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Thread: precision positioning needed for shifting the position of lenses

  1. #1
    Join Date
    Jan 2018
    Posts
    14

    Default precision positioning needed for shifting the position of lenses

    This topic was originally started in another forum but I have a feeling people here are more knowledgeable and can help find a solution.


    Need to automate the X,Y movement of a lens parallel to another lens.
    Need 1024 steps if using a stepper motor.
    Travel distance is 7.5 mm in both axis.
    Needs speed that will allow to go from one edge to the next in 1/3 seconds


    As others pointed out,
    1024 steps to move 7.5 mm = 136.5333 steps per mm.
    1024 steps in 333 ms = 3072 steps/sec
    Moving that distance in 333 ms means 22.5 mm/sec movement speed.


    For comparison a CD disc has 625 lines per mm, so it is only logical to assume the motors and controllers mass produced for CD drives exceed my requirement of 136.5333 steps per mm, right? Not to mention DVD or BD disc drives will be even more precise.


    So the idea came to my mind to use a screw drive motor for CD drives and good stepper drivers which became very affordable thanks to popularity of Arduino and desktop 3d printers.
    https://www.ebay.com.au/itm/301740290708?ul_noapp=true


    Not sure if the speed requirements can be met (3072 steps/sec, 22.5 mm/sec movement). I know the laser module inside a disc drive can jump from one point to the next pretty fast but I don?t know if just that jump is enough to get to the exact required line.


    What do you think? Could it work?
    Other options might be motors used for camera lens focusing and zooming.


    I also found some OEM suppliers of screw drive motors but they never seem to mention exact use cases.
    https://www.aliexpress.com/wholesale...ew+Rod+Stepper


    https://www.alibaba.com/product-deta...636137e3vNHKfx


    https://www.alibaba.com/product-deta...636137e3vNHKfx


    https://ru.aliexpress.com/item/Micro...ceBeautifyAB=0


    Someone suggested an alternative option of taking a XY Axis Stage and adding pulleys and motors to it but why reinvent the wheel if it can be achieved by off the shelf parts and less expensive.

  2. #2
    Join Date
    Oct 2012
    Location
    Germany
    Posts
    1,478

    Default

    Quote Originally Posted by widaxi View Post
    ...
    Someone suggested an alternative option of taking a XY Axis Stage and adding pulleys and motors to it but why reinvent the wheel if it can be achieved by off the shelf parts and less expensive.
    ... this "someone" could be me

    In the past I've developed several micro- and nano-positioners for optics, tools and other components for micro-assembly -- but this was more focussed on high precision, than speed.

    The small steppers used in DVD-drives aren't strong enough to give good dynamics, so my idea was to use bigger, stronger motors in an "external setup" and feed steel wires to the lens for positionig it in the active area ...

    Viktor

  3. #3
    Join Date
    Jun 2009
    Location
    St. Louis, MO
    Posts
    1,198

    Default

    You'll likely need to ramp the stepper up to speed. See:

    https://www.silabs.com/products/deve...ference-design

    This page calculates the top speed of a stepper given current induction and voltage:

    http://www.daycounter.com/Calculator...lculator.phtml

    PorteEscap makes a disk magnet motor that's similar to a stepper, but faster. I had one ramped up and screaming at 6000 RPM with a 3D printer stepper driver - with the emphasis on screaming.
    "There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso

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