Arizona T220Uv Safety Systems - Oce Arizona T220UV User Manual

Arizona T220UV Safety Systems

Introduction
Safety Systems and Machine Safeguarding
The Arizona T220UV safety system consists of several redundant Safety Systems that are described in this section.
Interlock System
The interlock system consists of a monitored contact set from the Category Four interlock system and a series circuit of the
emergency stop switches that all have normally open contacts (Please see attached schematic Machine Safeguarding
Category Four Interlock System T220UVR6MachineSafeGuard.pdf). A monitored contact set from the Category Four
interlock system must be closed in order to provide the interlock signal to the CAN Command board and dc motor driver
board). If any pair of contacts opens (either by pressing the emergency stop or opening any door) the H-bridge control chips
(HIP4081A1B - located on motor driver board) will be disabled by a hardware electrical means. The two motors directly
affected are the gantry motor and the carriage motor, which require the H-bridge control chips to be enabled in order to move.
Also, the DSP will read the status of the interlock (status updated once every 5 milliseconds) and initiate the shutdown
sequence which is defined as:
Disabling the H-bridge control logic on the DC motor driver board (via software control of the MTR_RST signal) and
disabling the 48-volt and 24-volt power supplies as well as systematically turning off all devices, and killing all processor
tasks.
The only way to recover from this situation is to restart (reboot) the machine. The exact means for disabling the 48-volt and
24-volt power supplies will be described below, as it is directly related to the watchdog timer method.
Gantry Error Detection
When the printer is switched on and the software programs have been loaded the gantry control system (executed by the
'DSP' means) is constantly servoing the position of the gantry to the current desired position. It obtains position information
about the gantry via the Renishaw linear encoder to the nearest micron. If the position of the gantry ever deviates from the
desired position by more than 50,000 microns (50 mm) the DSP initiates the shutdown sequence, which disables all motion.
Specifically, the gantry motion would be stopped by means of disabling the control logic and removing power.
Carriage Error Detection
The carriage control system is similar to the gantry control system except that it is primarily a speed control system. If the
carriage speed deviates from the desired speed by a significant amount, the DSP will again initiate the shutdown sequence,
which disables all motion. Specifically the carriage motion would be stopped by means of disabling the control logic and
removing power. In addition the carriage motion is monitored by a two-encoder system, one encoder reads the linear position
of the carriage and the other reads the angular position of the motor shaft. If the difference between the two-encoder readings
becomes significant the DSP will again execute the shutdown sequence.
110 T220UV User Guide