Well, imagine someone opening the door if the water hasn't fully drained out and the ensuing mess. If you're wondering if someone is stupid enough to do that, then the answer is unequivocally yes. There is a reason the door locks for that amount of time - so somebody doesn't brain fart, open the door, and flood the laundry room.
this post was submitted on 12 Aug 2023
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So why not make the washing cycle end when the water has fully drained? I get the impression the timer starts after the drain.
Maybe that's your machine being oddly programmed. Every machine I've seen unlocks right after it finishes it's cycle. It can also be stopped and unlocked anywhere halfway, but it takes some time to drain the water (usually a few seconds, not a full minute like you mentioned originally).
It’s not a component aware system. The last phase is generally the spin cycle. The controller knows to trigger the spin cycle, it knows to stop the spin cycle after a period of time. What it doesn’t know is whether those things actually happened. Particularly, it doesn’t know that the drum has actually stopped spinning. So, it just wait a predetermined amount of time before unlocking the door.
In the case of my own device the door actuator uses a wax motor. Put simply, current is changed to heat which melts the wax, pushing a pin the locks the door. To open the door, current is removed, the wax cools, hardens and shrinks and the pin slides back. Now the door can open. So, even if I remove power during a cycle the door will eventually unlock as the wax cools.
Of all the answers here, this definitely seems like the right one and the only one that makes sense.
My bet would be it's waiting for temperature to drop.
Edit for the downvoting folk: Some of the profiles of my washing machine have temperatures of up to 90°C
I would bet that the water for the rinse cycle would be cold though.
Many machines use a bimetal to lock the door, a stupidly simple design. Metal heats up, bends and triggers the lock. It takes a while to cool down which is why it'll take a while to unlock even if you unplug the machine.
In case you'd like to see bigclive explain it in detail: https://www.youtube.com/watch?v=PIm7q_U3UEM
It checks if the water is really truly out so opening the hatch is safe (as in no water coming out causing water damage). And for that it waits a time so the water has time to gather in the bottom.
But why not just beep after that? What’s the point of beeping before the door is unlocked?
Mine beeps when the door unlocks, but I've seen many that beep before the final check. Either to satisfy some "1 hour wash cycle" target or perhaps they expect people to walk to the machine when it beeps and the check isn't that long so it's probably going to be unlocked when you get there?
I’m looking for this beep-and-unlock feature next time I buy a washing machine…
My best guess is safety, if you had a heavy load in there the momentum could keep the drum spinning much longer than normal. I'm sure they could add a sensor to check, but that's just an extra cost. So rather than allowing you to open the machine while it's still spinning and possibly injure yourself reaching in, they keep it locked for a few more minutes.
It's so that the machine elves have some time to hide!
On a serious note, I found this explanation here:
Washing machines must have some way in which you can lock the door closing mechanism when the machine is started up and then unlock them with a certain delay (normally two minutes) after the current has switched off via the program or on/off switch, in order to ensure that the door cannot be opened while some of the components are still rotating initially (in particular the motor and the drum of the spin-dryer).
Washing machines have a bi-metal strip inside the door lock which is heated by PTC Heater (resister) when live and neutral are activated on to the pcts it heats up and bends the bi-metal strip which then moves the arm to activate the common terminal and push a pin into the closed door to lock it in place. Once this has happened (usually a second or so see video) the power then can flow through to the common wire, and therefore on to the rest of the machine allowing it to start.
Mine doesn’t do this, but it does do a few slow spins right at the end so that everything settles to the bottom. Maybe yours is also doing this by waiting?
Possibly.
I got a side loader and it generally is spinning at least a little slowly until right before the timer goes off. Generally I can push the pause button at any point during the wash and after a few seconds it will unlock. My top loaders i used to be able to open at any time during the wash.
I imagine they have a buffer period to let the load stop spinning but you probably can override for earlier if you really want.