All the Features you need, built for Tolerance Stack-Up Analysis and Optimization

The RD8 Tolerance Stack-Up and Optimization Software helps you to do tolerance stack-up analysis on the fly during the product development process.

Laptop screen displaying a 3D model of a mechanical device with a tabular interface showing tolerance parameters and status indicators.
Tolerance stack ups in 1D, 2D, 3D
Linear and non-linear calculations
Tolerance stack optimization by design simplification
Automated stack-up detection
Multiple calculation methods incl. Monte Carlo Simulation
Live collaboration with Engineering Team

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Step 1: Import.

Stay in sync with the latest CAD.

".STEP" File Import

To get started - import a ".STEP" file.

The system recognizes all meta data from your .STEP file; dimensions, tolerances, GD&T annotations, part names, part colors, sub-assemlies, ...

User interface screenshot showing a New Project creation form with fields for project name, description, length unit, file upload, and interface definition input.

Iteration Feature

Keep your work up-to-date anytime.

The "iteration feature" allows you to import a new .STEP file and keep track of design history.

The system then automatic recognizes parts and changes in the design. The user will only need to approve/adjust changes where the model looks different from the previous iteration - making it easy to reuse and refine the design during the development process.

See the example in the adjacent YouTube video.

Start without a ".STEP" File

If the user don't have a .STEP file yet - and start from a blank piece of paper - the user can create a project without a .STEP file.

This allows project teams to:

- Draft critical tolerance stacks
- Plan a shared vision of a product architecture
- Plan an exact constrained system design

Project overview screen showing 'My first project - without a step-file' with sections for Kinematics, Architecture, and Tolerances, no CAD model attached.

Step 2: Setup Your Project

Lay the foundation with the right inputs.

World's First Path Finder

Automatic stack-up detection
Get instant help to set-up tricky tolerance stacks and check if tolerance stacks are ambigious (to avoid overconstraints).

Define a 'Point of Interest' and let the system identify possible tolerance paths. See the video to see an example.

Functional Requirements

Set functional requirement:

Target, LSL (Lower Specification Limit), USL (Upper Specification Limit), Sigma Level.

Read projected DPMO and yield in a simple interface.

Monte Carlo method simulation results with calculation formula, 10 million trials, 3 sigma level, showing target and result values for LSL, mean, USL, DPMO, yield, and a corresponding bell curve highlighting lower, mean, and upper values.

Product Architecture Module

Setup a product archtecture from scratch or inherit the architecture from the .STEP file.

From an initial import-setting "interface definition" - the system identifies all interfaces between parts.

The architecture feature let's the user(s) arrange and re-arrange parts in assemblies and sub-assemblies to make tolerance analysis easy and simple.

3D CAD interface showing architecture of espresso machine parts including portafilter, lever, and piston with color-coded components and interface map.

Interface Map

The interface map feature aids the users by a graphical overview of the product architeture.

The system automatically generates the map. A mapping of part or sub-assemblies and their interfaces.

This feature is helpful to:
- layout product architecture
- divide work-tasks or areas of responsibility
- spot complexity (if the map looks like spaghetti you are most likely overcomplicating things and makes it imposible to make any valid tolernance analysis)

3D CAD model of landing gear with colored parts on the right, architectural parts list on the left, and an interface map diagram on the bottom right.

Quick Setup

From the "Path Finder" feature - automatically setup a given tolerance stack. Based in the identified path the system automatically sets up initial parameters for the stack to get the user off to a quick start.

Software interface showing a path overview between parts with a 3D model on the right and a pop-up window titled 'Use path in calculation' offering the option to create calculation parameters.

Pre-CAD Stack-Up Analysis

The system offer the ability to manually setup stacks - handy pre-CAD - to estimate performance of critical features before development.

Assign nominal values, tolerances, distributions, Cp, Cc and/or Cpk values.

Software interface showing a parameters table with columns for Element, ID, Description, Nominal, tolerances, Impact, Cp, Cc, Cpk, Distribution, and reuse count, with a red arrow pointing to the 'Add Parameter' button at the bottom left.

2D and 3D Stacks

Handle 2D and 3D stacks.

The system allows you to setup multi-dimensional stacks. In combination with the iteration feature the analysis can be refined during the development process.

Engineering software interface showing tolerance and clearance calculations for a cylinder and boxes, with a 2D technical drawing of colored boxes and a cylinder.

Non-linear Stacks

Set-up non-linear stacks. Calculate forces, pressure, your commute-time-to-work, only your imagination sets the limit - as long as you can provide a mathematical expression.

The system works with all standard math-operators such as cos, sin, cosh, sinh, Pi, etc.

Interface showing a calculation formula for F_input with variables L1, L2, A_deg, D1, Monte Carlo method options, trial number 1,000,000, sigma level 3.0, target evaluation table with LSL 8.5, USL 10.5, DPMO 2700, yield 99.730%, and result row with Mean 9.617, and a bell curve graph displaying values between LSL 8.5 and USL 10.5.

Apply GD&T Modifiers

Refine tolerance stacks with GD&T modifiers such as Symmetry, Straightness, Total Runout, Circular Runout, Profile of a Surface, Profile of a Line, Position, Perpendicularity, Parallelism, Flatness, Cylindricity, Concentricity, Circularity, or Angularity.

User interface of RD8 software showing a parameters table with dimensions, tolerances, and an Edit parameter panel highlighting geometric dimensioning and tolerancing options.

Sketch Canvas

Draft tolerance stacks and allocate estimated tolerances based on sketches or illustrations.

Annotate on sketches to draft and communicate design intents.

Keep the design history. After sketching - link the paramenters to the CAD model.

Engineering software interface displaying tolerance analysis for brew pressure with a hand-drawn mechanical lever schematic on the right labeled with variables Adeg, Finput, L1, L2, and D1.

Tolerance Lookup

The system allows you to look-up and assign tolerance on the fly based on the ISO 286 IT grade standard.

The user can either input a tolerance and then calculate the corresponding IT Grade or input a tolerance grade and then calculate the related tolerance.

Table with elements showing nominal values, upper and lower tolerances, tolerance classes, and impact percentages highlighted in an orange font.

Embedded 3D Viewer and 2D Canvas / Infinity Canvas

Take screenshots from the embedded 3D viewer directly into the 2D Documentation Canvas. No app-switching.

Easy annotation of stacks by:
- Point of Interest annotation
- Leader lines
- Arrows

Semi automatic link of annotation to parameters and parts.

The canvas is an "infinity canvas" and can be used to add notes, screenshots, stickers to support the development and thought process.

Engineering software interface showing filter basket sealing pressure analysis with a detailed CAD cross-section view, parameter table, and Monte Carlo calculation results.

Step 3: Analyze Tolerance Stacks.

Let the system handle the heavy lifting.
Spot and fix problems before they escalate.

Simulating Success or Failure

Easy switch between different evaluation methods:

Worst Case - for worst case scenarios and part fits.
RSS - Root Sum Square for conservative estimates.
Statistical - for analytical approach.
Monte Carlo - for real life variation simulation of up to million of samples in milliseconds.

Analyze the Stack

Read DPMO- and yield projections.

Identify impactful parameters - often a source for optimization.

Table showing tolerance and impact data for various elements with impact percentages highlighted in a column, ranging from 0.8% to 28.2%.

Parameter Studies

Analyze sensitivity and impact of parameters.

Software interface showing tolerance analysis with parameters, impact sensitivity values, and a 3D CAD model of wing parallel alignment.

Step A: Overview

Approve design with confidence.
Deliver clear 2D drawings.

The Great Overview

Tolerance Stack-up Overview

Summary of all calculations. If they pass or fail.
Easy browsing from sheet to sheet, illustration to illustration.

Linked Calculations Sheets

Each calculation sheet is linked to the 3D model and part/assembly parameters.
All documentation in one sheet: Parameters, specification, results, illustration, conclusion.

The "What if" feature.
Preview Impact of Parameter Changes

Easily preview the impact of publishing your parameter changes

"What if" this parameter changes? Instantly check the impact on other calculations.

E.g. handy in case if a part is out of specification. Check the impact in seconds.

Parameter List: The Foundation for the 2D Drawing

The systems parameter module makes it easy to filter out all relevant elements that should be transferred to the final 2D drawing.

The parameter module summarizes parameters from all tolerance stacks into a single list.

With respect to axiomatic design - the parameter list also reveals information regarding how many times/places an element is used which can be an indicator for how many couplings that exist in a design.

Engineering software interface showing a parameter list with nominal, upper and lower tolerance values on the left and a detailed colored CAD model of a mechanical lever mechanism on the right.

Time-Machine

Create iterations along the early to the late development phase. Track development over time and document decisions.

Step B: Collaborate.

Make Tolerance Stack-Up Analysis and Optimization a Part of the Product Development Process.

Live Collaboration

Collaborate real-time with colleagues 'google docs style'.

Cloud based system: no check-in or check-out.

Manage and control access/viewer rights.

PDF Export

Document your efforts with a few clicks by export a PDF-document.

Table titled Calculation exports with columns Created by, Created at, and Status showing two entries: maky@rd8.tech with a pending status from 1/3/26 12:46 AM, and maky@rd8.tech with a completed status from 12/15/25 10:47 AM, plus icons for delete and download actions.

Step C: Optimize.

Make life easy.
The secret sauce.
Simplify tolerance stacks by optimized interface design.

X-ray Interfaces and Identify Overconstraints

Our technology is built on world-leading interface engine.

Here you see an illustration of two parts - a grey and a purple.
Our 'X-ray' mode lets you inspect functional surfaces between the parts.

In this case almost all functional surfaces are highlighted in orange - indicating overconstraints. This results in unnecessary complexity for tolerancing.

Optimization Checker

Contrary to the other example with an overconstrained design - here's an example with no overconstraints.

The 'X-ray' and constraint evaluation engine determine that there are no overcontraints and that the part is ideally constrained - indicated by green functional surfaces. The parts are exact constrained and hereby easy to tolerance.

How-to create a Tolerance Stack-up Calculation in 2 min.

Easy Setup in minutes

Automatic tolerance lookup and comparison of tolerance class.

Automatic stack-up detection

Get instant help to setup tricky tolerance stack-ups and check if chains are unambigious.

2D Canvas and Annotation

Take screenshots directly from your CAD (3D) model into your documentation canvas and link 3D elements to parameters.

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Two ways to unlock value with RD8 Software

RD8 supports both traditional expert-driven workflows and modern, scalable team workflows. Choose the approach that fits your organization today - and evolve as your engineering process matures.

Centralized Expert Workflow

For the 1-3 specialists who handle tolerance stacks today.

Keep your current setup while replacing spreadsheets with a dedicated tool.
Gain faster, more accurate, and more reliable calculations.
Strengthen documentation and eliminate inconsistencies between projects.
Tolerance analysis software with cross-section
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Scaled Team Workflow

For organizations ready to democratize tolerance stack analysis.

Enable every engineer to run their own tolerance checks.
Remove bottlenecks around a few experts.
Improve collaboration across projects and design stages.

Ready to bring structure and predictability to your tolerance work?

Book a demo and see if RD8 is the right fit for your engineering team
Talk to an expert engineer to understand real value and ROI.
Get contacted by an RD8 engineer.
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By submitting, you accept RD8's Privacy Policy and Terms of Service.