Objectives

State the purpose of the model and answer the following questions:

  • What are the objectives or requirements of the model?
  • What is being validated or verified?
  • What, if any, are the suggested changes in items such as tolerances, locating schemes, or design?
Example:
  • Validate that the part tolerances and build process can meet customer requirements based on the OEM supplied GD&T.
  • Validate that the part tolerance and build process are within manufacturing capabilities (weld gaps). If they do not meet the requirements then suggest following changes:
    • Tolerance changes
    • Build sequence changes
    • Design changes

 

Summary

Provide an overview that describes the model and the study performed. Include a general discussion of what was found with relation to objectives. The summary should include the following:

  • A description of the model
  • Who the model was created for
  • The primary area of focus of the study
  • The results of the analysis
  • Any other noteworthy items
Example:

This three dimensional tolerance model simulates the assembly process and detail tolerances of the muffler assembly. It will validate the functionality of the assembly strategy and allocated tolerances through analysis of critical surface interfaces per the customer’s request.  An emphasis is placed on the weld gaps, weld region variation, and variation on the Inlet and Outlet. Measurements were taken at critical points to validate the above stated objectives. The results of a Monte Carlo simulation of the model show that the weld gaps will be out of the specified ranges 4.5% of the time. The analysis shows that the profile tolerance on the End Caps is the most critical tolerance for this model.

 

Critical Measurements

List the most important measurements. These should come from the objectives. Include the following:

  • Any measurements that require attention
  • Images of the measurement’s features
  • Any statistics relevant to the measurements
Example:

Critical Measurement Results are as follows:

  • Weld Gap between the Outer Shells
    • Weld Gaps having a Nominal Gap of 0mm goes up to 1mm with about 1.36% out of spec.
  • Gap between the Reinforcement Sheet Metal and Outer Shell
    • Gaps having a Nominal Gap of 0mm go up to 1.25mm with about 2.71% out of spec.

 

Observations

Include noteworthy items observed while working on the model.

Example:
  • J-bar and H-bracket hole/pin combination interferes in the X-direction by 0.9mm. Fails in 27.65% of 2000 builds.

 

Considerations

Include suggested considerations that can improve the model.

Example:
  • Recommend fastening shelf to pencil brace then to J-bar to avoid locating issues due to hole misalignment.

 

Revisions

List any changes to the model due to updates to the tolerances, locating schemes, or design.

Examples:
  • Lower Tray indexing pins that were 9.2 +/-0.1 mm and 12.7 +/-0.1 mm are now both 9.8 +/-0.1 mm
  • Rear Cover holes of size 9.44 +/-0.2 mm and 12.94 +/-0.2 mm changed to 10.1 +/-0.1 mm

 

Assumptions

List any assumptions.

Examples:
  • All dimensions are in millimeters
  • Model is Rigid
  • Gravity is assumed to provide no location bias
  • Effect of assembly forces is not modeled
  • Thermal expansion effect is not modeled
  • No safety factor is included in analysis
  • Part feature variation from nominal is assumed to have a normal distribution unless otherwise specified
  • Detail part tolerances are normally distributed and assumed to have a Cp equal to 1.0, Cpk equal to 1.0 (no mean shift)
  • Analysis is based on Monte Carlo Simulation (5000 simulation runs)
  • The input and output of this model is based on +/- 3 sigma standard deviation

 

Abbreviations

List any abbreviations.

Examples:

FA       Fore/Aft

CC      Cross Car

UD      Up/Down

ID        Inner Diameter

OD      Outer Diameter