Building of a laser digitizer

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  1. #1
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    Default Building of a laser digitizer

    Looks like it’s time for a new project. I’ve always been interested in metrology be it 3D laser scanning, blue or white structured light scanning, CMM’s, PCMM’s (Faro & Romer arms) and even some of the alternate products such as Prodim Proliners (use a cable and stylus to obtain 3D coordinates), and just today I discovered the LT-2D3D Laser Templator (almost $15kUS) from Laser Products LT-2D3D Laser Templator and knew immediately that something like this is do-able. Believe it or not, I even own a Romer 3000i PCMM arm however it doesn’t quite suite my needs due to among other things, the work envelope is too small.

    My requirements or wish list really, are:
    Working envelope of say 30m x 20m x 3m (max, think a swimming pool liner) and say a car panel as the minimum size.
    Medium accuracy is ok. Swimming pool liners and aircraft/boat covers don’t need great accuracy compared what most of us are used to in the engineering world. For a car panel, I’d like as accurate as possible. To digitise a kitchen benchtop I’d also need it as accurate as possible but once again that can only be described as medium accuracy compared to what most of us are used to. There was a thread here some years ago possibly started by Vacpress on a DIY digitizing arm but I can’t find it and possibly this thread is an extension of that discussion:
    http://www.cnczone.com/forums/digiti...are-posts.html
    (Digitizing arm options). Then there’s this one about digitizing of large objects: http://www.cnczone.com/forums/digiti...61887-cnc.html

    Here are my thoughts:
    Right from the outset I’ll state that I’m useless in the area of electronics & programming however I don’t see that as being a major stumbling block as there are plenty of people here that are very clever in those two areas. What am I good at? Anything mechanical & 3D cad.
    My idea is to do this as a collaboration between myself and whoever wants to be in on the project. At the time of building it costs very little extra to machine up 2, 5 or 10 pieces instead of one. The same goes for purchases.
    The problems I see with PCCM arms (Faro, Romer, etc.) for the DIY crowd are:
    (a) They have 6 and even 7 axes, each with a rotary encoder that is small in size but must be super accurate.
    (b) This leads to a mass of wiring going through the arm which often causes problems such as broken wires, pulled connections, etc.
    (c) Almost impossible for anyone but a team of engineers in a large company to set up/configure a machine with 6 or 7 axes so that a commercially acceptable resolution/accuracy is achieved.
    (d) Very expensive.

    So based on this I think we can make a unit very similar to the LT-2D3D.
    For the laser distance measurer/rangefinder/sensor part, at the bottom end there are PulsedLight | PulsedLight which costs $89US but not sure if it has a visible laser beam to see where you are shooting the thing. Then there is LR4 - USB Laser Rangefinder — Porcupine Labs and others which are hacked laser range finders. Then moving up the ladder, there are various industrial quality laser distance sensors from well-known manufacturers such as SICK. Depending on the model, $2 - $3k US.

    Then we move to the rotary encoders. As you can see in the attached picture, size is of no consequence so I’d imagine the bigger the better and the more ppm the better also. I’d originally thought I could get something large that doubled as a rotary joint instead of making the joint then fitting an encoder but we’ll see. Once again, I confess my ignorance of this subject so what would I be looking for? An absolute encoder (as opposed to an incremental) in 50mm diameter with 5000ppm? It would be nice to think that I could get 360deg movement on the bottom axis and up to 180deg on the vertical axis although in practical terms probably 120deg for the vertical would suffice. Would these encoders have enough resolution at say 5000ppm or would I have to gear it up with a belt drive. (I have an old ESAB router and the encoders are driven by tiny belts at about 1:4).
    http://www.ebay.com.au/itm/Rotary-En...item4161b8848e

    Rhino 3D seems to be one of the few that directly accepts input from things like this and PCMM’s, plus the fact that that’s what I use, so I’ll probably stick with that as an output destination.

    I only decided to go ahead on this today so the project hasn’t been fully thought through yet but hopefully there’ll be interest from others and I’ll/we’ll be able to move ahead with the project.
    What are your thoughts? Any interest? (particularly from electronics/programmer type people).
    Regards
    Phil

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  2. #2
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    Default Re: Building of a laser digitizer

    Here's the photo of the Laser Products LT-2D3D Laser Templator and the Prodim Proliner and also the LT-2D3D doing a template for a boat cover.


    Attached Thumbnails Attached Thumbnails Building of a laser digitizer-lt-2d3da-jpg   Building of a laser digitizer-prodimprolinera-jpg  


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    Default Re: Building of a laser digitizer

    Does it have to be laser? Photogrammetry is growing fast as the software advances, and can save you tons on hardware costs. I found that cheap camera based solutions didn't have enough resolution for reverse engineering or inspection, but that might not be an issue for bigger scale digitization.



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    Default Re: Building of a laser digitizer

    Quote Originally Posted by rkwadd View Post
    Does it have to be laser? Photogrammetry is growing fast as the software advances, and can save you tons on hardware costs. I found that cheap camera based solutions didn't have enough resolution for reverse engineering or inspection, but that might not be an issue for bigger scale digitization.
    Certainly a valid question. I have looked at Photogrammetry many times over the last couple of years and my conclusions rightly or wrongly were that:
    It's great for something visual (renderings, etc.) but I'm not sure about the capabilities where a physical output is required (cutting templates, milling, etc.). Ideally I would like to own a high end scanner (Creaform Exascan, etc.) but that just ain't going to happen.



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    Default Re: Building of a laser digitizer

    I am onboard to see how it goes, dunno if I will be of any help, though I had a mate that was interested in CMM's for a while, I'm unsure how far his reserch took him but will find out. I do remember something about a simple encoder based 3 or 4 joint arm generating impressive point clouds, possibly with software smoothing.

    So the size of a swimming pool you say ? Are you sure that will be big enough ? How about something big enough to scan the latest (biggest) airbus

    I think that at least for bragging rights alone a laser beam should be included in the final design somehow...

    Cheers.

    Russell.



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Building of a laser digitizer

Building of a laser digitizer