Double Bass Any DB CAD Drawings? or CNC Resources?

[George700DL]

here is a picture of a test plate run out of junk wood. from here it becomes very important for the ribs and form to be precise.

Looks like slab-cut pine, with plenty of knots. Looks great, I'll take it!

 

[powerbass]

So it looks like someone has actual experience with CNC carving and not just speculation. Can you fill us in on the process? How did you program your machine, did you scan a top or plot one from scratch?

 

[RCWilliams]

I suspect there are more than myself out there who have experience in this area. at the time I began this 3D scanning was pretty expensive. so I never got into it. all the work I have done in this area is from scratch. I am however investigating software to get measurements form digital pic.s. So far raster to vector (pixel to line) have been more work than I am generally willing to put up with.

the learning curve in 3d design is a bit steeper than 2d and even then the software people want to change the look of every thing constantly as though that some how makes it better.

to start you make a measured drawing, or take measurements from an instrument enter your points, connect the dots and make certain your critical dimensions are accurate. the nice thing about cad is that from the beginning your work is not in vain ... unless you don't have auto save on, you can keep refining it until it is right.

you start in 2d get your outline and sections all in in 2d then rotate in the various curves and turn them into position to generate your 3D surface. how this is done is dependent on how your software works. I use Mastercam.

once you have generated the geometry of your part, you generate tool paths from that to cut the part you created in cyberspace on a machine.

it all sounds pretty simple, until you try and do it. when I started out doing this stuff , I would call the tech support people at the co where I got my first cnc router, and tell the guy on the other end what I was doing and he would say with a mystified tone in his voice "You can do that?" and I figured I was pretty much on my own.

 

[powerbass]

Sounds like you have done your homework. How long did the machine take to route the top? Any issues with wood movement and routing? Did you also route the underside/inside shape? Are you planning on pursuing this further in instrument production? So many questions

 

[RCWilliams]

it takes about 5 hours to run the top. I use a vacuum hold down so the plate doesn't have an opportunity to move. it is not a problem to graduate a plate on a cnc, once you get the shapes right etc.

as to further persuit, that is what my post about bass kits was about. I'm spinning off a new company, KCNC Production and Design LLC, I will be offering these services in the general market. I just have no idea how much interest there will be and what percentage will be in the music industry.

 

[arnoldschnitzer]

Laarman plane...ooh...nice...me likey...me wantee...yum...

 

[gbaker]

... all the work I have done in this area is from scratch. ...

to start you make a measured drawing, or take measurements from an instrument enter your points, connect the dots and make certain your critical dimensions are accurate. the nice thing about cad is that from the beginning your work is not in vain ... unless you don't have auto save on, you can keep refining it until it is right.

you start in 2d get your outline and sections all in in 2d then rotate in the various curves and turn them into position to generate your 3D surface. how this is done is dependent on how your software works. I use Mastercam.

once you have generated the geometry of your part, you generate tool paths from that to cut the part you created in cyberspace on a machine. ...

it all sounds pretty simple, until you try and do it. ...

Thank you RC for a very straight-forward and informative answer. And your demo top looks good.

From your other thread, I understand that in marketing a kit that the parts are completely repetitive and you are probably doing market research and developing a business plan as you go. BTW I wish you well with your new venture.

Can I presume that the CAD part of the process is at this time prohibitive in respect to using a tracing of a customer's top and modifying your base top design to produce a new solid replacement top for the customer? I guess the question is how would the expense of modifying design and routing compare with labor of carving. Any idea yet?

 

[robobass]

...
Can I presume that the CAD part of the process is at this time prohibitive in respect to using a tracing of a customer's top and modifying your base top design to produce a new solid replacement top for the customer? I guess the question is how would the expense of modifying design and routing compare with labor of carving. Any idea yet?

This depends on the the equipment you own or have access to, but more importantly your fluency with modern 3D cad/cam, or willingness/ability to learn it. It seems like the latest generation of CNC routers out there allow you to easily scan a surface and tweek it - if you can use the programs effectively. The problem is that you need two entirely different skill sets to be able to apply Cad and CNC to making bass tops. The people I know who can fluidly manipulate 3D cad files are engineers who spent their college years learning to do it. I don't see any of them taking a few years off to learn luthiery. Likewise for luthiers, who having gained the skill of carving a top, and the understanding of how tops work, would be unlikely to take time off to become cad Jedi as well.

The two worlds are slowly integrating, of course. Gradually we will see young people who have cognition in both worlds. For us old guys, it is a question of time investment and learning ability. You can download a demo of Rhinocad, for example, and work with it for a month and decide if you have the wherewithall to learn to use it effectively. The cool thing is, just like making a violin, once you have made one, the second is far easier. But, it takes an amazing amount of time to learn to make that first one!

For myself, I produce a product which has a 3D surface, but I do that surface by hand. There is some fairly precise 2D machining involved, but although I have the cad skills to render a full 3D drawing, at my production volume it is not cost effective to machine in 3D at this time. Also, I like to think that the hand-worked aspect of my product adds some value. I think that most luthiers would be on board with this idea!

 

[fdeck]

In my view, the initial and primary challenge is getting the data points. Once that is done, a solid modeling program such as Solid Works can convert the points to a 3d splined surface. You decide how many data points you need based on how precise you want the model to be, and how much curvature you are dealing with. The points don't have to be evenly spaced.

Of course Solid Works ain't cheap, and your most cost effective approach might be to find someone with a license who will let you use their system for a while.

If somebody already has the CNC mill, a dial gage can be chucked into the spindle and used for measuring the profile.

As for the actual machining, I have dealt with this in metal parts, that the machining process relieves stresses in the material. So the workpiece is deforming itself while you are machining it.

 

[powerbass]

As for the actual machining, I have dealt with this in metal parts, that the machining process relieves stresses in the material. So the workpiece is deforming itself while you are machining it.[/QUOTE]

This was my initial question about wood movement, I understand that CNC machines have vacuum clamping. My concern is that in order to maintain equilibrium in the wood, carving both sides within a relative short period of time may be key to maintaining the shape of the plate. With any milling of wood removing a similar amount from both sides keeps the wood balanced and true. This is less of an issue with very well seasoned wood.

 

[fdeck]

One option, if time is not of the essence, is to carve the workpiece to near net shape on both sides while leaving an un-trimmed edge to hang onto. Then let it sit for a while to settle, then machine the final dimensions. This is done a lot with metalworking. Parts such as large castings and engine blocks get annealed in between these steps. I did this in a day job of many years ago, making molds for plastic lenses using CNC machines that I built myself. I made a face plate lathe with an air bearing spindle, and a single crystal diamond cutting tool on computer controlled axes.

 

[RCWilliams]

assuming the wood is dry, all the way through, and is not reaction wood, I have never had a great deal of deflection in a part I was cutting. even if the part remains un-graduated for a while it has never been a problem. seasonal movement, can be an issue, but in general they don't move that much. at least not spruce and maple. I did have an American sycamore back which totally changed shape, but it sat around for a very long time before it was used.

in the not too distant future I plan to get some new digital photo measuring software, if it is as accurate as the marketing indicates, It may significantly reduce the development time for new models.

the hardest thing I had to learn was the subtleties of getting the curves and surfaces correct. though the arch of a bass should look elegantly smooth and has very specific areas of re-curve etc. controlling those surfaces in the computer is not always easy. since every point is relative to the others around it a change in one place always creates a change somewhere else.

 

[powerbass]

Congratulations on seeing this project through. If you dial in the scanning process you may have a unique business making new tops for existing basses etc

 

[fdeck]

assuming the wood is dry, all the way through, and is not reaction wood, I have never had a great deal of deflection in a part I was cutting. even if the part remains un-graduated for a while it has never been a problem. seasonal movement, can be an issue, but in general they don't move that much. at least not spruce and maple. I did have an American sycamore back which totally changed shape, but it sat around for a very long time before it was used.

in the not too distant future I plan to get some new digital photo measuring software, if it is as accurate as the marketing indicates, It may significantly reduce the development time for new models.

the hardest thing I had to learn was the subtleties of getting the curves and surfaces correct. though the arch of a bass should look elegantly smooth and has very specific areas of re-curve etc. controlling those surfaces in the computer is not always easy. since every point is relative to the others around it a change in one place always creates a change somewhere else.

I suppose if the measuring process becomes widespread, it would be a good way to document historical instruments for posterity.

 

[james condino]

RC:

Thanks for generating this thread. I support your work completely and will be excited when you open this up to other builders as a subcontractor service. I'll gladly make the drive over your way loaded up with spruce, tops, and ideas to take advantage of your process and hard work. I've looked at a number of other folks with this same process in mind, but I've never been able to find anyone who can meet my needs properly or who can do more than basic cabinetry work. Having an expensive machine and technology is one thing; being able to use it to the maximum potential like we are talking about is a whole different story. I'm actually one of those engineering dorks who dropped the locked up in a cubicle with the CAD work in order to spend my time carving spruce by hand and making far, far, far less $$$.....

j.

 

[RCWilliams]

RC:

Thanks for generating this thread. I support your work completely and will be excited when you open this up to other builders as a subcontractor service.

j.

I can't take credit for this thread, only an attempted hijacking, but the sub contractor service is where I am looking to see if there is much interest in parts. we are in progress on our web page kcncproduction.com, and it will show a little of my history and work, along with our capabilities.

If the work is there, and it doesn't price things out of sight, it is the kind of thing that can save some repetitive stress injuries and help makers be more productive. Ultimately all I can do is use the computer to take out the trash, the maker still has to know his stuff, or he/she just ends up with a better looking pos., and even that is subject to interpretation.

 

[gbaker]

I can't take credit for this thread, only an attempted hijacking, but the sub contractor service is where I am looking to see if there is much interest in parts. we are in progress on our web page kcncproduction.com, and it will show a little of my history and work, along with our capabilities.

If the work is there, and it doesn't price things out of sight, it is the kind of thing that can save some repetitive stress injuries and help makers be more productive. Ultimately all I can do is use the computer to take out the trash, the maker still has to know his stuff, or he/she just ends up with a better looking pos., and even that is subject to interpretation.

You didn't hijack the thread, RCW. You generally if not specifically answered my question and became a possible resource.

Could the process of producing a new top for an existing bass include a proof step with construction grade lumber since a bass tonewood set can cost $500 and up?

As you develop specifics such as typical prices for services and other offerings please let me/us know.

 

[RCWilliams]

gbaker,

I always think it's a good idea to try things first with a test blank, it is the only certain way to make sure the shapes are as you want them.

just for the heck of it, if you want to of course, take a digital photo of your bass and put a sheet of copy paper on top of the bass . make it as square to the bass as possible do the same from the side. I will then see if I can use the measuring software to put together a drawing of your bass that is accurate enough to satisfy you. the target needs to be at the same plane as the part to be measured , and the lens needs to be as long as possible to avoid distortion of the shapes, zoom in to the max and then back up so the whole top is in the picture, I will , as time allows develop the drawings and measurements. we'll see how good they are.

just for the heck of it I threw in a pic of bass crates we just built for the Moscow Symphony's up coming tour of the us. after the tour, we can ship basses #7-9 of the 9 we are building for the Moscow symphony. half and half 4 & 5 string.

 

[gbaker]

gbaker,

. . .
just for the heck of it, if you want to of course, take a digital photo of your bass and put a sheet of copy paper on top of the bass . make it as square to the bass as possible do the same from the side. I will then see if I can use the measuring software to put together a drawing of your bass that is accurate enough to satisfy you. the target needs to be at the same plane as the part to be measured , and the lens needs to be as long as possible to avoid distortion of the shapes, zoom in to the max and then back up so the whole top is in the picture, I will , as time allows develop the drawings and measurements. we'll see how good they are.
. . .

OK I did the pix. PM sent.

 

[RCWilliams]

excellent, email sent, we'll see how it works.