New to CNC. Need help with design.

[jfmonod]

Hi,

I have been looking for solutions for a DIY CNC tangential knife cutter for some time now with very little luck. I would like to build a Solsylva R&P machine with a 36" x 48" base but fitted with a plotter / knife cutter head. (http://www.mucad.com/cmsmultilanguag...tp---pot&hl=en) This head would be interchangeable with the original router mount.
I am going with the knife rather than laser solution both for cost and aesthetic reasons. Sometimes the laser burn on the workpiece is just not acceptable.

I am in architecture and would be using this for architectural model building and design along the lines of what you can see on www.becausewecan.org. I would also be making extensive use of Lamina Design. http://www.laminadesign.com/index.html So I was hoping that someone with more mechanical engineering skills than me could give me some pointers.

I have been looking for commercial of the shelf cutter plotter heads, but most if not all seem to be proprietary and amazingly expensive. What I would need to do is build an assembly which includes a stepper driven knife rotating parallel to the z axis and a pen, both capable of a "pen-up" "pen-down" motion driven by a short stroke solenoid. I don't know if a pneumatic actuator is really necessary here or not.
The thickest cutting stock would be 3 ply (3/16") chipboard. But that would really be the worst case. One ply chipboard is like the crappy cardboard backing on a paper pad. I figure it would take about 10-15 lbs of vertical pressure at the tool tip to drive a sharp knife into this stuff and the same force again horizontally for cutting.
Basically this would see the same sort of use as one of those corrugated cardboard packaging machines.

If anyone has any great ideas about how someone like me (with a total lack of machining experience) could pull this off please speak up : ) I am pretty stoked about getting started with my machine build at this point, but I want to hold off until I have an idea about wether this cutting head is feasible or not.

Many thanks for your help.


JF Monod

[syscnc99]

Hello I would like to know if you achieve your goal ... I'm also very interested in the use of a tangential knife ... you can help me in this project ... thanks

[jfmonod]

Hi,

Sorry but no. I haven't finished building the machine yet. I'm a graduate student in architecture (final year now) and I just didn't have time to finish it before things got crazy at school. I have a lot of aluminum plate cut and drilled and a 6' long piece of acme rod all sitting gathering dust while I get through this school thing. Maybe next year : )

In the end I had decided to try using a power wood chisel with a knife on it. Like this : Foredom flex-shaft tools - Razertip Industries Inc The characteristics are similar to the oscillating knife on a Zund 1200 machine. 5000 - 15000 strokes/min , ~1/8" stroke length. It should work.

The advantage to the Foredom tool is that the motor is way off at the end of a flex shaft so you don't need to account for the weight or much of the vibration. Also the tool head is an easy 6" long and 1" diameter. All you need to do is figure out an offset motor and gear to rotate it on the c-axis... It should be relatively easy to add... once the rest of the machine is built of course. I'll get back to it after graduation.

[syscnc99]

ok thank you very much for answering ... and give me another idea to build the machine ... I will try to build it ... for now I'm looking for more information thank you very much for your support ... regards