Noob Here with question about cutting circles.

[eegor]

Hello all. I'm new to the CNC thing but am about to start my journey. What led me here is the fact that I cut out A LOT of circle disks in all different sizes from 6" to 18" diameter. I ussually work on 4 x 4 panels that are 3\16" inch thick . Currenlty I just use a jasper circle jig and my trusty Makita plunge router. Finally I said to myself "there's gotta be a way to automate this" and low behold here we are.

My only question before I start is this:
Will I get a good cut with a CNC being that there is nothing to hold the circle down once it is cut out from the panel? I would think that because the wood I work with is so thin, that once the circle is cut and is separated from the panel, the disk itself might fly out, or the friction of the bit will cause it to move around and ruin the edges of my perfect circle.

I made this observation because when I am cutting with the Jasper jig and my router, once it gets to the final cut of the circle, the circle will start moving and spin but because
a. I have the router and jig on top and
b. there is a center pin in the middle of the circle, the circle does not go anywhere and will most of the time just spin in place. (At this point I can use my finger to stop the spinning and clean up any rough edges.)

Sorry for the long explanation but while I would want to do a CNC build anyway because it's just so cool, my main reason is to help me with my circles and I just don't want to be disappointed that it couldn't do what I originally had in mind. Thanks for reading.

[Zygoat]

if it is ok to have a hole in the middle of the circle ( it sounds like that is what you do now.) then you can screw the circle down to another piece of wood under it. this second piece of wood is called a spoil board. with it screwed down to the spoil board it should not go anywhere, and you can end up with nice cuts.

[CarveOne]

You can set up your cut file to drill all of the small center holes first, pause for a tool change while you pin, screw, or use whatever hold down method you want, then resume to cut all of the circles.

CarveOne

[TommieK]

There is also double stick tape or even better, in programming, tabs.
Tom

[kling8]

I would agree with goat, for how your making them, a better machine to make them I think would be a laser or water jet. Time save in using a laser, by far..

[jsheerin]

Another way would be a vacuum fixture. There are several ways to do this, but if you are always cutting the same size and number of circles, you could lay out a 4x4 sheet that you would always cut and make up a custom vacuum platen (I think that's the right term) that would seal under each of the circles you'd cut. If you search here, there are lots of posts about vacuum hold down. You could use a low flow pump with this method which would be cheaper. The more expensive way is with a high flow pump that pulls through a spoilboard over the entire board. There you need a much larger pump which can maintain vacuum even in the presence of leaks (which would occur as you cut).

[eegor]

Thanks for the responses all. Yeah I never knew the thing was called a spoil board. I've been using one all along and just called it my scrap board. Now I can talk shop with other people. lol

Anyway my thing is I need to be able to work as quick and as efficient as possible.Plus the size of the circles are always different. So for me, the quickest way is actually CarveOne's suggestion. I could plan out what circles I need, have the cnc drill out the center holes first all the way into the spoilboard, and then stick pins in before the circles are cut.

I'm going to also check out all the other stuff with the vaccuum and the tape because maybe I might need to use a combination of thing since the pins will not necesarily stop the "spinning disk syndrome" which sometimes will cause that last final cut to not be smooth. (So my circle would ussually have a little bump where the final cut is made) But thanks everyone for giving me some direction!