Scannermax 506s

Just to try to limit confusion about substrate, because I mentioned it.. I mentioned 'shinier', not related to durability. The flatter the mirror, the better. Roughness will help bonding (same reason people rough up a surface before gluing it), but not help good reflection, so there's a conflict of interests because a good polish reduces the available atomic bonds by reducing surface area to a minimum. So good adhesion depends on the chemical bonds available. This does not imply a direct relation with substrate durability, and I didn't think, or say, that it did.

For example, acrylic would make for lousy durability but bonding might be excellent because carbon in compounds usually leaves lots of free atomic bonds.

If anything, the relation is inverted as far as I know. If a mirror were made of diamond it would be very durable, but so few bonds available might make it hard to stick a coating on it. I don't know what this might mean for silicon mirrors but I guess those might be hard to make coatings stick to as well.

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Originally Posted by kecked

ps: if I use fc in the future TO CLEAN I'll use the thread removal method rather than the tape method. I THINK THE TAPE JUST RIPPED IT RIGHT OFF.

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Why not just put the tape on sticky side up? (ie non adhesive side down). That way it can't adhere to the mirror. Either that or if FC doesn't set fast enough to allow that, (never used it so don't know the drying speed), buy some of that low tack masking tape that's specially design to pull away from surfaces with a minimum of force.

It seems to me though that in order to avoid residue, you don't want anything adhering to the mirror surface anyway. I'm sure some people on here recommended using paper / card tabs before but you'd have to cheack previous threads (again though we're back to setting time).

If you have to use adhesive tape wouldn't it be a good idea to bond it to the very end of rotor shaft rather than the mirror surface and just run FC onto the rotor end? (Just thinking out loud).

Al, you apply FC and then let it dry. Then you apply the tape, which needs to be relatively sticky otherwise it doesn't pull the FC off.
The tape should never come into contact with the mirror surface, otherwise you'd be leaving residue behind, which is sort of counterintuitive.

too bad you can't make the mirror from solid silver or some alloy. Then it would never wear out and could be repolished. Problem is the weight and ductility. I don't think I'll ever see this problem again. While I'm going back to solvent, if you do us fc I suggest putting dental floss in it as it dries and pulling the fc off that way. They describe that method in the handout they give with it. See I had thought the mirror had a protective sputter on it of silicon oxide that would have prevented pulling off the surface ever. Some first surface mirrors are really near first surface and have an atomic thick coat of ceramic oxide to protect the silver from tarnish and damage. Had that been the case it might as well as been a solid piece. By the way you can dope silicon easily to make the surface atomically active for the bonding of a surface. You might have to use a substrate metal first and then the final silver like a dielectric filter but it can be done by sputtering and it's cheap. This process is done when making circuits. I guess these mirrors are made from wafer silicon but there must be more to it because that material while hard is really brittle. If you hit it it will shatter. I would think there must be a metal finger along the back to help support he mirror and prevent it from shattering if hit. An other likely design has the silicon on a full nickle backing. This is done for IC's substrates many times but is generally silicon over oxide over doping over metal over oxide.

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Originally Posted by norty303

The tape should never come into contact with the mirror surface, otherwise you'd be leaving residue behind, which is sort of counterintuitive.

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That's what I thought. It is strange then as obviously it could only have been the FC that lifted the coating not the tape. There has to have been a surface defect therefore surely if no-one has had this issue before. My own experience of dope, which is obviously similar, is the adhesion is never that great to hard surfaces. It's only where you get surface penetration where you start to get real grip.

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Originally Posted by Pangolin

Words instead of pictures... sorry, I'm just not "seeing it". I don't know if it is old age or what, but words just don't do it any more.

I can interpret "optimal beam center height" in so many ways... Please post a picture.

If you're talking about the entrance aperture (which is a standard terminology for mounted X-Y galvanometer systems), this is 0.715 inches.

Bill

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Hi Bill,

As most of us here are engineers and allot are international, I think it would be better to use the metric system and use mm instead of inches, as metric units are used almost universally in science.

I also noticed the datasheets of the scanners are inconsequent, the bearings are measured in mm but the mirrors in inches.

I think all of us know how big 19 mm is, but I (and most others here) have no clue what 0.751 inch is without using a calculator.


(the Dutch made a big mistake selling New York to the British :p )

Yeah i remember the Cow balloon from a dutch music band called Mannekoor karrespoor. The size was ordered in cm but it got delivered in inches. It was exact 2.54 times to big. We call that ooops *retardo

scannermirrors are also in mm and size beam also measured in mm. Would be damn anoying when the scanner mirror size was standard given in inches and the beamsize in mm. >:)

First Contact is not "model airplane dope". Its a blend of four polymers and nitrocellulose. The long molecule polymers make the strength component allowing for easier removal.

Butyl compounds are added to airplane dope as a bonding agent, and you do not want the bonding agent on the glass. Airplane dope hardens somewhat, First contact does not.
Materials that harden may cause local stress on the glass, causing the coating to lift.

Other agents are added to "airplane dope" to increase ignition temperature etc.

I tried it, before I ended my model airplane career, and plane dope strongly bonds to glass. In fact it is the basis for the older "glass paints"


Steve

I agree with the requests to specify everything in metric dimensions, but I find it funny that it matters much. I am used to converting back and forth all the time especially when I am involved in a project and it's too unpleasant to spend much time outside because its below zero.

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I am used to converting back and forth all the time

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This is because you are American. The rest of the world isn't ;) :p

Are your inches even the same as ours, or is it a similar situation to the gallon and mile?