10.11.2025

Case: Leak-tight catheters — measuring high-aspect-ratio step-height with telecentric optics

For a leading global medical device manufacturer, every catheter has to be leak-tight. The connection between the catheter tube and hub depends on a tightly toleranced step-height deep inside a narrow cone — a high-aspect-ratio feature that conventional gauges struggle to measure quickly and repeatably. With the telecentric TopMap Metro.Lab, the team verifies this critical parameter fast, non-contact and with far less operator influence.

Challenge and situation 

For a leading global medical device manufacturer, leak-tight catheters are non-negotiable. The catheter tube must sit perfectly connected to the catheter hub; if it does not, fluid can leak when the needle is administered, risking contamination. A key parameter governing this connection is the step-height — the distance from the top reference area to a 1.5 mm-wide ring on the inner cone — which must stay within a defined tolerance. Measuring it reliably was the challenge. The existing digital height-gauge method was too slow, and its manual, contact-based handling gave insufficient repeatability. As production demands grew, the manufacturer needed at least a semi-automated solution that removed operator influence from the result.

The solution: telecentric step-height measurement with TopMap Metro.Lab

The catheter is a high-aspect-ratio part — a hole diameter of about 2.6 mm with a 17 mm-deep recessed cone, an aspect ratio of roughly 6.5. Reaching and measuring that deep cone surface demands both a large z-scan range and a telecentric (parallel-beam) optical setup; conventional systems simply cannot see all the way down. The Polytec TopMap Metro.Lab is built for exactly this: its telecentric design and large z-scan range capture the areal step-height non-contact and fast, while its large field of view allows multiple parts to be measured at the same time.

The result

With the TopMap Metro.Lab, the manufacturer verifies the critical step-height tolerance reliably and at speed, removing the operator variability of the previous manual gauge. Non-contact areal measurement, the reach to inspect a 17 mm recessed cone, and multi-part measurement in a single field of view deliver a faster, more repeatable, semi-automated check that helps ensure every catheter stays leak-tight. Polytec’s Pro.Surf offers the same telecentric, large z-scan capability for comparable high-aspect-ratio tasks.

Pro.Surf macro profiler for flatness, step height and other production parameters

Quick start into surface metrology

We take our claim Measure what matters seriously — and we support you in whatever way fits your situation. Even if your need is only temporary, or a full system isn’t in the budget yet, you have options: rent a system with PolyRent, or let our specialists run the measurements for you with PolyMeasure. And if you’re looking to buy, we’d recommend starting with a feasibility study or a rental — with the rental fee credited against your purchase price afterwards. Talk to our experts and we’ll recommend the best-fitting approach for your metrology tasks.

Discuss your demands with our experts

Let’s start with a short discussion about your parts, tolerances, and workflow
—and, if useful, we can add a feasibility study, PolyMeasure, or a PolyRent trial as optional next steps.

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