allow a stack of coasters to go through the first operation, change tools, and switch the roughed-in stock back to the input stack for the second round of machining. The other is just to build another work cell dedicated to lettering, which seems to be in progress. In fact, it looks as if there’s a third work cell in the works in [Maher]’s shop. The coaster business must be pretty good.

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Mat Boards Are Spendy, So DIY CNC Tool To The Rescue

May 29, 2023 by Donald Papp 22 Comments

Mats are flat pieces of paper-based material that fill the space between a frame and the art within. They perform a number of aesthetic and practical functions, and they can also be expensive to purchase. Making them by hand is an option, but it’s an exacting process. [wooddragon48] felt that a CNC solution would serve this need nicely, and began designing a DIY CNC tool to do exactly that.

One of the tricky parts about cutting mat boards is that cuts are at an angle, and there is really no tolerance for overcuts or any kind of visual blemish. CNC control would seem to offer a great solution to both the need for precisely straight cuts, as well as fine control over where cuts begin and end in a way that opens the door to complex designs that would be impractical to do by hand.

[wooddragon48]’s design has an angled cutter designed to plunge perfectly on demand, surrounded by a ring — similar to that on a router — which ensures the cutting tool is always consistently positioned with the material. It’s still in the design phase, but this is a type of tool that doesn’t yet exist so far as we can tell. The ability to CNC cut mat board, especially in complex designs, would be a huge timesaver.

Art and DIY CNC have a long history of happy intersection, as we have seen with a CNC router repurposed for string art, a CNC painting robot, and even an interactive abstract sculpture generator.

Learn How Impossibly Close-fitting Parts Are Actually Made

May 17, 2023 by Donald Papp 15 Comments

Most of us have seen those demonstrations of metal parts that mate together so finely that, once together, they have no visible seam at all. But how, exactly, is this done? [Steve Mould] has a video that shows and explains all, and we’ve never seen the process explained quite like he does.

The secret ingredient is wire EDM, or Electrical Discharge Machining, but that’s only one part of the whole. Wire EDM works a bit like a hot-wire cutter slicing through foam, but all by itself that’s not enough to produce those impossibly close-fitting parts we love to see.

EDM is capable of astounding precision in part because — unlike a cutting tool — nothing physically contacts the material. Also, there isn’t a lot of friction and heat causing small distortions of the material during the machining process. EDM is as a result capable of fantastically-precise cuts, but not invisible ones.

It’s pretty neat to see a water jet used to thread the fine wire through the workpiece.

In all good manufacturing, the capabilities (and limitations) of the tool are taken into account, and this is also true for making those close-fitting pieces. The hole and plug are actually made in two separate stages.

The hole is cut separately from the plug, and because EDM is capable of such finesse, the cuts can be made in such a way that they complement one another with near-perfection. After that, grinding and polishing takes care of the surface finish. The result is the fantastically-smooth and apparently seamless fitment we like so much.

The video is embedded below, and there are some great details about EDM and how it actually works in there. For example, we see how a wire EDM machine can use a jet of water to help thread the wire through a hole in the part to start a job, and we learn that the wire is constantly moving during the process.

As cool as wire EDM is, it is not magic and we’ve seen some pretty remarkable efforts at bringing the technology into the home workshop.
Continue reading “Learn How Impossibly Close-fitting Parts Are Actually Made” →

Wood game piece being carved by a CNC mill with a hacked rotary axis

This $12 CNC Rotary Axis Will Make Your Head Spin

May 15, 2023 by Michael Shaub 19 Comments

[legolor] brings us a great, cheap rotary axis to add to your small 3 axis CNC mills. How are you going to generate G-Code for this 4th axis? That’s the great part, and the hack, that [legolor] really just swapped the Y axis for the rotation. To finish the workflow and keep things ~~cheap~~ accessible to all there’s a great trick to “unwrap” your 3D model so your CAM software of choice thinks it’s still using a linear Y axis and keeps your existing workflow largely intact. While this requires an extra step in Blender to do the unwrapping, we love the way this hack changes as little of the rest of your process as possible. The Blender script might be useful for many other purposes too.

The results speak for themselves too! We thought the 3D printed parts were suspect in a CNC setup, but for the small scale of game pieces and milling wood, the setup is stable enough to produce a surprisingly accurate and detailed finish. If you want to try the same approach with something larger or a tougher material, [legolor] has a suggestion of a tailstock setup that’s still under $100 USD. Continue reading “This $12 CNC Rotary Axis Will Make Your Head Spin” →

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.

Continue reading “The $50 Pen Plotter” →