1. What is a Control Plan?
A Control Plan is a document describing the process, process’s quality control items, control methods, and a reaction plan. In other words, it is a plan to control production/service processes to assure the product, service, and process requirements are met.
Control Plan is also used to refer the methodology for documenting Control Plan document.
2. Why Control Plan?
Control Plan is widely used because it provides structure information for process control. It helps process owner:
• Easy to control the performance of a process: without Control Plan, you might find it is difficult to determine what needs to be controlled and how to control it.
• Easy to determine influenced characteristics when product/process changes: you can determine which characteristics and control methods are affected and should provide proper resources to control it when the change implemented.
3. The input of Control Plan
To process control and improvement take place effectively, the Control Plan should be developed by utilizing all information to gain the most understanding of the process. The information sources include but not limited to the following resources:
• Process Flow Diagram: Used to determine process steps (include process No. and process Name/Description)
• DFMEA and PFMEA: Used to define the control item in each process step. Product and Process characteristic.
• Special Characteristics Matrix: Used to define the critical characteristics in Process.
4. When should Control Plan be made?
Creation: The team should start to make Control Plan as soon as possible at the beginning of process design and complete before the trial production.
Revision: When process changes in the life cycle of the product or service, the corresponding information in the input material also changes. Therefore, the Control Plan must be change adequately. The team should continuously update the Control Plan to reflect the current methods of control, the measurement system used. That is why we call it a living document.
5. Type of Control Plan
A control plan is typically categorized base on process maturity level of in the product lifecycle. Determine the correct type of a Control plan helps the team define the scope of the output.
• Prototype Control Plan: this Control Plan describes the process and control need to be conducted and completed during manufacturing prototypes.
• Pre-launch Control Plan: this Control Plan describes the process and control need to conducted and completed during the trial production and before mass production (serial production) launched.
• Production Control Plan: this Control Plan describes the process and control need to conducted and completed during mass production.
6. Control Plan Form
There are many forms used to document the Control Plan. Most of the forms used are in Excel format. However, Excel is not specialized to handle a relation structure document as Control Plan. ABC software is an Excel extension to handle the relation structure document like Control Plan.
The following sections describe a common Control Plan form. However, each company or organization can customize the format depending on its process.
6.1 General Information
At the header of a Control Plan is general information. Depend on company/organization the information item could be different, below is a simple example:
1. Product Number: identification number of the output product of the process
2. Product Name: name of the output product of the process.
3. Change Number: the number that used to indicate the latest change in the product/process.
4. Team Member: members of the control plan team, who involves in making control plan process. The team member should include but not limited to the process engineer, production leader, quality engineers, supplier quality engineer and logistics engineer.
5. Project Manager: the leader of the project, who has a responsibility to approve and release the control plan.
6. Company: Name of the company/organization who own process.
7. Customer: Name of the company/organization who buy the product.
8. Control Plan Type: type of control plan (refer the section 5)
9. Control Plan No.: The number used to identify the control plan.
10. Revise No.: The number used to control revision of the document
11. Original Date: Data of original release
12. Revise Date: Revise date of last revision.
6.2 Content Columns
The main content of a Control Plan is listed in its columns; below we describe the primary columns of a Control Plan.
6.2.1 Process Identification
1. Process Number: The identification number of a process. Used to distinguish the process from others. This Number should match with the corresponding item in the process flow.
2. Process Name: The brief describes the operation being performed in this process.
3. Machine: The name and control number of the machines, equipment, and other tools required to accomplish the process.
6.2.2 Process Characteristics
4. Number: a cross-reference number to other documents.
5. Product: properties of components assemblies that are affected in the given process that is described on drawing and engineering specifications.
6. Process: process properties that relating to the identified product characteristic. There could be one or more process characteristics listed for each product characteristics.
7. Special Characteristic Classification: Letter representing the appropriate classification for any special characteristics. The letter or symbol are designated base on organization regulation.
6.2.3 Process Control Methods
8. Specification: Specification and tolerance (if any) of the corresponding characteristic of process/product.
9. Evaluation Methods: Evaluation or measurement method to evaluate the characteristic is meet specification or not.
10. Sample Size: quantity of assemblies/products in a sample that will be evaluated during the process by the corresponding evaluation methods.
11. Sample Frequency: the frequency at which the samples are taken during the process to conduct the evaluation described.
12. Control Method: brief information about how the process will be controlled. Example: Visual Check, X-R bar chart.
13. Reaction Plan: actions required if characteristic go out of specification to handling non-conforming products. The action plan includes but not limited to:
• The person has the responsibility to handle the situation.
• Quarantine and identification method the nonconforming product.
• Action to re-qualify the process after quarantine nonconforming.
7. Linkage with other documents
Control Plan is not a standalone document in product and process development process. To make a Control Plan consistency with other documents, the items in the Control Plan must link with the corresponding items in other documents:
7.1 Process Flow Diagram
The linkage between Control Plan and Process Flow Diagram is obvious: Process Number and Process Name in Control Plan must match with corresponding items in the Process Flow Diagram.
Control Plan should be developed and derived the information from PFMEA:
• Control Methods of Control Plan are consistent with Control Methods in PFMEA. In the case of Control Methods change, the team should update corresponding Control Methods in PFMEA.
• Product Characteristics in Control Plan may be derived from Requirements of PFMEA and Process Characteristics can be derived from Potential Causes of Failure Mode in PFMEA.
With Excel, maintaining the linkages of Control Plan is often painful, especially with a long Control Plan document of a complicated process. However, using ABC can help reduce the time and make the revision process much easier. ABC not only maintains the linkages between documents but also has a mechanism to create a relation structure document as Control Plan or PFMEA much faster.