Deming Must Be Wrong

Gary Wagner, General Manager (U.S.), Ophir Photonics

W. Edwards Deming said, "If you can't measure it, you can't control it," and "You cannot inspect quality into the product; it is already there." Instead of trying to inspect-in quality, focus on adding value once you're assured that the previous process was done right and to specification.

Since the mid-1980's, tens of thousands of machine vision camera systems have been installed along manufacturing lines and in assembly stations. They can be found in every conceivable industry where there are volume users - automotive, pharmaceutical, medical devices, electronics, aerospace, and, at this point, almost every industry that makes something. Why? Because subsequently adding value to a good part reduces the cost of goods, making the manufacturer more money. In fact, machine vision is one of the reasons the U.S. regained its world position producing quality products at reasonable prices.

I've been in the machine vision business for over 15 years solving manufacturing quality issues, and measuring and controlling manufacturing processes. A few years ago when I moved to a company that makes products for measuring the quality of a laser beam, I assumed the manufacturing industry would be a natural for these products. We make instruments needed to measure the various characteristics of beam quality and consistency…in other words, a machine vision system that measures and manages the quality of a laser beam.

So I asked our sales people how much we sell into the industrial manufacturing world, and the answer was shocking. Except for the guys that are under FDA scrutiny, almost none. I said, "What are you talking about? There are all kinds of lasers being used in manufacturing of high precision, high reliability parts in the aerospace, automotive, and electronics industry, to name just a few. They need constant precision and consistency, which definitely isn't synonymous with a laser over time." The answer was, "Might be, but they don't think they need it. We've tried for years to get them to understand the need for periodic or on-line measurement, but with very little success."

Not surprisingly, my reaction was, "OK, but I know something about these people and their needs and requirements, so let me try." What I discovered is that nobody thinks they need to periodically measure their beam because:

We've never measured it since the day it was installed, so it is probably OK, We have periodic service maintenance and we're sure those guys measured it then, or When we start making bad parts, we shut down the line and call the service tech. My head started spinning, taking me back to the early 1980's when these were the same kind of initial answers we got when talking about how machine vision would help make: 1) Consistently high quality, 2) Less scrap, and 3) More satisfied customers. We got our message through. What's happened since then?

Machine vision users are process engineers, the same users of laser systems. Why do they not see how beam measuring equipment can help?

Maybe they aren't seeing manufacturing inconsistencies from their laser? Wrong… It doesn't take many interviews to find out that the laser process can indeed make bad/inconsistent parts or that it may be shut down at unpredictable times for maintenance. So that can't be the reason for denying the need to measure.

We ask how are you measuring the laser now? They reply, a) Burn paper or b) Acrylic burns. These answers prove my point. Let's start with burn paper. I show them that burn paper is one-dimensional; the resultant burn is either burned or not. There is no spatial depth to a burn. Yet the power cross-section of a laser beam is 3D, not 1D. All of the information on how a laser is going to cut or weld or process is in how the power is shaped. In addition to its limited spatial depth, the burn paper is not dimensionally accurate. The burn only happens where there is enough power to burn; measuring it for useful information about power density is useless.

Let's address the second issue: acrylic burns. I hear, "I use acrylic plastic to make a 3D representation of the profile." Wait! Got you here…burning acrylic plastic produces carcinogenic fumes! I figure any big company that has to worry about OSHA compliance will not want that happening in their shop. But the reply is, "No big deal. We've got fans that vent it to the outside and the operator is safe." I'm thinking, you've got to be kidding! And from the little shops without fans, I hear that we only do it once in a while so the operator isn't in the fumes very often.

Does this mean you don't care about safety?

技術的な話になりますが、アクリルブロックは、レーザーパルスを1回だけ (パルスを使用している場合) だけでは作成できません。また、数秒以上かかる必要があります (CWを使用している場合)。 何らかの理由で、ユーザーは最初のレーザーパルスが100番目のパルスのように見えるか、最初のミリ秒のCWパワー分布が最初の1秒の終わりまたは2秒目の終わりのパワー分布と同じに見えると考えます。

しかし、それは真実ではありません。特に、初期のレーザー出力と、レーザーを一定期間オンにした場合とを比較した場合に顕著です。カメラまたはスリットベースのプロファイラーでレーザーを照射させてください。

実際、これがプロファイラーの販売方法です。ユーザーは、オンサイトのデモでその性能を示すまでの間、完璧なパフォーマンスを発揮するレーザーを手に入れています。これは、産業ユーザーを除いて、他のどの方法よりも多くのプロファイラーを販売します。彼らはそれを見て、「私が長年やってきたことはうまくいっているように見えるのに、なぜ変えたいのですか？」と言います。

その理由は次のとおりです。特定のレーザーのパフォーマンス特性を知ることで、これまでできなかったことを実行できるようになります。

• マシンビジョンシステムと同様に、未来を予測します。レーザービームに関する特定の測定値を定期的および長期間にわたって把握していれば、定期的なレーザーメンテナンスがいつ必要になるかを予測することができます。壊滅的な回線停止ではなく、ダウンタイムをスケジュールできるようになりました。
• 複数のプロセスで同じレーザーを使用している場合、各プロセスのビーム調整を最適化できます。
• 時間の経過とともに光学部品は汚れ、汚れた光学部品によりビームの照射やビームの特性が変化します。同じレーザーパラメーターは、汚れた光学系では機能しません。これが起こったら光学系を交換します、とよく言われますが、それは二元論的に考えています。初日から交換する日までの微妙な違いについてはどうでしょうか。それは一貫した製品の製造にどのような影響を及ぼすでしょうか。ビーム照射パラメーターは時間の経過とともに微妙に変化します。光学部品を交換する直前まで変化は避けられません。その変化がいつ許容できない点に達するかを知るには、測定する必要があります。

The next objection I hear is that there might be something to this electronic monitoring of the beam quality, but they've heard that it is too expensive for the shop. Now we have it out in the open. Yet another objection we also heard about machine vision -- too expensive to make quality product. So we go through the ROI.

We take the value of the product, number made per unit of time, cost of scrap, how many do you make before knowing there is a problem, cost of unscheduled down time, etc. The standard ROI stuff. Our ROI calculator can quickly and easily predict what the payback time will be.

But let me be give you a starting point. If you have more than one laser in production and you are welding with it at least one shift and your part is precision in nature, the payback will be 16.7 months or less.

Too big, too small, doesn't quite fit, operators are used to the old process, we don't use PC's on the floor, too complicated, doesn't give the same information as what we are use to, and on and on. I've heard it all. Sigh.

Does this mean Dr. Deming's "measure it and control the process" isn't right for most manufacturers that use lasers? Definitely no. But manufacturers first have to open their eyes to this lost opportunity for improvement. Especially now, when manufacturing needs all the help it can get.