2D Tolerance Stack-Up Cheat Sheet.
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2D Tolerance Stack-Up Cheat Sheet.
Tolerance analysis is like quality control math for assemblies. It checks how all those tiny part variations add up - so even when components aren't perfect, the final product still works like a charm.
Good tolerance analysis ensures that:
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Instead of relying on gut feeling or Excel-based stack-ups, RD8 gives your team a modern, visual, and collaborative piece of software to manage variation. Whether you're designing precision mechanisms or high-volume components, we help you brings clarity to complex assemblies - and avoid costly rework, ensure functionality, and speed up development cycles.
2D Tolerance Stack-up Analysis
1. Make a Clear Illustration
• Clearly mark the Point of Interest (POI)
• Make sure there are no unnecessary overconstraints in the design.
2. Identify the Stack
• Identify the tolerance stack / tolerance chain
3. Set up the Calculation
• Use trigonometry to set up calculations
• Calculate the nominal value
• Define your target values (mean, and acceptable range of variation)
4. Tolerance analysis
Try RD8 Software to let it do the hard part!
• Add tolerances to the calculation
• Identify the worst case combination of the dimensions
• Calculate the worst case or other methods
• Convert the tolerance window to a +/- tolerance by dividing by 2
5. Evaluate
• Compare to the target
• Make a clear conclusion: pass or fail
the three optimisation principles
Shorten Tolerance Stacks
• Reduce the number of parts in the stack
• Reduce number of parameters in the stack
See picture or download cheat sheet for examples
Maximise distances
• Short distance between alignment features
• Maximum distance between alignment features
See picture or download cheat sheet for examples
Optimise fits
• Obtain an Interface without play
• Obtain an Interface with local fit
See picture or download cheat sheet for examples
two types of ?
Calculating rotation from clearance fits
Type A: Angle
• Calculates angular misalignment at a POI
• Clearance fits create rotation
Main Idea
• Linear clearance becomes angular error
• Rotation depends on clearance and feature spacing
Key formula
Terms
• CLR1, CLR2: Radial Clearances
• x1: distance between features
• θ: rotation angle
Calculating offset with gearing
Type B: Displacement
• Calculates offset at a point of interest
• Clearance between two features creates rotation/hilt
Main Idea
• Small clearances can be amplified by geometry
• The further the POI is form the supports, the larger the offset
Key formula
Terms
• CLR1, CLR2 represents the two clearances
• x1 is the distance between features
• x2 is the distance to POI
Try The Napkin tools
Contact and Clearance Calculator
Snap Fit Calculators
Ensure your design is feasible before you model.
Spring Calculator
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