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Hello all,

I'm using Mastercam to generate toolpaths/Gcode for fretboards and have made several with flat bottomed slots without a problem (well, none I couldn't solve by using this forum and google.. )

Now I would like to try radiused bottoms. Which mastercam toolpath is the best for slots? I used pocket for the flatbottomed slots but it gives "construction plane" errors when I try with the radiused slots, tried assorted surface toolpaths but ran into problems as well.

I'm assuming there's a simple way to do this but it's eluding me........

thanks

bruce

Bruce I know nothing of MC,well, I do but it is Madcam instead of MasterCam!

Does Mastercam have the ability to use curves projected on surfaces as tool paths? That is how I would do it if it were available.

Mike

To second Bruce's post. You'll want to draw the arc in the xz or yz construction plane (depending on how you have the rest of the neck drawn.
Looking from the top view down onto the neck, it will look like a straight line, but when switching the view to sight down the neck you will see the arc. then I would just program it with the profile or line command (I use part maker more often so the contour name may be slightly different). Mastercam will follow the arc profile in the z axis.
I'm on lunch break so I cannot elaborate further now. If this is too vague let me know, and I'll make a better post after work...

It's the contour toolpath. It's a slotting operation, so it should be programmed with curves.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks Bob, that's exactly what I was looking for. I was certain it had to be some sort of pocket or surface, never even thought of trying contour.

bruce

yep. 2d contour. keep in mind though when you use a flat endmill you're not gonna have an contour that's trully normal to the fretboard surface so expect to go a little deeper to clear the corners of the fret tangs. an 90 deg angled head with a slitting saw would be the best way.

Arie, looks like the concavity of the slot would be miniminal and decreasing, of course, to zero at the center of the fretboard.
I was curious so modeled it based on an .025" diameter endmill and 2.250" maximum fretboard width.
I'm seeing .00108" concavity at the widest point on the fretboard based on a 12" radius.

Nelson

Nelson, you're right. it is very minimal. you'll be more than ok with it.

Hi Guys,

If the model imported into Mastercam already has the frets cut with a radius at the bottom, would a 3D contour not also work just as well?

When I design in solidworks, I usually do an "offset from surface cut" which basically cuts the bottom of the fret slots at precisely the same radius of a given fretboard. Doing a 3D contour then cuts them perfectly in Mastercam....at least this has been my finding.

_________________
-CyborgCNC
http://www.cncguitar.com
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It's the exact same thing, just using a different source for the input curve.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

With Mastercam:

1. Start by creating an offset surface -.07" from the actual fret board surface. This will represent the bottom of the fret slots for later use. You can do this in Mastercam or you can create this surface in in your original model.

2. Next make a contour toolpath and don't worry about any of the heights. This is a reference path to be used by the surface/project module. Set the left/right compensation to "off" so it cuts right on the line that represents the fret slots.

3. Then, using the toolpath/surface/project module....select the toolpath that represents the fret slots and "project" them onto the surface you created in #1 but offset the cut by .065". At this time your set all your tool heights correctly. This will create a contour cut that conforms to the -.07" surface but creates a cut -.005 from the fretboard surface. your first cut.

You then repeat this process using the surface/project module making sucessively smaller offsets until you make your final cut using .000 offset on the -.07 surface.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Thanks Stuart, I had the slot bottoms radiused in the imported cad model so using 3d contour with compensation set to off as you suggested looks perfect. ( Well in mastercam at least.. )

Cyborg - thanks, I did use the offset from surface option to make the radiused slots in solidworks, I'm happy to hear that's the way to do it as my knowledge of solidworks (and mastercam obviously) isn't exactly stellar..


bruce

3d contour will work just as well as 2d contour, surface project, pencil mill etc.... so the following is academic and food for thought and not to be taken as an absolute or the only way to do this task...

But think for a moment about what kind of cutting you are doing. In a typical 3 axis mill like a Haas or Fadal etc.. you fret board is laid out lengthwise along your x axis. All of your cutting motions are in Z/Y plane or G19. Choosing a toolpath like say, surface project or 3d contour forces the post to output splines where hundereds of lines of code are needed to generate a simple arc. Yes you could use an arc filter but even those are limited in effectiveness. If you have a mill that has plenty of ram or you are set up for FNC/DNC and program length is not an issue -cool, then go for it. But if you were to choose a more primitive method of cutting say 2d contour -now your code is vastly shorter with nothing more then an arc/radius move about the Z/Y plane. Furthermore you could program 1 arc (non-compound radius) and subroutine it across the length of your fret board for the entire scale length using a local subroutine (for the arc) and some macro variables (for the fret positions minus the offset).

All of the advice you guys have given is good and solid and will work. I merely submit another way.

BAsically like this except this is for a fretboard sanding block. the only difference would be the arc location in X for a -X if x and y origin is 0.0 vs a +X for the sanding block assuming the X axis is the length using a G19 Z/Y plane. Such as this.

(12"radius fretboard sander )
( 1/4" endmill with 0.125 incremental offset)

G0 G49 G40 G17 G80 G50 G90
G20 (Inch)
G64 F60
G00 Z1
G00 X0 Y0
G00 Z0.1
G01 Y-1.6701(Adjust Y for width 1/2 width of sanding board)
G01 Z0 F60
G19 G3 Y1.6701 K12 J1.6701 F102 ( adjust K for radius ) (Adjust Y and J for width 1/2 width of sanding board, watch +/- here)
G00 Z0.1

M98 P0001 L80(loop subprogram 80 times) ( loop # based on offset and total length needed)
G00 Z0.05
G00 X0Y0
M30 (end program and rewind)

O001 (subprogram)
G17 G91
G01 X0.125 ( adjust incremental offset as needed for bit used)
G90
G00 Z0.1
G01 Y-1.6701 (Adjust Y for width 1/2 width of sanding board)
G01 Z0 F60
G19 G3 Y1.6701 K12 J1.6701 F102 ( adjust K for radius) (Adjust Y and J for width 1/2 width of sanding board, watch +/- here)
G00 Z0.1
M99 (end subprogram)
%
G91 (set incremental)
G01 X0.250
mk

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

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