Cafelat Robot - hard to lock in portafilter and o-ring not staying in place

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Nwin23
Posts: 59
Joined: 2 years ago

#1: Post by Nwin23 »

I've had my robot for about a year. A few months ago I crimped the metal tube on my barista version so I used it without the tube for a few months until I ordered a new tube. I just replaced the tube yesterday and after a test run it kept pressure just fine.

Over the last few months the portafilter has been getting harder and harder to seat correctly. I find myself having to lift the handles all the way up and actually force the portafilter as high up as it will go on the piston before pushing it to the right to lock it in.

This morning I pulled a shot and 1) it was very hard to seat the portafilter and 2) it didn't do a great job at keeping pressure. I was able to go up to 4 bar but it was a very quick extract with most of the water staying up in the piston. I was able to tilt the robot on its side after the PF was removed to empty some water from the inside of the piston.

Here's how the gasket looked after the shot:



I know that's not correct. Here's how I made it look after:


Unfortunately I'm out of the packet of Dow 111 that came with the robot so I've got that on order.

I'm hoping lubing up the gasket will fix it. But while I wait for the mail, any other ideas?

I'm also concerned about water in the piston. That makes me think water is getting through the threads and into the piston because I'm not sure how else it would get there. I've got Teflon tape on those threads (the one which connects to the bottom of the tube).

ziptie
Posts: 106
Joined: 7 years ago

#2: Post by ziptie »

You probably don't have quite enough teflon on the plug...so water is getting by. A similar thing happens on La Pavoni levers (like mine) that have a PPK (pressure profiling kit). If insufficient teflon is used on the piston-to-rod connection, some water gets by the threads and maximum potential shot volume is reduced.

As for the lube, you could use a dab of plumbers silicone grease in the meantime. Some of the available plumbers silicone grease is Dow 111...go figure :) Not that it's the only viable option.
I'd also take this as a cue to clean & inspect the gasket. With reasonable care/use, it seems unlikely that the gasket is badly worn. From your description, it seems as if the gasket is not seated quite right...and some brew water is getting past the gasket as well. Are the levers a bit lower than usual when you complete your typical volume shot?

Nwin23 (original poster)
Posts: 59
Joined: 2 years ago

#3: Post by Nwin23 (original poster) »

Interesting about the Teflon tape...I wrapped it three times but can try to do it again and see if that affects anything.

learncoffee
Posts: 67
Joined: 7 years ago

#4: Post by learncoffee »

Try replacing the piston seal. When I had problem locking in the portafilter, it was usually a sign to replace the seal. Cleaning the seal and the piston may help a bit, but eventually I had to replace it.

If you are wondering how long the seal should last, I believe it is still an open question. There is a whole thread on it.

Bluenoser
Posts: 1432
Joined: 6 years ago

#5: Post by Bluenoser »

I also think replacing the seal will fix your problem. I had a seal go similar to that.. I don't have the barista version. But grounds would get caught behind the seal and it leaked as well. Clean really well when replacing the seal. About a year is all I get out of seals.

jpender
Posts: 3798
Joined: 11 years ago

#6: Post by jpender »

Nwin23 wrote: I'm also concerned about water in the piston. That makes me think water is getting through the threads and into the piston because I'm not sure how else it would get there. I've got Teflon tape on those threads (the one which connects to the bottom of the tube).
It could also leak at the fitting/tube interface.

Nwin23 (original poster)
Posts: 59
Joined: 2 years ago

#7: Post by Nwin23 (original poster) »

We have success. I emailed Paul and he quickly responded with a fix.

Regarding the tubing, it requires two separate "moments" of force. I was only pushing it to the first step and the second step requires quite a bit of force.

Here's what Paul said on the issue:

Ok first thing is to make sure that the tube is actually in the fittings properly. I would remove it and then check the fitting into the piston. There are definitely 2 stages to how the tube goes in. The first stage is easy and it will go in about 5mm. But the 2nd stage is what everyone misses out and this does the sealing. The 2nd stage should go in another 3mm or so and takes much more force to get it in. I usually use one of our microfiber cloths over the tube to give me some more grip. You will know when it goes in.

For the lower fitting I always insert it in the upright position and grip the tube in a fist with my right hand and push down. The left hand steadies the fitting. You then insert that into the piston.

For the top fitting install the sleeve and then put on the fitting. This is the part where I need a cloth for extra grip. Once you are sure it is in you then hook it up to the gauge.


Regarding the installing of the portafilter, always lift the arms up as far as you can. I would also guess that the seal is not really happy. Run your finger and thumb around it to make sure it is seated all the way around. Some of the Dow111 up in the rails where the portafilter locks in would also help.
I'm still waiting on the Dow111 to come in, but I fully cleaned the gasket and there was no issue with getting the portafilter to seat.

Nate42
Posts: 1211
Joined: 11 years ago

#8: Post by Nate42 »

Good to hear you solved your tubing seal issue. Regarding the piston seal, a good cleaning and some lube may well extend it's life but once it starts coming out of place it is on the road to failure. Be ready to replace it.

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yakster
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#9: Post by yakster »

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