When designing parts for an assembly, engineers are faced with a range of decisions, from material selection to defining joining methods. One of the most critical yet often overlooked factors is how individual component tolerances impact the final assembly.
While most teams focus on ensuring that the final assembly meets functional requirements, they may overlook how individual part tolerances stack up to affect that final assembly. Even when individual parts are in spec, the final product can fail, leading to rework, rejected parts, or equipment crashes.
Why Individual Component Tolerances Matter
It’s easy to assume that if every part meets its drawing tolerance, the final assembly will come together flawlessly. But this isn’t always true. When component tolerances stack unfavorably, assemblies can fall outside of spec, even if each part was made "correctly."
To avoid this, engineers should compare the minimum and maximum dimensions of each component against the requirements of the complete assembly. Consider how parts interact at their worst-case extremes – not just at nominal sizes.
Ask yourself:
Will the maximum and minimum combinations still result in an assembly that functions as intended?
Are there scenarios where the assembled part would not meet dimensional or performance requirements?
Could tolerance stack-up affect your forming or joining process?
Design engineers must understand how component tolerances interact. Parts that meet their own specs may still prevent the final assembly from meeting performance or dimensional goals. Performing tolerance analysis early helps avoid costly fixes later.
Internal Component Retention Failure and an Equipment-Based Solution
One manufacturer approached Orbitform with a cylindrical part consisting of two components. The goal was to create a lip on the external housing to retain the internal component using Static Roller Forming.
At nominal dimensions, the design appeared feasible. However, during evaluation in our Solutions Lab, we reviewed the min/max tolerances and uncovered two critical failure scenarios:
If the external part was at its max tolerance and the internal at its min, the rolled lip would fall short, creating too much clearance and a loose retention.
If the external part was at its min and the internal at its ma*, there would be insufficient material left to form over, risking a machine crash or leaving the internal part improperly retained.
Identifying this issue early led to an optimized equipment solution that used a probe station to measure the actual part stack-ip prior to forming. Combined with our servo-Z programmable hard stop, the machine is able to adjust the stroke height to match each assembly.
Tolerance Stack-Up in Riveted Stamping Assemblies
Another common issue we see is with riveted assemblies involving stamped components. Many stamping operations run close to the minimum thickness of their material range to save cost, while rivets can arrive at either end of their tolerance range.
When a maximum-length rivet is paired with a minimum-thickness part stack-up, there may be too much material to form. This can result in:
Over-formed rivet heads that don’t meet cosmetic standards
Interference with surrounding components
Assemblies that fail to meet key dimensional or functional criteria
On the other hand, when a minimum-length rivet is combined with a maximum-thickness part stack, there may be insufficient material available to form a strong, reliable head. This scenario introduces risks such as:
Loose assemblies or rivets that don’t adequately hold components together
Failed functional or performance requirements (e.g., pull-out strength, vibration resistance)
Machine forming tools bottoming out too early, potentially causing part or equipment damage
We frequently help customers evaluate these scenarios through prototype testing in our Solutions Lab. By reviewing min/max tolerance combinations, we can identify where tolerances may be too wide and recommend adjustments to ensure successful, repeatable assembly outcomes.
Design with the End in Mind
Designing for assembly means thinking beyond nominal values. A full understanding of component tolerances and how they affect the final part is critical, especially under worst-case conditions.
By proactively evaluating min/max combinations, manufacturers can:
Prevent field failures and warranty claims
Avoid unplanned machine downtime or equipment damage
Improve part quality and reduce scrap
Ensure first-pass success during production
At Orbitform, we believe that robust assembly starts with thoughtful design and validated processes. Our Solutions Lab offers hands-on prototype testing, tolerance stack-up evaluation, and process development support. Whether you’re working on a riveted, formed, or pressed assembly, we can help you ensure that your equipment and components are fully aligned for success.
Let’s collaborate to build smarter. Contact us to discuss your application or schedule an application review with our team. Together, we can help you identify and eliminate potential tolerance pitfalls before they become production problems.