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How long does it take to get started?

Questions, problems, comments and tips regarding the 3d scanning process.

How long does it take to get started?

Postby logbasket » Mon Jan 14, 2013 6:17 pm

Hi to everybody in DAVIDland,

I'm nearly at the point of ordering the DAVID starter kit, but before I do so it would be helpful to have some idea of just how long it is likely to take before I have obtained good quality 3D images which I can import into a CAD system.

I have spent some time trawling around the DAVID website and the forums and I have a good understanding of how it all works. My background and expertise is in electronic/electromechanical product design (this is what I have done for a living for over 25 years), including the development of optical equipment such as projection systems. I therefore have a good understanding of why all of the precautions described for DAVID are required (light levels, contrast, diffuse reflection, specular reflection, transparency, scan speed, frame rate, focus, mechanical stability etc etc etc). It all makes perfect sense to me and I understand the underlying physical principles. I also have good experience in the use of numerous 3D CAD and graphics PC applications.

In the first instance (in very general terms) I would like to undertake 3D laser scanning of items approximately the size and shape of a clenched fist with a surface texture similar to a walnut and with no difficult holes or recesses. I would like to obtain a model resolution of around 0.5mm. Absolute dimensional accuracy is of less imprtance to me as this work is essentially for aesthetic purposes.

So, my question is, how long it is likely to take me to get from the time when the postman brings me a DAVID starter kit to the point where I've got a nice 3D model in a CAD system? I know that this is a mighty question, but any well-informed estimates would be most welcome.

Thanks in advance and best regards.
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Re: How long does it take to get started?

Postby cnc Dave » Thu Jan 17, 2013 1:42 pm

Hi Logbasket.

If I were you I'd go for the projector kit. That's your fastest route to a good scan and it's pretty simple now-a-days. I guess it would take a few hours to set up and get your head around the software if you're starting from scratch.

Regards Dave
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Re: How long does it take to get started?

Postby logbasket » Thu Jan 17, 2013 6:52 pm

Thanks for the reply cnc Dave.
Unfortunately my budget is a little tight at the moment - hence the starter kit and not the SLS kit.
I'm guessing that you're pretty experienced in the art of DAVID and so I would welcome your best guess as to how long it might take me. From what I've read I think that my starting point will be to build a simple motor-driven rig to move the laser (probably synchronous motor/gearbox and leadscrew combination). I understand that I'm aiming for nice slow, vibration-free movement consistent with camera frame rate and required resolution constraints.
You mentioned that it might take a few hours to set up and get my head around the software. This sounds reasonable but what really interests me is how long it might be before I manage to get a tidy .obj file suitable for import into a CAD program. I'd like to think that I could achieve this in maybe a couple of days but maybe this is a little optimistic?
Any insight into what to expect would be useful. If I should really expect to spend closer to a week before I get good quality results then It would be good to know in advance.
Thanks and best regards.
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Re: How long does it take to get started?

Postby ShadowTail » Thu Jan 17, 2013 11:29 pm

One cheap way to build yourself a contraption to move the laser would be to use a kitchen timer.

To get a decent result you will want to do about 6 to 8 scans around the object, turning it in 60°/45° increments.

You may or may not need to do additional scans to capture the top/bottom of the object.

Using a line laser that is going to take you quite some time.

If the SLS kit is too expensive you can opt to get the starter kit and a cheap projector off ebay or some other place.
That will let you do structured light scanning at a pretty acceptable quality and take you much less time.
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Re: How long does it take to get started?

Postby cnc Dave » Mon Jan 28, 2013 3:12 pm

Sorry for the late reply.

The ultra precise laser movement is only for when you are doing planeless scanning without the calibration panel. Then you need to very, very acuratley reproduce that laser movement you did with the calibration panel.

Your "fist size" object will fit infront of a panel nicely, so you can do this without the complexities of planeless scanning.

You need to see this video... This is how long it takes..

http://www.youtube.com/watch?v=uC-99bjh2dE

It can be done holding the laser in your hand, but one slow precise sweep is much better/faster.

Regards Dave
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