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Fretboard Success
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Author:  Andy Birko [ Sun Nov 13, 2011 10:15 am ]
Post subject:  Fretboard Success
Finally!! After about 8 test runs, a couple broken bits, two vacuum fixtures and many hours at the tube, I made a fretboard yesterday that I'm actually proud of.

Part of the reason it took so long is that I've been working on a model in SolidWorks that takes five main parameters to automatically generate a fretboard model: scale length, width at the nut, width at the 14th fret, radius at the nut, and thickness. Additionally, I have a parameter to shave a little more off the nut end for nut compensation and one to control the faux binding width.

So now basically, I enter the 5 parameters, re-build the model and because I'm using CAM software that's integrated into solidworks - hit re-gen and I've got a custom program to cut a fretboard.

Having done this project, it really makes me appreciate more how much art goes into stuff. e.g. although my machine seems rock solid, you can tell visually that the gantry shakes a bit when changing directions too violently - it was showing up as a visual line perpendicular to the tool path for the fretboard radius. You could only barely feel it with your finger but visually, it was there. By changing the model and toolpaths, I was able to all but eliminate the artifact.

Fun Stuff!
Author:  Mike Kroening [ Sun Nov 13, 2011 11:29 am ]
Post subject:  Re: Fretboard Success
Andy Birko wrote:
>snip<

although my machine seems rock solid, you can tell visually that the gantry shakes a bit when changing directions too violently - it was showing up as a visual line perpendicular to the tool path for the fretboard radius. You could only barely feel it with your finger but visually, it was there. By changing the model and toolpaths, I was able to all but eliminate the artifact.

Fun Stuff!
Andy, the violent direction change may be more due to a high acceleration rate in mach3. You may want to play with those settings to calm that down. :)

Just some food for thought.

Mike
Author:  Andy Birko [ Sun Nov 13, 2011 12:01 pm ]
Post subject:  Re: Fretboard Success
It most definitely is but, I like it that way. :D

I have a need for speed!
Author:  Mike Kroening [ Sun Nov 13, 2011 1:16 pm ]
Post subject:  Re: Fretboard Success
Andy Birko wrote:
It most definitely is but, I like it that way. :D

I have a need for speed!
laughing6-hehe
Author:  Bob Garrish [ Sun Nov 13, 2011 2:56 pm ]
Post subject:  Re: Fretboard Success
A good way to keep the 'shakes' off of your part is to have an overrun in your path or finish a surface that's a bit larger than your 'real' surface to keep the turns off of your main part. The Fadal turns around alright, and no problems with the new control, but with the old control it would definitely leave a little divot turning around at 400 IPM.

I made a parametric fretboard model myself some time ago, though I think I was closer to 10 parameters. I have end treatments, start and finish radii, and two different taper options (constant string to edge or standard). It's really neat how easy it is to set all those things up!
Author:  Andy Birko [ Sun Nov 13, 2011 5:21 pm ]
Post subject:  Re: Fretboard Success
I love the parametric setup - I'm quite happy I picked up SolidWorks to do this stuff. I'm thinking of making either some additional spin off models or refining this one to add the exact features you mentioned. I was at the Michigan Luthiers Gathering this afternoon and everyone was shocked at how flat the radius gets if you keep a constant binding depth. Lots of requests to be able to specify an end radius.

The overrun is exactly how I solved the problem. I have .30 tacked on to the nut end and that pretty much gets rid of it. Would be nice if you could spec an overrun in Visual Mill. Do the more advanced packages have that feature?

What's your spindle speed at 400ipm? I'm running 18000rpm (my max) on a 1/2" round nose at 350ipm for the fretboard surface. I've been thinking of trying 400 but was worried about surface finish.
Author:  cyborgcnc [ Mon Nov 14, 2011 10:58 am ]
Post subject:  Re: Fretboard Success
This is good looking work!

That FretBoard looks really nice!

Love the vacuum fixture!

[clap]

And YES, SOLIDWORKS with Parametric Modelling is awesome isn't it?
Author:  Bob Garrish [ Mon Nov 14, 2011 3:57 pm ]
Post subject:  Re: Fretboard Success
My spindle speed is always 10K, because it's all I've got :)

I was using 1" balls at 400. Not sure how a 1/2" cutter would do, but you've got so much spindle speed that 400 would be about the proper feed rate for a 1/2" ball on aluminum. Never hurts to take a smaller chip if heat isn't an issue, though.

Mastercam has a feature to roll the cutter over edges or to add a tangential arc or line to the ends of finish moves, though it's just as easy to make the surface over size which is what I do most of the time.
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