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.
This was created about 3 years ago and made the rounds back then. Neat project though, but I don’t see what’s specifically new about this?
http://www.cnczone.com/forums/general-other-machine-discussion/205452-cnc-software.html
Also, the blades for the Tormach link you provided are cheap, despite your claims to the contrary. You don’t throw away the $149 blade holder, you reuse it by putting in a new $1 plotter blade.
Indeed. The only point I could see to this is to put a carbide (boxcutter) blade in.
C’mon waterjet… we all know the hacks do not have to be new!
I agree with you there. Was more stating that the contractual author for hire of this post did not fully research their post, pretending by omission that this post was about a contemporary item and not understanding the difference between a CNC knife holder and the knife that goes inside it (nor correcting it, eight hours later). The item itself is actually clever and cost effective, though certainly not novel. Additionally, oscillating knives are generally better overall, for finer detail work and cleaner cutting.
http://www.buildlog.net/blog/2010/07/tangential-knife-cutters/
Here’s a similar drag knife project from just about six years ago, for example.
Somewhat saddened by the stealthy edits and lack of editorial notification of said edits as well.
Very cool. And putting a ‘skip to end’ for anyone who doesn’t want to watch the whole milling process is a great idea!
Could you not use the motor shaft instead of external bearings?
Any permanent magnets in a motor will cause “detents” and prevent the shaft from moving freely.
So if you have a spindle motor without permanent magnets like ,say, an asynchronous motor, or a universal motor, then you are good to go. Those two types are used very often on CNC routers. (vfd watercooled or repurposed trim router).
I think you’d still have an issue with all the rotational inertia. Notice how quickly the knife changes direction when going around a corner. I’d worry that trying to spin and stop a spindle rotor would make it too slow.
I’m a bit worried about just the inertia of this, without adding more mass.
The blades are dirty cheap. And so are most simple holders.
Basically this is what you need: http://g02.a.alicdn.com/kf/HTB15IvhIVXXXXakaXXXq6xXFXXXs/1-pc-Gcc-SIGN-PAL-Cutting-font-b-Plotter-b-font-Blade-Holder-and-10-pcs.jpg
The blades can rotate freely and are held inside by a magnet. That’s it.
CB09 is the search term in ebay / aliexpress to find these neat little cutters. They are good for vinyl but these larger drag blades discussed in this article re good for for cutting thicker material like wood veneers
example cheap blade holder: http://www.ebay.com/itm/281696584736?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Wouldn’t one rather use a tangential plotter (a motor turns the knife into the desired direction, rather than _dragging_ it along) for those tasks?
Very cool. And putting a ‘skip to end’ for anyone who doesn’t want to watch the whole milling process is a great idea!
Could anyone suggest me a DIY highspeed-oscillating blade adapter for cnc?
I have not come across one personally but would think it would be a manageable DIY project. If you see one, I would be delighted to hear about it.
Seriously, i have a 300 drag knife cnc by silhouette. The blades cost $10. I have cut 100 feet of copper tape on the thing without changing the blade….
I am interested in the accessories which could be used in my DIY playing with CNC Routers. Any good choice?
http://www.cnc-router-diy.com, cnc router diy
Good news everyone! Latest git version of bCNC has dragknife postprocessor plugin!
https://github.com/vlachoudis/bCNC