Official Luthiers Forum!

Okay here's my question Gurus. I spent 4 precious hours yesterday drawing a historic guitar.

Is there a more efficient way to copy real existing instruments and use this information to make jigs. I don't really need a CNC machine to cut the guitar parts, just jigs.

Ideally I would plunk down a guitar onto the table, carefully as not to scratch it, and measure some things with a magic wand connected to a computer. This would input the information right into a program where I can send it out to someone to cut. Or perhaps get a small desktop CNC and cut it myself.

Yep that is what I want to do.

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Ken

Somewhere there is a tutorial that explains how with a straight on picture of the guitar, a side shot and the scale length, you can put the pic into a cad program and plot all of the sizes, curves, angles etc.

Yes that would come in handy. I would like to learn that.

I have guitars come in that I want to quick copy, at least the outline and some maybe pickup placement. Maybe where there are some bevels or something like that. I need super accurate dimensions, those that are impossible with a photo. Is there a pen that can be calibrated and used to plot a shape? A scanner is maybe overkill for me.

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Ken

this is the tutorial, it's on the telecaster.com forum. It's not quite as simple as running a pen around the finished instrument, but it's pretty dang clever. From Guitarnut:

http://www.tdpri.com/forum/tele-home-depot/291417-how-create-print-plans-photos.html

Oh yea, good old Guitarnut, he comes up with some good tutorials. I will view that, and thanks.

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Ken

I've not seen that tutorial, but I've done the "pic to scaled drawing" transition many times.
Basically, take a straight on image of a body and carefully crop to the exact body length and width (LB).
In a cad program, draw a rectangle (to scale) measuring the exact body length & width.
In a new layer, drop in the cropped photo & resize it 'till it exactly fits the rectangle.
In a new layer, trace the photo. You can now dimension it, use it for patterns or whatever.

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Dave
Milton, ON

Going from photos can get you started, but there is distortion in that transition that'll bite you if you're trying for real accuracy.

For things you can measure from a waypoint, like the distance from the Xth fret to the top of a pickup, use a caliper or a long steel ruler to get a dimension. Any linear dimensions you can get will help out later. For shapes, tracing them is the easiest way to go that doesn't start with a very hefty price tag. I have laser scanners, but it's much more time efficient to make tracings and then scan them on a flatbed scanner with a ruler in the shot. The ruler lets you scale the images properly. If you need to trace something bigger than your scanner, put some sort of feature on the individual sheets of your drawing so you can line them up after you scan them.

On the computer in my academic office, I have two 32" monitors so I've taken to just laying the piece on top of one of them and tracing it directly in my CAD software. I'd say that's the most affordable way to get accurate high-resolution 2D data.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks for the help so far. These things give me some good ideas, especially reconfirming that a pencil and paper is my best bet. Then I can scan it in, I have access to a large scanner at the local copy shop and learn to draw over it.

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Ken

I'll add that having accurate digital drawings is the first step in the direction you want to head. There are a couple more BIG ones to figure out before you can do anything with those drawings digitally.

1. you'll need to be adept at CAD to design the jig you want to make. This is way harder than I expected. A $500 course looks like a pretty cheap investment now compared to the time I've spent learning on my own. This can be hired out if you're good at that particular skill and have someone you can afford that's reliable.

2. CAM - this is pretty specific to the machine so will be done by whoever machines the parts.

I will say that making jigs and templates on a CNC machine is WAY better than manually. Paper drawings are more intuitive but hard to make backups of. I know from experience that they're pretty flammable and not much good if they burn.

Thank you for the excellent responses to my question. I have a friend down the way that is an expert at drawing CAD instrument plans maybe he will take me on for a fee. If anyone here has done some teaching and might think it would be worth their time, I would consider paying for that. Contact me through email or pm Thanks.

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Ken

Ken what you are looking for is a Microscribe. I took 5 aluminum transmission adapter plates to Dallas to have them digitized with one of the arms, and low and behold I believe I could have drawn them more accurately. On the other hand, it is a fast way to get real, and I mean real close.

Pm me as this arm is for sale,

Mike

This is what I need. I can see it being useful in the medical industry, to make prosthetic limbs and other uses. Wow.

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Ken

Update. I enlisted an expert in CAD design. I abandoned the copying part because it is very expensive adn maybe not quite worked out for guitarmakers yet.

Now I need someone to make some jigs and parts for me from my professional CAD 3D drawings.

Feel free to PM me if you offer these services.

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Ken

We use a cnc laser scanner, 1.2million dots an hr scan rate, it has some issues with pickguards with 45 degree angles, as it tends to get slightly confused here, but its pretty accurate

I was waiting for someone to mention laser scanning. It's fairly involved stuff if you are novice but the basic operation means having the guitar on a table while a laser thoroughly scans the surface. That scan results in something called a "point cloud" which is millions of points in 3D that are used to define a surface. Technically, one could cut something on a cnc more or less straight from that surface....but tooling could also be made from that file by making a series of planes though the surface created from the point cloud and then generate cross sectional drawings from where the surface intersects the plane.

If any of that is confusing I'll explain if you ask.

Also...you don't necessarily need a laser scan done. The magic wand you need may be what's called an CMM...Coordinate Measuring Machine. This device has the same approach as a laser scan...but doesn't create a surface file. You set the guitar on a table and then establish a plane. Using a probe you touch off the surface many times along that plane. When you're done you end up with a cross sectional drawing of the guitar in that plane. Then you establish another plane....say an inch from the first one...rinse and repeat. Pretty soon you have 40 or so 2D cross-sectional cad files of the whole guitar.

There are low end, small shop CMM's for sale new that don't cost all that much and are acurate enough for guitar work if you aren't copying intricate details. There also a number of shops that will do a CMM on a guitar but you'll have to have a relatively defined idea of what you plan to do with the files you get. I have the impression that you aren't far down the road cadwise.

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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

Our laser scan bed is 4ft by 4ft.

The main issue is cleaning the image up from stray lines, heres a quick one sided scan of a clarinet to give others an idea of how the point cloud comes in, this scan took about 2 minutes

And they are getting cheaper and more accurate all the time. I personally am a fan of the arm style CMM as opposed to the old rigid fixed style machine. The arm is much more diverse in its uses, is able to be easily moved around, and doesn't require as much care as the large fixed machines. You can just pick up the arm, touch off a plane and then go around your part plotting points as you go. Even the cheaper ones are plenty accurate for a guitar. Really cool little contraptions if you ask me. I don't have a lot of good things to say about the bulky fixed machines though. They require too much of a learning curve for people who will not be using it on a regular basis IMO

Ive used a faro arm before, that was really nice to use, super smooth and balanced, touch and click.

More difficult to re-assemble the point cloud, but I find solid works is a nice program for this sort of stuff.

The advantage of a (modern) fixed CMM is in accuracy and programming. A CMM is orders of magnitude more accurate than a laser, and isn't affected by surface reflectivity. A fixed CMM can be programmed to scan parts, so no sitting there collecting points like with an arm. The probes on current CMMs are strain-gauge based, too, so the probes can drag along a surface and continuously collect points rather than the 'touch, move, touch' that had to be done with the older style probes. If you want to reverse engineer a part to actual machining tolerances, they're the only way to go for a usable result out of the gate. A buddy of mine has one of the new Zeiss CMMs with an automatic probe changer, and I have envy

The nice thing about lasers is they can be really fast, and they're cheaper than CMMs. Structured light scanners are ultra-fast and also pretty cheap. The Faro-type arms are great for a couple things, especially for guitar building: they can hit all sides of a part in one setup and they have really large process areas. Good CMMs now can do underhangs to a certain degree using neat cross-shaped probes, and lasers just get one projection, but a Faro arm can go all the way around an object in one setup.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

But for getting the dimensions of a guitar or guitar parts neither of those is that necessary. No one is measuring a guitar down to microns, and if they are Id really like to know why. And you dont want to have to write a program to gather dimensions on a guitar, its much easier to take an arm and go to town gathering dimensions. fixed CMM machines are great for QC on large production runs of parts with high tolerences, guitars for the most part do not fit either of those qualifications. Plus a CMM has so much upkeep with keeping all the ways perfectly clean and dust free. Plus the faro arms are just cool little machines. I really want one . Like mirwa said solid works can make it pretty simple to get a model done and then just import that into your CAM software and cut away! Or if you use soldcam you dont even have to import anything just use your SW model and start making toolpath. And solidcam has recently become quite an impressive program, if you havent seen it you should. CAM software these days is just getting rediculous, too bad I hardly use it. I am a G code man myself. I just trust my own code more than a computer program. But with some of the recent jobs Ive been getting CAM is becoming more of a necessity. I just realized Im rambling on about nothing. Ill stop now.

You said you had little good to say about them, so I figured I'd at least explain what they're for rather than have the uninitiated assume they were bad tools. For guitar building, neither a fixed base nor an arm CMM makes sense purely based on price- the cost of even a microscribe is far larger than the cost of having a scanning company scan all the guitar parts you'll ever use it on. I'd totally use a Faro or a CMM if I had one, but I'd never buy one for guitar work. I will someday justify getting one for some other reason, though. I do really really want one!

I'd say at the end of the day you won't get a good result from any form of scanning (save maybe a high-res CMM or laser coupled with high-price software like Rapidform) unless you already have the CAD skills to make the model by hand. They all spit out data that's useful mainly as a guide for modeling the part, not something you can cut from, up until you're into the really pricey machines that can only justify their expense if you're offering scanning services is a big part of your business model.

OTOH, they're really cool to have and so they can be like CNC ownership is for many: more expensive than outsourcing, but way more fun.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Having access to a faro arm in my shop and the laser scanner, I will take the laser scanner any day, its quick its fast and its accurate to within a thou, for modelling guitar bodies or bridges or headstocks etc,the faro arm is just slow and the amount of modelling work to be done afterwards is huge.

We can laser scan and output direct to the cnc router and get an almost perfect cut, its just the stray lines you get that need to be cleaned up, so we put it through a rendering program first.

OK thanks guys. I kinda figured it out how to do CMM low tech. I will enter into Excel and give to my CAD designer who will create surface. Stay tuned.


My little helper after writing the coordinates, so happy to be done. 10 bucks earned!

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Ken

Here is a finished guitar body with plates pressed by a mold that was poured using concrete.
My current mold works perfectly well. In fact you can't get much better. But I need to make more jigs for closing the box, clamping, holding work etc and digitizing it is the way to go.

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Ken

Very cool Ken!! Nice guitars! I would have been excited after graphing a guitar by hand too!

Bob,

I see what you were doing now, though im still biased, I just dont care for the fixed style CMM I really want a FARO arm though and have been trying to talk my way into one for some time. After yesterdays discussion I gave it another shot, and to no avail. I guess we really do need a new lathe with C axis and live tooling more than an arm. Oh well. someday.......