3d scanning to shapeways files

[draskouasshat]

Sooooo, im dumb when it comes to 3d renderings.
Is it possible have a 3d scan of lets say a Santa fe 3800 class 2-10-2 boiler, abd have it either transferred into a shapeways accepted file?  Basically id like to scan a few HO boilers so i can shrink them down to N. 

Adam Draskovich

[peteski]

Check out https://www.therailwire.net/forum/index.php?topic=36011.0  and the other thread referred to there.

I also read that Rapido Trains did use some sort of 3D scanner assist in producing tooling for couple of their models. But I have a feeling that cleaning up the scans and making them ready for tooling took many hours of manual labor.

[C855B]

To scan an HO model and reduce straight across for N, you'll need a pro-grade setup. I found a $20K scanner good for 250 pixels per inch, which will resolve to ~0.002" reduced to N. That might work provided you have a software tool in the middle that can resolve that amount of data, which I estimate to be around 100 million pixels (or voxels), or approximately 1GB of data.

Best of the hobby-grade scanners resolve to no more than 50 pixels per inch. Useless for model-to-model scanning, might work for scanning 1:1 prototype parts similar to what Rapido did with the bus. However, I think a 2-10-2 boiler might crush the scanner turntable. Maybe a little.

[peteski]

Rapido does not use turntables for scanning 1:1 vehicles.  Here are some examples:
https://mobile.twitter.com/LocomotionSHD/status/585763347972415488
https://rapidotrains.com/3d-scanning/

This one shows them taping up the rear window for the scanner to pick up the shape of the window.

[C855B]

I was joking about the turntable, Pete. A crude hobby-class scanner was not what Jason & Co. used for the bus, they were architectural scanners. However, that was the relative resolution we're talking about, probably even less. Doubtless there was lots of manual post-processing involved.

The overriding message is 3D scanning is not where we want it to be for models. At least not yet.

[peteski]

I was joking about the turntable, Pete. A crude hobby-class scanner was not what Jason & Co. used for the bus, they were architectural scanners. However, that was the relative resolution we're talking about, probably even less. Doubtless there was lots of manual post-processing involved.

The overriding message is 3D scanning is not where we want it to be for models. At least not yet.

I guess the smiley should have clued me in.

[narrowminded]

While that subject is up, scanning 3d images, I've seen where Shapeways did something with that and got to wondering about doing that for N scale figures.  Scan a person and scale it down.  I could use a mine loco operator and it's time to figure out how I'm going to do it.  I'm not excited about trying to carve or cast one.

[Lemosteam]

I've shown this before, but not for a while. 

This is the difference between a million dollar HI-RES scanner file and a CAD model.  Note that there is MUCH CAD sweetening that must be done to turn a shell scan into a useable 3d model.

Which would you rather have printed?

[GimpLizard]

A "CAD" file is not an absolute requirement for 3D printing, as the file format for printing is 'stl', which is not a native CAD format. (For example; Solidworks part files are .sldprt; AutoCAD Inventor files are .ipt; Solid Edge files are .par; KeyCreator files are .ckd, ProEngineer files are .prt) An 'stl' file can be exported from CAD, but it can also be exported from a scanner. So all you really need is a well detailed scan of the part(s) you want to print.

There are some affordable scanners out there. Matter & Form (https://matterandform.net/scanner) is the one have. It will deliver what you need, but it takes a LONG time. A single scan can take 20 minutes, or longer. And it takes multiple scans to get the resolution you'll need. Each scan requires you to slightly adjust the position of the part on the scanning bed, so that you get the whole part. Then the software will combine the multiple scans into a finished file. There is also some "clean up" required, of each individual scan, before you combine them. The finished file can then be exported as an .stl, and printed.

STL files can also be imported into most mid & upper lever CAD programs. But converting them to a CAD format is another story. I've searched for software that will do that, but everything I've found (and that ain't much) has been prohibitively expensive. The only alternative, that I know of, would be to "trace" the .stl file within the CAD. And that, too, would be very time consuming. And I'm not sure how accurate it would be. (Being that I'm basically a lazy oaf, I haven't tried it yet. )

Here's a (very) basic "how to", on the Matter & Form scanner, on Youtube:

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[Lemosteam]

My point is this, if you start from an accurate CAD file and export it to .stl, that will be infinitely more accurate than any scan can produce.  Note the sharp corners missing on the scan in my image.  That was a handheld laser scanner, and the resultant data I received for a design study where I work.

Variability and tolerance accumulate with each conversion whether scan to cad- cad to stl- stl to printer or scan to stl to printer.  The reality is that the CAD will be nominally perfect to start where a scan will not.

It is simply always better to start with CAD.

We keep wishing these techs will solve all of our missing prototype model woes- it won't until someone actually designs and tools them.

I guarantee that Rapido bus scan did not go directly to tool cutting.  It was a starting point to get the proportions correct in the scaled CAD model, like an overlay.

[MK]

Make friends with someone in a dental lab.  They have some premo scanners. 

[draskouasshat]

So what I'm gathering is that i should learn how to use sketchup and draw the 2-10-2 boilers myself. I dont even know where to start with this. Is sketchup whay everyone's using?

Drasko

[Lemosteam]

Make friends with someone in a dental lab.  They have some premo scanners. 

LOL, How accurate do jaw scans really need to be?  I model to 5 metric decimal places in CAD.

Hate to say it Adam, and I know how badly you want this shell. but Sketchup might not do it justice.

[MK]

LOL, How accurate do jaw scans really need to be?  I model to 5 metric decimal places in CAD.

Hate to say it Adam, and I know how badly you want this shell. but Sketchup might not do it justice.

Better accuracy than what you need for N-scale.  If you ever get an implant and it causes pain, you'll be wondering if the scanner was accurate enough. 

[wcfn100]

Better accuracy than what you need for N-scale. 

But you guys are talking about different things.

Organic shapes like fruit or a tooth can be much better represented by a scan and the resulting mesh will be much easier to adjust to match the original object better.

To get down to maybe the simplest issue, right angles. 



Obviously the drawing is very simplistic, but it's just to convey the idea. A scanner can only map what it sees.  so in the drawing, if it can't see the two points in the red circles, it will take the next point it can see (the blue dot) and create the green line instead of the right angle line that should be there.


A tooth or an apple won't be as affected by this slight angle change or cabe modified much easier if it's a dimensional issue, but multiply this 100 time across one of our models and you have a pile of mush.


Jason