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CnC build help

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NJS Custom

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Spumco,
Sorry I have not responded was gone for a few days.
I figured I would do the tapering on the lathe and then use the offset. That is what I normally do using my indexed Chuck.
I guess I should have made my question a little clearer, I'm having a hard time figuring out how exactly to make the cue in cad(fusion 360), or even just the butt. Because a cylinder only has one face. So if I wanted to do say 4 diamonds equally spaced out around the cylinder how would I go about that in cad? Any ideas? I realize I would have to turn it by hand with my chuck because I don't have a 4th axis. Would I have to just make the one diamond in cad and run it 4 times?
 
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Boswell

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NJS, you did not say what cad program you were using. In Autocad,
1. I would first create model of queue stick using the Cone selection.
2. Next would be a diamond with a height or thickness more than the depth of the relief you want to cut.
3. Then position the Diamond shape above where you want the cut to be on the Cone
4. Sinke (move the diamond) into the Cone by the depth you want to cut
5. Then subtract the Diamond shape from the Cone
You will be left with a diamond shaped relief on the side of the cone.
There are a few problems with this technique though. It is the same problem in the simplified drawing instructions above as it will be when you use the mill without a 4th axis.
If you made the depth of the relief in the center at the desired depth then the Edges will we shallower due to the curvature of the cone
Also because the vertical sides of the Diamond shape are parallel to each other and perpendicular to the point of tangency, this might cause you some problems. However, I have never done any inlay work so these things might not be an issue. Good luck. The good news is for all practical purposes you could just model this as a diamond relief on a flat surface instead of a cone. After all without rotating the 4th axis during milling, that is effectively what you are doing and it would be much simpler to draw.
 

spumco

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NJS,

No worries, I've been busy with a plasma build. As Boswell mentioned, knowing what CAD software you're using would help. In Fusion 360 I would just sketch a circle of the large butt diameter, then extrude the length and set the extrusion taper angle - one shot and done.

Or you could create a sketch circle, then an offset plane the length of the butt with a smaller circle sketched concentric with the first. Select the first circle and 'loft' a body to the second circle. Two steps and done, but you don't need to know the angle - just the length and two diameters.

And the key point is that if you don't have a 4th axis and the capability of continuous cue rotation then the small diameter of the cue will be a problem. If you model the diamond as a flat plane then just extrude down the center of the feature will be deeper than the edges.

What you need to do is project the diamond on to the curved surface and then extrude (or whatever the CAD term is) down from the projected surface so that the depth is the same across the feature. The bottom of the diamond 'pocket' should have a curvature that matches the cue (smaller radius, however).

Then the CAM should be able to do a 3D contour operation that follows the curve and cuts the material.

Your other problem is that the outer edges will not be cut perpendicular to the surface, even with the 3D tool path. The edges will be slightly undercut because the tool stays at 90 to the center, but as it moves away from the center and moves down in Z the angle changes in relation to the outer (uncut) surface. The wider the diamond is in relation to the cue diameter, the more pronounced this will be.

Not a big deal if you're filling with epoxy, but if you are cutting wood veneer to inlay it might need quite a bit of hand-fiddling to get it in with tight edges.

And if you plan to turn it by hand, you might use your lathe to build some sort of indexing fixture. If you get the cutting sorted, look in to getting a cheap 4th axis off e-bay to use as an indexer. I wouldn't trust it for continuous cutting as there's going to be tons of backlash, but as an indexer it should be OK if you only rotate in one direction. That would open the possibility to multiple patterns on the cue as you work your way down the handle (4 big diamonds, then 6 small, etc.). The cheap belt or gear-head ones driven by a stepper should be pretty cheap to integrate. I wouldn't even post the Gcode with 4th axis moves - just run one diamond and then jog the 4th by hand to get to the next point.

Good luck. Keep us updated.
 

NJS Custom

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Hey guys,
The cad program I am using is fusion 360. Funny you should mention the 4th axis. I just ordered stuff to make a 4th axis. I already have a head stock with a pulley and indexing so I am all good there. I think I am just going to have to play with the programs to figure it out and watch a tone more youtube videos. I made my first flat sign and just tried to cut out a pocket. It did not work so well. It was cutting about 3 inches above the piece so something is wrong. Ill figure it out.
Thank you for all the info, I will try some of the above mentioned, and see what I can do.
Nick
 

spumco

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PM me your email and I'll invite you to a F360 practice sketch + CAM. You tell me what you want to make and what tool you have to use for the cue, and I'll cook something up for you.

PS - if you're making a 4th axis, make sure you have some sort of holding brake built-in. Even a manual clamp of some sort. You can live with backlash for indexing by only rotating in the same direction, but any play will cause havoc and possibly broken tools while cutting.

Don't ask me how I know this. :)
 
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