Need information or a procedure in how to inspect mylars. I have no idea how to set up and inspect to verify dimensions, grid lines and grid points. :frust:

Can anyone help with this one?

Need information or a procedure in how to inspect mylars. I have no idea how to set up and inspect to verify dimensions, grid lines and grid points. :frust:

I assume that you're referring to mylar overlays used on optical comparators? If so, you can use the comparator (assuming proper calibration) to verify the dimensioning and locations of gridlines, etc.. You can double-check by using the overlays to measure actual parts and then doing using another method to measure them to verify consilience.

Thank you Jim on your reply. I was not clear it's mylar drawings

Thank you Jim on your reply. I was not clear it's mylar drawings
Used for what purpose?

When I worked in aerospace, I made mylar layout drawings for the placement of fastener holes, and for verifying other feature locations. They were meant to be used by fabricators on the shop floor, and the quality people put them in the quality system as "for reference only". They can't be verified. If this is the type of mylar you mean, I wish there was a better answer.

Used for what purpose?

Usually for drawing reproduction purposes.

Mylars are often required as part of (civil) engineering-type contracts.

Stijloor.

Usually for drawing reproduction purposes.

Mylars are often required as part of (civil) engineering-type contracts.

Stijloor.

I understand the use of mylar as a drawing medium; what I don't understand is why they (as opposed to drawings on vellum or plain paper) should need to be verified in the way the OP is asking about.

I understand the use of mylar as a drawing medium; what I don't understand is why they (as opposed to drawings on vellum or plain paper) should need to be verified in the way the OP is asking about.

The OP needs to further clarify if he expects us to help him...

Stijloor.

Thank you Jim on your reply. I was not clear it's mylar drawings

When I worked for a company that mainly made sheet metal we used Mylars to perform the actual inspection of the sheet metal parts. They were to Scale so we would lay the Mylar over the flat pattern and verify that each dimension was correct.

This might not be what you were looking for, but that is the only experience I have had with Mylars.

Need information or a procedure in how to inspect mylars. I have no idea how to set up and inspect to verify dimensions, grid lines and grid points. :frust:

Mylar is a trade name for PET_film_(biaxially_oriented) (biaxially-oriented polythelene terepthalate) originally developed by DuPont, and has multiple usage viz: flexible packaging, thermal/electric insulation, PCBs, accoustic etcetra. It is a light weight plastic that resists 'swelling' or 'shinking' in normal temprature and humidity.

A drawing printed on this material, accurately retains the dimensions, irrespective whether the dimensions are stated or not. If dimensions of a slot are not given, it will be exact if measured on the drawing. Since the material is transparent and flexible, it allows for laying out contour surfaces. Coury has also shared his experience on this subject.

OP may give more input wrt what exactly he wants information upon.

Umang :D

For optical comparator mylars, I like to add to the mylar standard features, such as a 1" block with centerlines. Then I use gage blocks or calibrated digital readout to to verify the block to ensure the printout was exact (enough), and still OK over time.

For a table top drawing, to verify locations you could use the same approach - corner to corner to standard feature or layout the actual features (the hard way) with a calibrated gage with proper 10:1 (or 4:1 if you prescribe to that rationale) resolution.

I worked for a manufacturer who was also an FAA repair station. The Quality Manager there was a stickler for calibration of anything and everything. He told me that the mylar layout drawings could not be called 'calibrated'. The laser beam width of the printer we created them on was "about" .010" wide, and the accuracy could be checked on a comparator if the mylar was small enough (we made them as big as a D size sheet of paper), but use on the shop floor even once made them unverifiable. If a contour was being verified we printed a max and min contour based on print allowances, and the fabricator on the floor had to trim detail parts to the inside of the max line. If the detail was inside of the min line they could beat on the part a little to try to make it fit, but if it wouldn't, it was scrap. Quality people there were adamant that such mylar devices were reference tools, not gauges.

The Quality Manager there was a stickler for calibration of anything and everything. He told me that the mylar layout drawings could not be called 'calibrated'. Quality people there were adamant that such mylar devices were reference tools, not gauges.

I would disagree. It can be calibrated - whether it passes calibration for a particular use may be debated, but that is not the same as not being able to be calibrated. It can be checked to a traceable standard.

Thank you all.

I have not been clear with my posting. We produce commercial, military, space aircrafts for various suppliers so we have thousand’s of Mylar’s (MLO). Customer wants to see evidence that we inspect the MLO prior to use and thru our scheduled periodic inspection and our criteria for inspecting the MLO. My finding is as follows
(Lack of control on MLO (PCM/Mylar) tools uses as Media of Inspection.
* No objective evidence that MLO periodic check was performed
* No process to perform MLO grid check/dimensional targets check prior to use. )

Lucky me I was given the task to come up with a procedure or work instruction to inspect, record and identify such results. Creating ID labels a spread sheet to log and record dates used and inspected I have all ready created. I'm stuck on coming up with a procedure that shows how I go about inspecting them.

Thank you all.

I have not been clear with my posting. We produce commercial, military, space aircrafts for various suppliers so we have thousand’s of Mylar’s (MLO). Customer wants to see evidence that we inspect the MLO prior to use and thru our scheduled periodic inspection and our criteria for inspecting the MLO. My finding is as follows
(Lack of control on MLO (PCM/Mylar) tools uses as Media of Inspection.
* No objective evidence that MLO periodic check was performed
* No process to perform MLO grid check/dimensional targets check prior to use. )

Lucky me I was given the task to come up with a procedure or work instruction to inspect, record and identify such results. Creating ID labels a spread sheet to log and record dates used and inspected I have all ready created. I'm stuck on coming up with a procedure that shows how I go about inspecting them.

Have you looked here (http://www.google.com/custom?hl=en&client=pub-1385417534940691&channel=6124086287&cof=FORID%3A1%3BGL%3A1%3BS%3Ahttp%3A%2F%2FElsmar.com%2FForums%2F%3BL%3Ahttp%3A%2F%2Felsmar.com%2Fpng%2Fheader-G-search.png%3BLH%3A50%3BLW%3A350%3BLBGC%3A000099%3BT%3A%230000ff%3BLC%3A%23000000%3BVLC%3A%23663399%3BDIV%3A%23336699%3B&domains=Elsmar.com&ie=ISO-8859-1&oe=ISO-8859-1&q=inspecting+mylar&btnG=Search&sitesearch=Elsmar.com)?

Stijloor.

I would disagree. It can be calibrated - whether it passes calibration for a particular use may be debated, but that is not the same as not being able to be calibrated. It can be checked to a traceable standard.



Is ther such a traceable standard?

Is ther such a traceable standard?

There's no specific traceable standard as such. If whatever you measure it with is properly calibrated to traceable standards, the calibration of the mylar will be traceable.