Slide 1

Report
QBASE
Engineering
MECHANICAL TOLERANCE STACK-UP AND ALLOCATION FOR +/- AND
GD&T DRAWINGS
Overview
This training is designed to build-up the participant’s knowledge leading to improved skills in applying
mechanical dimension/tolerance analysis, dimension/ tolerance stack-up analysis, and dimension/tolerance
allocation methodologies. Tolerance and tolerance stack-up analyses can be performed either by using
Worst Case Methods (WCM) or statistical methods. The statistical method is more rigorous and it uses either
the RSS (Root-sum-of-Squares) or MRSS (modified Root-Sum-of-Squares) approach. Tolerance analysis is
performed to determine or to assess the characteristics of part features such as minimum and maximum wall
thickness, or distance between features to see if they met the specific dimension or tolerance or functional
requirements. The stack-up tolerance analysis on the other hand is used to calculate how each piece-part
dimension and tolerance contributed towards the final assembly’s dimension and tolerance .The final
assembly’s dimension and tolerance is then compared against the required dimension and tolerance to
determine whether the required functional performance goals are met. If the final assembly performance
requirement s is not met, then various tradeoff strategies can be employed to resize the dimension and
tolerances of each piece-part without negatively affecting its manufacturability and cost. Design engineers,
by employing any of these methods, can determine if the form and fit of related parts and assemblies will
satisfy their intended function before that part and assemblies are actually produced.
Manufacturing, inspection, assembly and service personnel can also use these techniques to review and/or
troubleshoot problems on existing designs, to verify that their in-process steps will have the capability to
meet the desired objective, or even to find ways to improve performance and reduce costs. There are two
methods used to specify dimensions and tolerances: traditional +/- dimensioning Tolerances ( which still exist
in many mechanical drawings) and geometric dimension and tolerancing, or GD&T. Since the +/dimensioning and tolerancing is still commonly used in part and assembly drawings, and this tolerance stackup analysis training will cover both methods. However, as an extension of GDT training, greater emphasize
will be placed on how to calculate Tolerance Stack-ups analysis and tolerance allocation on parts and
assemblies based on GDT based drawings. The ultimate goal of this training is to help the participants
understand why GD&T is a much better system from tolerances point of view and also to demonstrate how
Tolerance Analysis/allocation will ultimately prove that the selected dimensioning and tolerancing scheme
works. This training will also demonstrate that the only way to precisely specify the required geometric
conditions is through the use of GD&T.
This training will also cover how the results of the tolerance stack-up analyses should be documented and
communicated either for sharing purposes or to convince someone to make changes to those dimensions or
tolerances . The techniques must be used to ensure that the dimension and tolerance related problems are
solved correctly and that the results will be understood by all parties involved.
The knowledge in GD&T and its principles are therefore pre-requisite to this training.
© QBASE Engineering Sdn Bhd
QBASE
Engineering
Course Objectives
At the conclusion of this training the participant will have knowledge to be able to :
•Explain various tolerances available in +/- system and GDT system such as part size tolerance, Bonus
tolerance and datum shift.
•Explain the relationship between piece-part tolerances and final part assembly tolerances and performance
goal
•Understand parts variation and source of variation and these variations affect assembly variation and cost
•Explain the differences, the benefit, strength and weaknesses, and advantage/disadvantage between the
various stack-up analysis methods.
•Understand relationship between statistical distributions, nominal values, standard deviations and its effect to
the final assembly tolerances.
At the conclusion of this training the participant will have the necessary skills to be able to:
•Calculate the tolerance availability for a part and/or part features.
•Set-up tolerances that minimize cost and met the performance requirements
•How to convert various types of tolerances into equal bilateral tolerances. (+/-)
•Perform stack-up analysis of the final assembly based on each individual part tolerances either using WCM or
RSS or MRSS methodology either for part stated in +/- tolerances or GDT based tolerances.
•Modify the parts tolerances or dimension to adjust the final assembly tolerance to meet the performance goal.
•Perform tradeoff analysis when using various tolerance stack-up analysis methods.
•Prepare Stack-up analysis for management review and/or design change proposal
•Prepare the sketch or cartoon gage to visualize the extreme mating cases
•Apply Stack-up tolerance analysis using software.
Training Duration
• 2(two) days 9:00 p.m to 5:00 pm
Pre-requIsite
• Knowledge or able to read technical drawing
• Able to read part drawings and assembly drawings
• Completed GD&T Training
• Calculators or Scientific Calculator
Target Audience
•Design Engineer (Mechanical)
•Manufacturing and/or Assembly Engineer
•Quality Assurance Engineer/Manager
•Quality Control Engineer/Manager
•Product and/or System engineer/Manager
© QBASE Engineering Sdn Bhd
QBASE
Engineering
Training Delivery
• English and/or Bahasa Malaysia
Training Methods
•
•
•
•
•
Classroom lecture on concept, methodologies, theories and techniques
Exercises on selected topics
Workshop and case studies
Discussion on actual project ( bring drawings)
Test on end of each module
Course Fee
• RM1,300 per pax* (public Training )
• Contact QBASE For special Discounts
• * maximum 10 participants (additional RM600 per participant if exceeded 10)
• Fee include training manual and appropriate forms and certificate of completion
Level 3 training assessment.
Call QBASE Engineering for in-house training
© QBASE Engineering Sdn Bhd
QBASE
Engineering
Course Outlines
Module 1:
 Overview of Dimensions and Tolerance
o Dimensions/Tolerance formats
o Converting to equal bilateral format
o Part drawing vs. assembly drawing
 Overview of Size Tolerances, Bonus Tolerances and Datum
shift
 Statistical Distribution- Nominal value and variation ( +/-3
sigma form mean)
 Tolerances vs. manufacturing capability vs. producibility
 Piece-part Tolerances vs. Assembly tolerance
Module 2: Overview of Geometric Dimensional Rules
 Material conditions and its effect on final assembly.
 Calculation of Bonus tolerance and datum shift
 Worst case boundaries
Module 3: Tolerance Analysis
 Analysis for +/- Dimensional system
 Analysis for wall thickness
 Analysis for distance between features
 Gap analysis
Module 4: Tolerance Stack up for +/- Dimension
 Step for Tolerance analysis
 Loop Diagrams ( vertical vs. Horizontal Loop)
 Determining Dimensions Sensitivities
 Dimension Vector (direction)
 Calculation of Mean Value (nominal)
 Worst case Methods
 RSS method
 MRSS Methods
Module 5: Tolerance Allocations
 Steps by step calculation for Tolerance Allocation
 RSS and MRSS methods
 Dynamic and Static RSS
© QBASE Engineering Sdn Bhd
Module 6: Tolerance analysis and stack-up with
GD&T
 Form Controls
 Positional Control
o Floating and fixed fasteners
 Orientation Control
 Profile Control
Cartoon Gage for tolerance and stack-up analysis
for various material conditions
 Loop Diagram and Dimension Vectors
Calculations
 Maximum and Minimum dimension
 Determining tolerance
Module 7: Tolerance analysis /stack-up
/allocation reports
 Design Review Process
 Documentation
 Standard Report
Module 8: Advanced Dimensional Management
Methods
Module 9: Software for tolerance analysis,
stack-up and allocation.
QBASE
Engineering
Training Agenda
Day 1
9:00-10:00
10:00-10:15
10:15 – 1:00
1:00-2:00
2:00-3:15
3:15 – 3:30
3:30-5:00
Module 1:
 Overview of Dimensions and Tolerance
o Dimensions/Tolerance formats
o Converting to equal bilateral format
o Part drawing vs. assembly drawing
 Overview of Size Tolerances, Bonus Tolerances
and Datum shift
 Statistical Distribution- Nominal value and
variation ( +/-3 sigma form mean)
 Tolerances vs. manufacturing capability vs.
producibility
 Piece-part Tolerances vs. Assembly tolerance
Day 2
Module 6: Tolerance analysis and stack-up with
GD&T
 Form Controls
 Positional Control
o Floating and fixed fasteners
 Orientation Control
 Profile Control
Cartoon Gage for tolerance and stack-up analysis
for various material conditions
 Loop Diagrams/vector
 Calculations
 Maximum and Minimum dimension
 Determining tolerance
Morning Break
Module 2: Overview of Geometric Dimensional Continuation of Module 6..
Rules
Material conditions and its effect on final
assembly.
Calculation of Bonus tolerance and datum shift
Worst case boundaries
WORKSHOP & CASE STUDIES
Module 3: Tolerance Analysis

Analysis for +/- Dimensional system

Analysis for wall thickness

Analysis for distance between features

Gap analysis
Lunch Break
Module 4: Tolerance Stack up for +/- Dimension Module 7: Tolerance analysis /stack-up
 Step for Tolerance analysis
/allocation reports
 Loop Diagrams ( vertical vs. Horizontal Loop)
Design Review Process
 Dimension Vector (direction)
Documentation
 Calculation of Mean Value (nominal)
Standard Report
 Worst case Methods
Module 7: Tolerance analysis /stack-up
 RSS method
/allocation reports
 MRSS Method
 Design Review Process
 Documentation
 Standard Report
Afternoon Break
Module 5: Tolerance Allocations
Module 9: Software for tolerance analysis, stackSteps by step calculation for Tolerance Allocation up and allocation.
© QBASE Engineering Sdn Bhd

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