Author Topic: Super simple CNC Drag knife (vinyl/gasket cutter)  (Read 2733 times)

Offline pat_pending

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Super simple CNC Drag knife (vinyl/gasket cutter)
« on: January 01, 2018, 09:21:51 AM »
Hi, made this super-simple mod for my cheapo eBay CNC3040T CNC router. Works like a charm so I thought I'd share it with you.

Backstory: I was thinking how I could make tiny little gaskets for my model engines and solder masks for PCB manufacture when I came across the world of the ubiquitous Roland vinyl cutters. I was sure there was a way you could use the little cutting bits somehow to achieve what I wanted to get done. Since the vinyl cutters are so popular and the blades a standard size, you can get em on eBay for cheap as chips. This had to be the starting point.

Trouble was, the blade always needs to be facing in the direction of cut so you cant just mount a blade in the chuck and cut away. I started looking at mounting some sort of 5th axis to the machine and think how I could post-process the GCode somehow to turn the blade before taking a cut... needless to say... I reached the limit of my engineering and programming skills pretty quickly!

I then came across this excellent post which was almost exactly what I was looking for:

In true Open Source tradition, I thought I would 'fork' this idea and enhance it for my needs. Primarily I wanted something i could just slot in the 3mm collet chuck on the CNC router spindle and just cut away. the original design seemed to need quite a bulky setup.

Anyway. here is a vid of the finished product. and some plans below. It works really, really well. I have cut some tiny gaskets as per the video with 3mm circle holes for my Webster engine no probs. I cut out some vinyl stickers for my kids bedroom wall and that worked well too. You need a few passes so go make a cup of tea and leave it but apart from that fine!.

The cutter bits are readily available on eBay. Example here:

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This is what it looks like inside:

So the top is the tube it all fits in which is threaded M8x1.25 at the top for the tensioner bolt. Let to right: vinyl cutter carbide attachment, sealed 1.5x6x3mm 'deep v' ball race, 5x3mm rare earth magnet, 5mm Ball bearing, spring, another ball bearing and then the tensioner bolt. Above is a collar to lock the tensioner bolt into place when the desired pressure is reached.

There is another ball race (2x6x3mm) that i have lactated into the end of the tube.

some rough measurements:

« Last Edit: January 01, 2018, 12:04:27 PM by pat_pending »

Offline PK

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Re: Super simple CNC Drag knife (vinyl/gasket cutter)
« Reply #1 on: January 01, 2018, 04:08:31 PM »
Nice job. Vinyl cutting is one of those capabilities that adds value to a lot of projects, so its well worth the (small) effort to make a knife...