laser scan vs. probe scan?

[Grahamd]

Hello,
Has anyone imported a 3D laser scan of a part to cut. I build archtop instruments and have been using the probe to copy carved tops and backs. The accuracy of the cuts is not good enough. They require lots of time adjusting to only get a part that I still have hours working on to be able to use. I realize that my being a newbee is probably a lot of my problem. Just thinking about sending a finished top or back out to be laser scaned. Is it any better than the probe?
Thank you, Graham

[Brady Watson]

Laser scanning is the only way to go for precise work. The worst cases scenario with laser scanning (in my lab anyway) is that you will collect data 100x finer than the touch probe is able to resolve. More resolution is possible, but at that point picking up unwanted woodgrain texture becomes an issue later on...unless your design intent is to preserve the woodgrain texture. I get requests for both.

The probe is OK for decorative things but really doesn't do well when precise replication is required. First, it mechanically has too much hysteresis in it - isn't triggered as linearly as you want it to and at the end, all of the data is offset 1/2 the probe diameter, which means you now need to a do a 2D (for vectors) or 3D (for reliefs) offset to get close to the actual size of the part. So yes - by far - laser scanning is WAY better than the touch probe. I've probed well over 150 million points with the SB probe early on & it was 'fun' and OK for some decorative work, but it fell short for tight, precise projects where I needed more resolution and accuracy.

Collecting the data at a higher resolution is only one part of the job, depending on your own skill set. For instance, many instrument makers are brilliant at what they do day to day but simply lack the skills required to fully follow through on machining their parts successfully. (There's no shame in that...BTW) I do offer 3D scanner services where you can pay a fee and receive a file ready to be imported into CAD/CAM. However, in order to machine the body (or neck) properly, it should be defeatured (remove all pockets etc and digitally fill + 2D vector digitize their original locations for optimal 2D machining). If you are not certain how to toolpath the data, I can create sample toolpaths using your data and bit specs (either mine or yours) and finally, show you the entire process in a video that you can follow step by step (specifically using YOUR data in VCP v8+ or Aspire). It is all a la carte - so you can buy only what you need, but most importantly - get what you want finally in a very short amount of time.

The attached pics show an example of a body scanned (right off the scanner), the body defeatured and 2D vectors placed in original locations, and finally everything toolpathed and simulated in Aspire. One thing that may not be readily apparent is that the body is scanned from all sides, so you get a perfect marriage of the front, back and sides without any alignment issues to worry about - It truly is 'Full 3D'. I've done many mandolins, guitars, violins, bodies & necks, plus other instruments over the years.

Feel free to contact me off-list if you wish to inquire about scanning services. The easiest is to email me from the website: www.IBILD.com or send me a PM.

-B

[willnewton]

Wow, nice scan Brady. The SB probe couldn’t touch that kind of resolution. It’s like an old Atari vs. a new Xbox One.

Graham, it is not just because you are new. It is because you are seeing how primitive the SB probe results are. There is no magic button that “fixes it up” as you have noticed.

My own SB probe experience made me realize it is an absolute waste of time it is. Hours setting up to scan and MANY hours of trying to dump gallons of turd polish on that scan to no effect.

This is not a slight against SB, it is just that the probe has limits. Unfortunately, the limits are so low, it is easier to work with a tape measure and a photo.

[JMCS]

Graham,
Send your part to Brady. I just had him do some laser scanning and toolpathing on a quatrefoil plinth block. Excellent service and quick turnaround time. One of the best things was he'll send you a video of your part with what he did to it. The video is so good it should be on the Vectric website.

[willnewton]

Brady, how difficult is it get a scan transformed from a point cloud to splines or vectors? Do you have a software package to handle that?

For example, that guitar body could have 100k vertexes as an STL, but maybe 50 splines as a Rhino file.

[bill.young]

Let me jump in with one quick thought on duplicating items in general. If you want to make exact copies of a particular item then getting Brady to laser scan it at the highest resolution is definitely the way to go. You'll get a precise copy and great bang for your buck. If you plan on making any mods or cleaning it up, though, extremely high resolution may be counter-productive.

I was a boat carpenter and boatbuilder in a previous life and can guarantee that no boat that I ever built or worked on was symmetrical from side to side. Differences in the way planks bent, time spend fairing and sanding, variations in the setup of the frames made small but measurable differences in the two sides. An accurate scan of the hull would give you an precise copy of an imprecise thing.

If however you wanted to build a boat like the original design, you would at least try to make it symmetrical and all that extra precision would make your job harder. A scan with the minimum number of control points to define the shape is what you need, so that you can find and fix the deviations.

So if you want to make exact copies of that specific guitar then more is better when it comes to data points, but if like boats there may be some "anomalies" that you want to smooth out in software, maybe less resolution is better.

Bill