Control Plan! You must have heard about the control plan, its application during proto-type development and serial production. The control plan word itself resembles a plan with a set of control measures to keep the manufacturing process within desired control. Control plan helps to achieve a better quality control and assurance by taking preventive and corrective measures.
What is control plan in quality?
A control plan act as a control measure or a live manual with a set of manufacturing/business process parameters, prevention action to avoid rejection/defect, prevention action to maintain control on manufacturing/business processes. It also covers, reactive/corrective action if a defect/error is detected during the process.
A control plan is an output of Process Failure Mode Effect Analysis (PFMEA)
A control plan is a live document which subjected to amendment/changes. If there is a change in process or changes in product design, relevant control parameters shall be updated in the control plan.
Types of Control Plan
Mainly 3 types of control plans are used in the industry.
- Proto-Type Control Plan
- Pre-Launch control plan
- Production Control Plan
All the above 3 types of control plans are used in the APQP.
Each control plan types are interlinked. Let’s review each type of control plan one by one.
Prototype Control Plan:
This type of control plan is useful in the early stage of product and process development where the only prototype is to be built.
Pre-launch control plan:
A pre-launch control plan is an upgraded version of the prototype control plan. A pre-launch control plan is developed based on prototype build experience. A pre-launch control plan is being updated considering a final product specification.
Production Control Plan:
A production control plan is the output of the pre-launch control plan. A production control plan is used in a regular serial production environment and it is being updated based on customer feedback, internal defects/rejection, customer complaints, continual improvement.
Prototype Control Plan Vs. Pre-Launch Control Plan Vs. Production Control Plan
The following table helps you to understand the difference between each control plan type.
| Input & Control Parameters | Prototype Control Plan | Pre-Launch Control Plan | Production Control Plan |
| APQP Phase | Phase 1: Product Design and Development Verification Phase 2: Process Design and Development Verification | Phase 3: Process Design and Development Verification Phase 4: Product and Process Validation | Phase 5: Launch, assessment, and corrective action |
| Control Parameters | 1.Material Specification 2. Dimensional check 3. Key characteristics 4. Prototype functional test | 1.Material Specification 2. Dimensional check 3. Key characteristics 4. Prototype functional test 5. In-coming inspection 6. In-process inspection 7. Final inspection 8. Product Testing 9. Statutory and Regulatory Requirements 10. Statically Controlled Process | 1.Material Specification 2. Dimensional check 3. Key characteristics 4. Prototype functional test 5. In-coming inspection 6. In-process inspection 7. Final inspection 8. Product Testing 9. Statutory and Regulatory Requirements 10. Stastistical Controlled Process 11. MSA / Gauge R&R 12. Mistake Proofing 13. TQM 14. Audit 15. Calibration |
| Discontinued? | Yes (Once Phase 2 APQP completed) | Yes (Once Phase 4 APQP completed) | No (live document) |
Application and Advantage of Control Plan
There are many advantages of a control plan. Control plan used in various industry sectors, however, the end goal is the same in all industry sectors.
Application/Usage of control plan in the various industrial sector
No doubt control plan is a part of APQP and APQP tools developed by the automotive industry. However, the control plan is nowadays used in other industry sectors too. Please refer to the following picture to understand the usage of control plans in various sectors.
Input to Control Plan:
The following parameters act as an input to the control plan,
- System FMEA
- Design FMEA
- Process FMEA
- Process flow diagram
- Key Characteristics
- Design Review
- DoE (Design of Experiments)
- Product Historical Data
- Mistake Proofing
- Statutory and Regulatory requirements
- Standard operating procedure
- Inspection (Incoming / In-Process / Final)
- Calibration
- Special Performance Test
Control Plan Format / Template:
Following the control, the plan snapshot helps to understand the content of the control plan format/template.
A control plan is mainly divided into five sections
- Header Section
- Process & Infrastructure
- Product & Process Characteristics
- Method
- Reaction Plan
Let’s review each section one by one.
Section 1: Control Plan Header Section:
In the header section following elements/fields are covered. Basically, the header section covers, project name, type of control plan, team member, and other descriptions.
Section 2: Process & Infrastructure Section:
This section covers process step description, machine, tools, fixture/jig specification.
Section 3: Product and Process Characteristics
In this section, product and process characteristics are specified with its CTQ (Critical to Quality). CTQ section is also known as special characteristics including safety and regulatory related sections. In this section, product and process characteristics are specified with its CTQ (Critical to Quality). CTQ section is also known as special characteristics including safety and regulatory related sections.
Section 4: Method
In the method section following elements are covered,
4.1 Product / Process Specification:
This section covers manufacturing/engineering specifications of the process or product which need to be achieved.
4.2 Measurement Method:
Measurement methods can be an attribute inspection or dimension/specification check (variable) inspection. Measurement methods can be using an automated tool or manual tool usage.
4.3 Gage Repeatability and Reproducibility:
MSA (Measurement System Analysis) to be conducted in order to achieve precise and accurate results. If tools/instruments are,
MSA Condition 1: If an error is above 30%, the tool is not acceptable.
MSA Condition 2: If an error is between 10% to 30%, the tool can be conditionally acceptable considering the situation and accuracy and precision level.
MSA Condition 3: If an error is below 10%, the tool is acceptable.
4.4 Sample / Sampling:
Sample / Sampling: This section covers sample size in each lot or subgroup, sample frequency (how frequently process or product characteristics are to be inspected, and how to record the same.
4.5 Control Method
This section covers preventive and corrective action. A defect or error can be avoided by preventive action (i.e. by mistake proofing), whereas corrective actions are initiated to rectify root cause analysis and initiating corrective action to avoid recurrence of the same problem.
Section 5: Reaction Plan
The reaction plan section covers action to be taken if the process output does not fall within desired specification limit. The reaction plan further covers,
5.1 SOP (Standard Operating Procedure):
SOP may include informing or escalating process out-of-control issues to supervisor or production stoppage to avoid further production of defects/error.
5.2 Trigger:
A trigger or alarm is initiated to all relevant stakeholders in case the process is out of control. Eg. Informing the supplier and procurement team about raw material issues.
The following action can be taken as part of the reaction plan,
- Updating Procedure & Work Instruction
- Revision of PFMEA
- Brainstorming
- Updating process flow diagram
- Initiation of mistake proofing
- Lean Manufacturing initiatives
Root cause analysis tools like 5M-1E (Fishbone diagram), 5Why analysis can also be part of the reaction plan.
We hope this blog post helped you to understand about control plan, usage, and application of the control plan.