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What type of Mylar is used as inspection media templates?

What type of Mylar is used as inspection media templates?

(OP)
I worked at General Dynamics-Convair on the MD-11 and we used mylar templates for parts (like longerons) that had loft or other features that were difficult to inspect out in the shop. I believe we used .005-.007" thick mylar but recently discovered that there are ~ 140 different types of mylar and have no idea what we used 23-years ago. I read D6-51991 and it wasn't very helpful.
I'd like to use this method of inspection on parts that have +/-.030 tolerance...well, more like distinguishing between different revisions that we receive from suppliers. These parts usually involve a bolt hole pattern and I have no problem drilling two diagonally opposed holes to orient the mylar... I'm really trying to keep this sort of thing off of my cmm.

Any feedback on this matter would be greatly appreciated!

Thanks in advance.

Tony Adkins
Tadkins@RELL.com

RE: What type of Mylar is used as inspection media templates?

(OP)
IRstuff,
Yes, I did see that there are companies that offer this service (and did, in fact, see the StenTech link you'd sent me). However, I was looking to buy the mylar and make our own here as a cost-saving inspection media and wanted to make them here at our facility. We have an HP T520-36 Inkjet "plotter" that can use mylar up to .010" thick. I've been given the funds to pursue my idea, only to discover that there are over 140 different types of mylar. I'm pretty sure that I want .005" thick and recall that it was a bit like vellum, in that it was slightly opaque so that the printed lines were clear but still allowed the user to see the part beneath it.
We do thousands of parts at detail, sub-assembly and assembly levels where we could use this medium, especially when sorting parts of various revision levels. We have toolmakers, but that's time, design and cost; I wanted this for on-the-fly sorting, awkward configurations, etc., rather than putting it on my cmm, so I actually need to generate these templates here. I'm not sure that StenTech would tell me the material I should use but I'll ask. I've contacted C.S. Clyde but the young lady I spoke to had no idea what I was talking about. Having templates made by a vendor would defeat my purpose but thanks for the suggestion.

Tony Adkins

RE: What type of Mylar is used as inspection media templates?

Tony,
I too used to work in building 1 on the MD11 production, I thought I knew the thickness of Mylar but was not sure , so I consulted with a friend of mine who was an inspector there. She said on smaller sheets up to D size .005" was used. On the frame sized parts .010" and on some Longeron parts over 15'-0" long .03" was used. the .03 templates were kept in the loft and not normally allowed on the shop floor. Does this help?
B.E.

You are judged not by what you know, but by what you can do.

RE: What type of Mylar is used as inspection media templates?

(OP)
Berkshire,
To a degree, it helps. Our plotter will accept up to .010" thickness, although I was thinking that the mylars for longerons were thinner (I worked in buildings 1, 2 & 3 (if I have the numbers right). I worked as class 4 inspector on MD-11, Tomahawks, Cruise Missiles and ACM's, then class 2 as a machined parts inspector. Bobby Mota was my 1st MD-11 (C-D 1/3 fixtures) boss, then Clyde Kominski for 1/10 panels & doors after cruise missiles, tomahawks and ACM's. I just need to know what type of mylar, as I'm using it for a slightly different inspection purpose. I think .005-.007" thick is fine.
I program a CMM & do some reverse engineering & design fixtures and putting everything on the cmm isn't always cost-effective, if you know what I mean. I'm not dealing with loft but still...at least I'm not an ISO management rep anymore, lol...what a thankless job.
We may know one another, if I may ask your name: Tadkins@rell.com

Tony L. Adkins

RE: What type of Mylar is used as inspection media templates?

I suggest that your CAD file include a dimension to be printed on the actual mylar, just to make sure that the mylar was printed to the size desired.

I used to make cut/trim templates for tubing parts made of very expensive material, and got a few 'scaled to fit', so our SOP evolved to include measuring the dimension on the template, and signing the template.

Mike Halloran
Pembroke Pines, FL, USA

RE: What type of Mylar is used as inspection media templates?

(OP)
IRstuff: the sizes will vary to accommodate the large assortment of parts but on average for my use, I'd say 17-20" diameter? I'm aware of the +/-.030 tolerance limit but some of this stuff comes to sorting parts that have a 5-degree rotation in one hole in a bolt circle or a 7-degree rotation of a notch.
I may approach the VP about go/nogo for his PCB's (I'm strictly mechanical and he's electrical, RF, etc).

Tony

RE: What type of Mylar is used as inspection media templates?

(OP)
Mike,
We already did some testing on our plotter and the big secret seems to be to not print it in a b/p template, lol.
I think your suggestions are good ones; I'll make sure to incorporate them into our procedure. I decided a while back (and this is, perhaps a result of having done reverse engineering) to validate our own mylar templates by having a part that was measured using a different method (and a worst-acceptable one if I can manage that) and back-check the mylar to that.

Tony

RE: What type of Mylar is used as inspection media templates?

Scottishgent,
Tony,
I do not think we met, I was working as a supervision candidate in building 1, my General was Ron Thomas , I was for the most part on a one month rotation around the departments they would run you to one day short of getting the classification . I worked in Hydroforming and hand straightening , I worked in disposable toolmaking under Ed White, I worked in the routing area, then in press brake forming, then the large stretch forming area, I finished up in the hand straightening section of the large stretch forming area, and had just finished my supervisor training when they pulled the rug out from everybody. At that time we had generals busting back to milling machine operators to keep their jobs for a while, to say the least it was ugly.
B.E.

You are judged not by what you know, but by what you can do.

RE: What type of Mylar is used as inspection media templates?

I've never seen roll mylar film thicker than 5 mil, and most plotter roll mylar films are 3-4 mil. Mylar film media always has a matte finish on at least one side in order to allow the ink printing to adhere. Most plotter mylar roll media now has a double matte finish to allow printing on either side. It's the matte finish that makes the mylar film opaque.

When using your drafting room plotter to create an inspection template, you still need to validate the accuracy of each template after printing, since you are not likely using a calibrated plotter to produce them.

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