Cafelat Robot piston seal life

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#1: Post by jpender »

I think my seal has sailed.

Occasional hissing has given way to more significant amounts of water bypassing the PF and exiting ingloriously into the cup. I've had my Robot for a year and change and, accounting for periods of being away from home and other periods of coffee overconsumption, I estimate that I've pulled somewhere in the neighborhood of 700 shots. I tried lubing with the Molykote or whateveritscalled and it helped a little, for a little while.

How many shots / how long a time has yours lasted?

I'm just curious if that's about what one should expect from a little piece of silicone repeatedly exposed to pressure, heat, and friction.

It's dead, Jim.


#2: Post by Nate42 »

My original seal is still working after a year and a half ish. I was one of the initial kickstarter backers. I would say that I have noticed some wear though. If I am not careful about keeping it very clean it can let some air out. Haven't had a water leaking problem yet though. Have you tried taking it off and thoroughly cleaning it? I finally broke down and removed mine for a more thorough cleaning (had previously avoided it) and found there was substantial coffee build up under the seal in the groove it sits in. This probably wasn't helping it seal any. I was considering replacing it but I think now I can stretch its life a while longer.

I would also estimate that I am currently in the 700 shot total neighborhood. I pull one shot per day most workdays, but more on weekends, and lots more during the current covid-19 situation.

BTW, mine came with a spare seal, which I think is still the standard? So double check that you don't already have one before you go ordering a new one.

jpender (original poster)

#3: Post by jpender (original poster) »

A leaking gasket with a new Robot is a different issue than gasket life.

And the arms aren't designed to stay up. They do for some people, at least at first. They never did for mine. I added a little loop of silicone to one arm of my Robot so that they would stay up. Other people use a bungie. Discussion about this is in the big Robot thread. You can probably find it by searching.


#4: Post by thirdcrackfourthwave »

Over 800 ish and no signs of imminent failure. . . .this week. Thanks for the heads up.


#5: Post by Jonk »

Haven't counted the shots, could be anywhere between 500-1000 on my Kickstarter Robot. I'm thinking wear will depend a lot on how it was used as well - like high or low pressure, how often it's cleaned and if the portafilter is removed immediately or not.

The only times I've had leakage is when I've tried pre-heating the piston with hot water.

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#6: Post by yakster »

Kickstarter Robot, still on first gasket. I've had leaking a handful of times, but not consistently. I usually clean and lube the gasket when this happens and everything is fine.

LMWDP # 272

jpender (original poster)

#7: Post by jpender (original poster) »

Same issue or same symptoms?

My seal worked flawlessly for a year, something like 700 shots. It hasn't just leaked recently. It actually looks different, with whitish spots. It's also physically larger in diameter as compared to a new seal.

That said, I took it off, cleaned the little bit of coffee residue that was on the inside part, and lubed it. I've only pulled four shots since then but there has been no leakage. So maybe there is still life in it. Maybe a little bit of dirt in the wrong place made a difference. We'll see.

If I have to change the seal once a year I'm completely okay with that. That would be normal wear and tear. But if it leaked after 7 weeks I'd look at it completely differently. It's not the same thing.

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#8: Post by samuellaw178 »

Coming from a different but related perspective...I wonder what causes the failure of the seals? I haven't racked up enough shot counts to see leaking on mine (I was pretty much expecting them to last for 'life'). Since silicone doesn't get hardened or losing elasticity, it did make me wonder why would they fail? For those with leaking seals, do they get scored or deformed? Is there any correlation between the surface finish of the inner basket or the roundedness of the basket somehow?

jpender (original poster)

#9: Post by jpender (original poster) »

Good questions. The basket on my Robot looks flawless and I have a hard time imagining how it might have been warped enough to be out of round. Looking at the seal, it doesn't seem that bad. It's lost color, with blotchy white areas. Elasticity is more difficult to ascertain but it didn't seem stiff or hardened. When I laid a new seal over top of the old seal the old seal was clearly larger:

New seal laid over top of old seal (~700 shots)

More curious is why some people are reporting issues with relatively new Robots.
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#10: Post by Paul_Pratt »

I have 2 Robots on the go, 1 at home and 1 in the office and both have seals >3 years old and never been touched. The one in the office gets the most use 3 shots a day M-F.

Water leaking past the seal is almost always a seal that is not seated properly. On a relatively new machine I would say 99% it has to be that reason. The other 1 % could be overfilling the basket with water (leave about 10mm gap) and I suppose only using 1 Robot arm to initially lower the piston into the basket would kink the piston to 1 side and cause a leak.

One of our good resellers in Thailand sells to coffeeshops, and they do >100 shots a day. Seals are ok - their hands probably not so much :D

The basket is made from tooling so although there is a tolerance, the flared nature of the seal takes up any slack. Besides I made tester and we check each basket to make sure they are within specs. I do not think we have have found any over size baskets, oversized screens yes, plenty of those and they are never used.

We have only had a few emails of people asking when to change seals, all of those were KS backers from October 2018 deliveries.