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Author Topic: DIY oscillating tangential knife cutter.  (Read 20089 times)

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DIY oscillating tangential knife cutter.
« on: May 06, 2010, 03:27:26 PM »

 I am new to CNC and was hoping to build a Solsylva rack & pinion 36" x 48" machine for cutting museumboard, chipboard and corrugated cardboard for architectural models. As these are all paper products that don't machine well, this calls either for an oscillating knife or an ultrasonic knife. For the oscillating option I was thinking of using a power chisel style handheld wood carver. These have a 3000 - 4000 oscillations / min frequency and a stroke between 0.5 - 1 mm. If this doesn't work my second option was to adapt a handheld ultrasonic cutter if I can find one in the 300 - 400$ range.

 If anyone can bring any experience with this sort of build to the table and give me any pointers I might need, I would be most grateful. Especially concerning actually mounting and controlling whichever knife i wind up choosing. What kind of motor do I need for the c-axis and how do i go about turning the actual knife ?


Re: DIY oscillating tangential knife cutter.
« Reply #1 on: May 06, 2010, 04:08:55 PM »
I have worked on F.L.Smithe paper cutting machines, but these use a stamping blade principle, but they have a C axis that is timing belt geared down off a servo and is programmed in degrees, which I assume you would have to do.
Is it possible to use a stamping blade in your application? It might make it simpler if so.
« Last Edit: May 06, 2010, 04:12:41 PM by NosmoKing »
Re: DIY oscillating tangential knife cutter.
« Reply #2 on: May 06, 2010, 04:45:30 PM »
The best impression I can give of what I'd like is here :  http://www.comagrav.com/oscillating_tangential_knife.html

 This gives a decent overview of the capability I'm looking for. In my previous incarnation as an architecture student at the Swiss Federal Institute of Technology in Lausanne, Switzerland (EPFL) we had a Zund 1200 machine in the shop that still makes my palms itch whenever I think of it : )  Now imagine that my available budget is about 1/10th the cost of a regular machine .... I'm basing this on this model here :  http://solsylva.com/cnc/rack_pinion.shtml    and adapting this    http://www.razertip.com/foredom.htm   to it as a tool tip.

At least that's the theory. If you can tell me what kind of motor size I'm looking at for rotating the knife and what a good approach would be to mount it that would be great. Did I mention I'm an architecture student ? : ) I'm only dabbling in mechanical engineering . As the Comagrav video shows, the tool typically raises out of the stock when rotating acute angles. Obviously curve cuts will require rotating in the material but this still shouldn't require a very big motor to do.

Re: DIY oscillating tangential knife cutter.
« Reply #3 on: May 06, 2010, 05:25:58 PM »
I don't see rotating a tool taking much of an effort, It will depend on the radial force needed if you are actually cutting when rotating the axis, I would look at some kind of high reduction system so a small motor could be spec'd in.
I'm assuming the motor shown in the first link is for rotation?
What I have used in the past is something like a Bayside planetary gearbox with a through hole design drive, this allows the Z axis to move up and down and the rotation controlled by the servo in degrees.
Could be pricey however, unless you are lucky on ebay.
Re: DIY oscillating tangential knife cutter.
« Reply #4 on: April 03, 2011, 02:37:49 AM »
I have cnc 3 axis router milling machine. cna i fix tangentile cutter on it?

Offline Tweakie.CNC

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Re: DIY oscillating tangential knife cutter.
« Reply #5 on: April 03, 2011, 05:19:40 AM »

Welcome to the forum.

Obviously you need to build or buy your hardware, knife etc but Mach supports Tangential Control and it is not too difficult to set it all up. A few have already done this and there is some useful info if you search the forum.
This is one of Robotmar's videos of his setup. http://www.youtube.com/watch?v=anspATAZZQA

I often cut sign vinyl and have found that a drag knife system works just as well, costs less and is simple to use but it is only suitable for very thin materials (like sign vinyl  ;) )