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Engineering Design Controls

In 1999 when I was working for Coherent Star the company applied for ISO9000 certification. For more than a month all R&D and Engineering activities were stopped except for Manufacturing support and everyone in the group was sent to detailed classes on what was necesessary to meet the requirements for certification. Engineering Design Control was one of the subjects for which we received detailed training in preparation for the certification audit.

Design Phases

There are 8 major phases in the life of a product design. These are:

  • Design Planning
  • Design Input
  • Design Output
  • Design Review
  • Design Verification
  • Design Validation
  • Design Transfer
  • Design Changes

Typically you would keep all of the documents generated by this process in a DHF (Design History File). The DHF can be either paper or electronic or even a mix of the two, as long as it can be read by any auditors at need.

Design Planning

In this phase you plan what will be needed to build your device and what the external requirements are. How much should it cost, what will it do, how big can it be, etc.

The output documents of this phase of design control would include the PRS (Product Requirements Specification).

Design Input

In this phase you gather everything needed to design the final product and determine what it actually will be. Here you will determine the detailed requirements for the device and its components.

The output documents of this phase would include the SRS (Software Requirements Specification), HRS (Hardware Requirements Specification), etc.

Design Output

In this phase you create the actual initial revision of the design including any software code that might be part of it. If there is hardware involved then you also will need to construct a number of prototype units conforming to the initial revison of the product design.

The output of this phase would include the SDD (Software Design Description), HDD (Hardware Design Description), and any software code that was written for the project.

Design Review

In this step you review everything that has been done up to this point and determine if it is ready to proceed to verification. In previous steps you will have had design reviews of various components and component designs. This is a design review of the entire product design which should be a complete initial revision at this point.

Design Verification

In this phase of the process you verify the design output meets the specified requirements. This must be done by some form of objective testing with results which are recorded in the DHF.

One of the questions I remember from the audits is "What is the difference between Verification and Validation?"

Design Validation

In this phase of the process you determine if the result so far meets the requirements for the intended use. It is possible that as a result of this phase major or minor changes to the design might result, making it necessary to repeat part of the process again. The Validation should include some form of objective testing with results recorded in the DHF.

Design Transfer

In this phase of the process everything is finished and the design is transferred to manufacturing to begin production for sale.

Design Changes

This phase applies after the product has been released for sale and encompasses any changes that are made subsequent to the initial release.


  1. Design Control Guidance for Medical Device Manufacturers, US Food and Drug Administration 1999.
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