Cutting Solid Wood

[twiles]

I have two potential customers, one very large, that could easily allow me to justify purchasing a shopbot. Both of them want a lot of stuff cut from solid wood from 3/4" to 3" thick. Mostly Oak and Maple...one is items such as clock parts and misc. small parts, the other is for kitchen cabinet parts.
Does anyone have any good or bad experiences with cutting a fair amount of solid wood? Can I cut out parts such as fretwork style panels (above sinks) in a "profitable" amount of time? Say at least 5 minutes each +/-??

Thanks in advance,

TW

[jkforney]

Terry
I often cut hardwood up to 2" thich including the valance type you describe. The time will be less than you indicate (depending on difficulty). The problem I see is a cutter that will cut 3 inch wood. It would require a cutter with a long cutting length or turning the part over.

John Forney

[greg@germanguitars.com]

John,
I'm making arch top guitars that are carved from a 1" thick slab of Maple for the back and Spruce for the front. I don't have a ShopBot yet, so I am hogging out the concave and convex sides of each plate with a forstner bit in the drill press, and by hand with a toothing plane. It takes a while.
My question is this: Do the stepper motors ever accumulate a position error when cutting very hard wood like this? Accuracy is pretty crucial for me...
-gg

[olivier]

Greg,

As many problem with the shobbot, it is all down to the programming. If your a make a proper programm that never plunge your cutter too much in the wood, cut at the right speed with a sharp cutter your will not loose accuracy whatever the job.
I am making bowl out of 2" mapple and oak wich is even worse, milling with a 1/2" bit at 1,8 inch sec, the bit never goes more than 1/2 inch in the wood. No problem.
Hope this help.

[greg@germanguitars.com]

Thanks, Olivier.
Do you decide on your cutting rates by trial and error?
-gg

[ron_cleaver]

Olivier,

Are you making a typical half-sphere bowl? Are you laminating the oak and maple?

How do you cut both the inside and outside? Do you use concentric circles of decreasing radius for the outside and just the opposite for the inside?

What bit(s) do you use for this?

I'm really curious about this (while waiting for my ShopBot to be delivered)

[olivier]

Greg,

Yes , at the end of the day, is it by trial and error, but you get very quickly to some rule of thumbs that help you get the speed and plunge depth right, or at least safe (meaning you try to speed up if you want to optimise your files latter on.
Ron,
My work being about using a CNC machine as a creative tool, I try to make things that would not be possible with a lathe. I would model some funky NURBS shape in a 3D package, then export an STL in Millit to get a roughing path and then contruct a finish pass using ball end bits that follow the shape to make a nice finish with not to much sanding involved. (I do not not if this is clear : the idea is that if you machine shapes with the aim of getting a smooth finish, like most 3D toolpath generation software would do, by making parallel lines, it takes a long time to machine, and even if you are left with tiny ridges or cups, it is time consuming to sand. Therefore, I incorporate the tool marks in the design, thus the neccessity of building the tool path "by hand" following your general shape, to create a good looking texture.
I will try to post some pictures to make things more obvious.
I cut top and bottom by flipping the block of wood around to dowels on the center line : perfect fit.

Good luck with the new tool , it seems that they upgrades the only area I would have criticised on the shopbot, so you should get a perfect tool.

Olivier.

[sheldon@dingwallguitars.com]

Olivier, please expand on how you approach programming your finish path. That sounds brilliant.

[greg@germanguitars.com]

Thanks again.
I have posted some images of my guitar geometry here:
http://www.greggerman.com/temp/wireframe.html
I'm wondering how much trouble the toolpath creation is going to be.
Am I going to need to create a horizontal slice for each depth of cut?
-gg

[sutter@iinet.com]

One method of creating a concave cavity or an external bowl is to use a variable and perform a simple incremental math function. for instance: lets call our variable &dia and our depth variable = &depth

you could

Input "Enter step in diameter" &size
Input "Enter the depth step" &Deep
Input "enter larger diameter" &large
&dia=&large

cut:
CP &dia,x,y,I,1,,,&depth 'x,y is the center
&dia=&dia+&size 'INCREMENT THE SIZE
&depth=&depth+&deep 'INCREMENT THE DEPTH
IF &DIA<%20 THEN END 'TEST FOR CENTER
GOTO CUT 'REPEAT AT NEXT DIAMETER

END

This program should create a concave profile of any diameter or depth if you enter the steps as negative numbers
If you enter posative numbers it will create a convex profile.

The program may take a little tweaking as I have not been able to test it while I am on-line writing this but it should work fine and be simple to operate.