Appendix B Arizona T220Uv Safety Systems; 0.4Safety Systems And Machine Safeguarding - Oce Arizona T220UV User Manual

Appendix B

0.4Safety Systems and Machine Safeguarding

The Arizona T220UV safety system consists of the following redundant Safety
Systems:
1. 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 (3012000507) and
dc motor driver board (7500-3009). 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 in section 4 below, as it is directly related to the watchdog timer method.
2. 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.
3. 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
6/2/04
Arizona T220UV Safety Systems
|
-117-