Uneven water dispersion from La Marzocco Linea Mini grouphead - Page 2

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nuketopia

Postby nuketopia » Yesterday, 3:10 am

Everything seems normal for your flow rate and water screw. The LMLM flows significantly more water than e61 style espresso machines.

The thing you might want to check into is the screen. Over-tightening the screw can distort the screen. Perhaps a new screen and group gasket would help? The screen and gasket are essentially consumable components.

The espresso extraction is not unusual, but generally my experience is that is caused by the coffee and grind, not so much the machine. I don't know the dose of coffee or the grinder, but you may experiment with the dosing and basket size to see if you can achieve more uniform results.

Since I got the Monolith, my flows tend to be very uniform. However, as the coffee beans age beyond the ideal resting from roast date, I get increasingly uneven flows and spritzing.

lattenewbie

Postby lattenewbie » Yesterday, 5:19 am

Thank you very much for your diagnosis.

I use both the stock LM screen and IMS nano-coated screen. I cannot discern the difference of water dispersion pattern between the two. But I think there is a difference between the stock screw and the 6-hole screw, when tested by attaching only the screw w/o screen. I have not yet replaced the group gasket since I bought the machine some 9 months ago.

My grinder is LM Lux D, which is OEM by Mazzer. I know it does NOT belong to the high-end grinder category. But, due to a budget constraint, I have to continue to use Lux D for one or two years... I will elaborately dose, level and tamp to avoid the uneven dispersion.

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erics

Postby erics » Yesterday, 2:35 pm

Is that rate faster than ideal?

Yes it is. The flow rate for the LM Linea Mini should be equivalent to that of the GS3 which is ~475 ml/minute at a brew pressure of ~9.0 bar.

The only significant restriction in your flow path is the 0.6 mm(?) gicleur so lowering your brew pressure will dramatically affect the flow. I believe LM has flowrates and gicleur sizes on their website.
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at erols dot com

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JmanEspresso

Postby JmanEspresso » Yesterday, 4:17 pm

The water dispersion doesnt look THAT bad to my eyes. Personally, Ive never put much value into how the water "looks" coming out of the grouphead. Ive currently got the precision screen in my E61 group, but for years before that, in all the E61 machines I owned, I use the stock OEM screen, and the water never "looked" like it poured evenly. It always looked biased to one side or the other. The precision screen does provide a more aesthetically pleasing "even raining" effect.

It may be the lighting, but, honestly, it looks more like an issue with coffee and prep. Again, it may be the lighting, but the coffee looks like its a little stale. It looks on the thin side, viscosity wise. What kind of coffee are you using, when was it roasted, and also, whats your dose and basket choice?

Wattbe

Postby Wattbe » Yesterday, 5:42 pm

The flow rate (water debit) in the LMLM is higher than the GS/3 due to a larger gicleur. The GS/3 comes stock with a 0.6mm and LMLM comes with a 0.8mm. According to La Marzocco, the GS/3 flow rate should be 500ml/min plus or minus 10%. I'm not 100% sure of the LMLM rate but it will be significantly higher than the GS/3.

Have you tried cleaning the dispersion screw and the area behind the shower screen? I don't mean backflushing but actually wiping the area with a damp cloth. The coffee oils which which naturally accumulate in this area sometimes affect the water flow out of the machine. It's a shot in the dark but might be worth trying.

Simon345

Postby Simon345 » Yesterday, 9:15 pm

The truth is that the LMLM struggles to perform pretty pours on anything other than medium/darker roasted beans.

lattenewbie

Postby lattenewbie » Today, 12:09 am

Thank you for all the guys!

For these few weeks, some changes has come to my Linea Mini.

1) A tech guy exchanged the gicleur from 0.8mm to 0.6mm. That changes the flow rate dramatically, from over 500 ml to approx. 250 ml per 30 sec.
2) An IMS precision shower screen and a six-hole screw have arrived. Seemingly, they contribute to the uniform dispersion.

I currently never stick to any one coffee. I enjoy changing several coffees. But my consumption speed is slow (one or two shot per week-day) compared to that of serious coffee lovers. So, as someone pointed out, my coffee gets obsolete in the refrigerator,,,

I will try a larger basket for wider headspace, a leveling tool for even distribution in the basket.

LATrapp

Postby LATrapp » Today, 1:32 am

lattenewbie wrote:I confirmed that the machine is set level.
And seemingly, the group is situated level, not tilted.


Did you level the machine while water flowed through the screen? I'm assuming yes, but of course the machine frame being level is secondary to the group flow being level.

lattenewbie

Postby lattenewbie » Today, 1:59 am

I now double-checked the tilt of the group head by measuring the angle of suspending thread with a sinker.
Almost level.