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In a previous life I did a lot of 2D drawing with various CAD packages, but now I'm coming up to speed with 3D using Rhino. I've discovered that for a flat top solid body guitar that doesn't require a neck angle, the process with RhinoCAM is simply a lot of 2-1/2D pocketing and profiling.

Now I'm trying to mill a body that does require a neck angle. I drew the entire body in 3D (look at me go!). With 3D horizontal roughing RhinoCAM wants to mill the entire body including removing all of the waste area of the blank (bad!). I tried extracting the neck pocket and just milling it, but it still created tool paths for the entire body. I can't seem to restrict the MOP in RhinoCAM to just the angled neck pocket.

Can anyone point me in the right direction?

Mike

Copy the 2d contours of the neck pocket to the XY plane. Then, select this closed shape. Then, with the shape selected, setup your toolpath. Selecting that initial shape will limit the cut to fall within that shape.

(I think this is what you were asking...!?)

Trev

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http://www.PeakeGuitars.com

If I select the 2D contours I assume I can only use 2-1/2D pocketing. How do I configure the toolpath to generate a 3 degree angled pocket? Here's a picture that probably explains it better than I can.

You can see the 2D representation of the neck pocket hovering above the body. If I use 2-1/2D pocketing, the bottom of the neck pocket will be flat (parallel to the top of the body). I want it to be angled 3 degrees so I assume I need to use one of the 3D MOPs?

I gotcha...I would use a parrallel finish with an end mill and a small stepover (select that 2d geometry initially as described above to limit the area that you want to carve). Ideally you would fixture the body so that the bottom of the end mill is flat on the bottom of the neck pocket. If you don't, your end mill size and the angle of the neck pocket will determine how scalloped the bottom of the pocket is.

This is basically the same procedure that is used for carving a carved top, a neck, or anything else with a 3d carve (except that those typically use a ball mill).

Trev

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http://www.PeakeGuitars.com

Thanks Trev. I stumbled across the secret of using the 2D geometry to restrict the 3D milling. I think you're right; an angled fixture to hold the body so that I'm effectively milling a flat pocket is the way to go. Now I just need to wrap my brain around aligning the body on that fixture so that the neck pocket will be located correctly

Mike

you can use the location of screw holes, pickup cavity's, tremolo spring cavity etc for making temporary locating pins for mounting the guitar in different jigs.
the jigs themselves can also have locating pins to position them on the same spot on the CNC router surface.

you need to think like someone who is using routing templates with a pin router, they also have to find out clever ways to position the templates

so if it is aligned and you know the depth, why not just add some Code to angle the pocket after roughing it in? I may be new to this but I would think it would be much easier to do some simple surfacing parallel passes from the body to the neck opening?

Something like this would work.

So if B=base, H=hypotenuse
A=angle in degrees of B+H
s2 = the distance change needed in depth of cut

B=4"
A=1.0
H=4.0006
S2= 0.06982

B=4"
A=1.5
H=4.0014
S2=0.10474

B=4"
A=2.0
H=4.0024
S2=0.13968


B=4"
A=2.5
H=4.0038
S2= 0.17464


So
G1 X0 Y0 Z0
G1 X4 Y0 Z-0.6982

should result in a cut that starts at
a depth of zero and and ends at a depth
of -0.6982 which should yield an angle of 1 degree in 4 inches.

So if I was cutting a neck pocket,I would first use a pocket cut to a rough depth Lets say
Z-0.50

then change my code to do slot cutting from the body out of the neck pocket to give me
the resulting neck angle I was trying to achieve in the pocket.Such as something like this (see below)
This also assumes that X0 value is the back edge of the pocket and the Y0 value is the lower edge of the pocket for orientation purposes thus making the lower left corner X0,Y0

(I HAVE LEFT OUT OTHER NEEDED CODE FOR THE MACHINE),

AS THIS IS JUST ONE EXAMPLE OF A WAY TO GET A NECK ANGLE IN THE NECK POCKET
BASED ON A START DEPTH OF 1/2" DEPTH AND A 1/2" CUTTER DIAMETER SINCE THE ROUGHING WOULD GET US TO THIS POINT.

THE FINISH PASSES WOULD YIELD A 2.5" WIDE POCKET WITH A 1 DEGREE BOTTOM FACE

G1 X0 Y0 Z0.50
G1 X4 Y0 Z-0.56982
G0 Z0
G1 X0 Y0.5 Z0.50
G1 X4 Y0.5 Z-0.56982
G0 Z0
G1 X0 Y1 Z0.50
G1 X4 Y1 Z-0.56982
G0 Z0
G1 X0 Y1.5 Z0.50
G1 X4 Y1.5 Z-0.56982
G0 Z0
G1 X0 Y2 Z0.50
G1 X4 Y2 Z-0.56982

I'm new to this as well but this seems to work on my machine.

Mike

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I'm outside looking in, just farther from the window than most.

So here is just one line of that. I know blurry picture. you can see the angle cut. The code I wrote is very raw but you get the idea.

Mike

_________________
I'm outside looking in, just farther from the window than most.

Mike,
Are you talking about milling the angle while the body is laying flat? I was under the impression that the edges of the pocket (the high and low E sides if you will) would be somewhat rounded at the bottom of the pocket because a round cutter simply can't get in there to square them up.

MikeP

Yes they would have scalloped shape unless you make a pass along the Y axis ( rear edge) to true this up at the finish depth before the finish passes. I think that's what you are asking? I'll run a set and try and get better pictures tomorrow to show what I done. Now the corners will have the radius of the bit but getting the bottom flat is not a problem that I have run into so far. Like I said I am still very new at this but I have already done this on another type of project. My Gcode is very raw and I still run test pieces first and tweak it. I'm sure there are faster methods but for my needs I get it done.

Mike

edited to add: here's a better pic of the test piece, It's flat from end to end in the cut. the only radius is the corner from top to bottom from the bit radius, this will happen no matter what size bit diameter you use?

_________________
I'm outside looking in, just farther from the window than most.

Hi Mike,

Cutting like this you will also get a slight scallop across the width of the neck pocket (assuming your toolpath runs along the length) . A one degree angle might not be enough to make it noticeable, but it will be there...! A larger end mill will result in a larger scallop height in this case.

Trev

_________________
http://www.PeakeGuitars.com

Thank you Trev,

I understand what you are saying, I think though that in this case with minor steps in the passes as well as 1 maybe 2 degrees the finish is acceptable for gluing purposes using say a 1/4" or even an 1/8" endmill for the finish passes. The scallops would be maybe a 0.001" or less. Most likely if milled today and then glued tomorrow the same will happen in some manner in ( width or ?) due to moisture and humidity levels. So , if you want dead on then my method is not perfect. I believe that it is well within gluing norms so, I'll continue with it. But thank you for pointing this out as this may be what Mike was referring to and I did not understand his concern and question.

MK

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I'm outside looking in, just farther from the window than most.

I did some tests using RhinoCAM's "3 Axis Pocketing" and the results are promising! Basically I had the body laying flat, used 2-1/2 axis pocketing to rough out the shape, and 3 axis to finish up with the 3 degree angle.

This will work for any neck that ends inside the neck pickup route, but otherwise an angled fixture will be required or else you'll see a gap between the neck and the end of the body (hope that made sense).

Mike