Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: Robs homebrew adjustable optics mounts

  1. #1
    Join Date
    Jan 2007
    Location
    Sheepsville, Wales, UK
    Posts
    3,396

    Default Robs homebrew adjustable optics mounts

    This post has been waiting in the wings for a while but I have been prompted to post by a reply by the Doctor to a question on alt.lasers about parts being suitable for kinematic mounts.
    So here is how I have acheived this using cheap or recycled (ie nicked from something else) parts.
    Photos and some description here...
    http://photonlexicon.com/gallery/Homemade-Optics-mounts

    I have built about 4 variants of this design 2 of which can be seen in the last image. The projector shown now incorporates 3. the 2 you see with the dichro mount modded slightly and a third that is turning the beam from my twin DVD diode setup through 90 degrees to point it at the dichro.
    All of the variants I have made have used the same magnetic spring arrangement that relies on the attracting force of pairs of strong magnets to hold the otherwise unsecured adjustable mirror plate to a fixed upright. most use 4 pairs of magnets but the 90 turning mirror for the dual red is a smaller version that uses 1 pair of magnets only.The Dichro mount is made so the upright is lower than the beam path with the optic mounted in a hole drilled in the green firbreglass adjustable portion that is tall enough to put the dichro into the beam path - if that makes sense!
    The magnets are stolen from the focussing part of a cd/dvd drive and are glued inplace with superglue (long before the optics are taken out of thier protective wrappers . The green fibreglass is some really cool and very useful stuff a mate gave me some years ago. its 3mm thick and is the same stuff (but thicker) that PCBs are made out of. It cuts, files, drills and taps with ease and is pretty stable with temperature change. I have also used 2mm aluminium to do the same job.
    The greatest thing with this setup is if the tapped hole in the upright for the adjusting screw is snug enough on the screw - ie the screw holds itself and doesnt flap about you can lift the adjustable plate off, clean the mirror and pop it back on without upsetting adjustment/alignment! Well cool.

    hope you all like my idea.

    Rob

  2. #2
    Join Date
    Feb 2007
    Posts
    33

    Default

    Rob,

    Why do you prefer magnets, rather than compression springs, or perhaps some resilient material such as neoprene, to push the movable plate away from the fixed one?

    Neil

  3. #3
    Join Date
    Jan 2007
    Location
    Sheepsville, Wales, UK
    Posts
    3,396

    Default

    I wouldnt say I prefer. I just had an idea and it seems to work very well using free parts from scrap devices. Plus as I stated the optic can be easily removed and replaced without buggering up alignment. Can you do this with something that uses springs?

    Rob

  4. #4
    Join Date
    Feb 2007
    Posts
    33

    Default

    Oh, now I get it. Very clever. I somehow missed that the magnets are attracting, not repelling. The magnets not only hold it in tension against the adjusting screws, but also hold it in alignment vertically and horizontally. Brilliant!

    Do you use threadlocker, once it's adjusted?

  5. #5
    Join Date
    Jan 2007
    Location
    Florida
    Posts
    4,382

    Default

    Hey Rob,
    Is that G-10 PCB material?
    <edit>
    D'oh! I just read the rest of your post and you said it was. Good stuff to wrk with. MSC sells it by the sheet.
    Last edited by steve-o; 06-15-2007 at 15:04.

  6. #6
    Join Date
    Jan 2007
    Location
    Sheepsville, Wales, UK
    Posts
    3,396

    Default

    Pixpop - up to now i have not used real threadlok though I may well do when I have completed the projector. What I have used to gently hold the screws and other things too - while still allowing for twaeking is a touch of clear nail varnish. it takes a bit to go off - but not too long - holds the threads etc firmly but is easy to clean off and the bond can be broken easily if you need.

    Steve. I dont really know what type it is but it is that sort of material. My mate who gave it me worked in a plant where they made lminate for pcbs. He also gave me some rolled up shett that is copper with about .25mm of fibreglass on it. it was basically one layer from a multi layer board before lamination. This I have not found a use for but will one day. I have used the thick plain board for all kinds as I had 2 sheets about .5m square and I have another thinner piece. I wish I could get some more cos one day it will run out and I will be sad

    Rob

    dont think we have msc over here.....link...?

  7. #7
    Join Date
    Jul 2005
    Location
    Flying over a town near you
    Posts
    1,404

    Default

    Carefull with those neodymium magnets......they will defeat and just generally screw with your scanners if they are close enough !!!! I would use caution with these , but it is a great idea nontheless.............even the resonant field may manifest problems near any cables......
    You are the only one that can make your dreams come true....and the only one that can stop them...A.M. Dietrich

  8. #8
    Join Date
    Mar 2006
    Posts
    2,478

    Default

    While I think magnets have real problems, partly the gathering of dust, as it only takes a tiny amount of ferric dust to make an easy gathering point for all other kinds, I really like the idea that you can remove the entire front part and replace it with another optic with very little effort.

    It won't work on mine though, I've made them too small for that, and they need a compression spring, as the plate is pulled toward the base mount, and must resist shocks, as it will be used in a very small mobile case. My alt.lasers post came up when someone mentioned rubber BB's for sporting guns. I need very small beads, spherical, cylindrical or obloid, around 2.5 mm diameter, a tad longer if cylindrical or obloid, and only 1.6 mm diameter if cylindrical. Cylindrical is ideal for maintaining roughly equal force over a wide range of movement, spherical is ideal for firm, damped maintenance of lateral position. Obloid (rugby balls US footballs, certain antidepressant pills) are the best compromise of both shapes, but the hardest to get, no doubt... Material MUST have excellent recoverability from compression, and must have a long service life, and a combination of elasticity and damping and stiffness like PVC cable sheath. (Can't use PVC though, or any materials that have a plasticiser, because they age and go brittle.) One ideal choice of material is the stuff that 'jetballs' are made of, those things with the amazing bounce and clear bulk with the little coloured whorls inside, but I don't think anyone makes jetballs an 8th of an inch wide, or less. I might be able to do something with Tempflex silicone sealant, but forming that into unsupported shapes is a nightmare, very hard to repeat anything accurately.

    One question: Don't those magnetic mounts have a problem with the two screws they rest on? I can't see how it can strongly favours just one of those points. It has to do this to allow alignment on X and Y, with one corner floating. In my mounts (just 1 cm wide, and a mm or two higher), I have an all brass construction with a pointed pin made from fine brazing rod, very tightly fixed in the brass base part, anchoring the movement, and two very fine screws (thankyou Jem, I'd be up for more, if you're willing) to pull the optic plate (brass, 1/16" thick) against the compressible bead in the corner opposite the pin. Like all kinematic with the rotation centre offset from optic surface centre, alignment makes the beam shift as well as steer, but it won't drift much, and it will be very repeatable and accurate to control. The only reason I haven't completed a mount and taken pics is I don't want to mess around risking wear and damage while experimenting with suboptimal spring methods. I think I posted a model of them here though, somewhere. SketchUp design file, and a picture.

    Suggested use for very thin copper clad fibreglass PCB: capacitive based postition sensors, if you need electronic feedback for automatic postition control and maintenance.
    Last edited by The_Doctor; 06-15-2007 at 23:00.

  9. #9
    Join Date
    Jan 2007
    Location
    Sheepsville, Wales, UK
    Posts
    3,396

    Default

    Hi Doc
    No they dont have a problem with 2 screws. The reason there is 2 is that originally there was a single screw but I found that during adjustment sometimes the plate would be pulled in the wrong direction by the magnets and the open corner would allow the plate to hinge in the wrong direction - if you know what I mean. I put the extra screw in just as a support to hold the plate in the right area - as soon as adjustment begins there is no contact with this screw. The reason this happens I think is down to positioning, strength and number of magnets and this is what im working on now - mark II.
    The original idea was to use a ball bearing as the corner pivot but with the magnets glued to the surface of the parts I would have needed a sphere with quite a large (and unpractical) diameter to allow clearance. So MKII will use a 3 or 4 mm ball bearing - which i havent found yet (but equally havent looked too hard) and will see more scientific positioning of the magnets which will have thier surfaces flush or almost flush with the upright and moveable portion by using milled slots to sink them in. I am also likely to use epoxy to mount them as opposed to super glue and had considered putting a plastic sticker over them to collect any debris that might attach to the magnets - for easier cleaning. Will post pix and details when I have something worth showing.

    Mech - as for problems using these magnets - I know they have the potential to cause probs but up to now I have not had any issues from that but its obviously something to bear in mind. The layout as it stands has no cables especially not signal cables near where the mags are, its the scanners that are threatend the most and the nearest one lies roughly 50mm from the magnets. What I might do however is look at the ilda tp both with and without magnets in place and see if there is any noticable difference.

    Rob

  10. #10
    Join Date
    Nov 2005
    Location
    Melbourne, Australia
    Posts
    3,695

    Default

    magnets, what a clever idea
    KVANT Australian projector sales
    https://www.facebook.com/kvantaus/

    Lasershowparts- Laser Parts at great prices
    https://www.facebook.com/lasershowparts/

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •