See Sidney's post from earlier today.
Indentifying human error as a root cause
- Thread starter Lee Taylor
- Start date
Ron Rompen
Trusted Information Resource
Sidney definitely has the correct ideas. I implemented the same type of controls (particularly 2 & 3) when I contracted with Hewlitt Packard years go. Precise kitting will help in detecting mistakes (although now you have the problem of making sure the kits are correct), and an end-of-line functioinal test will prevent n/c product from leaving your facility.
Involving the operators is a key to correcting most issues - they are aware of what REALLY happens on a day-to-day basis, as opposed to what it says on the process flow chart. Involve them, ask them to help, and you will be surprised by the answers they come up with.
Involving the operators is a key to correcting most issues - they are aware of what REALLY happens on a day-to-day basis, as opposed to what it says on the process flow chart. Involve them, ask them to help, and you will be surprised by the answers they come up with.
We did exactly this. We purchased an off-the-shelf product from a supplier in enormous volumes ($ Millions per year). We would periodically receive products that didn't work properly with our device. We tried and tried to figure it out but could not. What we did was asked them to use our device in QA testing prior to shipping their product to us for each lot since lot# was the smallest unit of measure we could isolate. We added this test into our receiving inspections and the problem was majorly reduced.
Operators do commit errors, but you should always look for the underlying causes. There are certain conditions that will greatly increase the likelihood of an error:
A further comment on training as a root cause or corrective action:
Ask the following questions:
If the answer to 1 is no or the answer to 2 is yes, then determine the reason the operator was not trained.
- Near symmetry - opposite sides of part, tool or fixture seem to be identical, but are not
- Rapid repetition
- High volume
- Poor environmental conditions
- Disorganized work cell or poor layout
- Need for adjustments
- Tooling and tooling changes (e.g., more than one torque driver with different torque settings)
- Deviations from standard
- Many part variants or mixed parts
- Multiple steps (forgetting a step, incorrect sequence, repeating a step)
- Infrequent production
- Lack of an effective standard / Complicated standard
A further comment on training as a root cause or corrective action: Ask the following questions:
- Has the operator correctly performed the required task prior to this issue?
- Has the required task recently changed?
If the answer to 1 is no or the answer to 2 is yes, then determine the reason the operator was not trained.
outdoorsNW
Quite Involved in Discussions
One problem in electronics is the nature of through hole parts makes error proofing difficult. Parts are frequently small to tiny making the use of overlays to aid assembly not possible. Many parts look similar but have different operating values. Component manufacturers use pin layouts that can be installed two ways even when it seems easy to use a pin layout that only fits one way.
On top of that you have PCB designers who know nothing about PCBA manufacturing and don't put easy error reduction methods into the design. They locate similar parts next to each other, sometimes in mixed patterns such as two of part A, one of similar looking part B, and then another part A all in a line. The put large and small parts close together in ways that make machine assembly difficult.
On top of that you have PCB designers who know nothing about PCBA manufacturing and don't put easy error reduction methods into the design. They locate similar parts next to each other, sometimes in mixed patterns such as two of part A, one of similar looking part B, and then another part A all in a line. The put large and small parts close together in ways that make machine assembly difficult.
Randy
Super Moderator
Sometimes crap happens regardless of training, experience, competency or whatever, accept it.
(Nearly 40 years ago now)....There we were on the gun range, our governor a congressman and others watching. One of my favorite and one of our most experienced pilots on the stick ready to fire off a load of 17 lb, 2.75in rockets as a demonstration. I'm in the back in my position, George (the pilot) is in the right seat and another great pilot is in the left. George had spent nearly 2 years with the Navy's "Seawolves" flying gun missions in the Mekong and he'd been with the National Guard for the last few years , he'd done this hundreds of times. We're at a hover about 15ft above the ground, George reaches back for the "Arm" switch and accidently triggers the "Pickle switch" instead (he activated the jettison system). Off drops 2 rocket pods containing 19 rockets each with 17lbs of high explosive and at the same time we shoot straight up about 500 feet from the rapid loss of all that weight.....George recovers control, the pods roll around on the ground, nobody is hurt, nothing is damaged except for pride....The point of the story.........No matter how qualified, no matter how well trained or motivated, crap can happen and an operator can make a mistake. Stuff just happens.
I'm sitting in the back, George is seated up front and the other pilot (Dan, our commander) is standing in the middle. This is just before the "demonstration"
(Nearly 40 years ago now)....There we were on the gun range, our governor a congressman and others watching. One of my favorite and one of our most experienced pilots on the stick ready to fire off a load of 17 lb, 2.75in rockets as a demonstration. I'm in the back in my position, George (the pilot) is in the right seat and another great pilot is in the left. George had spent nearly 2 years with the Navy's "Seawolves" flying gun missions in the Mekong and he'd been with the National Guard for the last few years , he'd done this hundreds of times. We're at a hover about 15ft above the ground, George reaches back for the "Arm" switch and accidently triggers the "Pickle switch" instead (he activated the jettison system). Off drops 2 rocket pods containing 19 rockets each with 17lbs of high explosive and at the same time we shoot straight up about 500 feet from the rapid loss of all that weight.....George recovers control, the pods roll around on the ground, nobody is hurt, nothing is damaged except for pride....The point of the story.........No matter how qualified, no matter how well trained or motivated, crap can happen and an operator can make a mistake. Stuff just happens.
I'm sitting in the back, George is seated up front and the other pilot (Dan, our commander) is standing in the middle. This is just before the "demonstration"
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Lee Taylor
Registered
Many thanks for all your replays and advice. I will take time to reflect on the advise and will respond acordingly.
You look at some circuit boards these days and wonder how any of them have all the right parts in all the right places, at least I do. It's amazing technology. Many times the buyer can't or won't supply a functional test, and the price pressures are like everything else.
If you have to rely on human eyes detecting the presence or absence of a part on a densely populated board, you will never get 100% accuracy on that. And add on top of that looking for minor soldering defects on those parts... If you try it sometime it doesn't take long to realize that even highly skilled and caring employees will never be 100% accurate on that task.
That's not to say you can't do some things to improve the quality levels, there are some good suggestions above, but if you're trying for 100% via human assembly and/or inspection of circuit boards, you're dreaming, IMO.
If you have to rely on human eyes detecting the presence or absence of a part on a densely populated board, you will never get 100% accuracy on that. And add on top of that looking for minor soldering defects on those parts... If you try it sometime it doesn't take long to realize that even highly skilled and caring employees will never be 100% accurate on that task.
That's not to say you can't do some things to improve the quality levels, there are some good suggestions above, but if you're trying for 100% via human assembly and/or inspection of circuit boards, you're dreaming, IMO.
In my experience (little in this area...watched it or heard description of it, never done it), all but one PCB manufacturer used automated pic & place of SMDs followed by solder reflow.
That one that did it by hand...that's this OP on this thread...
Seeing the boards I get for equipment repair (CMM, timer circuits, etc, or computer repair or expansion...I can't imagine doing all that by manual placement without full functional testing. There are literally hundreds (or thousands) of those little buggers even on a small board.
That one that did it by hand...that's this OP on this thread...
Seeing the boards I get for equipment repair (CMM, timer circuits, etc, or computer repair or expansion...I can't imagine doing all that by manual placement without full functional testing. There are literally hundreds (or thousands) of those little buggers even on a small board.
