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Flexible manufacturing cell

How an automated line works from start to finish: sensing, actuating, controlling and storing, with the model's interactive guide.

Also available in: Català · Castellano

A flexible cell handles each part according to its material and colour: it feeds it, sorts it, machines it, checks it and puts it away in the warehouse. This path goes through the concepts behind it, from each sensor up to the PLC that coordinates everything.

Overview

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Industrial automation

Flexible manufacturing cell

An automated line in three phases: feeding and sorting, machining and storage. Two PLCs coordinate sensors, pneumatic cylinders and servomotors to handle each part according to its material and colour.

Sensing

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Sensors

Presence detectors and limit switches

To know whether a part or a piston is in place: contact limit switches, magnetic reed sensors on the cylinders and optical sensors that detect whether the part breaks a light beam.

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Sensors

Inductive and capacitive proximity sensors

The capacitive sensor detects any material because it changes its capacitance; the inductive one only detects metals because currents are induced in them. Using both, you know whether a part is metallic.

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Sensors

Voltage divider to read a resistive sensor

A PLC can't read a resistance, but it can read a voltage. Put the sensor in series with a fixed resistor and the voltage at the midpoint changes with the sensor: Vout = Vcc · RS / (RS + Rfixed).

Actuation

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Actuators

Pneumatic cylinders and solenoid valves

Compressed air moves the cylinders; solenoid valves are the bridge to the PLC. A monostable valve springs back to rest on its own when it loses the signal; a bistable one needs a signal for each movement and remembers its last position.

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Actuators

Suction cups and the venturi effect

When compressed air is forced through a narrowing, it speeds up and its pressure drops: this creates a vacuum in the suction cup, which holds the part. A vacuum without a pump.

Control and positioning

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Industrial automation

PLC and GRAFCET

A PLC cyclically reads all its inputs, runs the program and updates the outputs. GRAFCET describes the process as a sequence of steps and transitions: each step waits for a condition before moving to the next.

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Industrial automation

X-Y Cartesian manipulator and servomotors

Two perpendicular axes driven by servomotors with encoders. At start-up it finds the zero of each axis; then it converts coordinates in millimetres into pulses to reach each position exactly.

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Sensors

Rotary encoders

An encoder tells the motor where it is. With two phase-shifted channels (A and B) you know how far it has turned and in which direction.

Safety

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Industrial automation

Safety in automated machines

A mushroom-head emergency stop halts the whole machine, light curtains stop the movement if someone enters the area and a signal tower shows the status at a glance.