October 27, 2017
Once or twice a month, we like to share IAI Actuator News with the automation community.
Here is a new Easy Automation Application Improvement video Vol.7-2.
Easy Automation Improvement Example Vol.7-2
Loader / Unloader for Grinding Machine
This processing machine grinds the inner faces of parts. Its loader/unloader uses air cylinders.
Problems when Air Cylinders are used
As the rotary unit turns to the horizontal position, the part being transferred may shift or drop due to a shock upon stopping.
Accordingly, the moving speed must be set lower, which prevents further cycle time reduction from the current level.
The current cycle time is 5.6 seconds, the production volume is 9,000 pieces a day, and the line operates for 14 hours.
The thrust force of the rotary air cylinder used for the rotary unit becomes unstable due to deterioration of gaskets, etc. If the thrust force drops below the drag(*1) of the shock absorber, the rotary unit can no longer reach the set stop position and thus contacts the part removal unit, causing a failure.
To prevent this contact failure, the air pressure was adjusted, and the stop position was confirmed once every two days (11 times a month). These operations take two maintenance people about 30 minutes.
Once a contact failure occurs, recovery operations, including replacement of the rotary air cylinder, straightening of the bracket, position adjustment, and test operation, are required. These operations take three maintenance people eight hours.
During the 18 months from the start of production, five contact failures occurred.
(*1) Drag: Force applied by an object as a counteraction to the force that was applied to the object by another object upon contact.
Improvements Achieved by the ROBO Cylinder®
1. Shorter cycle time through optimal operation settings
The ROBO Cylinder lets you set the position, speed, acceleration and deceleration separately. By setting gradual deceleration, high speed and high acceleration, high-speed operation with shock-less stopping became possible.
After the air cylinder was replaced with the ROBO Cylinder, the cycle time was reduced by 0.8 seconds to 4.8 seconds, and the system operating hours per day became shorter.
System operating hours:
2. The system always operates consistently, and there are no more contact failures.
With the ROBO Cylinder®, anyone can easily perform adjustments in the same way by simply entering the position, speed, acceleration, and deceleration on the teaching pendant.
At least three years has passed since the ROBO Cylinder was implemented, but the system still operates normally based on the same initial settings. There hasn't been any contact failure.
Periodic maintenance (22 days of operation a month)
3. Reliable positioning operation
With an air cylinder, completion of positioning operation is generally detected using an auto switch. When the auto switch turns ON, however, the operation is not yet completed. So, a timer is set, and the system waits until the positioning operation is completed.
However, if the speed or thrust force drops due to air pressure fluctuation or deterioration of gaskets, etc., the positioning operation may not complete within the timer period.
Still, the control sequence may determine that the positioning operation has completed and perform the next operation, and a problem may occur as a result.
The ROBO Cylinder comes with a motor unit with encoder(*2).
Feedback control(*3) is performed based on the position data from the encoder to ensure reliable positioning operation.
(*2) Encoder: A sensor that detects the number of revolutions and rotational speed and direction of a motor.
(*3) Feedback control: A type of automatic control method to control the output to be the same as the command by comparing the two.
Cost Cutting Effect
|Required production quantity||9,000 pieces/day|
|Annual operating days||264 days (22 days x 12 months)|
|Number of operators||Production line: 2 operators|
|Line inspections: 2 operators|
|Line recovery: 3 operators|
(2) Comparison of air cylinder and ROBO Cylinder®
|Item||System using air cylinder||System using ROBO Cylinder|
|Cycle time||5.6 seconds||4.8 seconds|
|Operating hours (day)||14 hours/day
9,000 pieces x 5.6 seconds =
50,4000 seconds = 14 hours
9,000 pieces x 4.8 seconds =
43,200 seconds = 12 hours
14 hours/day x $18*/hours x
2 operators x 264 days/year = $133,056*
12 hours/day x $18*/hour x
2 operators x 264 days/year = $114,048*
|Loss due to failures that occured before the modification||Time||596 hours
 Periodic inspection
0.5 hour/time x 11/month x 18 months x
4 operators = 396 hours
(2 inspection operators, 2 standby production line operators)
 System recovery
5 failures x 8 hours/failure x 5 operators = 200 hours
(3 recovery operators, 2 standby production line operators)
Total  +  = 596 hours
596 hours x $18*/hour = $10,728*
|Cost of repair parts and materials||$1,500*
 Cost of replacement air cylinder
$200*/unit x 5 replacements = $1,000*
 Bracket correction cost
$100*/unit x 5 corrections = $500*
Total  +  = $1,500*
(3) Cost Cutting Effect
|Air cylinder||ROBO Cylinder|
|Labor Cost (annual)||$133,056* -||$114,048* =||$19,008*|
|•Loss due to the failures that had occurred before the modification
(over 18 months) Labor cost
|$10,728* -||$0 =||$10,728*|
|Cost of repair parts and materials||$1,500* -||$0 =||$1,500*|
|Total loss =||$12,228*|
By adopting the ROBO Cylinder®, the cycle time was reduced, the utilization ratio increased 14%, and annual cost savings of $21,220* was achieved.
After the modification, the loss of $12,228* due to the failures that had occurred before the modification was eliminated.
* Exchange Rate: 1(USD) = 100(Japanese Yen)
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