OT: Sanyo Vacuum Cleaner Failure

Must have been designed by the Comet Jet roof hatch engineers. It's been a long time since such things were an issue for appliance engineers and it's a foreign concept for appliance "Designers" obsessed with style.

At the same time when all layouters and engineers learn not to use sharp corners in their PCB artwork for mission critical stuff. Which probably means never because it doesn't look cool :-)

When are consumers going to learn that most manufacturers *design* products so they won't last forever? I'm betting the vac was out of warranty, right?

MrT.

Sharp track corners don't look cool!

I spend years listening to a SW engineer in our office criticising me for spending time laying out boards correctly. He just didn't get it that the layout had consequences even for lower speed stuff.

Yes, but I'm sceptical of the idea that a part could be designed to suffer this failure mode in anything like a predictable time. I'll stick with the hypothesis that this was due to incompetence, not planned obsolescence.

Sylvia.

products

Of course it's not predictable, it's just guesswork. IF they get too many coming back under warranty they fix the design, otherwise it's a "feature".

MrT.

It's an expensive thing to get wrong.

Sylvia.

During the run of the Model T, Henry Ford sent investigators all over the US to wrecking yards. They were told to investigate old Model T cars and report on what components had failed on the vehicles.

The investigators reported that most of the components of the Model T failed at more or less similar figiures. Except one. One component was surprisingly reliable on the Model T. The king pins.

Henry Ford then, allegedly, instructed his engineers to make the king pins cheaper.

It's a matter of taste I guess. Young engineers like those sharp 45 degree turns. Totally rounded ones are better, of course, but I've heard people say "Eeuw, that looks like the old Rubylith spaghetti layout". Well, yeah, it does but it'll last.

And it has reliability consequences if rough handling is to be expected. There's a reason why bush pilots drill a hole at each end of a tear.

"Trevor Wilson"

Quote:

The first production version Merlin I was assigned for Fairey Battle production. Only 175 had been built and these were considered to be rather unreliable. As a result, Rolls-Royce introduced an ambitious reliability-improvement programme to fix the problems. This consisted of taking random engines from the end of assembly line and running them continuously at full power until they failed. Each was then dismantled to find out which part had failed, and that part was redesigned to be stronger. After two years of this programme the Merlin had matured into one of the most reliable aero engines in the world, and could sustain eight-hour combat missions with no problems.

..... Phil

I'd have thought you'd just have to remind him that he's a software engineer, not an electronics engineer.

I've seen recommentations from board manufacturers that one avoid 90 degree bends, but I took that to be more about manufacturing tolerances that stress concentration. Neither of the two layout programs I've tried provided the option of curved traces, as far as I can remember.

I'm surprised if track fracture shows up as a significant cause of failure, but if it does, it wouldn't be the first true thing I've been surprised about.

One would also have to consider the corners formed where traces become component mounting pads.

Sylvia.

I've used the same technique on a plastic pedal-bin in the past :)

It can be hard to judge where the end of the crack actually is :(

Sylvia.

Sanyo initially replied to my initial complaint by reference to the warranty period, and that I'd have to buy a new part if the machine was out of warranty.

I sent a rather caustic second email pointing out that I wasn't making an inquiry about spare parts, but was making a complaint about a design flaw. I said that such a flaw meant that the goods were not of merchantable quality from day one, and that this meant that there existed the theoretical option of my suing them. However, I indicated that I didn't consider it worthwhile.

I didn't expect any response. But instead Sanyo have said that they'll send me a new part.

Sylvia.

Oops - my mistake. On seeing the copy of the receipt, they've said it's out of warranty.

Sylvia.

However, after my further comment regarding the Trade Practices Act and design flaw, they have, without conceding my point, said that they'll send me a replacement.

Sylvia.

True. Sometimes it helps to shine a really strong light through there. Most plastic, even dark stuff, is to some extent translucent and that way faults can show themselves.

That is one reason why good layout software offers things such as teardrop pads as a feature, meaning you don't have to write your own macros to create those:

The main area where stress fracture play a big role is connectors. No matter whether they are additionally secured via screws there will be forces tugging at the pins. That tugging continues into the board to some extent. Especially if a right-angle connector has the pins in the board but is then bolted to a panel.

Another useful hint in such letters can be that the matter is currently being discussed on the Internet. This often results in a sudden outburst of courtesy :-)

I usually try to find the name and valid email address of one of the higher-ups. VP or quality control, CEO, or similar. And if I really have my druthers I tend to always find that kind of information.

Drill the hole a bit further away from apparent end of cut and then work the crack to see it hit the hole. Repeat if you misjudged end of crack ;)

Grant.