3.1 Data Acquisition Layer
The data acquisition layer is responsible of the
observation, gathering and delivering of the
variables of the machine to the persistence layer.
The general solution provided by IK4-IDEKO is
a device and software built jointly with Cyril data
systems (www.cyril.es) that is able to connect via
Ethernet to different types of machines, read data
and sends them to the cloud. This data gathering
device can connect to diverse numeric controls as
Heidenhain, Fanuc or Siemens, or even a data
gathering sensors.
Once the device is connected to a machine, a
web management tool can be used to remotely
configure the device, define the signals or variables
that will be read from the machine etc (Figure 4). In
this case, the memory address map of the PLC will
be used to match the real world with its
corresponding virtual counterpart. Moreover, the
sampling or data gathering frequency has to be
defined, in that sense, the concept of group of
capture has been defined, in order to read and
transmit together the set of variables that have the
same observation frequency.
Figure 4: Remote configuration of PLC variables.
The commonly available variables of a machine
tool are obtained through the numeric control and
the programmable logic controller (PLC). These
components manage a wide set of variables that can
be categorized in the following groups: state, alarms,
speed, temperature, power, revolutions per minute,
advance,… All these variables are related to the
machine or to specific components as engine, axis,
spindle, tool,…
Other useful variables that can be obtained are
related to the interaction of the worker with the
machine as the different types of overrides,
modifying the programmed operation behaviour,
interruption of the cycle of the machine etc.
Although the numeric control is the main data
acquisition device, there are other variables, for
example the ones related to dynamics, like
vibrations that have to be obtained using specific
sensors. This way, the monitoring of the machine
implies the monitoring of a numeric control, PLC
and sensors, depending on the observational
requirements.
3.2 Data Persistence Layer
The management, transformation and treatment of
the data is the most important stage in a data-driven
approach in order to make sense of a myriad of
variables (temperature, speed, override, power,
revolutions, vibrations,… ) obtained from cnc/plc
and a set of sensors.
The data persistence layer is divided in two parts.
First, a data lake model is the general repository
where the data from the different groups of capture
and sensors is stored and tagged using metadata in
order to provide data lifecycle and management
capabilities. A NoSQL document oriented
MongoDB database is used for this purpose.
The second part of the persistence layer is an
analytical database based on a data mart model. The
initial implementation relies on a PostgreSQL
relational database management system with three
datamarts: production, process and condition.
The whole set variables of a machine can be
grouped conceptually in production, process or
condition data. The production variables focused in
the state of the machine and closely related to the
concept of availability. Process variables provide
information about the machining process through
speed, temperature, power, revolutions,…process
and production can be used to approach the overall
equipment efficiency of the machine in a great
extent. The third group of condition monitoring
variables, besides cnc variables, vibration, noise, and
temperature measurements are often used as key
indicators to provide health information about the
machine and help detect machine faults early, which
prevents unexpected failure and costly repair.
The dimensional model of the data warehousing
conceptual framework has been used because the
observed variables make more sense once they are
organized and combined with dimensions, like
machine, program, tool, engine, spindle…
3.3 Data Visualization Layer
The visualization layer is divided in two parts.
The first one is machine monitoring. The
information is shown in real time, the monitoring
can be about production (state, alarms), process
(current machining process) and condition (health
and symptoms).