OT: Sanyo Vacuum Cleaner Failure

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The cleaning head fell off my Sanyo vacuum cleaner while I was using it
today.

A 3cm plastic tube has sheered all he way round. I looks like a typical
crack propagation failure, with the break completely clean for 2/3 of
the way round, before it obviously failed in overload.

And the origin of the crack? Yup, you've guessed it. A sharp corner.

When are designers going to learn that you cannot have sharp corners in
load-bearing plastic components?

Sylvia.

Re: OT: Sanyo Vacuum Cleaner Failure
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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.

Re: OT: Sanyo Vacuum Cleaner Failure
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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 :-)

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: OT: Sanyo Vacuum Cleaner Failure

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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.



Re: OT: Sanyo Vacuum Cleaner Failure
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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.


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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.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: OT: Sanyo Vacuum Cleaner Failure

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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.

Re: OT: Sanyo Vacuum Cleaner Failure
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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.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: OT: Sanyo Vacuum Cleaner Failure

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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.

Re: OT: Sanyo Vacuum Cleaner Failure
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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.

Re: OT: Sanyo Vacuum Cleaner Failure
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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:

http://www.moodle.ee.ttu.edu/file.php/1/layout/lay_ug.pdf

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.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Sanyo Vacuum Cleaner Failure

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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.



Re: Sanyo Vacuum Cleaner Failure
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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.


Re: Sanyo Vacuum Cleaner Failure

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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.



Re: Sanyo Vacuum Cleaner Failure
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It's an expensive thing to get wrong.

Sylvia.

Re: Sanyo Vacuum Cleaner Failure
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**There is an apocryfal tale told about Henry Ford. It goes something like
this:

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.


--
Trevor Wilson
www.rageaudio.com.au



Re: Sanyo Vacuum Cleaner Failure

"Trevor Wilson"
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** Then there is the *non apocryphal* story involving the famous Rolls Royce
" Merlin " V12 aeroplane engine of WW2 ( used in Spitfires, Hurricanes,
Mustangs and Lancaster bombers) that goes the OPPOSITE  way.

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.

http://spitfiresite.com/2010/04/the-development-of-rolls-royce-merlin-engine.html



.....  Phil






Re: OT: Sanyo Vacuum Cleaner Failure
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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.

Re: OT: Sanyo Vacuum Cleaner Failure
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Oops - my mistake. On seeing the copy of the receipt, they've said it's
out of warranty.

Sylvia.

Re: OT: Sanyo Vacuum Cleaner Failure
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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.

Re: OT: Sanyo Vacuum Cleaner Failure
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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.

--
Regards, Joerg

http://www.analogconsultants.com /

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