Causes Of Tact Time Deviation - Mitsubishi Electric MELFA CR750 Series User Manual

17.12.3.

Causes of tact time deviation

With this software, you can use the simulation function to calculate the robot movement tact time.
However, the calculated tact time varies with the capacity of the computer used and its load status and does
not completely match the actual robot operating time (tact time).
Use this function as a rough yardstick for tact time study.
Also, there are the following causes for the tact time calculation results deviating from actual robot tact time.
(1) An application other than "program editing" of this software is running.
This software's tact time calculation has parts that are processed on the computer in the background. For
example, if you are working running an application such as a Word document that is saved automatically,
it takes more time for the background processing for this software and sometimes the correct tact time is
not calculated. The tact time is increased.)
When calculating the tact time with this software, first close other applications.
Also, on this software itself, first close all the screens beside "Program edit".
(2) This uses commands that depend on the robot main unit status and external equipment.
There is no connection with the robot main unit or external equipment in this software's tact time
calculation. Therefore, commands that are executed communicating with that equipment are executed as
if ideal information were sent from that equipment. Therefore, the calculated cycle time is shorter than the
actual cycle time.
The commands to which this applies are shown in the following table.
Function
1 Positioning
completion wait
2 Compliance
3 Collision detection
4 Servo control
(*1) The Fine command be used with this software Ver.2.40S or later and selection RV-F/RH-F series.
For example, if the servo On command is executed in the program, the actual robot takes a few seconds,
but the simulation requires almost no time at all (500 ms or less). In order calculate the tact time precisely,
program using only movement commands and none of the above commands. If you are executing a
program you already have, either comment out such commands or extract and use just the part you want
to measure.
(3) This uses functions that depend on the CPU processing speed and OS.
The tact time calculation in this software runs on Windows, but the robot controller control software runs
on a real-time OS, so the internal operations are different. For example, with a real-time OS, the tact time
may be increased by the postponement of calculations with a high load that could not be fully processed,
but in this software's tact time calculations, such an increase in the tact time can not be calculated.
Therefore, if you use the high-load functions below, the calculated tact time may be a few percent less
than the actual tact time.
The commands to which this applies are shown in the following table.
1 CC-Link
2 Multi tasking
3 Added axes
4 Maximum
acceleration/deceleration control
5 Collision detection
6 Maintenance forecast
(*1) On actual robots, the tact time is roughly 3-10% longer.
By changing a robot program to eliminate the above factors, you can reduce the
difference between the simulation tact time and that on the actual robot. However,
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Command
FINE(*1)
CMP JNT/POS/TOOL/OFF
CMPG
COLCHK、COLLVL
SERVO ON/OFF
Function
Monitors the robot's status until it
reaches the target position.
Monitors external force on the robot.
Monitors external force on the robot.
Monitors the servo amp status
Cause of increased processing on actual robot
Because there is more signal processing with the CC-Link
option than without it
Because multiple robot programs are executed at the same
time
Because of the need to control the additional axes
Because the optimum movement for the robot load is
calculated
Because processing to detect collisions is executed (*1)
Because the processing time is longer when the maintenance
forecasting information collection level is raised (*1)
In tact time calculation, the same results are calculated as for
information collection level 1 (the factory default setting).
Explanation
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