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Hello, I am new to this forum and I own a PRT Alpha Shopbot. I make ukuleles and am wanting to machine as much as I can on the shopbot. I have all necessary software (Rhino, VCARVE, CUT3D, and ARTcam). I have already modeled a neck to the best of my ability, I actually did it in sketchup. If anyone has any photos or documentation on how they successfully carved out a neck I would love to see it. I thought about slicing the model down the middle and carving each half then gluing them together but I don't know if I will get accurate results. Any ideas would be awesome.

Hey betarash
I am moving there very soon I hope. I have also been fooling around with sketchup and have completed the preliminary designs, somewhat similar as yours. I am also considering doing it a half at a time but only the machining. I am going to make a holder that will index the truss rod slot and hold the neck on it's side, do one side then flip it over and machine the other side. I do the headstock in another operation so in this case I am only machining the heel and the neck shaft including the transition to the headstock.
I hope to give this a try in the coming weeks so I will report back then.

What version of sketchup are you using and how are you planning to convert your files to something shopbot compatible?

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Tickle your guitar daily, and it'll tickle you back.

Here is what I have so far in sketchup.

I don't expect to get a result that I can just use without some further refining but it should be pretty close to useful I hope. We'll see. I'm already doing the headstock on the shopbot (buddy 32 by the way) and the dovetail will be done by other means.

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Tickle your guitar daily, and it'll tickle you back.

Greg German carves his necks in two side-on passes, I think; I think he was around here for a bit. Most of the factories do it in the same orientation the models are set (heel up, fretboard face down). If you're making necks for yourself and therefore speed isn't a big issue, you can get away with much less rigid fixturing and pretty much any method can work pretty well. Holding the necks starts to become the main problem once the speed increases. My neck fixtures required a lot more work and R&D than the neck toolpaths!

From what I've read, only the Pro (and massively, massively overpriced) version of Sketchup can export files to 'real' 3D formats. I'd like to see the geometry it creates in something like Rhino where you can get a really good look at the smoothness of the curves, fit of the surfaces, etc.

Parser had a tutorial up here on how to get started modeling a neck in Rhino, but the images are all broken right now.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

There are a number of conversion utilities to convert from sketchup to the various 3d formats needed for toolpathing so it's not a problem. The newest version of sketchup v7 does a pretty good job and I don't expect to get a finished neck from the cnc anyway. I will be doing custom shaping of the individual necks anyway but it'll get me close a lot faster. And speaking of overpriced, I think Rhino and Auto quailfy there as well. For me, it is just so much easier to work in the intuitive style of Sketchup and it is as accurate as I need it to be. For 2d stuff even the free stuff will export files in already usable formats.

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Tickle your guitar daily, and it'll tickle you back.

alright. here is what i have thus far. i need to come up with a way to register the piece on my machine. i figure that i will use some dowels and some drilled holes. another issue is that if i want to continue doing these this way i will have to make sure that the thickness of the wood blank is exact for each one or it will be off when i flip the piece (or i will have to recalc the machine path in my software each time). this model was made in Sketchup pro then exported (as a 3DS) to Vectric Cut3D to do the tool path. i would love to do this model in rhino and have given it the good old college try but i tend to get some mess ups here and there and the main thing that i want to model is a volute, which has proven to be very difficult for me.

images are showing a roughing (1/2" straight) pass and then a finish pass (1/4" ball nose)

Nice work betarash. You might consider that stock is unlikely to be found in the sizes needed to machine such a pair of necks. You could glue up some lams but it seems like there is a lot of waste material. I have seen Martin's neck machining operation several times and they machine 12 necks at a time on huge high $$$ Fadal machines. However, they orient their blanks in the same orientation as John's drawing. A lot can be learned from large OEM operations where waste is critically analyzed in each step of the process.

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tim...
http://www.mcknightguitars.com

Tim is right you'll want to work out a scenario where you will waste less wood and reference mounting the material using the fret board glueing surface. The reason I intend to do my neck mounted sideways is due to most likely using shorter bits and to get the tool around the heel of the neck, also the shopbot buddy has a limited Z axis though I have found a method of increasing the Z height by about 2".

Here is a pic of the jig I am working on. Even though it doesn't have a neck installed and is just a rough draft, I think you will get the picture. I'll do half on one side, flip it to the other side and repeat with an opposing file. The key is referencing to the truss rod slot and the heel end blocks. Clamping the neck in place is the next challenge.

Also consider that you don't need or necessarily want to cut the whole neck from one tool path. I will be doing the headstock separate and possibly braking up the heel and shaft parts of the file.

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Tickle your guitar daily, and it'll tickle you back.

Good old double stick tape should have more than enough holding power in your setup, John. By the looks of it, you have the blank supported at both ends from 'sliding' and besides that there should only be the upward pull of the cutter which shouldn't be very strong in the sizes of cutters you'll be using.

Software prices are a matter of perception, I suppose. My measure is capability, speed, then usability but the opposite approach is just as valid. Either way, I still take offense that AutoCAD was mentioned in the same breath as Rhino . The only real 'steal' I know of right now, in CAD software, is Moi3D which is quite under priced by all measures.

Beta: Tim's right on the blank cost. By my guess, a blank like that (if you can find it for sale at all) would be in the $3-400 range if there's no premium paid for extra thick stock!

The length of the cutter used can be a big concern in machines with less rigidity or smaller collets. I don't like the rigidity of 1/2 inch cutters in the length you'd need for a 'fretboard down' carve, and I'd run them very slowly unless there's a lengthy roughing pass first. On a side-on carve, you only need one half the cutter length protruding (around 2" vs almost 4"). Side-on carves are less economical on space, but they're easier on your machine and most routers have giant tables anyhow. They're harder to fixture, but John's solution will definitely do the trick.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Hey Bob, I meant no offense really in mentioning Autocad. Actually I haven't a clue about it except that I can't afford it and don't want to spend the time it takes to learn it anyway. And that is the problem with most cad software. Sketchup is simply drawing with the aid of software that helps you get your lines in the right place. Perhaps not as sophisticated as the bigger cad-wares but close enough for this woodworker. I rarely use the 1/32" marker on my tape measure but I never seem to go beyond that and I need magnifiers to even see that.

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Tickle your guitar daily, and it'll tickle you back.

Hey Tim! It's me! Your good buddy Shawn Hines. I usually go by BetaCrash on other sites but I mistyped when I signed up for this board, but now I want to go by my given name. I sent a message to one of admins about changing my name but havent gotten a reply yet.

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Agreed, that would be one big chunk of wood. I was actually planning on using a laminated block but it still seems wasteful. John, your jig seems like its a leap in the right direction. The truss slot is a great registration point. Well, for me it would be a CF rod slot. I'm very excited about the direction that this is going.

Hi Shawn,
Glad to see you here. Hang around and your will learn a LOT from these guys.
3 years ago at NAMM there was a CNC company there that had a small table top unit. I think it was K2. They were carving necks in the same orientation as Martin too and if memory serves me correctly they were using a long 1/4" ball nose end mill and the results were pretty amazing. I think cut time was in the 1/2 hour range from blank to finish.

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tim...
http://www.mcknightguitars.com

I've changed my website around - I'll have to repost the original tutorial with new links to the pics.

I carve my necks in the heel up position using my K2. I've got it down to about a 1/2 hour, which I think is pretty decent given the limitations of the equipment. I use a 1/2" 2 flute ball mill and take little bites at between 20 and 40 ipm. As mentioned, the factories can crank necks out pretty quickly. Those multi headed machines up at Martin are Heins I believe - nice solid stuff! I believe they carve using 3/4" ball mills.

I'm building necks with a scarfed headstock currently; this allows me to 1) construct the whole neck from 4/4 roughsawn lumber 2)machine the headstock & HS inlay in the flat position before gluing it up to the shank. The straight grain on the top of the headstock more or less negates the need to have a headstock veneer unless I goof up on the inlay..! I'm still developing a nice technique for cleaning up the back of the headstock where the scarf joint is more obvious.

As for CAD - I think Rhino is tough to beat. I did not feel that Sketchup gave me the control I needed to really make nice surfaces.

Trev

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http://www.PeakeGuitars.com

parser, it makes me happy that you would be willing to do that. my frustration in modeling dictates my decisions more than it should. I think that I would be more open to different mays of machining if I was more fluid at modeling. I will get there. I have all the tools and plenty of time. That's why I was so eager to view your tutorial. Sketchup just doesnt give the power that is needed (for me at least). It has its place, but complex curves and shapes are best left to Rhino. I hope that I can get things rolling within the week.

I just spent a good part of the morning playing with Moi3d that BobG mentioned. It looks very interesting and at $195 it's not too expensive. My thing is I like drawing and getting things done quickly and most all of the cad software is to quirky and not intuitive at all or myhaps my intuition falters but...... This one is a little more like how I work. It is new though and there seem to be a few issues to work out. I do know that the real cad-ware are typically more powerful than a program like sketchup, but if it does what I want quickly and easy, I'll use it.

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Tickle your guitar daily, and it'll tickle you back.

I reposted the original neck carve tutorial at the bottom of that thread...drop me a line if you need a hand with anything.

I will be out of town for a couple weeks for work, but I should be on the forums....probably won't have much else to do in the evenings! (unless I can get into some fishing one way or another!)

Trev

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http://www.PeakeGuitars.com

alright. still working on it. getting ready to have a new neck modeled but am trying to get the jigging ready. wondering why you would consider doing the neck and heel in seperate files john. is it to give each area different amounts of detail? i was figuring that i would use vacuum below the indexing plate.

A couple things to think about regarding neck jigs..

First of all, the most important location on the neck is the nut line. Whatever you do, make sure you can always accurately locate the nut line!

I think the main reason you would want to carve each side separately is that you do not have enough Z capacity. Other than that reason, you should be able to fixture the neck on the fingerboard glue up surface and carve everything in one operation.

Martin, and I believe Taylor as well, break their neck carving programs into 2 sections: the heel and the shank. If I remember correctly, I think they run more of a vertical pattern on the heel (stepping over in X) and they run a longitudinal pattern for the shank (Stepping over in Y). I'm pretty sure they use longer 3/4" ball mills. With my little K2, I have changed things around a bit to compensate for the limitations of my machine (it's nowhere near as rigid as the mid priced routers much less a VMC). I use a RhinoCAM parallel finishing program for the shank and I use a Horizontal Roughing program for the heel. I carve with a 1/2" ball mill and take little bites so that I don't get excessive vibration when cutting. Even with the limitations of the machine, I'm able to carve a decent neck in roughly 1/2 hour. Production equipment should be able to carve necks in a fraction of this time.

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http://www.PeakeGuitars.com

Glad to see your making progress Shawn. I'm stalling here.
Actually the reason I consider doing the different parts of the neck with different toolpaths, has to do with the software I have available. Right now all I have are the partworks tools that came with my machine. One of the limitations is that it wants to start every cut file with a cube that is big enough to contain the entire part and so the file would be huge and wasteful since I rough cut the neck block into two blanks before I start. So I was going to have smaller starting points by dividing the project. I will glue up some sacrificial pine blanks and start trying but I am waiting to try some other software soon.

_________________
Tickle your guitar daily, and it'll tickle you back.

Another reason to do them in halves as Shawn has shown, is that you can get an undercut in the heel if your design call for one.

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Jim Watts
http://jameswattsguitars.com

Just to add to what Parser said about keeping your index point (whether it be pins or the nut line), you're going to want to have as much contact between the fixture and the part as possible. Instead of stopping it at the midline of the neck, have the fixture in contact with all or nearly all of the fretboard gluing surface of the neck. This helps with vibration, deflection, and all kinds of other nastiness.

I can't recall how Taylor was carving necks toolpath-wise, but they're using long 1" ball end mills. I think that most of the router places are using 3/4" balls and the mills are using 1" balls just because of the standard toolholder sizes they have access to.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Parser,

I am just about ready to give my DIY machine a first go. I too thought of doing scarf joints so I could mill the headstock flat and join it to the neck after it has been milled. I do have some questions about how the to mill (and index) the transition. For eg. are you doing an over or under scarf joint (headstock piece under the neck shaft or over)? If under, do you partially mill the neck profile into the back of the headstock? Do you mill a volute? How do you index it?

As always, a picture is worth a thousand words. If it is not too much trouble, it would be really helpful if you could post a picture of the two parts before glue up.

Thanks,

They carve them FB down. I only caught them finish carving the heel, the shaft and headstock were already done.

I think I was a bit ambiguous there . I meant I didn't know what toolpathing strategy they were using (parallel path, cutting it into two toolpaths, etc). The toolpath is what the tool does, the setup is what the stock does. They do indeed cut them FB down and, more interestingly, they carve their necks with the fretboards already glued on and fretted! (and they glue them on with those awesome firehose clamps...those are definitely on the list if more customers start demanding their necks and FBs pre-glued)

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

My apologies.