Official Luthiers Forum!

Hello fellow forum members,


I am currently trying to design an aluminum guitarneck and I stumbled across a
small problem I don' t seem to get past. I try to hollow out my neck using a cut
extrude and the preview shows the nice cut. But when I press ok, the cut is not
there. Anyone with an idea how to resolve this?
below is the file i am referring too,

thanks,

best regards, graan

No file attached. Do you get an error message?

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Yeah your link isn't working

Everything worked as it should but you get fined 27 microsteps for overcomplicating your drawing.

What was happening is that your surface was a closed shape. Extrude cuts don't go through surfaces so even though the extrude cut was there, you couldn't see it because the surface was blocking your view. Hiding the surface showed the cut (see the screenshot). You could also do a body delete on the surface as well.

All that said,

First, if you wouldn't have had the line segment at the top (fretboard plane) you would have gotten the result you were expecting.

Edit to clarify: for your loft sketches, if you would have made them "C" shaped instead of "D" shaped you wouldn't have had a surface at the fretboard plane and you would have seen the extrude cuts.

Second, no need to do the first boss extrude at all. You'd be better off skipping it and just crating two planes at the end points of your neck and simply doing an extrude-loft to make your neck. Then you skip the cut with surface as well.

Better yet, you should have only done half of it and mirrored it when you're done with all of the symmetrical features of the neck.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

waw, what a great reply, I applaud your kindness for helping me!

I am just learning solidworks from cyborgs videos and I only have been using the software
for about 2 weeks so I still have a lot to learn. I will review your answers and try to create
the neck with the extrude loft.

If I only draw half the neck, I am worried that i don´ t get a nice shape at the bottom of the neck.

Does the mirroring have more advantages than only making shure everything is symmetrical?

Thanks again!

best regards

I'd say that no, the mirroring doesn't have any advantages other than automatic symmetry...unless you choose to make the neck with surfaces rather than solids. Doing so has some advantages as there are some very flexible tools for surfacing.

There's a few different ways to make a neck. In your case, probably a extrude-loft would be the best but you could also do it with pure surfacing. In this case probably a boundary surface would be a good choice but to make that work right, you would indeed have to make only half and mirror.

To make the neck profile, what I would do is to make 4 sketches - a line at the back of the neck, a line at the edge of the neck and two profile sketches at the nut and bridge end of the neck.

For those profile sketches, I'd use splines with the control handles locked to vertical and horizontal at the top and bottom respectively to ensure continuous curvature at the mirror point. If that wasn't enough, you can add curvature control points to the spline and set the end curvature to zero to ensure that you'll get a smooth boundary condition. If you use arcs instead, you can obviously just set tangency at the back of the neck to ensure a smooth transition at the back of the neck but, you lose some other abilities. i.e. if you select tangency at the start and end of an arc, SW get's to decide the radius.

After doing that, use the boundary surface feature and select normal to profile as the start/end conditions. This will ensure that there is curvature continuity at the mirror plane.

The other cool thing about using splines is that even with the start and end points locked to zero curvature, you can still adjust the shape of the neck by pulling the handles to get your desired shape.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

You might want to add cross braces every 4" or so. I'd go so far as to add x-bracing. This will dramatically increase the torsional stiffness of the neck...allowing for dramatically thinner walls. It'll give you a little more stable support under the fretboard too. I drew this with .125" radii so you can see how it looks cutting with a 1/4" ball.

_________________
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

Little better visual.

_________________
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

I like Stuart's idea. I think if I were to draw it, I'd do the following:

Boundry surface (half)
thicken
extrude to surface
mirror.
Possibly do the fillet's in the X - intersection afterward because it's harder to draw them when only doing half. Probably I'd do it without fillets and just have them come out in the CAM step (although that adds some problems when machining).


How'd you do it Stuart?

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Lessee now...

1. Drew the lattice sketch on the top plane.
2. Lofted a surface for the outer neck surface.
3. Created an offset surface for the inside neck surface.
4. Trimmed the offset surface flush to the top plane.
5. Extruded the lattice sketch down through the outer surfaces.
6. Used the inside neck surface as a cutting tool in a surface trim.

If I was to actually make this though...I'd draw it as depicted and then use the flat geometry above the model to use as boundries for all the surfacing operations that carve out the inside of the neck. These would all be projected operations.

I used to get a little obsessive about drawing things perfectly but with enough experience I knew how it would look when finished and then only drew what I HAD to draw.

_________________
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

So, you'd use the lattice work above as regions. The CAM would "see" the halfpipe and cut to those Z's, but use the lattice as borders for the X,Y?

Yes, Saul. Doing it this way has a lot of benefits. One being that choosing boundary chains is simple when they are separated from the rest of the model. Another benefit would be when choosing the bottom surfaces...well there's only one surface to pick. Another thing is that one can usually use the full pallet of surfacing operations when projecting toolpaths onto a surface. Projecting toolpaths usually provides a much larger range of options and control over using any one type of module. Maybe the best benefit is that it's simpler to draw things when you think this way.

In the case of these pockets, I'd create a 2D pocket cut using the floating geometry. Then I'd project that cut onto the inside surface only I'd offset the cut on the z-axis by 1". Then again at .9" and again at .8" and so on until all the depths were cut. Establishing the proper minimum cut would make sure one didn't cut air on the upper level cuts.

If I wanted a smoother finish than the pocket provided, I'd either use a simple surfacing operation or make a surface operation from the floating geometry and project it down.

Nice to see you here, Saul. In case you hadn't noticed I'm Stuart Keith Guitars from Facebook.

_________________
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

Wow.
All of this talk about splines, boundary surfaces and trimming is getting me WAY EXCITED!
Glad to see I'm not the only 3D guitar geek on the planet.

Interesting concept on the "chambered neck". It should make any guitar less "neck heavy".
Just wondering... Are you going to add a slot for the truss rod?

Speaking of surfacing, here's a look at the inside of the front-half of my next acoustic project:



The thinner pockets are down to about .095" thick. (Some of the fillets for the rib-to-surface intersections aren't shown, becuz the CAM program does that automatically)

Comments, critiques and questions always welcome!

Cheers,

Jeff
http://www.kozmguitars.com

hello everyone,

So I drew the neck again using an extrude loft and then the extrude cut to get my 2 chambers. I do it like this because I want to attach my fretboard
on the middle "rib". Don' t know if this makes sence. I will try to draw my neck according to zlurgh idea next, although it looks a little complicated. I can
see his idea improves the strength of the neck, but since I will be making this out of aluminum I am a little bit worried it will add too much weight.

I am also a bit concerned about my transition on the sides of this neck and my fretboard. Is there a good way of dealing with this?

Andy: What do you mean by locking the control handles of the splines?

below is the improved version

http://www.megafileupload.com/en/file/3 ... LDPRT.html

In the spline control handle, there is a diamond shaped thingy. You can add relationships to that control point just like anything else. In the attached pic, you can see that I assigned the relationship of "horizontal" to the diamond control point at the bottom of the spline.

I also added a curvature control point as well to set the curvature to zero at that point as well. That's not totally necessary but I thought I'd throw it in there just for reference. That's a tool to be used if you're having issues getting mirrors to have smooth transitions.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

If his mechanics are better, then the weight should be lower no matter what. You can always thin the walls of a better design to get the weight down.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

if i may ask, why did you choose to use surfaces?

try this:

-use your neck profile to sweep or revolve an extrusion to form your neck.
-use extrude, cut, to part your your neck in half at the fretboard
-draw your ribbing structure
-choose extrude, cut,-shell to create your hollowed out areas.

i was only able to import your first attempt. the link for your second version is bad.

Surfacing gives you much more control over the final shape of the neck. Using a revolve really limits the shapes you can choose for your neck section.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

how so?. setting aside revolve, loft and sweep provide for control via your drive curves and the number thereof. where surfacing often fails is in the exportation to cam systems in terms of tesselation and the amount of time needed to heal the surfaces. solids provide for near seamless translation via .sldprt, .step, or .iges format

Well - as you get into more complex control of surfacing, you'll find that surfacing indeed provides a lot more control than the respective lofts and sweeps using solids. Additionally, there are more techniques such as the boundary surface etc. There's just things you can't do with the solid versions of the surface methods.

What I usually do is create complex surfaces using surfacing techniques then either replace face of a solid or extrude up to surface then do a body delete on the surface to create a fully healed solid. My cam software BTW has never had trouble following a surface.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I should add that I use solids whenever possible but when I'm looking for smooth, organic or complex shapes, I usually turn to surfaces because it's much easier. I can do with 4 sketches and a single feature (boundary surface) things that would be really difficult or possibly impossible with solids Once you're used to mixing surfaces and solids, it becomes second nature..

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

sounds good -clearly a different approach. having moved mostly away from surface modeling in the early 90's i find little use for them at this point other then for quick and dirty repairs, toolpath boundries, coons patches, filling holes, etc.... most of the kids coming out of engineering schools these days have never had to deal with surfs btw. i remember driving surfacing toolpaths with just an along and an across coutour -no surfaces required!