Inconsistent volumetric dosing

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Jon V
Freeze Dried
Posts: 4
Joined: Tue Apr 01, 2014 6:30 am

Inconsistent volumetric dosing

Post by Jon V » Tue Feb 27, 2018 12:30 pm

The volumetric dosing on my Mini Vivaldi II has always been inconsistent (with or without portafilter / coffee in place), but I don't know if this is typical?

I programmed one of the buttons to 58 grams, without portafilter in place.

I ran the shot 6 times (still no portafilter) and got these results:

58g, 8.5 seconds
52g, 8.7 seconds
55g, 8.7 seconds
40g, 8.8 seconds
45g, 9 seconds
73g, 8.6 seconds

The times are consistent, and not completely accurate as measured by me with a stopwatch. The weights out are obviously quite variable.

Is this normal / expected? If not, what should I be looking at in terms of parts or other possible problems?

Jon V
Freeze Dried
Posts: 4
Joined: Tue Apr 01, 2014 6:30 am

Re: Inconsistent volumetric dosing

Post by Jon V » Wed Feb 28, 2018 1:09 pm

Did some more testing, immediately following a backflush.

The times are always the same, around 9 seconds.

1. 82g
2. 55g
3. 72g
4. 59g
5. 59g
6. 59g
7. 38g
8. 80g
9. 63g
10. 40g
11. 78g
12. 45g
13. 77g
14. 48g

As the pours take the same time, there is a noticeable difference in flow rate. It also seems that when I get a short pour, the next one will be long to compensate.

Adding the weights of the short pour and the following long pour, they generally average out to 60g (the volumetric target).

Eg:
Pours 7&8: (38+80)/2 = 59g.

Pours 10&11: (40+78)/2 = 59g.

Pours 12&13: (45+77)/2 = 61g.

daveR1
Americano
Posts: 5
Joined: Fri Feb 02, 2018 12:32 am
Location: Salt Lake City

Re: Inconsistent volumetric dosing

Post by daveR1 » Thu Mar 01, 2018 9:53 pm

Hey Jon,

Saw your post & it got me thinking. I’ve had my Dream T for a month now. I really like the machine overall. I have just started setting up the volumetric dosing as part of the various user profiles. I’m seeing some inconsistencies too.

I set a dose for one of my main coffees today. With 17 gr coffee in the PF, I’m pulling 28-29 gr out in 27 sec @ 201 deg.
I emptied the PF and tried measuring the water mass without coffee in the PF.

Like you found, my run time has been pretty consistent @ 15-16 sec. The first volumes were 142, 146 gr. Consecutive shots kept climbing in volume ranging from 155 gr. - 173 gr. water. I paused a couple of minutes between shots so that the boiler could get back up to temp.

These variations seem like a huge difference in volume. Explains why when I think I have a volumetric dose set right, the next shot or two is either too short or too long.

I guess I’ll give Chris Coffee a call and ask them what’s going on.

Tobias
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Joined: Fri Dec 29, 2017 10:12 am
Location: Sweden

Re: Inconsistent volumetric dosing

Post by Tobias » Fri Mar 02, 2018 12:19 pm

I also have the mini vivaldi 2, and getting inconsistent shots. I measure my double espressos, and with same bean/grind/dose it can vary 3-5 grams per shot.

daveR1
Americano
Posts: 5
Joined: Fri Feb 02, 2018 12:32 am
Location: Salt Lake City

Re: Inconsistent volumetric dosing

Post by daveR1 » Fri Mar 02, 2018 1:39 pm

I spoke with Chris Coffee today. They are going to test their Dream with & without coffee and get back to me. I’ll post what I find out.

Velcro
Latte
Posts: 18
Joined: Tue Mar 06, 2018 5:28 pm
Location: PA

Re: Inconsistent volumetric dosing

Post by Velcro » Tue Mar 06, 2018 7:32 pm

Any update?
I had similar inconsistencies with my Breville Oracle
it got to the point I stopped using volumetric dosing.
I'm hoping that's not the case for Dream's too.
Velcro
Sette 270
La Spaziale Dream v1.24
IMS Baskets & Reg Barber C-Flat 53.3

daveR1
Americano
Posts: 5
Joined: Fri Feb 02, 2018 12:32 am
Location: Salt Lake City

Re: Inconsistent volumetric dosing

Post by daveR1 » Tue Mar 06, 2018 9:44 pm

Velcro wrote:
Tue Mar 06, 2018 7:32 pm
Any update?
Haven’t heard back from Chris. When I get a free minute I’ll give them a call

alanmd
Freeze Dried
Posts: 3
Joined: Sun Feb 14, 2010 10:10 pm

Re: Inconsistent volumetric dosing

Post by alanmd » Sat Apr 21, 2018 4:24 pm

The volumetric dosing on my mini Vivaldi II didn't work at all from day 1. Based on what I read here I stripped it down and removed the usual brass shavings from inside the little doser spinner thing, and it has worked perfectly and consistently ever since.

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