Official Luthiers Forum!

Hey guys, here is a quick tutorial on how I surface an acoustic neck. There are certainly other ways to do it, but this is the basic process that I use.

In order to do this, you need to understand some of the basic drawing functions in Rhino such as how to create and edit lines and splines. You should also have a working understanding of how to construct geometry by using commands such as offset and mirror, as well as have a good understanding of the object snaps.

The basic procedure is to create a wireframe using splines and lines. Then this wireframe is used as a guide for the actual surfacing commands. You need to set your wireframe up correctly such that everything is tangent and coincident where appropriate. If you don't the surfacing commands won't work!

A good tip is to always keep the splines as simple as possible; don't go overboard and put more nodes on the spline than you need!

Without further ado..

1) this first step consists of laying out the fingerboard in 2D. I also drew a line from the center of the 14th fret, parallel to the Z-axis 3.5" to set the depth of the heel.


2) Next, I begin drawing the center guidlines. I drew lines along Z at the first fret and a bit in front of where the heel transition would be. These lines indicate the thickness of the carve at these positions. Next, I draw a line from the endpoint of this first line to the endpoint of the one closer to the heel.

Next I draw a spline from the end of the heel as shown, and connect it to the end of the center line drawn previously. At this point the heel center line is not tangent to the neck center line. This is OK, we will fix it later.


To make those lines tangent, I turn on heel spline's edit points by clicking the button below and selecting the spline.


Next, I move the highlighted nodes around so that it looks about like I want it to. Note that it is still not tangent, but it is closer.


Now I use the match curve command to force that heel spline to be tangent to the neck center line.


The first step in doing the headstock is to create a spline like the one shown with the edit points on (yep, that's a straight spline..but still a spline!).

In the next couple of steps, I move the edit points for this spline along the Z and X axes in order to make it round as shown.




Next, I draw the neck profiles at that first fret position, and at the beginning of the heel transition. These are probably the most important curves on this model!


Next, I sketch in a profile for the end of the heel using splines and playing around with the edit points as before.



These next two screenshots show the heel profile and some of the refined neck carve profiles.




We are now ready to surface the neck. I like the Network Surface command..it gives very consistent results. You basically click the Network Surface command and then pick the two edges of the fretboard, the center line for that section, and then the two profiles for that surface.

I surfaced this neck in 3 parts; the heel transition surface, the neck shank, and the headstock fade-out surface.

Please note that some editing was done (using split, and match curve) in order to partition the wireframe in the 3 sections that I want.




Carve surface is now finished..


And just because it is easy to do (took less than 2 minutes to do this CAM portion)...here's a screenshot showing a toolpath that I could use to cut this. Using a .050" stepover between toolpaths and running at 40 inches (this is slow in the world of CNC), we can carve this neck in about 27 minutes. It would be prudent to do a perimeter cut as well..but that would not be time consuming.


I hope you enjoyed checking this out, let me know if you have any questions. Rhino is good stuff!

_________________
http://www.PeakeGuitars.com

Just as an aside...a production machine like a Fadal can run stuff like this at about 240 ipm or greater. That's 6 times faster than my little K2...so it would take about 5 minutes to carve this surface on a more production oriented machine.

_________________
http://www.PeakeGuitars.com

Parser (if that's your real name):

Thanks a ton for doing the neck tutorial. Both the Shopbot and the K2 suggest Rhino and I have read on this forum that most luthiers use it as well. I look forward to studying your work this evening. I am tire kicking CNC's at or under $10K, but not confident enough to pull the trigger. I'll get on the Rhino website, too.



Thanks again

Danny R. Little

Cool, let us know if it works out for you.

I got the K2 machine and all software for under 9k...just wasn't a big fan of the shopbot stuff.

_________________
http://www.PeakeGuitars.com

Just to show a completed model...here's a Martin-style neck that I modeled up for another board member:

_________________
http://www.PeakeGuitars.com

I don't know much about it, but it is a very cool tutorial. Great job.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Thanks for sharing!

I have been working on up-sizing my CNC router table to accomodate necks. I just got everything working this afternoon and will see how this does on a neck tomorrow.

PS: I'm the one he drew the neck for. I'll be having necks for sale shortly after I get all of the bugs worked out. I ahve also upgraded from a dremel router to a laminate trimmer, so the extra horsepower needed for heavier shaping like necks should be no problem for me. My new table is 24"x48" so I should be able to whip out some electric bodies as well soon. I have my eye on doing a Les Paul

_________________
Reguards,

Ken H

I've done carved tops before as well...let me know if you'd like some help with that one as well.

_________________
http://www.PeakeGuitars.com

I found the dxf file for a les paul Jr and also a double cutaway les paul today on a internet site. Some time int he near future I'll take a look at trying my luck on one or both of them.

I have a pretty nice piece of maple that I have been saving for a LP body.

_________________
Reguards,

Ken H

Hi Parser,

I just wanted to thank you for that tutorial. I've been
slaving at my computer for hours trying to figure it out.
You really saved me a bunch of time. Ill post some pictures
of my necks when they're done (Although they will be necks
for ukulele's).

Thanks Again,
Nalu

Cool, I'm glad it has helped you out!

I'm actually thinking of building some ukes in the near future...maybe I can bounce a couple ideas off of you? I'm going to start with some sitka topped curly maple tenor ukes...

_________________
http://www.PeakeGuitars.com

Parser is the large radius at the head to create the radii for both the little volute thing and the junction of the head stock and neck?

Mike

Hey Mike, I honestly don't recall. I think I had actually made a different surface for that one, there is no real reason that it needs to be the same.

The tutorial shows how to generate a simple surface that can be used to make a neck carve, not how to model an actual neck. Most of the steps are the same though..

_________________
http://www.PeakeGuitars.com

Fascinating toot Parser!

_________________
Ann Arbor Guitars

Hi Parser,

While going through the screen shots I could not figure out why you had the "odd" shaped bell shaped curves at the head, but I came to the conclusion that it formed the blend of the head to the neck as well as the radius on the surface of the volute.

I just didn't have the time to model the neck to verify!

Mike

Dear Parser,

It appears that your "Martin" model is done differently than your tutorial. I notice that in your tutorial the surface carve of the heel would leave small corners on the body/fretboard side of the heel un-carved. The transition between these vertical surfaces and the carved surface would be a slight ridge. However, your "Martin" model has no ridge or seam between the surface carve and the vertical edges.

How did you model the Martin neck without having a transition or ridge?

Also, do you use your CNC to carve a V-neck join? Can you profile/carve your headstock and neck shaft separately on your CNC and then glue them together using the "V" join? I'd love to see how you did that!

Thanks,

The original tutorial shows a quick and easy way to generate a neck carve surface.....the Martin neck was done a little differently as the goal with that was to actually draw the whole neck.

I believe the actual neck was constructed using a network surface from the tip of the heel down to those iso-lines you can see on the heel that line up at about 45 degrees (about halfway around that heel transition). The shank of the neck is just a straight loft. Then I believe I did another network surface to connect the two. I made sure to select the edges of the two surfaces i wanted the new surface to go between (not the curves they were actually made from); this allows me to constrain the new surface to be tangent or curvature continuous to the existing surfaces.

The difference between tangency and curvature continous is like the difference between a circle and a french curve. A circle is curvature continous (by definition, a circle has constant curvature) while a french curve is made of a curve in which the curvature continually changes. If you play with the match curve tool in Rhino a bit, you'll see what I mean.

I actually don't carve the volute on my necks. I'd like to in the future....I'm still thinking about what type of volute I would like, etc..

I actually use a scarf joint on my necks. It's been the best way for me to make necks so far. I'm not a big fan of the v-joint, though I'm sure it works fine for some folks.

_________________
http://www.PeakeGuitars.com

Parser,
Thanks a million for posting this tutorial. I look forward to studying it. I'm working up the nerve to enter into 3D land on my CNC, and this may help get me there.

_________________
www.davidbeede.com

Cool, I'm glad you found it useful!

Feel free to drop me a line if I can answer any questions for you.

Thanks,
Trev

_________________
http://www.PeakeGuitars.com

Does anyone have a copy of this post when it had images still attached? I have been battling with getting my ukulele necks machined on my shopbot, but have been unsuccessful so far. I have everything modeled but I feel that I could do a better job. If anyone has the images from this post saved or has another resource for modeling a neck in rhino I would love to see it. Thanks. -shawn

Hey guys, here is a quick tutorial on how I surface an acoustic neck. There are certainly other ways to do it, but this is the basic process that I use.

In order to do this, you need to understand some of the basic drawing functions in Rhino such as how to create and edit lines and splines. You should also have a working understanding of how to construct geometry by using commands such as offset and mirror, as well as have a good understanding of the object snaps.

The basic procedure is to create a wireframe using splines and lines. Then this wireframe is used as a guide for the actual surfacing commands. You need to set your wireframe up correctly such that everything is tangent and coincident where appropriate. If you don't the surfacing commands won't work!

A good tip is to always keep the splines as simple as possible; don't go overboard and put more nodes on the spline than you need!

Without further ado..

1) this first step consists of laying out the fingerboard in 2D. I also drew a line from the center of the 14th fret, parallel to the Z-axis 3.5" to set the depth of the heel.


2) Next, I begin drawing the center guidlines. I drew lines along Z at the first fret and a bit in front of where the heel transition would be. These lines indicate the thickness of the carve at these positions. Next, I draw a line from the endpoint of this first line to the endpoint of the one closer to the heel.

Next I draw a spline from the end of the heel as shown, and connect it to the end of the center line drawn previously. At this point the heel center line is not tangent to the neck center line. This is OK, we will fix it later.


To make those lines tangent, I turn on heel spline's edit points by clicking the button below and selecting the spline.

Next, I move the highlighted nodes around so that it looks about like I want it to. Note that it is still not tangent, but it is closer.


Now I use the match curve command to force that heel spline to be tangent to the neck center line.


The first step in doing the headstock is to create a spline like the one shown with the edit points on (yep, that's a straight spline..but still a spline!).


In the next couple of steps, I move the edit points for this spline along the Z and X axes in order to make it round as shown.




Next, I draw the neck profiles at that first fret position, and at the beginning of the heel transition. These are probably the most important curves on this model!


Next, I sketch in a profile for the end of the heel using splines and playing around with the edit points as before.



These next two screenshots show the heel profile and some of the refined neck carve profiles.





We are now ready to surface the neck. I like the Network Surface command..it gives very consistent results. You basically click the Network Surface command and then pick the two edges of the fretboard, the center line for that section, and then the two profiles for that surface.

I surfaced this neck in 3 parts; the heel transition surface, the neck shank, and the headstock fade-out surface.

Please note that some editing was done (using split, and match curve) in order to partition the wireframe in the 3 sections that I want.









Carve surface is now finished..


And just because it is easy to do (took less than 2 minutes to do this CAM portion)...here's a screenshot showing a toolpath that I could use to cut this. Using a .050" stepover between toolpaths and running at 40 inches (this is slow in the world of CNC), we can carve this neck in about 27 minutes. It would be prudent to do a perimeter cut as well..but that would not be time consuming.




I hope you enjoyed checking this out, let me know if you have any questions. Rhino is good stuff!

_________________
http://www.PeakeGuitars.com

Man, I've been banging my head trying to blend the shaft into the ends for so long, doing extreme workarounds etc. Ryan, I owe you big! This is brilliant!

I have one VisualMill question. How do you set the boundries/regions (you can tell I'm new to VisualMill) so that the cut doesn't overshoot the ends of the surface but cuts deep enough on the edges where the tip of the ball needs to be below the edge by the radius of the ball?

Who's Ryan and why aren't you thanking Trevor?

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

dang brain farts! Sorry Trevor.

Thanks Sheldon, this shows the minimum amount of surfacing that you need to do in order to carve a neck. Drop me a line if you ever need help with anything, I love checking out your work!

The contour that you use to limit the toolpath should be offset from the actual geometry by the radius of the ball mill (make sure you use the radius...not the diameter!).

This contour controls where the center of the ball mill may go. This is why you offset that contour by the radius of the ball mill.

This way, if the slope of the surface at the edge is perpendicular to the table, the tool will be able to cut this via the tip extending to a maximum depth of the cutter radius below the surface, at which point only the cylindrical portion of the tool would be contacting the part (as opposed to the way most ball mill cuts are made using the spherical tip).

I hope this helps...!

Trev

_________________
http://www.PeakeGuitars.com