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What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
I am a product engineer that makes drawings for parts that need to be vapor polished. In the past I have received parts that were spec’ed to be vapor polished, yet showed up not polished. The parts were buffed slightly so it was a bit hard to tell if they have been polished or not, this was the first time I had ordered the part, so it was hard to tell if it was polished or not. (Very small part, about the diameter of a BIC pen and a thickness of 0.053"). I used the parts thinking they were polished. Later to learn from the vendor they were not. This problem got sorted out, but in the future inspection will not be done by me, it will be done by a non-technical QA employee. How do I make sure they know what a polished part looks like? Give them a polished and a non-polished piece and allow them to do a visual comparison? My company is very small (I am 1 of 2 engineers) so we don't have a lot of cash for inspection equipment.

Thanks for any insight.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Perhaps you can rely on your supplier more heavily. Can they provide a QA certification or statement on their end that the part has been vapor polished? Then your QA employee will simply verify the receipt of the cert.

-Dustin
Professional Engineer
Pretty good with SolidWorks

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
Thats what I wanted to do, but the engineer I work with brought up the point that the vendor already lied about polishing the part the first time, what makes us 100% sure they won't, or any other vendor won't in the future?

I hate working with vendors that make me have to think like this, but it is simply the truth. Maybe it is becuase we are small fish, so we need to use small fish vendors that are not as stellar as other companies that we simply can't afford.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Dennisbernal91z:
Include in your PO and contract paperwork an item which allows you to pick a testing lab of your choice, X number of random selected parts, you pick them, for verification and certification, at a fixed price to the supplier. Non-conformance has a significant penalty cost to the supplier. And, you have already arranged this inspection and testing, and its cost with the local lab of your choice.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

how do your inspectors verify that a part made in house has been polished ? hopefully not asking the guy if he did it !?

how critical to the performance of the part is the polishing ? how critical is the function of the part ? (if it fails, can it kill people?)

if you can't trust your vendors, get different vendors! if you have to work with them ('cause their your boss' buddies) get them to pay for 3rd party inspection. (how will the 3rd party inspection comfirm the polishing?)

Quando Omni Flunkus Moritati

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

You say this guy "already lied about polishing the part," but that's only the lie you caught him in. Did they pay reparations? Why would you go back at all to someone who has already been proven to be dishonest? What assurances do you have that they won't or haven't lied about something else, like material composition or anneal?

TTFN
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RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Vapor polishing is generally done for optical reasons, so it would seem that the inspection would be optical in nature.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

is there a difference between something at is polished and something that looks polished ?

how do you know if a surface is 128, 64, or 256 (surface roughness)?

Quando Omni Flunkus Moritati

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
OK, a lot of questions here... I will try to answer you all in a nut shell so I do not drag on.

My origional question was about how to spec out vapor polish and that the person inspecting parts is not an engineer. That question still stands. First are there people here that spec out polish of some kind and need to inspect their parts? If so how is this inspected?

I know I can use outside vendors to verify things, I will tell you right now that is 100% out of the question for how things are run here. Simply put, never ever going to happen. Cost and time is far to great. No parts have any potential to hurt anyone, ever. We always strive to look for new competent vendors, but what about if you have been using a vendor for 10 years with no issue and all of a sudden they make a mistake? You walk away? If that is how you work you will spend all you time looking for vendors, and not designing products. As for the company that messed up, no, they did not pay anything. That is not part of my job though, I do not deal with what happens after the failure, I just try and guarantee that they don't happen as best I can (practically for free). It is a whole differnt mind set when working for a fast moving small company, there is little time to do inspections and things like that. For example, when I make a drawing for a stainless steel probe that must be 316 to avoid rusting how do I verify that it is 316? I use a COC (Certificate of Compliance). That is all I can rely on, I do not have time of $ to send the parts out for verification.

Does no one else have these issues? All your companies have the capital to get evey part analyzed before use to ensure that it is truly the material you speced out? Same goes for plastics, how to confirm that White ABS is not actually White PVC. They look extreamly similar.

I guess that is my main point, how do others verify or feel confident about things that can not be checked???

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

i quite agree that a CoC doc (even one from China) is supposed to show that the part conforms to the drwg. in your case it sounds like a vendor whom you have a long and positive relationship with screwed up once; not sure if it is nice or foolish that they admitted it to you.

i understand narrow margins and no time to check.

the person doing the inspection doesn't need to be an engineer, these days they only need to be able to read ! (CoC, tick; more along)

a lot of things look alike (different steel tempers and alloys, plastics, etc) ... there are no doubt tests for comfirming this type of plastic or that, etc; but you don't have time for that. you trust the CoC and that's the end of it.

remember everyone, and i mean Everyone, was caught out some years back with "bogus bolts" ... H11 bolts that didn't meet spec.

Quando Omni Flunkus Moritati

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

I don't understand why anyone would want vapor polishing (partial dissolution) rather than mechanical polishing, or, infinitely better, polishing the mold and eliminating the secondary operation altogether.

Mike Halloran
Pembroke Pines, FL, USA

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
rb1957: Thank you for understanding where I am coming from.

I have had vendors polish things that were not supposed to be polished too, simply because they, and I quote "polish and anneal all acrylic parts". Just strange. Of course we can stop using them someday, but that is not my question, my question is how do you stop them during inspection the first time, not leave them after the damage is done.

Maybe there is no way, without spending $ and time. Just wanted to gauge the rest of you guys to see if there was perhaps something I was not thinking of.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
Parts are machined, not molded. The internal structure is critical for the visual appearance of the part for customers and for ease of final assembly.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

How to spec vapor polish on the drawing: "Finish: Vapor Polish" Hopefully there is a specification or process that can be added to the note.

How to inspect that something has been made correctly: You specify vapor polish for a reason, right? There is something quantifiable that works correctly when the part is vapor polished and doesn't work correctly when the part is not vapor polished. So you perform an inspection to measure that quantifiable thing. You need to identify what that quantifiable thing is, then perhaps someone can suggest you to inspect for it.

Inspector is not an engineer: Then you write an inspection procedure at a level of detail appropriate for their level of education and train them on how to perform the procedure.

How to perform an inspection for free: Don't do an inspection.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Quote:

I guess that is my main point, how do others verify or feel confident about things that can not be checked???

This is not the right question to ask.

Anything can be checked. Some things more easily than others.

What you want to ask is "How can I feel confident that things are made correctly so that I don't have to check each and every one?"

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

It all costs time and therefore money. If you are really worried, call up their QA and Manufacturing Engineers and have them send copies of the process they will follow in making parts for you. If they are a good supplier, they probably will, presuming the cost of doing so still lets them make money making the part.


"how do others verify or feel confident about things that can not be checked???"

You don't, particularly if your supplier is not cooperative. It also doesn't matter how long you've used them. If they make a mistake, that's one thing. If they actually lie about it, you can elevate the problem through their management, but if there is no resolution, run away. There are enough good suppliers that can and will do a job as quoted, per drawing, for the same or less cost than one that ships unuseable items.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

dennisbernal91z,

This is one of the reasons you specify the results, not the process.

Specify how shiny and transparent your part must be. You do not care how they do it. Now, the thing is checkable.

--
JHG

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
Ok let me touch on a few points here from different people. A lot of stuff is being said and it is a bit hard to sort out since in the end no one knows exaclty what I am talking about and I have not described it all perfectly.

So let me start at the top and give a little more detail since everything everyone has stated is quite obviouse to everyone else in here, as well as me.

Here we go:

The part is made from clear cast acrylic, is about 0.240" is diameter x 0.053" thick. It has some small features to it like ultrasonic energy directors, flash traps and a thru hole of 0.080". Looks a lot like the smallest pieces LEGO makes. During my prototype phase of my project I speced out Vapor Polish in my "Finish" box of my drawing. This is what I always do. I got the parts from a very trusted supplier that does good work. The got me the parts and I could not tell if they were polished or not seeing as how they were so small and I figured maybe it is hard to polish such a small part well. I used them and they worked. Later on after buying the parts again, this time my purchasing department used a vendor with a shorter lead time, the part parts showed up looking VERY clear. This was the first time I thought to myself. "Maybe the first lot I got was not polished". The polishing ended up making my parts weld slightly worse. The parts that were NOT made to the drawing actually worked better! So of course I changed my drawing, but that is not why I started this thread. What I wanted to know is that for something that is clearly subjective, like clarity in this instance, how do people spec things out? Of course there are ways to spec anything in the world, but I can't make this thing cost more than $2, and I only need to buy a couple hundred at a time. The part is small, and my company is not going to send the parts out for testing, we are also not going to buy expensive equipment to test for clarity. Those ideas are literally on another planet in terms of something a company like this would ever spend its money on. Also it not so critical that someone could ever get hurt or anything like that. It is litterally like making a LEGO that needs to be clear, (or actually not clear, due to the welding), not to any specific spec, just clear. We can't test this and I can't expect the QA person to know what the correct level of clear is. Can I? I have thought of setting up a part catalouge that shows how polished parts should look. This would give a gold standard, and if a part comes in not looking like the standard the lot can be failed, or engineering can be called to confirm the failure?

Anyways, I have gone on long enough. I have so much more to ask but feel like this example is maybe a bit too convoluted to get thru here. General consesuse seems to be test or find a new vendor, or to add a clarity spec. Something I can't even measure. Maybe the gold standard and training of the QA inspector is the way to go... or only way to go given the constraints I have...

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

do you want the part to be clear (there's got to be a mil-spec for that) or weldable? is it important for the final product's function that the part is clear, or is it an appearance thing? often parts are prototyped so the best way to do things is developed over time (as you've discovered, unpolished makes for better welding).

i think it's a problem with out-sourcing ... it's hard to have the discussions about how a part is going to be used, what's better for the ultimate product ? with out-sourcing, the vendor gets the drwg and makes it; sure sometimes the vendor works with the prime to develop the part (but that often breaks down into squabbles over SoW and cost).

Quando Omni Flunkus Moritati

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Give them a laser pointer and do some sort of light diffusion test where they shine through to a white backdrop. Keep reference samples. Make a fixture so position of part and laser is constant. Take pictures (or video, why not?) of pass/fail and keep it handy.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
All the clear parts we use are for appearance. If there is a MIL spec, my vendors either won't be able to check it, or we won't be able to afford them. I can't stress that enough. This is simply an appearance thing. The small part I am talking about now, is what I DON'T want to be clear. I had a vendor that made it clear and didn't tell me. In the future I want to make sure that the parts come on NOT polished, yet all other parts polished. How do I get the QA inspection person able to understand the difference appart from training them and leaving an example with them?

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
Thats exactly what I thought of yesterday but after thinking about it more thought it would be way to over the top to check how clear something is. I have larger parts as well, around 1" x 3/4" that are also clear. Where do you point the laser? There I want the enire part to be clear, yeet due to the nature of vapor polishing you get some areas more polished than others. We have not had an issue with this yet, nor do I think we will. Just saying that becuase something is a certain clarity in one area doesn't mean it is in another. That is not easy to spec unless to tell someone to check many areas on one part ($$$). When it is cheap part that just needs to be "clear" there is a lot left up to the inspector.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

i think QA are the check for how clear your drwg is ! though you can cheat and tell them what you want. but why have a QA department, if you rely on CofCs ? for your own build ?

i think in your case the easiest way is to get a prototype part, a little trial and error, then say "build like that one". maybe let your QA keep the reference sample. if the parts do come polished, you could always scuff them on next stage of ass'y.

Quando Omni Flunkus Moritati

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

While it's not particularly robust and is somewhat subjective, given you limited requirements and resources having 'coupons' or 'gold standard' for matching may be a reasonable approach.

I suggest having samples sent to the vendor as well as keeping in your own inspection, drawing note something like.

FINISH: PART SHALL BE VAPOR POLISHED ON BOTH SIDES TO MATCH SAMPLE COUPON XXXXX. COMPARISON SHALL BE MADE AT 2X MAGNIFICATION IN A WELL LIT AREA.

As to your in house inspection I'd prefer to leave that off the drawing and record it either in your quality plan or your routing or some such - nail down any other points you can such as sampling rate.

I work at a place that is struggling with inspection and relatively low volumes etc. too and sometimes the practical measures that can easily be implemented are pretty limited. That's potentially OK, just don't kid yourself that they're anything more than getting a warm fuzzy feeling.

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RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Getting back to the OP's posted question as written, there is NO way to "guarantee" that ANYTHING ever gets done. Training and repetition can only create some higher probability, but that's not a guarantee. You can at least come close by having a procedure or checklist for Incoming to follow. This will hopefully ensure that the checking is done consistently.

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RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
Thanks for all the replies everyone.

- After talking over with some other departments and getting other opinions here, someone suggested a photo of the part on the drawing so that QA knows what something looks like. An enginner that works with me brought up metal platting and how QA never knows what "clear zinc chromate platting" looks like over not platted steel. The plating is just a general anticorrosion plating we have applied to out sheet metal parts to keep them from rusting over time. Nothing critical, sort of like plating you would have on your IKEA bed frame, you need something, but don't want to pay tons of money for checking, it just isn't that critical. The photo may be the best "cheap" idea at being able to show QA what a plated part looks like. Only do this for parts that have special not easily checkable features. Apprt from that, there is the "gold standard" sample idea, I would like to stay away from this simply due to the amount of parts we would need to catalouge.

Anyways, I think I have a fairly good idea as to what others may be doing and what my options are. Also learned that trying to describe a part and the way my company works is quite hard to describe over the internet. haha. I will make sure to start off all my future posts with "OK so can't afford just about anyting..." and go from there.

Thanks for the help eveyone.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

I do not think putting a photo on a drawing is a good idea at all. There are so many variables involved in taking and reproducing the photo that it would be worthless. Are they going to look at the drawing on a monitor or hard copy? Photo quality paper or typical low grade laser printer paper? Will the monitor be color calibrated? I have two identical monitors on my desk side by side and the difference between their color rendition is pretty large.

I think KENAT's suggestion of keeping masters on hand is good, provided these are properly stored and handled. Ive seen 10 or 20 year old "masters" on somebodies window sill that have yellowed and warped.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Agree with dgallup that the picture probably isnt' a good option for the reasons he lists.

Visual comparison to a known good part is already pretty marginal in its usefulness for quality control, comparison to a photo is worse.

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RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

(OP)
Photos don't wear out or get dusty and warped. Color calibration is a non issue at all. I am not having pantones cross referenced. I am simply showing what a part should or shouldn't look like. Like I said in my example before, if you were working at IKEA incomming inspection and had no technical background at all and say that a bracket had zinc plating and you were in charge of checking this (with no testing apparatus) you would just want to look at a photo to see that it looks like zinc plating, and not raw steel. That is the level of inspection I am going for. Saying that the screen needs to be color corrected is simply a level of precision that I do not need. Our drawings that show anything in color are looked at on a monitor, not printed.

With that said, I agree that "masters" are a good idea. We have thousands of parts that we machine, blow mold, injection mold, rubber transfer mold, sheet metal stamp, cicuit boards, and buy as stock items. Saying that we will have a place that can house one "master" of all these doesn't sound like a completely reasonable solution.

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

One master can cover many parts, as you are only interested in the finish. A square coupon with the appropriate finish will suffice for a multitude of parts that are to have the same finish.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

Several things that can happen to comparison pieces -

One, the QC item is altered and unusable parts become accepted
Two, production is short one item, but they know where a good one is...
Three, an 'extra' item is found in production, and discarded, because it wasn't needed
Four, the inspection item is moved to production and an incoming piece is substituted.

A photo is OK subject to a bunch of assumptions. If it was that easy everyone would do it.

Perhaps a drawing note refering to a controlled QC video that is used to teach inspectors is possible. The tough part is determining what the limits are at which you want to reject parts.

***

For appearance control the usual methods are to either spend a lot of money on inspection equipment or to qualify the process, and sometimes both. For example a weld callout goes on the drawing. The welder is typically required to create a weld of the same type, which is tested, for approval before creating deliverable welds. The inspector gives a visual on the welds to see that they appear to be the same as the qualified welds. Even then, welds may require dye-penetrant or x-ray inspection. Paint is another one - samples are done for gloss and adhesion and the process adhered to.

Here's a strong article on why depending on visual inspection controls can be costly and why understanding process is critical to success: http://edn.com/design/analog/4427151/The-last-half...

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

A lot size of a couple hundred gets into the range where low volume injection molders can be more than competitive with machining and bonding.

So take a look at molding in one piece what is now an assembly.

Mike Halloran
Pembroke Pines, FL, USA

RE: What to put on a drawing that guarantees that your part is vapor polished? How to inspect?

1. Specify a Roughness Average Value.

2. Inspect using one of these. Link

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