Plastic strikes again!

Discussion in 'Digital Photography' started by RichA, Aug 14, 2011.

  1. RichA

    RichA Guest

    RichA, Aug 14, 2011
    #1
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  2. RichA

    PeterN Guest

    PeterN, Aug 14, 2011
    #2
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  3. RichA

    Robert Coe Guest

    : Damn that contraction plastic experiences after hot molding!!
    :
    : http://forums.dpreview.com/forums/read.asp?forum=1041&message=39111658

    IOW, you can make a bad product out of a good material if you cut corners or
    don't handle the material properly. Actually, I think we knew that, but thanks
    anyway for reminding us. It's a dog-eat-bone world out there, and one can
    hardly be too careful.

    Bob
     
    Robert Coe, Aug 14, 2011
    #3
  4. RichA

    PeterN Guest

    I wonder how much effort Rich has put in to compare the coefficient of
    expansion used, with the coefficient of expansion of likely metallic.
    And if so, how they are treated in the finished product.
     
    PeterN, Aug 15, 2011
    #4
  5. RichA

    MG Guest

    MG, Aug 15, 2011
    #5
  6. RichA

    RichA Guest

    People need to understand that a frigging jetplane isn't using the
    plastic scrap used in a cheap camera body. Example: A carbon fiber
    tube, aircraft grade, 2" wide and about 4ft long costs about $500.00.
    The polycarbone scrap used in the cameras is about 1/1,000th of that
    cost. The two also have VASTLY different structure. So WHY are you
    people comparing the two, there is no KINSHIP between them!
     
    RichA, Aug 15, 2011
    #6
  7. RichA

    PeterN Guest

    Proof, please!
     
    PeterN, Aug 16, 2011
    #7
  8. RichA

    PeterN Guest

    It's in their blood, right?
     
    PeterN, Aug 16, 2011
    #8
  9. RichA

    PeterN Guest

    PeterN, Aug 16, 2011
    #9
  10. RichA

    PeterN Guest

    Plastic is plastic.

    A rose by any other name .....
     
    PeterN, Aug 16, 2011
    #10
  11. RichA

    PeterN Guest


    to clarify my prior response.

    What adjustments are needed for the coefficient of expansion for each of
    the materials, when removing them from the mold?
     
    PeterN, Aug 16, 2011
    #11
  12. RichA

    Robert Coe Guest

    : On 8/14/2011 5:22 PM, Robert Coe wrote:
    : > : Damn that contraction plastic experiences after hot molding!!
    : > :
    : > : http://forums.dpreview.com/forums/read.asp?forum=1041&message=39111658
    : >
    : > IOW, you can make a bad product out of a good material if you cut corners
    : > or don't handle the material properly. Actually, I think we knew that,
    : > but thanks anyway for reminding us. It's a dog-eat-bone world out there,
    : > and one can hardly be too careful.
    : >
    :
    : I wonder how much effort Rich has put in to compare the coefficient of
    : expansion used, with the coefficient of expansion of likely metallic.
    : And if so, how they are treated in the finished product.

    I believe that some kinds of plastic are more likely to shrink than to expand
    under excess heat, as volatile substances are driven out. I wonder if the
    problem is that the camera was left for hours in a broiling hot car.

    Bob
     
    Robert Coe, Aug 16, 2011
    #12
  13. RichA

    Robert Coe Guest

    On 2011-08-15 13:26 , Savageduck wrote:
    : > On 2011-08-15 10:10:40 -0700, "MG" <> said:
    : >
    : >> : >>> Damn that contraction plastic experiences after hot molding!!
    : >>>
    : >>> http://forums.dpreview.com/forums/read.asp?forum=1041&message=39111658
    : >>>
    : >>
    : >> I heard a rumour that Boeing is building an aeroplane out of plastic.
    : >>
    : >> MG
    : >
    : > Aerospace composites are an old story, and you are a lot closer than you
    : > might have intended, see the Boeing 777 with several major airfoil and
    : > floor components built with composites, and then there is the AirBus
    : > A320 & A380;
    :
    : 787 takes it quite a bit further with composites - main fuselage is a
    : composite structure. This allows higher cruise altitude (no metal
    : fatigue from the pressurization cycle) thus saving fuel and allowing
    : higher cruise speed. (787 pushes in many areas: vastly reduced
    : hydraulics and no hydraulic pumps hanging on the engines; pressurization
    : is not from the engines but separate electrical compressors (saves a lot
    : press ducting ...) etc.)

    The power for the electrical compressors comes from the engines too, of
    course. But generation of electricity must be pretty efficient, or the
    diesel-electric locomotive wouldn't be so successful.

    Bob
     
    Robert Coe, Aug 16, 2011
    #13
  14. RichA

    Martin Brown Guest

    Just because the Rich troll made a statement doesn't mean it is
    automatically false. However, he is over stating the problem.
    Manufacturers are not stupid enough to make cameras out of extruded
    acrylic sheet which has about the worst properties at 200ppm/K.

    The best engineering plastics are heavily filled with alumina, carbon
    or glass fibre and as a result are closer to being well behaved than the
    raw plastic materials. But the fact remains that many metals typically
    have 10ppm/K linear expansion whereas the best heavily filled
    engineering plastics are more like 20ppm/K and the worst are 200ppm/K.

    Worth noting here that the best engineering plastics are now better in
    terms of thermal expansion coefficient than the magnesium alloy that the
    makers are using in high end cameras. Pure magnesium is 25ppm/K.

    common engineering materials
    http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

    pure metals and alloys
    http://gphysics.net/tables/148.html

    Regards,
    Martin Brown
     
    Martin Brown, Aug 16, 2011
    #14
  15. RichA

    RichA Guest

    They don't believe in quality control. Milk, toys, sheetrock, all
    FILTHY and contaminated. Shoddy workmanship all round. The ONLY
    reason anything ever comes out of their that is marginally decent is
    due to some Japanese control in the plants and product
    specifications. But the poor quality we've seen in the last 3-4 years
    shows it isn't bullet-proof.
     
    RichA, Aug 16, 2011
    #15
  16. RichA

    RichA Guest

    Yeah, and uranium is aluminum too.
     
    RichA, Aug 16, 2011
    #16
  17. RichA

    RichA Guest

    You are assuming the mold is actually any good and the problem isn't
    happening there, with the equipment. 20 years ago, an optics firm in
    California was turning out terrible products because old mold masters
    were worn. Didn't fix the problem until they replaced them.
    Half the Chinese production used to be (still?) done in their
    backyards over bonfires. That's how they render down old electronics
    to scavenge metals to this day.
     
    RichA, Aug 16, 2011
    #17
  18. RichA

    RichA Guest

    Hey! It's possible there is "aluminum" (as opposed to alumina) in
    Sony camera bodies since they render down old CD's to make them!!
     
    RichA, Aug 16, 2011
    #18
  19. RichA

    RichA Guest

    Only heavy metals and effluents from burned plastic. China is a
    polluted cess-pit.
     
    RichA, Aug 16, 2011
    #19
  20. RichA

    PeterN Guest

    Whoosh!

    Interesting. Just when have you made a distinction in one of your posits
    that are apparently intended to be inflammatory.
     
    PeterN, Aug 16, 2011
    #20
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