Official Luthiers Forum!

Hey all you SW folks out there. I am looking for an approach as to how to model an archtop "carved" top in SW 2009. I have tried sweeping profiles along the body curve - but it can only do a single profile and not merge multiple profiles. I then tried using boundary boss, but it only allows 2 profiles.

Basically, I have the guitar outline, then I have 4 profiles (based on Benedetto's book) - the hips, waist, to the upper left, to the upper right.

Any suggestions?

Hi,

Most "carved" shapes for guitars in solidworks, will require you to work with surfaces. you need to master surface modeling in order to do what you are after. In many cases, you can combine surface modeling with solid modeling, which is where greater flexibility comes in. However, any type of archtop, like you are trying to do, will require you to work in surfaces.

The process, is like in other applications:

-Create curves, to define what the surface should look like, and act as a guide to the surface.
-Use multiple surface tools, to achieve the look you want (like extrude, loft, patch, sweeps etc).
-Create a solid from your surfaces (easy to do with one click in Solidworks, on water tight models).

Make sure your curves all have proper relations, like pierce, Tangency etc.

That is how to do it...it takes some practice and study, but the results are worth it.....

Look at the carve I did for a "prs style" guitar....did it mostly with surface lofts and sweeps....

viewtopic.php?f=10106&t=29836

So surfacing is the answer for what you are trying to do....

_________________
-CyborgCNC
http://www.cncguitar.com
https://www.facebook.com/CncGuitar

huh? Odd response. Like: ya gotta know it before ya know it. Not too helpful for me.

PRS body is not the same as an archtop - thats just a sweep along the edge with some surface cuts. Done lots of that. An archtop comprises the whole surface - the profile changes as it goes along the edge. And it goes up to centre - much, much more complicated.

I need some specifics... please.

You might think about breacking the surface into multiple patches instead of doing it all in one shot.
I did an archtop that way about 15 years ago in Pro/E and Solid Works is now pretty similar to that. I actually like it better now.
If I remember I put an oval cut out up on top of the surface to set up better boundry conditions and came back and patched the hole. Don't know if that makes since to you or not though.

_________________
Jim Watts
http://jameswattsguitars.com

The only way I can manage any true control of a complex surface like this with Solidworks is to generate a lofted surface from hand drawn, progessive contours in seperate planes.

I can't easily explain this but perhaps I can explain a shape that is analogous to the concept.

Let's say you want to draw a shallow elliptical serving platter....upside down on a table. The platter measures maybe 12" across the long end. Got that image in your head?

1. Start by drawing the outside profile using a spline....not curves and lines. You can draw the shape with curve and lines but you have to trace it later using a spline and erase your original reference lines.

2. Generate a plane .1" above that and draw another profile that tracks 1/2" inside the orginal profile.

3. Then generate another plane .1" above the last plane and draw a new profile maybe 1" or so inside of the last profile.

Then you loft the sections together. The trick is.....each spline must have the same number of defining points and those points must be in the same relative position on each spline. After making the loft, each point can be moved one at a time to make adjustments to the shape of the lofted surface.

Mind you, because of the shape of an archtop, the second plane will be some depth lower than the original plane on which the outside profile is drawn. It's a sublime hassle....but it's the only way to have complete artistic control of the shape. I created this surface using this technique.

viewtopic.php?f=10123&t=29991

This top is a single lofted 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 for the help guys. Zlurgh - it looks like you technique will work. From my profile lines, I just draw contour lines on succeeding stacking planes. Then from these I drop a surface fill - et viola! With surface fill I dont need to have the spline points match.

One thing to note: Solidworks for surfacing is using what it is referred to as a "parasolid kernel." it is basically technology which they have licensed over the years from Siemens. They then developed an interface to front end it, and make the way surfaces are created easier and intuitive.

The reason why I mention this, is because each time you use the "surface patch" command, it works at it's best, if it has other surfaces around the patch you are trying to create. Using then tangent relations, the patch tool does an excellent job. As such, for what you are trying to accomplish, like Zlurgh said, lofting might be a better choice.

The result is in the pudding, so use the best one that looks better to you I guess.....just an FYI....

Would love to see your results....

Cheers!

_________________
-CyborgCNC
http://www.cncguitar.com
https://www.facebook.com/CncGuitar

Zlurgh's technique will work. The key to that is getting the proper curves. You can end up with a lumpy surface pretty easily though.
Like he said use splines and learn how to manipulate them, add points, move points, move the control points, add tangency, etc ..
Good curves are a necessity for a good surface, also less is more when it comes to smoothness.
You may know all of that and I apologize if I'm preaching to the choir.

_________________
Jim Watts
http://jameswattsguitars.com

Hehe.....I made it sound easy? Once you start on this you'll see it's pretty painstaking.....BUT.....if you want full artistic control of this surface...well....I can't figure a better way to do it.

One thing I forgot. If you like you can bust up the splines into sections but then all the splines must be broken up into similar sections that radiate inwards or outwards as your perspective dicatates. The end points of each section will need to line up and follow through the loft....or Solidworks will get confused as to what you are thinking.

Doing this sort of project must be viewed as an artistic endeavour. You must have patience, be willing to make tiny adjustments, and spend a lot of time looking at your model from various angles. But....once you get a little experience with this you'll better under how the software thinks and these types of projects will become much faster and easier to complete.

_________________
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

Zlurgh, here is what I did, only took a couple of hours:

Starting from the plans in Benedettos book, sketch picture the outline to scale.
Then I laid down cross section lines and then planes to correspond to his arch curve profiles at the back of his book.
For each of the arch curve profiles, I sketched picture from scanned copies - using splines.

(I tried using a surface fill based on these lines alone, but the mesh got way out of hand, so I did the following)

I created a series of planes parallel to the top of the guitar 0.1", 1/8, 1/4, etc.

On each of the planes I drew a closed spline that has a "pierce" relationship each of the arch curve splines. I needed to add only an additional point on each curve near the cutaway.

Finally rather than lofting, I simply did a surface-> fill. Using the outline as the boundary, and then then contours as the control. I also used the tail to neck arch curve profile as control.

I am a big fan of relations, the arch curve profiles are connected to the body outline, and to each other. The contours are connected to each of the arch curve contours. So to adjust for anomloies, I just tweak the appropriate curve and regen.

It won't be perfect - but it will be very close. Which is fine for me, because I will then just finish up by hand.

Since it sounds like you're already quite CAD literate, you could get away with using some stronger surfacing tools (Rhino, MOI3D) with save-limited trial versions to get a perfect surface. Just import that one surface and do the rest in SW.

Parser gave some good advice in a thread about modeling a mandolin recently that'll allow you to get your model done easily in Rhino. Since you can just build it in the trial version (15 saves) and export to IGES, there's no real cost.

Refining lofts is a really slow and painful way to go when you have access to proper blend surface and network surface tools. Downside is you lose parametrics on that surface, but for one off complex surfaces it usually isn't an issue once it's done.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

There's one big difference between surfacing a carved top in Rhino and doing it in Solidworks. With Rhino, you can actually loft larger portions of the top surface all at once than you can with SolidWorks.

When doing this stuff in SW, I've had the best luck defining the edge of a "section" being that point at which the surface curvature changes from concave to convex. In Rhino, you can get away with lofting thru complete cross sections, right up the "quad" points (those points on the edge with perfectly horizontal & vertical tangents).

Fill surfaces & patch surfaces will get you results quickly, but you'll have a hard time getting it "perfect" like that.

I did the SCJ for PRS using Solidworks back when I was working for them - this one was surfaced inside and out (with carved bracing in the top). The private stock guys would hand carve the prototypes, then we'd digitize them and model from the point cloud (we'd use Rhino to clean up the point cloud).



Best,
Trev

_________________
http://www.PeakeGuitars.com

I have too much invested in SW to switch to Rhino. But it turns out SW does an excellent job of the surface without much effort - if you know how to do it. Here is how I did it.

I started from an outline of a guitarand then used the profiles from Benedetto's book. So I will assume you have JPGs of an outline and curve profiles.

- draw the outline by using sketch picture, a simple spline with perhaps 7-10 points
TIP: draw half the guitar, then mirror consruction lines to help guide with draing the other half
- draw a series of construction lines that correspond to where the profiles are to be positioned
- create planes for each of the profiles
- draw each of the profiles using sketch picture
TIPS:
- make sure the profile has a pierce relation with the outline and where they meet other profile curves
- use a spline with perhaps 4-5 points
- make sure where the profile lines meet the line is flat - otherwise you will get a pinch in the surface
- Insert->Surface->Fill
- Select the guitar outline as the "Patch Boundary"
- Select the profiles as the "Constraint Curves"
- Uncheck optimize, and set resolution med or high

IF your surface has pinches, anomalies or waviness. Check your profiles where they meet. Zoom right in, make sure they are flat.

You may also need to add a control contour: Create a plane parallel to the outline, perhaps offset by 0.3 or 0.4". Draw a spline that "pierces" each of the profiles. Use this to help control the mesh.

NOTE: this technique will produce an excellent surface, just pay very close attention to make sure your splines properly intersect (pierce) associated curves, and where they meet each other. You will not have to do **any** surface patching or the like.

I'll work one up eventually Chris...Not much free time at the moment...! I'm glad you guys find those short tutorials useful

Trev

_________________
http://www.PeakeGuitars.com

no Trev, I think you mis understood him. We are not looking for a short video, and we want talking on it too!

Just to let you know, thank you for all your stuff you have posted!

Mike

And to further finish it off in SW, prepping for CAM:

- create an offset surface for the thickness of the top Insert -> Surface -> Offset
- loft from each edge of the main surface to the offset surface Insert -> Surface -> loft (do as many times as there are edges)
- then knit the surfaces together and form a solid:
Insert -> Surface -> Knit
form a solid
minimal adjustment

What version of SW did you use? I dont seem to be having much difficulty in SW 2009 Premium getting the surface that I want. From my description above using a outline spline, plus 5 cross section splines got me to 98% with a mesh surface. One additional control curve on the upper plane (like a contour) and the mesh produced an excelent top. The whole key is to make sure the splines properly intersect each other and when they meet each other in the middle to have them meet flat.

A good SW carved top construction technique is to start modeling with a solid body (i.e. a body blank) and then to add features just as they would be "added" during processing. In other words, the feature tree should pretty much mirror the construction process. This is also a good way to mentally verify that your build process is setup well.

As for the carved parts, I found it pretty useful to model the carve surface as a surface and then to use that to "cut" the solid body blank model (which typically has neck pockets, pickup cavities, etc. cut into it as well). Use Insert>>Cut>>With Surface to see these options. Note that the surface must pass thru the solid along all edges in order for this command to work well.

Trev

_________________
http://www.PeakeGuitars.com