Leveraging the ISA-88 Standard--in a Multi-Station Dipping Process
John Parraga & Marcus Tennant
Rockwell Automation
Industry and Requirements
Challenges of the Process
How ISA-88 was Applied
Benefits and Conclusion
Questions
Processing objectives:
Surface cleaning
Chemical Milling, Wet etching
Layer thinning, Layer stripping
Parts anodizing, Plating
Gas deposition
Multiple parts types:
Small semiconductors components.
Very large piece for building construction.
Aerospace components.
Vehicle parts.
Steel zinc galvanizing
Some of the requirements for these type of processes are:
Modularity
Flexibility
Traceability
Agility
Simultaneously being moved from station to station by one or multiple means:
Robot arms.
Crain.
Conveyors.
Human.
Procedural or sequencing requirements:
Many recipes.
Many equipment paths.
Processing time in harsh solution station is critical.
Arbitration and allocation of resources.
Parts processing data.
Procedure visibility
Life cycle problems:
Typically custom code has been written for each application built.
Problems with change control and update.
Challenges of system expansion.
Understanding the code when author leaves the company or retires.
How ISA88 was applied...
First, focus on what the equipment is capable of...
Then on what to do with the equipment...
The following is a list of steps that are typically used in determining the equipment model for a traditional batching process, this same was used for these processes.
Step 1) Determine the boundaries of the project.
Step 2) Determine the units and containers.
Step 3) Follow the material flow:
3-1) Bring materials
3-2) Move material
3-3) Remove material
Step 4) what is done to the material while in the unit.
Step 5) Identify “unit tags”
Step 6) Determine the equipment arbitration.
Step 7) Define the Parameters and Report values required.
First we did step 1 and 2...
then step 3... Follow the material flow:
3-1) Bring materials
3-2) Move material
3-3) Remove material
Then steps 4, 5, ane 6: Step 4) what is done to the material while in the unit.
Step 5) Identify “unit tags”
Step 6) Determine the equipment arbitration.
Then we did Step 7:
Transfer IN (X_IN).
Transfer OUT (X_OUT).
Processing.
Ready to Receive / Send. (Pick / Place)
Inter unit Synchronization.
Operator prompts.
Equipment initialization.
Timer, etc.
Parts are transported from unit to unit using Equipment Module...
1) Move to source.
2) Lift (pick) the part if “Source Ready”.
3a) Move to “Destination wait point”.
(if ”Destination NOT Ready”)
3b) Move to “Destination”
(if ”Destination Ready”)
4) Lower the part then release it.
5) Move to a “post destination end point”.
The use of the Phantom unit enables a part that has been processed in unit 1 to acquire a robot, start the transport process to it’s next destination before its destination unit 2 has been released by the previous ISA-88 Procedure.
Reduce the overall cycle time.
Releasing source unit sooner.
BENEFITS:
Arbitration or Coordinated (is handled through)
Custom Off The Shelf software product
Not application specific custom engineering code
Considered part of an overall scheduling realm.
Reporting and visualization.
Custom Off The Shelf tools give significant insight into the process.
Flexibility and agility.
Adding new control Recipes and let the system solve the resources
Adding new Master Recipes with no additional engineering
Re usable of ISA-88 Operations and Unit Procedures
Respond efficiently to break downs.
A disabled robot or crane is reserved by allocation not selectable.
The operators can issue workarounds or allow system to select.
A disabled Unit (tank) is reserved by allocation not selectable.
Equipment selection.
Set up ISA-88 Procedures to allow the batch server to select the first available units.
Use of Pseudo or Phantom units for each real unit in the process.
This enables the equipment to start transferring parts from one unit to another before the receiving unit has finished processing its current part.
(Two distinct control recipes using the same unit at the same time, this helps reduce the cycle time).
Used by active recipe park unused parts carriers.
Conclusion:
Applying the S-88 design principles in non traditional applications is shows the benefits to a wide range of industries. In the case of multi-station dipping processes, applying ISA 88 design principles provides a modular strait forward solution to a complex problem.
