[Bucka]

Hello, I could really do with some advice on my idea.

I do some woodworking and like the idea of having a CNC like system to speed up my production work. However I don't feel I need it to be computer controlled at this stage, so I would make a system that relied on templates with guided bearings bits / template bushings to control my cuts.

My current idea is to make a system for cutting area of 100cm x 40cm. This would be made using 2 x (25/30mm) supported ground rails for the Y axis, then 2 x 30mm ground rails mounted on bearing blocks to make the X axis. I would mount a router in the center, i'm thinking i'd use a router i've found which weighs 3.5kg and is 1100w power, my other is 2400w weighs 6kg so seems on the heavy side. Depth of cuts would be controlled by manually adjusting router depth.

What I don't really know about is whether the shafts are sufficient for this routers weight and what kind of accuracy I could expect with cutting depths and if this project is even a viable idea.


If anyone could help at all i'd be very grateful.

[awerby]

Sorry, but I don't see what the point of all this would be. To mount a router overhead on slides and move it by hand seems like almost all the work of building a CNC machine but none of the fun part (where you get to watch it work). Why would it be any better than simply using the router and templates in the normal manner? If you're suspending your router over the template, how would the bearing manage to ride along the edge? Your depths would be inconsistent compared to simply running on the template, since your rails would sag at least a little. And it would still have a tendency to run away with you if you tried to cut in climb mode. So what did you think you'd gain by building this thing?

Andrew Werby
www.computersculpture.com

[louieatienza]

Hello, I could really do with some advice on my idea.

I do some woodworking and like the idea of having a CNC like system to speed up my production work. However I don't feel I need it to be computer controlled at this stage, so I would make a system that relied on templates with guided bearings bits / template bushings to control my cuts.

My current idea is to make a system for cutting area of 100cm x 40cm. This would be made using 2 x (25/30mm) supported ground rails for the Y axis, then 2 x 30mm ground rails mounted on bearing blocks to make the X axis. I would mount a router in the center, i'm thinking i'd use a router i've found which weighs 3.5kg and is 1100w power, my other is 2400w weighs 6kg so seems on the heavy side. Depth of cuts would be controlled by manually adjusting router depth.

What I don't really know about is whether the shafts are sufficient for this routers weight and what kind of accuracy I could expect with cutting depths and if this project is even a viable idea.


If anyone could help at all i'd be very grateful.

They have something like this already, it's called the overhead pin router developed by CR Onsrud early last century and still in use today. You can find them used pretty cheaply. Basically your workpiece is held by a vacuum fixture which is also the template, and has a guide groove, and you manually maneuver the template along the pin. No need for linear rails! The other mechanism is the Duplicarver, mainly for 3D work but youu can theoretically use it for 2D work as well.

[Bucka]

Sorry, but I don't see what the point of all this would be. To mount a router overhead on slides and move it by hand seems like almost all the work of building a CNC machine but none of the fun part (where you get to watch it work). Why would it be any better than simply using the router and templates in the normal manner? If you're suspending your router over the template, how would the bearing manage to ride along the edge? Your depths would be inconsistent compared to simply running on the template, since your rails would sag at least a little. And it would still have a tendency to run away with you if you tried to cut in climb mode. So what did you think you'd gain by building this thing?

Andrew Werby
ComputerSculpture.com ? Home Page for Discount Hardware & Software

I felt I would have extra security by being able to have the router supported on all sides. With templates you often have half the router hanging over the edge.

My plan as far as the bearing running along the template is just to use a template that fairly thick so the distance between the tip of the router bit and the bearing could be easily covered.

I was wondering when you say it could sag, I can understand that but why isn't that also the case with a CNC machine? Or isn't it? Does the programming maybe factor it in? I'd love to go the full way and get a real CNC someday but at the moment don't feel I have the money or the time to learn how to make one.

[Bucka]

They have something like this already, it's called the overhead pin router developed by CR Onsrud early last century and still in use today. You can find them used pretty cheaply. Basically your workpiece is held by a vacuum fixture which is also the template, and has a guide groove, and you manually maneuver the template along the pin. No need for linear rails! The other mechanism is the Duplicarver, mainly for 3D work but youu can theoretically use it for 2D work as well.

Interesting i haven't come across these. It seems quite like a upside down router table.

I previously tried duplicating parts with flush trim bits on the router table but ended up getting kickback on the concave faces which put me off. Maybe I was taking too big passes but I think my stock piece also didn't stay exactly 90% to the table, so it got fed in.

I'd like to try and smaller diameter spiral bits as I believe its less likely to give kickback.

[ger21]

I previously tried duplicating parts with flush trim bits on the router table but ended up getting kickback on the concave faces which put me off.

Kickback while flush trimming on a router table is almost 100% due to poor technique. As long as the cut is started carefully, preferably with a pin of fence to brace the part, if you cut in the proper direction, moving the workpiece clockwise around the bit, you shouldn't get any kickback.

I was wondering when you say it could sag, I can understand that but why isn't that also the case with a CNC machine?

It is also the case. Any CNC using round unsupported rails will get some degree of sagging and/or flexing of the rails.

[Bucka]

You could be right. The piece I was trying to make (and I did have some success on the router table) was quite narrow, and higher than it was wide which made it unstable.

Maybe I will do some more reading up and experiment again with the router table. My new projects are not now narrow like the last. The kickback completed ruined my work piece and was a bit scary so i've been wanting to avoid it since then.