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Thread: Metal shims for optics & lasers ?

  1. #1
    Join Date
    Jul 2007
    Location
    Knoxville, TN & Huntsville, AL, USA
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    3,098

    Default Metal shims for optics & lasers ?

    For the metallurgists out there -

    Any problem stacking together different shims of various thicknesses, some made of aluminum and some of brass, for use as heat-conducting mounting blocks for laser heads & scanners? I'm curious as to the effectiveness of heat transfer and/or possible corrosion problems when stacking the two metals.

    For those of us without ready access to custom-milled aluminum blocks, brass and aluminum stock from the local home improvement and hobby shops could be a fairly quick and affordable way to make height adjustments on the various components during alignment, IF the heat-conducting properties are suitable. I'm open to comments and suggestions from anyone in the know.

    Thanks!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  2. #2
    Join Date
    Mar 2007
    Location
    Rotorua New Zealand
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    528

    Default

    Hi Stuka,

    I have done just this with my RGB. I used only aluminium. It is an excellent way to move up and down with good accuracy.
    Although I dont know what the long term issues are like re adjustments etc and if that will be required as the laser ages etc. I have "taped" my holes so fitting more is easy.

    This material can be purchased from a number of sources like Aircraft supply shops, Model suppliers etc.

    So far so good nothing even gets vaguely warm with my setup.

    Not sure on the mixing metals bit re corrosion etc.. hopefully someone has an answer to that.

    Cheers

    Ray
    NZ

  3. #3
    Join Date
    Jan 2007
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    Sheepsville, Wales, UK
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    Default

    Ally is better at heat conductivity than brass and if you use differing metals thier heat expanding proportions will be different. I would do as Pitts suggests and use Ally only. Its easy to get and to cut and drill.

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
    -----------------------------------------------------------------------------------------------
    Laserists do it by the nanometre.

    Stanwax Laser is a Corporate Member of Ilda

    Stanwax Laser main distributor of First Contact in UK - like us on Facebook http://www.facebook.com/FirstContactPolymerCleaner
    www.photoniccleaning.co.uk

  4. #4

    Default

    Yep, all aluminum! Just use some thermal paste in between the layers if you're doing it that way. I don't really see any significant benefit to using brass. If you have a difference in heat between two different contacting metals you CAN end up corroding them too, so all the more reason for a pure Al setup.

  5. #5
    Join Date
    May 2007
    Location
    Milwaukee WI
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    Default

    Yeah all aluminum here too... Well I will be once my metal shims I just ordered come in

    If you are having a hard time finding the metal you need I used two companies

    The first:
    http://www.speedymetals.com/
    Which was cheaper in sheets.
    I bought 1 sheet of 12 x 12 x .062" and one sheet of 12 x 24 x .08"

    The second company was:
    http://www.metalexpress.net/
    These guys had better prices on Plates so I bough some 3/8" and 5/16" aluminum 6061 alloy

    I spent about $70 including shipping, and everything I buy can be cut using a jig saw or my compound miter saw (my favorite to use).

    These shims will get me within about .025" of my target point. And heavy duty aluminum foil will get me the rest of the way. I got pretty crazy about measuring all of the apertures, mirror heights etc.

  6. #6
    Join Date
    Mar 2007
    Location
    Rotorua New Zealand
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    528

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    HI
    Another observation on this matter..

    The issue of heat conduction and heat transfer grease.

    My two CNI lasers (Blue 250mw and the green 500mw) both have small fans installed at the rear of the laser head.
    Of interest is the bottom plate is removable by way of very small screws. This plate, which is most of the footprint area is very slightly recessed "up" and therefore doesn't make any physical contact with what it is sitting on at all. In fact it is only a small strip all the way round the laser head that would make any heat transfer contact surface.

    This is quite different to my two larger Viasho units which have the fan on top and they do have a good solid base for heat transfer.

    Perhaps a new way of doing things ??

    Using heat transfer grease (or whatever) would appear to be of no use with the CNI units I have.

    I guess its a case of looking at what you have and doing what is appropriate.
    I have not used heat-sinking compound on any of my laser heads and they all stay cool. I do have a lot of heat sinking aluminium in my designs though mainly in the chassis / frame assembly.

    Have a happy new year you guys..

    Cheers

    Ray
    NZ

  7. #7
    Join Date
    Jul 2007
    Location
    Knoxville, TN & Huntsville, AL, USA
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    Default

    Thanks for the replies guys - good info!

    Happy New Year to all of you!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

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