2020-04-29

After years of talking about upgrading our espresso equipment, we finally bought a used E61 single-boiler machine. Paired with a hand grinder, the process is refreshingly analog.

As part of learning how the machine works, I sketched a schematic diagram with Graphviz:

schematic diagram of an ECM Classika PID

Graphviz source

graph {
  nodesep = 0.2; ranksep = 0.2;

  water [shape=plain, group=a];
  reservoir [shape=oval, group=a];
  split_a [shape=point, group=a];
  filter_a [shape=box, label="filter", group=a];
  pump [shape=box, group=a];
  one_way [shape=diamond, group=a, label="one way", margin=0];
  split_b [shape=point, group=a];
  capillary [shape=box];
  gauge [shape=box, label="pressure gauge"];
  split_c [shape=point, group=a];
  pressure [shape=diamond, label="pressure\nrelease", margin=0];
  top [shape=oval, group=a, label="boiler\ntop"];
  valve_a [shape=diamond, label="valve", group=a, margin=0];
  wand [shape=box, label="steam\nwand"];
  steam [shape=plain];
  bottom [shape=oval, label="boiler\nbottom"];
  warming [shape=oval, group=a, label="warming\nchamber"];
  filter_b [shape=box, label="filter", group=a];
  restrictor [shape=box, group=a, label="flow restrictor"];
  valve_b [shape=diamond, label="valve", margin=0];
  split_d [shape=point, group=a];
  valve_c [shape=diamond, label="valve", margin=0];
  buffer [shape=oval, label="compression\nchamber"];
  valve_d [shape=diamond, label="valve", margin=0];
  waste [shape=plain];
  portafilter [shape=oval, group=a];
  espresso [shape=plain, group=a];

  water
    -- reservoir
    -- split_a
    -- filter_a
    -- pump
    -- one_way
    -- split_b
    -- split_c
    -- top
    -- warming
    -- filter_b
    -- restrictor
    -- valve_a
    -- split_d
    -- portafilter
    -- espresso;

  { rank=same split_b -- capillary -- gauge };

  { rank = same pressure -- split_c};
  pressure -- split_a;

  { rank=same top -- valve_b -- wand -- steam };

  { rank=same bottom -- top };
  bottom -- warming;

  { rank=same split_d -- valve_c -- buffer -- valve_d -- waste };
}

All of that comes together to produce one magnificent result:

espresso extraction using a naked portafilter