Most catheter tubes come off an extruder as a plain, straight polymer shaft. Before it reaches a patient, however, it typically goes through a series of additional manufacturing steps collectively known as secondary processing — operations that reshape, join, and refine the extruded tube to meet the precise performance requirements of its clinical application. At ONEX RF, with more than 30 years of experience in catheter forming and bonding, we work with medical device manufacturers every day to optimize these secondary processes using RF (radio frequency) induction heating technology.
Secondary processing refers to any post-extrusion manufacturing step that modifies the geometry, structure, or functional characteristics of a catheter tube. The extruded shaft is the raw material; secondary processing turns it into a finished medical device. Common secondary operations include tip forming (tipping), section bonding or welding, flaring, and neck-down forming. Each of these steps can be performed thermally using induction-heated tooling — which is the method ONEX RF specializes in.
The goal of secondary processing is twofold: functional performance and clinical safety. A well-formed tapered tip improves trackability and reduces patient discomfort during insertion. A clean, strong bond between a soft distal tip and a braided shaft ensures the device won't delaminate under torque. These are not aesthetic details — they are engineering requirements that directly affect device clearance and patient outcomes.
Catheter tip forming — also called tipping — is the process of reshaping the distal (or proximal) end of a catheter tube by heating it inside a precision-machined metallic die. The die is heated via an RF induction coil that generates a magnetic field, which in turn heats the die through electromagnetic induction. Heat from the die conducts into the polymer tube, softening it. A servo-controlled slide then advances the tube into the hot die cavity under controlled pressure and speed. After a defined forming time, the die is cooled with air, and the tube is released, now holding the shape of the die cavity.
Common tip geometries produced through this process include:
ONEX RF tip forming systems handle catheter sizes from 2 French to 36 French and are capable of reaching die temperatures up to 500°C. The systems support both Time & Power mode and closed-loop Temperature Control mode, giving process engineers precise command over every thermal variable. Forming dies are available in stainless steel, carbide, and nickel, with lead times of 2 to 4 weeks for stainless and 3 to 5 weeks for carbide.
Many catheter designs combine materials with different mechanical properties — for example, a stiff braided proximal shaft joined to a flexible, soft distal tip. Bonding these sections together without introducing stress concentrations or delamination risk requires careful thermal control. ONEX RF's bonding systems accommodate several joint configurations: butt-weld joints, over-under joints, soft tip to multi-lumen shaft, and soft tip bond-and-form (where the tip is simultaneously bonded and shaped in a single heat cycle).
The physics of catheter bonding via induction heating differ depending on whether the joint is heated from the outer diameter (OD) or the inner diameter (ID). In OD heating, the die is heated externally and conducts heat radially inward. In ID heating, an RF-heated mandrel is inserted inside the tube, transferring heat outward from the lumen wall. ONEX RF's Butt Joint Weld System (BJW-807-LX) is designed for both approaches.
Not every polymer behaves the same under thermal forming conditions, and understanding material-specific processing windows is essential. ONEX RF's systems have been validated across a broad range of catheter polymer materials, including:
Material selection affects not only the processing parameters but also the die material choice, cooling strategy, and process window width. ONEX RF engineers work with customers during process development (PD) to establish nominal parameters, document process windows, and support IQ/OQ validation activities.
A catheter secondary processing line built around RF induction technology typically includes several specialized systems. ONEX RF manufactures the following platforms:
All systems run on 110–240VAC, 15A, 80PSI compressed air. The machine footprint is approximately 13 by 22 inches (roughly 1 by 2 feet), making them suitable for cleanroom environments with limited floor space. Machine lead time is 2 to 3 weeks. Each system ships with a 1-year warranty. Expected machine service life exceeds 20 years.
Reproducibility is the core requirement in medical device manufacturing. ONEX RF's PC-based HMI and PLC control architecture supports up to 40 saved recipes per system — each recipe storing the specific power, time, temperature, coil position, slide speed, and cooling parameters for a given catheter and die combination. Switching between applications is as simple as swapping the die-and-coil cassette and loading the corresponding recipe, a changeover that typically takes only a few minutes.
The closed-loop control system monitors die temperature in real time via welded thermocouples and adjusts RF power output accordingly. This is particularly important when running consecutive cycles — die temperature tends to drift upward during production, and a system relying on open-loop time-and-power control will produce inconsistent tips as the die heats up. The Air Tipper and Servo Tipper platforms eliminate this variability through continuous feedback control. Data collection mode also allows process engineers to capture forming data across cycles for machine learning-assisted process optimization.
Secondary processing with RF induction technology is used across a wide range of catheter-based medical devices. Products that routinely require tip forming, bonding, or flaring operations include:
Each of these product types has specific geometric requirements at the distal end — requirements that extrusion alone cannot deliver. RF-based secondary processing allows manufacturers to meet tight dimensional tolerances and achieve consistent, flash-free tips in production volumes.
Introducing a new catheter design or a new material to a secondary processing line requires disciplined process development. ONEX RF offers three levels of process development (PD) support. Feasibility PD demonstrates that the part can be formed and validates the machine's capability with the customer's material. Basic PD establishes a set of nominal process parameters and delivers good, usable parts. Advanced PD defines full process parameter windows, supports DOE (Design of Experiments), and provides documentation suitable for IQ and OQ validation protocols. Process development lead time is typically 2 to 4 weeks depending on the complexity of the specification.
ONEX RF also manufactures all forming dies and induction coil assemblies in-house, with a state-of-the-art Tool & Die department. Standard stainless steel dies are available in 2 to 4 weeks; carbide dies, which offer superior wear resistance for high-volume production, are available in 3 to 5 weeks. Being vertically integrated — manufacturing both the equipment and the tooling under one roof — allows ONEX RF to respond quickly to design changes and reduce the total lead time for new product introductions.
Catheter secondary processing is not a finishing step — it is a core manufacturing discipline that determines whether a device performs as designed. The quality of a tapered tip, the strength of a soft tip bond, the repeatability of a flare geometry: these characteristics are set during secondary processing, and they directly influence clinical performance, device approval, and patient safety.
RF induction heating technology, as implemented in ONEX RF's catheter forming systems, offers a combination of thermal precision, process repeatability, and design flexibility that is well-suited to the demands of medical device manufacturing. With closed-loop control, recipe-based process management, and servo-driven forming mechanics, these systems give engineers the tools to develop robust processes and maintain them across high-volume production runs.
For medical device manufacturers working through a new catheter design, evaluating a new polymer, or looking to improve consistency in an existing secondary processing operation, ONEX RF's engineering team is available to discuss process requirements and recommend appropriate equipment and tooling configurations. Contact ONEX RF at +1.626.358.6639 or visit onexrf.com.