Polytetrafluoroethylene — commonly known as PTFE or by the trade name Teflon — is one of the most demanding materials to process in medical device manufacturing, and also one of the most indispensable. Its combination of exceptionally low friction, broad chemical resistance, and proven biocompatibility makes it a go-to material for catheter liners, guiding catheters, introducer sheaths, and other minimally invasive devices. At the same time, its high melting point and non-stick surface energy create real manufacturing challenges, especially when it comes to forming precise, atraumatic catheter tips. This article explores what PTFE is, why it is used so widely in interventional devices, and how specialized induction-based tip forming systems from ONEX RF address the process challenges that this material presents.
PTFE is a fully fluorinated polymer — every hydrogen atom in a standard polyethylene chain is replaced by fluorine. That structural difference accounts for virtually all of PTFE's distinctive behavior. The carbon-fluorine bond is among the strongest in organic chemistry, which is why PTFE resists degradation by bodily fluids, contrast agents, and standard sterilization methods including autoclaving at 121°C and ethylene oxide exposure.
Low coefficient of friction. PTFE has a static coefficient of friction of approximately 0.05–0.10, lower than virtually any other solid polymer. Its surface energy is 18–20 dynes/cm, which means liquids, adhesives, and melted plastics do not wet or bond to it easily. In a catheter liner, this translates to smooth, low-resistance passage of guidewires, balloon catheters, and stents through the lumen during complex interventional procedures in cardiology, neurology, and peripheral vascular surgery.
High melting point. PTFE does not melt in the conventional thermoplastic sense. It undergoes a crystalline transition at approximately 327°C and can be processed only above that temperature. For context, ONEX RF tip forming systems are designed to reach die temperatures up to 500°C, which is why they can successfully process not only PTFE but also other high-glass-transition materials such as PEEK (Tg ~350°C) and polyimide.
Low surface energy as a manufacturing challenge. The same non-stick property that makes PTFE valuable inside a catheter lumen makes it difficult to bond, coat, or mold. Adhesives do not adhere well to untreated PTFE surfaces, and the material resists taking on a sharp, defined shape from a mold unless very precise temperature and pressure control are applied. These properties make PTFE catheter tip forming one of the most technically demanding forming operations in the catheter manufacturing industry.
PTFE appears in catheter assemblies in several distinct roles, each exploiting a different aspect of the material's properties.
Tip forming — sometimes called tipping — is the process of shaping the distal end of a catheter tube into a defined geometry. For patient safety, catheter tips must be atraumatic: smooth, rounded or tapered, free of sharp edges, and dimensionally consistent across an entire production lot. For PTFE catheters, achieving that consistency is significantly harder than for softer thermoplastics such as PEBAX or polyurethane, because PTFE's narrow processing window demands precise, repeatable thermal management.
The fundamental forming process, as used in ONEX RF systems, works as follows: a metallic die — machined to the target tip geometry — is heated by an induction coil within an electromagnetic field. The catheter tube is inserted into the heated die, which conducts heat to the PTFE and causes it to soften and flow into the mold cavity under controlled pressure. After a defined forming dwell, the die is cooled by an air jet, the PTFE solidifies in the mold shape, and the finished tip is released.
Induction heating is ideally suited to PTFE tip forming because it heats only the metallic die — not the surrounding environment — and can reach the temperatures required (above 327°C) in seconds. ONEX RF systems use eddy currents and hysteresis generated by a high-frequency RF coil to elevate die surface temperature rapidly and uniformly. Because the heat is concentrated exactly where the mold contacts the catheter, there is no thermal damage to adjacent tubing or assembly components.
PTFE's narrow processing window — the temperature range between adequate softening and degradation — makes open-loop or manually controlled tipping processes prone to inconsistency. Under-heated dies produce short shots (incomplete tip formation); overheated dies cause burning, dimensional variation, or material degradation. ONEX RF tip forming systems address this with multiple simultaneous closed-loop feedback channels:
The result is a forming process with documented, traceable parameters for every tip produced — a significant advantage when validating a PTFE catheter tip forming process under FDA quality system regulations.
ONEX RF catheter tip forming systems support the full range of tip geometries required by interventional device designs, including for PTFE catheters in sizes from 2.5Fr to 36Fr. Achievable tip forms include:
Die materials compatible with PTFE forming on ONEX RF systems include stainless steel, carbide, and nickel — all selected for their magnetic properties, which determine how efficiently the induction coil couples with the die.
Beyond bulk PTFE tubing, thin PTFE coatings — typically 1–10 micrometers thick, applied by spray or dip-coating methods — are widely used on forming dies and mandrels to prevent adhesion and aid part release during the tipping process. On the product side, PTFE coatings on metallic guidewires and needle surfaces reduce insertion friction and improve trackability. Understanding the interaction between PTFE-coated tooling surfaces and the catheter material being formed is an important element of process development for any tip forming operation.
Because PTFE presents unique process challenges, engineering support during process development is often critical to a successful validation. ONEX RF provides process development services before and after equipment delivery: engineers test customer materials, optimize cycle parameters (temperature, pressure, heat zone position, cycle time), and ship equipment with a production-ready process already established. This approach reduces the time manufacturers typically spend working through PTFE's narrow processing window on their own — a step that can otherwise extend new product introduction timelines by weeks or months.
ONEX RF systems are also designed for the production floor environment. Equipment ships in 2–3 weeks, dies in 3–4 weeks. The compact footprint — approximately 13 by 22 inches for standard systems — fits into existing manufacturing cells. Air-jet cooling replaces water-cooling systems, eliminating the infrastructure, maintenance, and contamination risk associated with water-cooled equipment. All components, including electronics and RF systems, are manufactured by ONEX RF in Duarte, California, enabling rapid support and short lead times on replacement parts and custom die modifications.
PTFE remains an essential material in medical catheter manufacturing precisely because its performance characteristics — low friction, chemical inertness, biocompatibility — are difficult to match with any alternative. Its high melting point, combined with its non-stick surface energy, mean that forming consistent, atraumatic tips from PTFE tubing requires equipment engineered specifically for the task. Induction-based tip forming systems with closed-loop temperature, force, and position feedback — operating at die temperatures up to 500°C — provide the process control necessary to work reliably with PTFE and other high-performance catheter materials across production volumes.
For engineers and product developers working with PTFE catheters, the key is matching material behavior to equipment capability and supporting that combination with rigorous process documentation. ONEX RF designs its systems with that goal in mind, from the closed-loop HMI controls to the data logging and calibration modules that support FDA process validation requirements.