Anyone successfully model a guitar neck?

[rlrhett]

Although CAD is only a hobby for me, I did study design in school and consider myself pretty good at CAD design. However, I have been completely unable to model the heel and neck of an acoustic guitar. I am using Rhino v.3 and just seem to have too many curves to define all the compound surfaces.

I can easily model all the countours: In x plane you have the two tapered lines that represent the edges of the fingerboard and the arch that is the top of the heel cap; in the y plane you have the mirrored curves of the heel cap to fingerboard (like the cross-section of a ship) and arches that are the cross-section of the neck; and finally in the z plane you have the flat of the fingerboard and the curve that is the taper from the apex of the heel cap to the apex of the neck cross-section.

All these profiles blend smothly and seemlessly into a shape that is reminicent of a baseball bat that has melded into the bow of a ship. How, has proven beyond me.

Is there anyone who has successfully modeled an acoustic guitar neck and heel? Feel like proving to the world you superiority by sharing how you did it?

[PBMW]

Most guitar necks are hand made by old world craftsmen and then scanned by some form of CMM. That information is then taken as a point cloud and converted to surfaces and machined.

[michael_e]

I model jewelry in Rhino and some of the complex surfaces are close to those at the heel of a guitar neck. Since you pretty much know the shape where the neck fits to the body and the neck itself, you can arrive at the transition by creating a number of separate curves which all tie together into what appears to be a single complex surface when you're finished. To get the appropriate lines on the initial curved surfaces I use the " Curve, Freeform, Interpolate on Surface" command string. This allows me to pick the lines that I will use to create new surfaces that blend well with the initial surfaces, (this in conjunction with blening and matching surfaces). You can use this to sort of build or carve your original surfaces in a more complex way that by just using the Blendcrv or Blendsrf commands alone.

For instance, the neck itself can the formed easily by lofting multiple curves along a fairly straight line. The heel can be formed similarly as a separate piece, (since the heel cap is flat and can be formed from multiple sections of varying shape which are close to perpendicular to the direction of the neck sections), and the the two parts can be blended by using the above procedure as many times as needed to get the surfaces the way that you'd like them.

This is probably clear as mud, but if you'd like to send me the neck and heel sections that you've arrived at, I can make a cursory blend for you and send it back with the blend sections in a different color and layer so that this becomes obvious from just looking at it. My address is: michael@gemshoppe.com

I had to laugh at the "superiority" comment. Most of the solutions that most people come up with have nothing to do with superiority, but rather need, luck and a whole lot of hacking away at a problem. Let me know if this helps at all or if you'd like to see an example.

Michael E.

[RandK]

Here's a quick whack that hopefully gives you some ideas on the heel by using some simple geometry and a curve network. There are a lot of different approaches.

[FAJ]

I explained my method here, you might want to take a look:

http://www.cnczone.com/forums/showthread.php?t=25141

The explanations are far from being complete. If you have some questions, ask, and I'll try to answer them.

[rlrhett]

Thanks to all. Looking at what you did FAJ helped me to visualize ti quite easily.

One question on the heel. I see that you did a one rail sweep from the heel cap to a neck contour. That, of course, leaves no surface on the bottom corners. I used patch from the edge of the sweep surface and the two straight edges of the heel and fingerboard surfaces to fill the area in. I think that is what you describe as well without pictures.

The only problem is that it isn't a very smoth transition. Not a manufacturing problem because I can knock down an edge easily enough with sand paper or a rasp (after all I've been shaping these things out of a block of solid wood using a rasp up until now ). Still it seems like there should be a way of automatically smoothing the transition of two surfaces so that there is no crease. How would you do that?

[FAJ]

rlrhett:

Yes, I use a patch for that surface. However, I don't cut it with the CNC, because the edge between it and the sweep1 surface is "in line" with the fingerboard taper. It is almost a plane, and I cut it as such, ignoring the exact shape of that surface. The finished necks are very very good.

I can guess a probable cause for your problems. If you are going to have a straight part for the heel cap, as I do (I use a semiellipse plus to straight lines), you must paste each fingerboard taper to the heel. This is a little more complicated in my design: my heel is for an archtop with an angle between the neck and the soundbox, so that these lines are not parallel to each fingerboard taper line. Instead, each line is contained in the plane that is perpendicular to XZ (see the axes in my construction) and which contains the fingerboard taper line above.

I have machined many necks with this design, and I only have to sand a little to remove the machining marks, because I prefer that instead of having the CNC running half an hour more. They are machined from behind, and only a small part must be carved by hand. It is in the neck to peghead transition, and it is inaccesible to the machine because of the peghead angle. I also carve 17" archtop necks; in this case, I carve them from both sides, because otherwise the heel angle combined with its length makes the inside of the heel inaccesible. This won't be a problem for acoustic guitar necks.

[RandK]

Merge may smooth it out a little but a 1 rail sweep doesn't give you control over the shape of surface at the ends of the cross sections and may overshoot. If you try to build a patch using an overshot edge a merge won't help. A 2 rail sweep won't let you use a middle rail and also won't work well with a 90 degree corner. Turning a 2 rail sideways using the curved cross sections for the rails sometimes works, sometimes garbage. A curve network will let you use 3 rails and multiple cross sections to create a single surface but you will need a decent wireframe.

[FAJ]

My tolerance is usually adjusted to 0.01 mm. With this value, I cannot use a plane instead of a patch. However, if I set my tolerance to 0.03 mm, then I can use a plane, like this:



0.03 mm is a VERY small tolerance for for a wooden guitar part. However, surface analyses for those adjoining surfaces give better results with the patch if the tangency adjustment is set. This means that there is a crease there, the normals to both sides of the edge don't coincide exactly, although the error must be very small. I have learned that these small things are often regarded as defects when you are sitting at the computer, that magnifies them. I perform surface analyses and renderings before cutting a piece, but when I am reasonably satisfied I stop and make a test cut. The step size used for machining will surely be larger than the errors in the design.

[Jens H]

Hello. This is my first post on this forum.
I have today make a model of a Les Paul neck. It is more wide in the nut area, my customer wan't it that way (45mm).

I am using Rhino (evaluation, only 15 saves left )

But soon I will slice it up at mill it in layers of 1 mm.

[Powershaper]

Hellow everybody:

This is my guitar model, and I used a surface modeller.
Iges available .

[seansear]

Powershaper, you have a PM

Bruce