CNC Drag Knife Upgrade with Off-the-Shelf Blades

Drag Knives seem to be the overshadowed awkward kid on the playground of CNC equipment, but they have a definitive niche making stencils, vinyl stickers, and paper cuts. Unfortunately, the drag knife blades for CNC routers are pricey — over $100 for a single blade. [Brian] at the Grunblau Design Studio took the price point as a challenge to build his own end-effector. A few iterations later, he’s created his very own drag knife blade tool that accepts replaceable steel blades for cutting.

From constraint-driven concept, to a 3D printed proof-of-concept, to a fully machined aluminum prototype, [Brian’s] efforts hit all the highlights of a well-engineered project. At the end of the day, dull blades can be swapped for a few dollars, rather than shelling out another $150 for the off-the-shelf variant. We’ve seen bootstrapped CNC vinyl cutters before, but nothing that takes an original re-envisioning of the tool itself.

CNC Scrapbooking with a Raspberry Pi

It is perhaps a surprise that the widespread adoption of CNC machinery in the home has not come from 3D printing or desktop mills, but as a quiet revolution in the crafting industry. CNC cutters for plastic or card have been around for quite a while now, and while the prospect of cutwork greetings cards might not set all maker pulses racing these cutters do have significant untapped potential in other directions. Perhaps you have to own a carburetor whose gaskets have been unavailable since the 1960s to truly appreciate that.

[James Muraca] has a KNK Force, something of an object of desire in the world of desktop CNC cutters. The computer inside the Force is a Raspberry Pi, so of course [James] set about investigating its potential for running his own software. His progress so far is on GitHub, a web interface through which you can upload and cut an SVG file, but his plans are more ambitious. He hopes to turn his machine into a complete PCB manufacturing station, able to both cut the PCB, and with the addition of a vacuum attachment to pick and place components.

The KNK Force is an interesting machine not just because it is powered by a Raspberry Pi. Its cutter head is a rotary tool with a Z axis, so it can perform more heavy-duty and complex cutting tasks than its competition. In addition it has a camera built-in, and it is this feature that [James] hopes to use in his PCB project.

We’ve covered plenty of cutter projects before, from projects turning CNC machines and pen plotters into vinyl cutters to using a cutter as a laser engraver and even cutting solder paste stencils with one. We look forward to further progress on [James’s] project.

Turning your CNC into a Vinyl Cutter

This may seem like a no-brainer, but it’s actually pretty easy to modify your CNC machine to hold a vinyl cutter blade in order to do stencils or even cut out vinyl logos!

[Jouni] designed a holder for a standard Roland vinyl/sticker cutter blade (replacement with 5 blades is about $10 on eBay). It’s made to fit his specific CNC which uses a 65mm spindle, with a 49mm mounting ring — but the file could be easily modified to suit others.

Simply clamp your plastic or vinyl onto a flat piece of wood, and get stenciling! [Jouni’s] included his .STL file on his site in case anyone wants to try it out. While he’s designed it for 3D printing, you could probably CNC mill it as well — which would kinda make more sense…

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