Can You Trust Pick & Place Machine Ratings?

Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting. Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up CEM Selection/Qualification, SMT Training/Seminars, Legal Disputes

Phil Zarrow With over 50 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes. Jim Hall A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.

Transcript

Phil
Welcome to Board Talk. This is Jim Hall and Phil Zarrow from ITM Consulting, otherwise known as Pick and Place, the Assembly Brothers. And today, our topic is on Pick and Place.

Jim
The topic comes from Q.R. in Phoenix, Arizona. Q.R. asks, "We're setting-up an SMT line. In estimating the capacity for equipment selections, why can't we use the Pick and Place manufacturer's rating for components per hour? They design the machines, don't they?"

Phil
Oh, yes, they do and they're trying to sell you machines. I think the real answer to your question is we don't live in an ideal world. Let's look at it from two major components.

First, the Pick and Place machine manufacturer, is trying to sell a machine. He's got to demonstrate the machine at some specific rate.

Cycle rate is ridiculous, because that would be putting down the same component in the same place in the same location, and we all know that's totally meaningless. So, generally, what they do is they have some rate they designate, and it might qualify if you're doing passives or simple ICs.

Generally, when you go and look at the machine, you'll see a demo board, and the demo board is usually optimize for the machine under ideal conditions. There have been attempts to come up with standardized boards. The IPC has worked on it, but they're not widely used.

Let's face it, from the manufacturer's perspective, before we get a lot of nasty-grams from them, there are no two applications that are the same. So where do you benchmark it? How do you benchmark it?

So, we have what we call de-rating factors. The biggest thing with the de-rating factor is the real world, your environment, and there's a lot of things going on here.

Let's start with your factory. If we're taking an eight hour shift, are you really working eight hours? Well, most likely you're not. Your employees take lunch. Do you give them breaks?

Maybe there are a few slave masters out there that don't in certain parts of the world. What about change-over time? That's probably one of the biggest killers. In addition to change-over time, even if you're running high volume of a single board, there's transfer time, or from the printer to the pick-and-place machine.

Typical conveyor transfer time is about four to six seconds? So, this is all adding up. There's of course, what we call bumbling time, or Dr. Rhine called, "floundering time." 

Jim
We should start with a more generic thing of down time, and down time is when you're attempting to run the machine, you're all set-up, there's a board waiting to go, or there's a board in the machine, but something happens.

Of course, we all know, what is the thing that happens most of the time? The feeders jam, the feeder runs out, the tape doesn't peel-back right. The machine stops, an operator comes over, ideally very quickly, fixes the problem, and pushes the reset button and away you go.

How often does that happen? Once an hour? Once every half hour? Once every 15 minutes? And you start subtracting this significant percentage of the available operating time, and that all takes away from capacity.

Phil
The sad fact of the matter is, if you were to look at overall efficiencies, typical machine through-put rates running 20% to 40% of what was originally specified?

Jim
The actual capacity rated over the time that the machine is theoretically available, if you can get above 25%, that's very good.

I wanted to follow-up on your floundering time. It is when a machine goes down, an operator comes and doesn't know what to do. So, they walk around trying to find somebody who understands the problem, trying to call a maintenance person, trying to call the supervisor, and the bottom line is: capacity is lost.

When you average these out over a significant length of time, what you need to do to estimate your capacity for a new line, you find that you're actually only going to get 25 percent of the machine's capacity.

Phil
So, that's the difference between what you might read on paper and might get in the real world. And that's about it for today's installation of Board Talk. Jim Hall and Phil Zarrow of ITM Consulting saying, whatever you do, don't solder like my brother.

Jim/Phil
Don't solder like my brother. And keep the kids from sticking their hands under the pick and place machine, for crying out loud.

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