Material suggestions

[MacGyverS2000]

I'm looking for materials suggestions for a somewhat unique app... camera iris leaves. We need material that's 3 mils thick (0.003"), opaque to visible and near-IR light, has good dimensional stability (the leaf is <1" across), and good wear resistance (dust inside of the lens is a no-no).

Any suggestions? We've looked at PET, but at those thicknesses we're told it's not opaque. We're currently looking into FR-4 with carbon black, but I'm not confidant much will come out of that one.

An off-the-shelf material would be best as we don't want to have someone manufacture 1,000 pounds of material (minimums) for what amounts to a few ounces of leaves.

Thanks!


Dan - Owner

http://www.Hi-TecDesigns.com

 

[CoryPad]

Why not metal?

 

[Pud]

Hi Dan,

Must they be plastic? My immediate thought would be shim steel, wire cut or chemically etched profile, possibly black phosphated finish for lubricity and reduced reflections. Might wire 50/100 at a time by stacking sheets.

I suspect .003" thick plastic 100% opaque will be a tough call.

Cheers

Harry

http://www.tynevalleyplastics.co.uk

 

[MacGyverS2000]

Cory/Harry,

We are leaning towards (and I'm doing my best to push them towards) a photo-etched metal leaf. I do not know why plastic was the initial material suggestion, but it's irrelevant in our group... only "what's next" seems to matter Things change fast around here, so one moment you're looking for a solution using spec 'X', the next moment the spec is now 'Y'.


Dan - Owner

http://www.Hi-TecDesigns.com

 

[Pud]

I also doubt if you'll find any plastic in .003" sheet that's any good for wear. If FR4 is Lexan sheet, don't bother. It's a crap bearing material and also very "draggy" (don't know the tech term, but I'm sure you get the gist!)

Metal way to go - plan "Z"

Harry

http://www.tynevalleyplastics.co.uk

 

[patprimmer]

Third vote for metal. I think plastic is a plan for disaster in this application.



Regards
Pat
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[MacGyverS2000]

Unfortunately we don't know what material the camera manufacturer is currently using, but it's a plastic of some form and it's opaque... it has all of the desirable properties, but it has too much slop in the guide channels leading to flutter in the image at high levels of vibration (what we're trying to avoid with a new leaf).

Well, I've made my recommendation and it's anybody's guess on whether it will be accepted.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Pud]

Dan,

Another reason not to use plastic! - It doesn't actually work!!

I'm soooo pleased I don't have "management". Note the lower case "m"

H

http://www.tynevalleyplastics.co.uk

 

[patprimmer]

If it MUST be plastic, carbon fibre/epoxy is your best bet

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[MacGyverS2000]

Well, they're sticking with plastic... I have no idea why <rolleyes>

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Pud]

Have you tried the link at the bottom of this page (Plastic Sheet)? - Acetal less than .005" thick. Have to register so I haven't gone further.

Harry

http://www.tynevalleyplastics.co.uk

 

[patprimmer]

0.003" is film not sheet. I think typical builders film for use under concrete is about that thick.

Regards
Pat
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[Pud]

Acetal for builder's film? Dan says he wanted .003" thick (which is, as you say, film effectively.

I've found CF sheet but it's 0.8mm thick...

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=4927101

Harry

http://www.tynevalleyplastics.co.uk

 

[btrueblood]

"I'm soooo pleased I don't have "management". Note the lower case "m"

Pud, you say you're married, how can you say you don't have management? Or is that what gives the capital...

One more vote for steel. A certain brand of high-speed cameras used aluminum for shutter leaves, they would erode and gall(?) over time. Can't recall the name of the camera brand, but I know the ones that worked (Hycam?) used steel.

 

[Pud]

Steel, steel, and more steel!

How are you intending to cut the plastic sheet assuming you can source it? Not many processes cut plastic without burrs (expensive water jet springs to mind if you'll excuse the pun!) Tell them plastic rubbing on plastic generates a few million volts of static which will bu**er the CCD thingy! Anything! Make it up! You're an Engineer remember - you tell the truth!!

Ben, we (that is, my lovely* wife and I) own our business - the amazing* Gill is Managing Director (I think you would call it CEO), but as she's out shopping or with her other girly business owners' clique (aka drinking club), most of the time....I have POWER!!!

btw - I don't say I'm married - the wife says it!!

Harry

* She sometime reads this site - must remember to change password.

http://www.tynevalleyplastics.co.uk

 

[MacGyverS2000]

Pud,

Unfortunately, everyone in the group is an "engineer". We're all degreed in one form or another, but I use the quotes because all too often the group falls into the "I didn't think of it so I'm going to ignore it" mindset. Justification for decisions is only provided when continually pressed for it, and even then it's often with an attitude of "why do you care, the decision has already been made?".

We also appear to have the bad habit of taking the expensive route without properly investigating less expensive routes. For example, instead of using a common flat bed scanner that provides nearly 0.1mil accuracy in its scans, we're sending things out to be laser scanned by another company at God knows what kind of cost... but hey, "They're local!", so it's a fast turn-around! <rolleyes> I was told: 1) the scanners don't give that kind of accuracy, and 2) we need better accuracy than that. <sigh> I guess the fact that when we have them manufactured (either laser or waterjet) the accuracy won't be anywhere near 0.1mils is irrelevant.

All of that said, I was informed simply "We're sticking with plastic". It's days like that I wish I wasn't an engineer... ignorance is bliss.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Pud]

Dan, I feel for you...I note you spelled engineer with a lower case "e".

If I was anyway religious I would even pray for you...

Good luck.

H

http://www.tynevalleyplastics.co.uk

 

[patprimmer]

What will be the problems that arise out of a need to triple the section thickness to get the required section modulus.

You have already mentioned the problem you will acquire due to dust from wear.

In such a political situation, I would be inclined to fire of a memo, that firstly expresses respect for seniority and the right to make decisions nd my willingness to take direction, but I would then say, even though I will take the direction, I am concerned I might suffer repercussions when the part fails for the following reasons.

Regards
Pat
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