Cafelat Robot day 1 issues - Help needed - Page 6

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#51: Post by jpender »

mixespresso wrote:I will go finer tomorrow morning and see what happens. I have little experience but I do think the grind is already really fine (powder-like). I am not far from getting the burrs touching, but who knows this might be the way. let's try it
Too coarse a grind is the most likely explanation for a shot that runs too fast. But it still does not explain your report that you can't push higher than 4bar without extreme effort. How can it be both too easy and too hard at the same time?

mixespresso (original poster)

#52: Post by mixespresso (original poster) replying to jpender »

Very fair point. I could not go higher than 4bar last week indeed. This Monday, I changed beans and now it is way too easy

Honestly, I don't understand it either: last week vs this week's contrasting experience, and how can such a fine grind offers such little resistance... At 2 bars with such fine grind, I d have "theoretically" expected a really really long shot.
I will go finer tomorrow and see what happens



#53: Post by imp96 »

I agree with others, everything looks ok and you need to grind much finer. I would also recommend you up the dose to at least 18g or even better 20g. This in itself will significantly increase the puck resistance and a deeper puck is less likely to channel. Once you figure things out you can go back to a smaller dose.

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#54: Post by Ken5 »

Looking at your video I too would say to grind finer. The flow looks fairly good and by judging the hand, very hard to really know from video, it looks quite relaxed and probably right for 4 pounds of pressure. If you grind too fine, and press to 9 bars it takes a lot of pressure, so much that the hand sort of shows tension and possibly some shaking in your arms, which it too fine.

You want the flow to be about that size at first with higher pressure. I bet if you got it up to 8 or 9 bars with that grind the diameter would increase quite a bit and the shot would be much shorter. Grind finer and you will have to press harder to get that flow.

mixespresso (original poster)

#55: Post by mixespresso (original poster) »

Hi all, I pulled another couple of shots today
  • I stuck to 16g so I could compare it to previous shots
  • I paid more attention to straight tamping so the coffee was well levelled
1st shot: with preinfusion
  • preinfusion happened at 1bar'ish
  • The max pressure I managed to get was 4bars
  • I was not aiming at any recipe, but it was on the lungo side and the extraction was running fast I felt
Link: ... n.mp4?dl=0

2nd shot: without preinfusion. I tried to pull as quick and as hard as possible (of course, as b4, with a grind as fine as possible)
  • The max pressure I managed to get was 5'ish bars
  • Again, I was not trying any recipe, but it was probably a lungo in less than 30s
Link: ... n.mp4?dl=0

My general observations:
  • even grinding as fine as the grinder can, I cannot choke the machine,
  • For such a fine grind, the flow is still fast I think. I cannot go any finer with this grinder
  • I cannot reach high pressure
  • the pre-infusion happens at 1bar'ish. I don't have any robot experience but, in the videos I have watched online, I think 2bars was the norm. It is like the theoretically expected pressure had been divided by two
Maybe I am incapable of understanding the Robot experience, but I don't feel I am in control of the flow at all.

Thanks for you help everybody! I do hope I am not being a pain!


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#56: Post by Ken5 »

Not a pain at all!

Did not see your videos as they were not responding for me.

I am still wondering about the 3 week old beans that came out of a bin. Stale beans could be the whole reason for your issues. Try to find beans with a roast date on the bag and a bag that has been sealed.

Dose also has an impact on pressure. The more coffee that there is the more resistance you will get. Even if you want to stay at 16g in the future, at least try 18g just to see if you can get the pressure higher.

Just having the tamper level when you press is not enough. you want the grinds evenly distributed before you tamp. If their is a void, or if the bed itself is angled all that a level tamp will give you is a bed of different densities as it will press the higher grinds harder that any low spots. The water will find the least dense areas causing a quicker flow through these less dense areas.

I am assuming that when you say you can't get above 4 bars that you mean it just gushes out after that?

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#57: Post by Ken5 »

finally was able to see videos, second shot was better!

First thing to try is to change coffee if it is still that coffee you got 3 weeks ago.

Never used that grinder, I am sure it is capable as I bet someone would have said it was not by now.


#58: Post by Jonk »

The burrs in your grinder - they don't look like this right?

One thing you can do to make your grind even finer is to use the hopper - filled with a decent amount of beans, say 100g. You can even up the dose to 25g, just to exclude that there's anything wrong with your technique. Not sure if it was mentioned already in the thread but you get best control of the shot if you fill water almost to the top of the basket.

mixespresso (original poster)

#59: Post by mixespresso (original poster) »

Ken5 wrote:finally was able to see videos, second shot was better!

First thing to try is to change coffee if it is still that coffee you got 3 weeks ago.

Never used that grinder, I am sure it is capable as I bet someone would have said it was not by now.

I bought new beans this Monday from my local roaster, labelled and sealed. roasted on Sept 20th,
It is a good roaster so the beans should be OK. I bought new beans today though, so I will change them soon and see anyway

The 2nd shot was better indeed but it was an extreme shot I think: grinding as fine as possible, and pushing the arms as quick as possible as hard as possible. Hope that does not become my new process :D

I will updose next time
I d like to use a bathroom scale too. I only have a digital one and turns itself off with low weights



#60: Post by thirdcrackfourthwave »

I'd try and borrow a different espresso grinder to experiment with. I'm pretty sure I could choke my Robot with three week old beans (it really doesn't take all that much to get to 10-11 bar) but if you can't find a different grinder you might look at the beans.