Some of the terms used for a factory with good control is 6 sigma.
You track the CPk of the product. It has been a while, but if my memory
serves me correctly, CPk above 1.9 is good. Another term is Defects per
million opportunities DPMO. Some believe if it is under 200 is very good.
Regards,
Ramon
> -----Original Message-----
> From: Steve MacDonald [SMTP:[log in to unmask]]
> Sent: Wednesday, November 06, 2002 2:24 PM
> To: [log in to unmask]
> Subject: Re: [TN] Efficiency / Effectivity of your SMT lines
>
> Greetings all. I'm not sure if I'm side tracking here, but...
>
> As a Quality manager burdened with PWB Fab, Assembly, and among other
> things, ISO systems, the idea of a Benchmark that defines "World Class" is
> intriguing to me. I have heard the phrase used. Can anyone enlighten me
> to ANY set of guidlines, in any kind of business, that define, demarkate,
> outline, or otherwise identify the point at which any part of any process,
> or output can be "officially" quantified as "World Class?"
>
> (Just as a side note: I have asked Quality Consultans about it, and they
> don't seem to know either. We might all love a point of reference. I
> just hope it's not another ethereal, unquantifiable, Buzz term)
>
> Thanks,
>
> Steve MacDonald
> QM / ISO MR
> Mass Design Inc.
>
>
>
> ----- Original Message -----
> From: Howard Watson <mailto:[log in to unmask]>
> To: [log in to unmask] <mailto:[log in to unmask]>
> Sent: Wednesday, November 06, 2002 1:08 PM
> Subject: Re: [TN] Efficiency / Effectivity of your SMT lines
>
>
> Thanks Ryan, very accurately stated. It has been my experience that
> the machine manufacturers like to use the third method of stating cycle
> time. While this is the target, I have not seen this achieved often,
> because there are those machine stoppages that seem to occur way more than
> desired. You are right on target regarding the "mother lode", and this is
> an area that I have been trying to optimize. For example, we had
> significant part rejects, 40 - 50%, on a dome LED, and the final solution
> was to ream out the nozzles to obtain a seating on the flat part of the
> body. Rejects dropped to .2%. We have issues with tube parts that
> require a lot of attention and are a big contributor to the mother lode.
> Reloading feeders is still an issue to be resolved.
>
> I'm curious if there are machine run time numbers that are a
> standard for "World Class". It seems like the term is used often these
> days, but what exactly does it mean from the perspective of operating
> efficiency? Anyone?
>
> Howard Watson
> SMT Manufacturing Engineer
> AMETEK/Dixson
>
>
>
> rgrant <[log in to unmask]>
>
> 11/05/02 05:27 PM
>
>
>
> To: "'TechNet E-Mail Forum.'" <[log in to unmask]>, "'Howard
> Watson'" <[log in to unmask]>
> cc:
> Subject: RE: [TN] Efficiency / Effectivity of your SMT
> lines
>
>
>
> Ehem...(clearing my voice as I climb on the soap box)
>
> With tracking efficiency, you are essentially trying to get the most
> amount of product out of a set of machines that you possibly can. To
> figure that, you want to know what is theoretically possible and how close
> you come to theoretical. Since many brands of pick and place machines
> keep a record of what state they are in, you can query that data and get
> some eye opening results.
>
> I have found that cycle times can be figured three different ways,
> giving very different results. First, looking at a 24 hour period, how
> many boards came out of that machine. This is real world cycle time
> planning should use, and is the ultimate bottom line. This time includes
> set up time and any decreases in change over will positively affect you
> cycle time.
>
> Second, looking at the time that the line is actually running
> divided by the number of board produced. This is the cycle time that
> determines your constraint and paces the line.
>
> Third is the time it actually takes for the machine to assemble the
> board. This is the theoretical cycle time.
>
> I'm guessing here, but you probably do 2-3 change overs per 24 hour
> period. Not using docking carts, change overs could be as high as two
> hours. Assuming you get it down to 10 minutes, that means you gain 5 1/2
> hours of number two time. That would be awesome, and would improve
> efficiency by 25%. This is probably an extreme case, so adjust the
> numbers accordingly.
>
> However, if you look at the numbers between number two time and
> number three time (theoretical time), you will typically find a difference
> by a factor of three or more. This is the "mother load". Your
> efficiencies are lost by not focusing all attention on your constraint and
> keeping that machine fed, up and running. In other words, any time the
> constraint "waits" for product to arrive so it can start working, you have
> lost time. Any time the machine stops for any kind of error, you have
> lost time. Any time the machine stops for a feeder to be reloaded, you
> have lost time. These time losses are only a dozen seconds or a minute or
> two, but they add up over a 24 hour period. As a constraint, there is no
> reason that machine shouldn't be able to run continuously at near its
> theoretical limit. I'm not talking about improving the placement time,
> just keep that machine busy. ! By improving the "working" time on your
> constraint, there is an easy 100% improvement in line efficiency, and it
> doesn't cost anything. Just an attitude change from management down to
> the production line to identify the constraint and focus on keeping it
> working.
>
> I have worked in factories where this concept has improved output by
> a factor of three, therefore I'm extremely sold on it. As far as what is
> possible, I have seen lines where the constraint was "working" 80% of the
> time the machine was plugged into the wall. What is realistic... I have
> heard reports from machine manufactures that the CM industry is at about
> 20-40% machine working time. Of course, those at 80-90% working time are
> not high mix, low volume.
>
> Not that improving change over time is bad, I just think that
> attention should be focused on the place with the greatest potential for
> improvement.
>
> Ryan Grant
>
> -----Original Message-----
> From: Howard Watson [mailto:[log in to unmask]]
> Sent: Tuesday, November 05, 2002 3:47 PM
> To: [log in to unmask]
> Subject: [TN] Efficiency / Effectivity of your SMT lines
>
>
> Dear TechNet subscribers,
>
> I am curious about the level of productivity of your SMT lines,
> particularly for those in a high mix environment. We are getting pressure
> to reduce changeover and cycle times, as I am sure most of you are too,
> and I am curious as to what level of effectivity (hours available in the
> day do you actually build product) that you are at. Would 80% be
> reasonable? Also, how efficient are you at building your product to
> standards, for those who track efficiency?
>
> As far as changing over from one job to the next, what are your
> average times? It was suggested to me by management that the goal for
> changeover should be 1 minute or less. I am a reasonable person, and I
> believe that single digit (SMED) changeovers, like 8 or 9 minutes might be
> reasonable, but 1 minute is a stretch that I can't see happening, even
> when using docking carts for the feeders. Thanks in advance for your
> input.
>
> Howard Watson
> SMT Manufacturing Engineer
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