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Comment by Lunatic666 | Hacker News Reader

Those cafes are a great idea! I recently opened a high quality blender (forgot the brand) and found a cog made partially of metal with one small part made of plastic which will break first due to wear and tear. Otherwise this little motor would run forever.

Is it normal these days to put in breaking points to artificially shorten the life of appliances or does this have a purpose?

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That little cog might be more like a fuse -- a part of the system that's relatively easily replaced and designed to fail first.

And so the company send a spare one in the box when you buy it, yes? Because they wouldn't be so crass as to make you hunt down a part that cost them a few pennies and disables the machine would they?

Same issue for me with food mixer, mostly metal, key part is plastic and gets stripped, can't be replaced. Same with bread maker, rubber belt decays and company don't make the part available.

Right, that's a fair criticism of the business practice, but from an engineering perspective it might not be a terribly unreasonable design. It's a good idea to design a system to fail predictably. Electrical engineers use fuses, mechanical engineers use shear pins, and so on.

Perhaps it was to protect the user, not the machine. If you drop a spoon in, it might break the fuse before pinging it into your face? Or it might have been a sliding contact that needed better wear performance than metal on metal, or it might have been an odd shape that was expensive to make from metal.

Outboard motors for boats work like this. If you hit a rock with the propellor, a piece of plastic in the drive train breaks. This prevents the propellor or some other part of the motor from serious damage.

Yes. As others said, it could be a mechanical fuse. However, engineered obsolescence is a real possibility. A friend of mine had a product manufactured in China. He said the factory he partnered with asked him straight-up "Where do you want the weak part? When do you want it to break?" So, I guess it is pretty standard practice to do this (admitted anecdote here, but still)

The plastic component could also be acting as a mechanical fuse in case of overload. Like a shear pin.

That would make sense, instead of breaking the cog-setup, the little plastic part breaks off and saves the motor. Thank you for the explanation, one conspiracy theory less!

It's called engineered obsolescence.

Or mechanical fuse as someone else pointed out: something cheap and easy to replace that will break before something expensive and hard to replace when over the design load.

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