How do you eat a whale? One bite at a time.
In a March 2016 blog post entitled CIMControlFramework Work Breakdown, Cimetrix listed eleven points to be taken into consideration when starting an equipment control application using CIMControlFramework (CCF). One of the things to consider is how you want to control the material moving through the tool – or scheduling of material. This blog post delves a little deeper into the scheduling aspect of equipment control applications.
Doctoral dissertations and entire books have been written to discuss scheduler theory. Because of sheer volume of information available regarding scheduling and scheduling theory, the topic can come across as a little (or a lot) intimidating. CCF aims to take the scare factor out of scheduling and allow equipment control application developers to fully control the movement of material through their tool.
CCF provides a framework for a reactive, rule-based scheduler. You, as the application developer and in conjunction with your customer needs, get to decide what decisions are important when creating your scheduler. One of the first things you need to do when developing a scheduler is to ask questions to help you determine the rules for scheduling. Some questions you may ask:
- What is the most important thing I am attempting to accomplish with my scheduler?
- Is throughput the most important?
- Is path predictability most important?
- How can I ensure that when I pick material up that there is a destination available to put it?
- If two components need a robot to take action (pick up or place material), which action takes precedence?
- Do the process chambers need to be prepared before receiving material to process?
- What is the wafer flow scenario (is there a specific order that material must follow)?
- Does the material need to be aligned before processing?
- Does the material need to be acclimatized before processing?
- Does the material need to be cooled before returning to the carrier?
- Are there any maintenance tasks that have to be performed periodically in the tool that have to be accounted for in scheduling?
This is by no means an exhaustive list of questions, but these are the types of questions that need to be answered when creating your scheduler.
The scheduling framework provided by CCF allows you to translate these rules into C# conditional statements. No proprietary scripting languages need to be learned. No specific configuration training is required. C# developers can use industry standard IDEs to put these rules into scheduling practice.
Once the scheduling rules are determined, it can still be intimidating to know how to start creating your scheduler. Cimetrix provides a few basic, as well as more advanced,of scheduling labs that fully explain how to translate your rules into a functional scheduler. These labs can be completed in as little as a few hours. The labs explain the scheduling theory used by Cimetrix and allow users to create functional schedulers in a short amount of time. Many CCF users can create a working scheduler in one week.
Cimetrix also provides complete working examples of atmospheric and vacuum schedulers as part of CCF. Another lab provided by Cimetrix clearly describes how to start with one of these working schedulers and modify it to suit your scheduling needs.
The CCF scheduling framework allows the software to be hardware agnostic. In other words, it is not tightly coupled to device drivers. This allows tool manufacturers to change out hardware without having to make scheduler changes to support the new hardware.
Although scheduling may seem like an intimidating whale to eat, CCF helps break the tasks down into bite-sized chunks.