Having trouble with Cafelat Robot - Page 4

A haven dedicated to manual espresso machine aficionados.
Starguru (original poster)
Posts: 78
Joined: 9 months ago

#31: Post by Starguru (original poster) »

Jonk wrote:Try this:

Grind 2 samples at a bit coarser setting.

Then pull one shot without pre-infusion. Just 'slam' the levers to a high pressure right away.
The second shot, let the puck pre-infuse at very low pressure until you get droplets from every hole of the basket before applying 6-8 bars or whatever you're able to reach.

The first puck should meet with a lot more resistance. The second might not even allow you to hold the desired pressure. If you understand this, you can exploit it to get more acceptable shots by quickly adjusting the pressure profile to how the puck reacts. For example you can actually reach semi-high pressures with say a 30g dose of pre-ground supermarket coffee if you apply immediate pressure. It won't hold, but if you'd do it again with just the weight of the levers that might be enough to push all the water out at near 0 bar.

The puck is compressible and the more it's compressed the more resistance you'll get.
I'll definitely try, for science.

But you mentioned a scenario where you originally targeted 1:3, but noticed you "needed" to adjust to 1:5x. What did you notice that informed that decision? And why does slamming the levers help?

Ken5
Posts: 977
Joined: 4 years ago

#32: Post by Ken5 »

I went from using a barista express for a week or two to the robot, it took me some time to get used to the robot, it will come to you soon.

How long did you use the Bambino? Did you use the single wall basket with it? Reason I ask is you said you never saw channeling with the bambino, not sure why you would see it with the robot and not the bambino as channeling seems to be more of a prep issue than a machine issue. If you did use the single wall basket then I think you are grinding too fine for the robot and therefore you are pressing so hard you are degrading the puck. Preinfusing longer, or grinding coarser will take care of that. From what you said earlier I think you should start with the grind at this point.

I would say to grind coarser. Go in steps and as a STARTING point get a shot that starts to drip in about 5 seconds at 2 bars, then press to about 8 bars till you get to your goal ratio in an additional 20-25 seconds. Total shot time 25 to 35 seconds. For now press the levers smoothly to the 2 bars and again up to shot pressure. I believe this will solve your channel problems. From there adjust to whatever gives you the shot that you want as there are many options for grind, pressure, ratios etc that you will experiment with.

Also... don't be afraid to lighten up on the levers at the end if the shot starts to run to fast.
★ Helpful

sympa
Posts: 135
Joined: 1 year ago

#33: Post by sympa »

1. If all you can get out is 40g, you're doing something wrong, or there's a problem with your machine. Getting 50g+ out is easy with the Robot.
2. If you can't produce more than 8 bars of pressure, you're doing something different (not necessarily wrong), or there's a problem with your machine. If my grind is fine, I can get 12+ bars out. Not that I/you want to do this: in my experience, 7 bars is ideal for darker roasts, and 6 bar intial pressure going down to 4 bar final pressure (end of shot) is ideal for lighter roasts.
3. As for sour/bitter, there's a huge number of variables that go into this. You've not yet posted your recipe/process, from start to finish (ratio, preheating, pressure profile being the most important).

User avatar
Jeff
Team HB
Posts: 6879
Joined: 19 years ago

#34: Post by Jeff »

I'd add to that list that coffee is high up on the list of causes of unpleasant results.

The better your grinder, machine, technique, and skills become, the more you taste what is in the coffee. Frustratingly, often that includes finding out that there are weaknesses in your coffee that now are more evident.

Nate42
Posts: 1211
Joined: 11 years ago

#35: Post by Nate42 »

I just did a quick test - after a shot of 17g coffee, yielding 36g espresso, I swapped cups and measured another 34g liquid. So 70 total. If you can only get 40 out something weird is going on. You can fill closer to the top than you think. Are you level? if your shower screen is way off it might be preventing the levers going all the way down?

I never use a pressure more than 7bar. I have achieved up to 10 and choose not to tempt fate by going any higher.

You should let your pressure ramp down during your shot. This will help tame things at the end. I don't put a lot of thought into this it happens pretty naturally. Aim more for a constant flow rather than worrying about pressure. I look at the gauge when I am ramping up after preinfusion and then pretty much ignore it.

I routinely heat my portafilter by letting it sit on the lid of my kettle while heating water. Even for dark roasts. I rarely bother with any other form of preheating but when I do the "pour to overflowing" method is my favorite. Robot is easiest to use for medium to dark roasts but with preheating I have had success with very light roasts such as Wendelboe filter roasts.

The cures for sour are grind finer, brew hotter, longer shots, or switch coffees. Be careful with grinding finer though, as a mix of bitter and sour often means uneven extraction, which can be caused by poor distribution or grinding too fine. My grind rule of thumb - finer is better until it isn't. When in doubt start out coarser than you think you need, then move a little finer and rather than trying to diagnose the details just ask yourself the simple question - better or worse?

Jonk
Posts: 2195
Joined: 4 years ago

#36: Post by Jonk »

Starguru wrote:you mentioned a scenario where you originally targeted 1:3, but noticed you "needed" to adjust to 1:5x. What did you notice that informed that decision? And why does slamming the levers help?
If water starts dripping almost immediately during pre-infusion, the grind was too coarse / offered too little resistance (not an unlikely thing to happen with light roasts and SSP cast).

Instead of following instinct and backing off the pressure, I increase it as much as possible, providing enough resistance to pull espresso instead of some kind of 'sprover'.

It likely means I'd overshoot my target ratio as well, but I'd usually prefer 1:5 pulled in 15s over 1:3 pulled in 10s..

Starguru (original poster)
Posts: 78
Joined: 9 months ago

#37: Post by Starguru (original poster) »

Nate42 wrote:I just did a quick test - after a shot of 17g coffee, yielding 36g espresso, I swapped cups and measured another 34g liquid. So 70 total. If you can only get 40 out something weird is going on. You can fill closer to the top than you think. Are you level? if your shower screen is way off it might be preventing the levers going all the way down?

I never use a pressure more than 7bar. I have achieved up to 10 and choose not to tempt fate by going any higher.

You should let your pressure ramp down during your shot. This will help tame things at the end. I don't put a lot of thought into this it happens pretty naturally. Aim more for a constant flow rather than worrying about pressure. I look at the gauge when I am ramping up after preinfusion and then pretty much ignore it.

I routinely heat my portafilter by letting it sit on the lid of my kettle while heating water. Even for dark roasts. I rarely bother with any other form of preheating but when I do the "pour to overflowing" method is my favorite. Robot is easiest to use for medium to dark roasts but with preheating I have had success with very light roasts such as Wendelboe filter roasts.

The cures for sour are grind finer, brew hotter, longer shots, or switch coffees. Be careful with grinding finer though, as a mix of bitter and sour often means uneven extraction, which can be caused by poor distribution or grinding too fine. My grind rule of thumb - finer is better until it isn't. When in doubt start out coarser than you think you need, then move a little finer and rather than trying to diagnose the details just ask yourself the simple question - better or worse?
I should clarify this, the 40g issue is no longer a problem. I was leaving about a cm of free space when adding the water, I add more now. I just pulled a shot to 43g and easily could have got another 10g out, although the levers were almost completely pressed.

Starguru (original poster)
Posts: 78
Joined: 9 months ago

#38: Post by Starguru (original poster) »

sympa wrote:1. If all you can get out is 40g, you're doing something wrong, or there's a problem with your machine. Getting 50g+ out is easy with the Robot.
2. If you can't produce more than 8 bars of pressure, you're doing something different (not necessarily wrong), or there's a problem with your machine. If my grind is fine, I can get 12+ bars out. Not that I/you want to do this: in my experience, 7 bars is ideal for darker roasts, and 6 bar intial pressure going down to 4 bar final pressure (end of shot) is ideal for lighter roasts.
3. As for sour/bitter, there's a huge number of variables that go into this. You've not yet posted your recipe/process, from start to finish (ratio, preheating, pressure profile being the most important).

1. Ignore the 40g issue; I just add more water now.

2. I can get it to about 10 now, but it's not comfortable at all so I don't try for more. Plus most people keep saying 8 is enough, so I try to get to that.

3. The process I just followed 5 minutes ago for my dark roast:

1. Kettle on, 18g dose, RDT, grind at 155um (today)
2. After grind, give the grind cup a shake (saw LH do that), put into basket, WDT by going in circles around the perimeter twice, then the center. Then use WDT to level the bed
3. Tamp by laying the tamper lightly on the bed, putting my thumbs on the top of the handle, fingers around the edge of the portafiter, then pushing with my thumbs to the edge of it being comfortable.
4. Paper filter with metal filter on top, pressed firmly and gently on top of bed
5. Orient Robot so the gauge is facing away from me
6. Lock in portafilter, put scale and cup under, start timer
7. Try to get a 10 second pre infusion at 2bar, usually the handles are parallel with my counter during this step
8. Ramp up to 8 bar for about 20 seconds, until I get to about 30g out. I lean over the robot (which is why I orient it away from me) so I can see the gauge.
9. Lower pressure to about 4 bar for the last 10 or so grams.
10. When I hit target mass, I lift the handles up to stop the flow, remove the portafilter to the sink (I ground fine enough so I didn't have any drip) and taste



This shot was not very intense, but it was pleasant. No sourness or bitterness, just....coffee? Texture was nice too.

Jonk
Posts: 2195
Joined: 4 years ago

#39: Post by Jonk »

Sounds like a solid routine. A leveling tamper (3d prints can turn the stock into one) warrants less attention.

You can up the intensity with a full pre-heat.

User avatar
Jeff
Team HB
Posts: 6879
Joined: 19 years ago

#40: Post by Jeff »

You may be tamping too hard, unevenly, or both. Tamp as square to the basket as you can. Once the grinds get firm and offer resistance, that's about enough. If the tamp isn't level you may get uneven extraction. If it shifts while tamping you may cause weak spots that then cause unevenness.