International Institute of
Geometric Dimensioning & Tolerancing
 
April 2010   Edition 2010.2

GD&T Seminar Series

April 22-26, Salt Lake City, Utah
May 3-7, Minneapolis, Minnesota

GD&T Seminars
GD&T Seminar Series, click here for Seminar Home page

IIGDT has developed a multi-step Geometric Dimensioning and Tolerancing Seminar Series built upon years of proven experience in training new users in the fundamental to advanced topics of GD&T. Whether you are new, or an experienced user of GD&T, there is a Seminar level designed for you.

Click here to visit the GD&T Seminar home page 

Precision GD&T and Requirements for
Software Validation
The precision language of Dimensioning & Tolerancing is explicitly defined in the ASME Y14.5M-1994 Standard on Dimensioning and Tolerancing, and is mathematically complimented by the ASME Y14.5.1M-1994 Standard on Mathematical Definition of Dimensioning and Tolerancing Principles. Both of these Standards form the basis for a precise definition of complex surface geometries and should be the basis for mathematical analysis using validated software intended to be in compliance with “FDA 21 CFR PART 11.”

3D Engineering Drawing Example
utilizing Profile of a Surface
GDT Example Drawing 
Profile Example 
 
Case study for the application of Profile

The availability of advanced CAD design tools and manufacturing capabilities often incorporate complex, blended shapes. These surfaces are not easily defined by the prismatic shapes that we have grown accustomed too and requires an offset profile band, or halo surrounding the CAD model.

Test Criteria for Compliance to Engineering Requirements
Stated Compliance to the engineering requirements as defined per the ASME Y14.5 and Y14.5.1 Standards and therefore FDA 21 CFR PART 11 require compliance with the following “Test Criteria.”

  1. Size, which is defined as having two parts based on “Limits of Size” criteria defined in section 2.3 of the Y14.5.1 Standard. This requires compliance to both the “Actual Local Size” and “Actual Mating Size.”

  2. Datums which are based on criteria defined in section 4.3 of the Y14.5.1 Standard which requires:
    1. Datum “Features of Size at RFS” (Regardless of Feature Size) to be simulated as “Actual Mating Envelopes.”
    2. Datum “Features of Size at MMC (Maximum Material Condition) or LMC (Least Material Condition)” to be simulated as “Virtual Conditions.”
    3. “Multiple Features of Size” defined as a “Single Datum” to be “Simulated as Patterns” based on “Actual Mating Envelopes” (RFS) or “Virtual Conditions” (MMC or LMC).

  3. Position Tolerances which are based on criteria defined in section 5 of the Y14.5.1 Standard which requires:
    1. Analysis of axes based on “Actual Mating Envelope” principle.
    2. Analysis of “Bonus Tolerance” based on applicable features defined at MMC or LMC.
    3. Analysis of “Simultaneous Requirement” which requires all features to simultaneously be within their respective tolerances when the feature control frames have the same datum, in the same sequence with the same datum feature modifiers.
    4. Analysis of Single-Segment -vs- Composite Feature Control Frames.

  4. Profile Tolerances which are based on criteria defined in section 6.5 of the Y14.5.1 Standard which requires:
    1. Minimum Zone fitting algorithms are used.
    2. Profile results must always look for the smallest possible deviation of the actual geometry (worst case measured point) from nominal geometry, ideally a CAD model that can be compared to the profile tolerancing in the feature control frame.
    3. Must ensure “Simultaneous Requirements” are being met which requires all features to simultaneously be within their respective tolerances when the feature control frames (Single-Segment) “have the same datum, in the same sequence with the same datum feature modifiers.”

  5. Revision changes of software must be validated to original “Test Criteria” for continued “Proof of Compliance” to ensure ongoing integrity of measured results and conformance to requirements.  
 
IIGDT Seminars
IIGDT offers 6 levels of training courses to suite your business requirements. These are:
Level 1 Blueprint Reading 
Level 2 Precision GD&T:
Introduction & Fundamental Principles  
Level 3  Precision GD&T:
Advanced Applications & Analysis  
Level 4  Applied Dimensional Metrology  
Level 5  Tolerance Optimization & Analysis  
Level 6  TBA  
 A complete overview can be found here.
 
 
Announcements:
To see our complete schedule please visit the Seminar page, click here:
Seminar Schedule
 
 
 
 
Dr. Hetland discusses the critical challenges facing today’s medical OEMs and suppliers in validating analytical software used for determining compliance to mechanical drawings for components and assemblies. This article will make visible some of the risks and limitations in current software validation and provide direction to simplify future validation initiatives. click here.
BoneZone GDT Article 
 BONEZONE Archives
 
 
 
   
Contact Information:

Dr. Greg Hetland
Phone: (651) 275-8952
Fax: (612) 395-5405
email:  greg-hetland@iigdt.com
IIGDT Logo Headquarters:

IIGDT
12159 Quail Ave. Lane N.
Stillwater, Minnesota 55082
U.S.A.