As the medical device industry evolves, product quality and safety standards continue to rise. Tolerance simulation software has become an essential tool for designers and engineers to optimize designs and ensure compliance.

This article examines how DTAS dimensional tolerance and stack‑up analysis supports medical device development—and its critical role in safeguarding product quality and patient safety.

Medical Device Linkage Tolerance Analysis

The mechanism shown features two V‑shaped rockers rotating on a shared shaft. While ideal design assumes coaxial alignment, manufacturing tolerances cause angular deviation between each rocker's mid‑plane and the vertical reference at top‑dead‑center.

Objective
Determine the max angular deviation between rocker mid‑planes while ensuring interference‑free motion.

Manual calculation cannot fully predict tolerance‑induced variation or locate tangential contact in this dynamic assembly. DTAS addresses this through iterative virtual assembly, simulating both tolerances and kinematics.

Assembly Logic
Link 5 is fixed. Motion is driven by Link 1 via the drive shaft, propagating through the linkage as follows.

To account for the possibility of tolerance fluctuations causing the shaft to be larger than the hole, leading to assembly failure, the software is configured to allow interference fitting in this situation. See the diagram below:

Furthermore, during movement, links 3 and 4 will come into contact at their limit states. Therefore, iterative assembly is required to limit their movement and prevent interference. See the diagram below:

Additionally, during actual operation, all pin‑hole pairs—except a few untolerancedfits—are in tangent contact, with consistent tangent directions at each joint. The simulation must therefore prevent contradictory alignments, such as one pin contacting the left side of its hole while another contacts the right.

To maintain correct joint kinematics, the float direction of every pin must be coordinated. Pins in joints sharing the same motion direction are assigned a standardized float angle, as shown below.

This method resolves all key assembly challenges, allowing precise tolerance allocation and measurement.

In short, tolerance simulation enables medical device manufacturers to precisely control dimensional variation—enhancing quality, reducing defects, shortening cycles, and lowering costs. It represents a strategic tool for innovation and progress in the industry.