Cafelat Robot Piston Seal Life - Page 3

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#21: Post by Ken5 »

Maybe the barista model works differently than the one without the gauge when it comes to that air gap between the piston and the grounds, seems that it would since the gauge and the tubing creates a pathway above the piston.

I had a conversation with a forum member a while ago that said his early barista robot did not come with the metal sleeve on the plastic tube and that he likes being able to see the tube as he knows when to clean it as water, and some coffee, makes its way up the tube during the shots. If the water is going up the tube then I doubt there is an air gap at the piston anymore. I am thinking that the non barista version would have a better chance of maintaining some gap.


#22: Post by jpender »

Yes, you're right. I had forgotten about that. With a Barista model the gap would be zero instead of a sub-millimeter of water vapor saturated air. But in either case the water would still be limited to the bottom of the seal for the time it takes to pull a shot.


#23: Post by Nate42 »

jpender wrote:My understanding is that silicone rubbers have a very long shelf life, as in 10-20 years or longer. The seal I installed earlier this year I had purchased two years earlier. It appeared pristine. After just three months of use it had enlarged significantly. I think use is what ages them, not time.

I suppose the seals could still be different out of the box in some invisible way either due to Q/C variation or maybe it's even possible that those manufactured earlier on were "better" somehow. That seems like a stretch, but I can't figure out what it might be.

I'm on my fourth seal in three years. I have six new ones in my cupboard.
I've just thought about a change in my routine that might be relevant. My normal routine would be to make a shot, drink it, and then immediately purge any remaining water, clean up, and store the robot with the basket/portafilter removed.

More recently I have taken a job that is a long commute, and perennially running late I often haven't cleaned up yet before I run out the door.

So long story short - I wonder if time the seal spends compressed (or perhaps even more relevantly hot and compressed) is more meaningful than time or number of shots. Just a thought.


#24: Post by Jonk »

I'll admit that I just leave the basket and portafilter in place most of the time when I'm done with a session and clean up some time after everything has cooled off. Could be next day.. I'm also often pre-heating the piston.

I'm on my second seal, changed the first one after 3 years out of convenience, not necessity. Actually I had more issues with both when brand new, there's a break-in period of a few weeks after which the seal has been improved.


#25: Post by YeetSkeeterson »

I have been pulling the same shot for about 2 years, on a few different Robot machines. I measure the quantity of water I put into the basket at 68g, this, with my coffee, provides roughly 39-41g out when the pressure begins to decrease since I don't have a scale that fits the Robot. Unless the government has been modifying the water my 68g should not be changing volumes and causing it to be "overfilled".

Seal is probably about 1 year old, at least 3+ shots a week, often one a day, sometimes I miss one here or there due to time constraints. I put some lube on and then wipe it away until you can barely see it.

I will be changing the seal soon. I think that once you pop the seal on, it's best to avoid removing it to clean underneath it. I feel that every time I have removed the seal even once, it's never been the same.

I leave my PF and basket off, on the rubber shot mat right with my Cafelat leveling tamp since they both fit well together underneath the piston. I do remember reading Paul usually leaves his attached to the Robot, so I do not think it's a concern.

I know it's foolish to even bother with this because I guarantee that changing the seal will bring it back to its well oiled life. Just another from the peanut gallery wondering how the seals seem to vary in use/lifespan between users.

I've been a big fan of preheating the piston by soaking but now, for my sanity's sake, I might just see if I can get the water just under the seal so that it steams just a bit, I'm sure anything will help. I'm starting to think it's the culprit. You always see graphs about how preheating the piston helps but I really don't care if I end up having to deal with this every time.
Nate42 wrote:Here's a test you can do without wasting coffee:
Thanks for the suggestion... I've done this before, sometimes you just get flustered and don't think. Honestly, I think doing this with my basket full of water every single time, even the extra 2 seconds or so, is absolutely worth it to avoid the headache of a missed seal shot. My basket does not slide over the seal whatsoever, there's always a tiny bit that flairs out, which I have to use my finger to push into the basket, it's not terrible, and this is a satisfactory fix in the meantime.


#26: Post by Jonk »

Perhaps not filling the basket up near the rim could be part of the issue for you? That'll also result in a cooler shot. A "neoweigh" would only set you back $16 (my near identical JoeFrex was $39 over here).


#27: Post by jpender »

Nate42 wrote:Edit: one more possibility I guess: if sliding over gasket when piston is down works but locking portafilter doesn't, maybe something is physically preventing the arms from lifting all the up?
I had this issue at one point. Somehow the pressure gauge worked it's way up the arm a little ways, presumably from the tension in the tube. I moved it back down 1cm or so and voila, locking in got way, way easier.


#28: Post by jpender »

YeetSkeeterson wrote:I think that once you pop the seal on, it's best to avoid removing it to clean underneath it. I feel that every time I have removed the seal even once, it's never been the same.
Unless you are reinstalling it improperly or actually damaging it I suspect that's just coincidence that you feel this is happening. Those seals are very stretchy.

Frankly, I'm impressed that you are still at it with a Robot given how much trouble you had before. And this is your third one now? I love my Robot but if it caused me a lot of grief I'd get a Flair 58 or something else.


#29: Post by YeetSkeeterson »

It's really not been troublesome... until it is... I don't know how to explain it. It's probably 99% trouble free until I get a hitch I can't fix quickly. So far it's always been basket/seal related, except for the paint scratching off down into the chamber on my first Robot.

It's quite easy to look at the seal... that's all you have to do to determine if the seal is seated correctly and I am capable of looking at something.

The seal is seated correctly when I start, but given my experiment, the fact the basket has so much trouble covering the seal during placement, it must be what disturbs it. I am quitting with the soak, I am moving onto a steam piston preheat, I would reckon this affects it, I'm surprised I've never heard anything from other people that soak the piston, seeing as I learned about the vapor barrier, I can't imagine that constantly soaking DOW in near boiling water doesn't have an effect, or how near boiling water affects the elasticity of the silicone seal. I am going to clean it all up and lube it again, will see if this helps.

I absolutely love my Robot for what it is, nothing better for the money. I don't want to spend $3,000+ for espresso like this or have the hassle of maintaining an electric machine at home. Yes probably my third Robot. I always come back. Literally the day after I sold it last time I missed it. That shows how good it is, I was planning on going electric last time but I stopped myself.

I came here for good espresso but now I barely visit. That shows the power of the Robot. I don't feel the ned to troll the forums for advice too often and spend valuable time trying to marginally improve something. The espresso I get is amazing and I spend my time enjoying it.


#30: Post by jpender »

As long as you're happy with it. But underfilling and then manually inserting the seal into the basket is not normal operation and shouldn't be necessary. They are evidence of some problem that you are having.

I can't help but wonder what it is. I remember when you shipped your Robot #1 back to Paul. I was expecting that he would find some sort of discrepancy with the Robot or the seal and instead he said it worked perfectly. It's natural to be curious about what was going on then. And now.

What happened with Robot #2?