Acceptance Criteria (Tolerances, Deviation)

Acceptance Criteria (Tolerances, Deviation)

It is better to live your destiny imperfectly than to live an imitation of somebody’s else life with perfection: Bhagavad Gita

When an organization calls a person for an interview, both parties have their own guidelines to work before going ahead. During marriage proposal, both boy and girl have their unique criteria for saying YES. When we purchase the mobile phone online, we have our specifications to choose from like a service provider, model, colour, features etc. Even birds and animals have their unique criteria about the food that they will eat when offered.

Acceptance criteria are a set of predefined standards that must be accepted and satisfy the user, customer and other relevant interested parties. It specifies the scope and requirements that must be executed by the organization.

Acceptance criteria is a key component of any Control Plan. It clearly defines the scope, desired outcomes of and testing criteria for functionality which is expected by the customer. The process of creating and agreeing on acceptance criteria itself is also an invaluable activity between the organization and the customer.

In ISO 9001 and IATF 16949 clause 8.1 and 8.6.6, there is a specific requirement related to ‘acceptance criteria.’

Who can define acceptance criteria? Based on the key inputs from customer, statutory & regulatory requirements, past experience etc.

• Cross-functional team (CFT)
• Personnel from different processes like Design, Production, Quality, Purchase, customer etc.
• Brainstorming and decide

Why do we need acceptance criteria?

• Managing expectations: Organization, customer and other relevant stakeholders can have a different expectation for the same situation. By defining the acceptance criteria, the expectations become realistic and manageable. Example: For any painted component, customer can approve a master sample so that organization or supplier can follow it for colour, shade and texture.
• Defining scope and reducing ambiguity: In an organization, the persons who are doing inspection can have their interpretations about the requirements which may be stringent or vague. By defining the acceptance criteria, it is easy to identify the boundaries and avoid any confusion. Example: in MSA study (Measurement System Analysis), for R & R study, 3 different levels are specified (less than 10%, 10 to 30%, More than 30%).

When an organization should define acceptance criteria?

• During Product and Process Design
• Whenever any change happens
• Major customer complaint
• Warranty failure or Recall
• When internal rejection increases

Different stages of identifying acceptance criteria:

• Prototypes
• Simulation study
• Design Verification & Validation
• Trial production
• Function/performance testing
• Incoming inspection
• Onsite Supplier inspection
• In-process inspection/First Piece Inspection
• Final inspection
• Laboratory testing
• Field return inspection
• Third-party qualification etc.

What are the different types of acceptance criteria?

• In MSA Study, as per AIAG manual, there 3 categories for accepting the R & R results
• In SPC study, CpK & PpK criteria are defined (1.33, 1.67)
• During the PPAP stage, acceptance criteria for Prototype, Prelaunch and Production phases are defined.
• In FMEA, acceptance criteria are based on RPN number or severity ranking
• For Special characteristics related to Safety and legal requirement, acceptance criteria are defined
• For Incoming inspection, acceptance criteria are based on evaluation of statistical data, testing, 2^nd or 3^rd party assessment results, laboratory test results, Master / Limit samples, Tolerances, packing standard etc.
• For in-process and final inspection, acceptance criteria are based on Process capability studies, the competence of the operator (like Level 1 for Welding), past experience etc.
• For calibration of Vernier caliper, acceptance criteria for master slip gauge can be 0 grade.
• For internal and external laboratory approval, it is based on compliance to ISO 17025
• For Preservation of shelf life items, criteria are defined for its storage like temperature, humidity etc.
• For deviation/concession, acceptance criteria are defined based on the quantity or time duration.
• For non-conforming products, acceptance criteria are defined in the reaction plan and escalation process   
• Internal Audit (System, Process, Product) compliance is based on auditor competency, the number of findings, customer requirements etc.
• In the HR process, for a job interview, acceptance criteria are defined based on education, training and skill.

Traits of Effective Acceptance Criteria:

• Verifiable: When the customer or any relevant interested stakeholder wants to verify the acceptance, it can easily verify. Example: Hardness of Metallic component   
• Clear & Concise: The acceptance criteria should be specified in a simple and easy language like 5.0 +0.1 mm.
• Easily understood: Different level of the organization with varied competence uses acceptance criteria. It should be easily understandable to the user for understanding and implementing it.
• Fulfil requirements: The key purpose of the acceptance criteria is to meet customer requirement. It should be specified so that it can meet the intent of the customer. Example: RoHS requirement for the plated component. Since the customer has to export the vehicle, all components should be RoHS compliant.

How to measure the effectiveness of acceptance criteria?

• Improved customer satisfaction level
• Number of customer complaints
• Low COPQ
• Internal employee satisfaction level
• Internal rejection trend

The organization has to maintain records of the acceptance criteria so that its implementation and effectiveness can be verified by the organization, customer and any other relevant interested parties when needed.

Some of the key IATF subscribing OEM’s also have their requirements related to Acceptance criteria. They are

Daimler: MBST 14/06, section 3, paragraph 1

FCA, Italy: 9.01102 9.01102/08 9.01102/10

Ford: For guidance on product monitoring and reaction plan techniques for product conformance to specification, see the references AIAG SPC and APQP

Possible Challenges:

• How often acceptance criteria are clearly defined and communicated to all the relevant employees in the organization?
• When an organization revise acceptance criterion which impacts the final product, how often do they communicate and take approval from a customer?
• How often acceptance criteria are reverified and reviewed for its effectiveness?

References:

ISO 9001: 2015

ISO/TS 9002: 2016

IATF 16949: 2016

This is the 63^rd article of this Quality Management series. Every weekend, you will find useful information that will make your Management System journey Productive. Please share it with your colleagues too.

Your genuine feedback and response are extremely valuable. Please suggest topics for the coming weeks.