Design TipsLatest newsTips-Tricks

Tolerance Stack Analysis

Some of you engineers out there may have spent time calculating tolerances. Simple concept. In practice however this can become complex very quickly, depending on the number of parts and features involved. We know your pain!

Why tolerance stack analysis?
In a perfect world everything would be made spot-on and would fit together perfectly. In reality we have to deal with imperfect parts, so the question is – how much ‘imperfection’ is allowable before things don’t fit together (and you need a bigger hammer). Tolerance stack analysis is essential to:

  • Assess the manufacturability of your parts and assemblies
  • Reduce risk! Reduce the chances of problems during production and assembly
  • Reduce manufacturing costs. Rather than tolerance everything to 0.01mm, be smart about the tolerancing scheme and still get great results.
There must be an easier way…
Fortunately there are inbuilt software solutions in several of the common CAD packages. Here is a brief overview of how TolAnalyst works in Solidworks Premium:

The steps to set it up are:

1. Define part feature tolerances and datum’s using DimXpert – this also pulls directly through onto the drawings so you only have to define the tolerances in one place
TolAnalyst1 (1)
2. Define the measurement you want to analyse. For example the concentricity of the axle bores
3. Define the assembly order and constraints
4. Output results. The worse case max dimensions between the bores is:
5. Iterate the tolerances to achieve the required result The analysis shows you the percentage contribution of each tolerance, so you can identify the biggest factors on the tolerance stack and adjust them acoordingly

Very cool as it calculates both the RMS values (statistical distribution) and the maximum values (all tolerances at worst case). It also lets you see the the influence of assembly order and each feature tolerance on the overall stack.For more information about TolAnalyst checkout the Solidworks video here or read this helpful question and answer from javelin tech.At Motovated we’re big fans of making technology work for you, and this is one of those Solidworks features that many people may be unaware of. Why don’t you check it out for yourself or explore what sort of tolerance stack analysis is built into the CAD package you’re using and let us know how it works for you?

Happy tolerancing!

Graeme Howard
Design Engineer
Motovated Design & Analysis

Related Posts

Additive Manufacturing Process Selection Additive Manufacturing Process Selection SAE International recently announced the release of its first suite of Aerospace Material Specifications (AM...
University of Canterbury Guest Lectures on “... Greg's University of Canterbury Lecture Canterbury University is really changing things up! Greg really enjoyed visiting the engineering campus aga...
Congratulations KiwiRail – 15 million bogie kilome... Congratulations KiwiRail!15 million bogie kms and counting, with no cracks!Another Motovated Engineered product. Kiwirail AK Carriages with P11 B...
A new recruit’s first six months within Motovated... A new recruit's first six months within Motovated Design & Analysis Ltd! When I came to Motovated in February I really didn’t know what to expect...