Every polymer used in catheter manufacturing tells a different story when it meets a forming die. The material's glass transition temperature, melt viscosity, moisture sensitivity, and crystallization behavior all dictate how a catheter tip must be processed — and how unforgiving the process becomes if those parameters stray out of range. At ONEX RF, where we develop and manufacture RF induction-based catheter tip forming systems for sizes ranging from 2 to 36 French, we work across the full spectrum of catheter polymers: Pebax, Nylon (Polyamide), Polyurethane (PU), PEEK, PTFE, HDPE, and more. The following is a practical breakdown of what makes each material distinct from a forming standpoint and what process controls matter most.
In RF tip forming, heat is delivered to a metallic die via an induction coil, and the die conducts that heat to the catheter tube. The tube is inserted into the die cavity while it is hot, pressed, and held to take shape, then cooled with an air jet until it solidifies. This four-step sequence — insert, heat, form, cool — sounds simple, but the acceptable window for each step shifts dramatically depending on what the catheter is made of.
ONEX RF systems support two process control modes: Temperature Mode, where a thermocouple welded directly to the die provides closed-loop feedback to maintain a target die temperature, and Time & Power Mode, where the operator sets RF power level and heating duration. Both modes are useful. Temperature Mode delivers repeatability and reduces operator error — the system knows exactly when the die has reached the set point and stops adding energy. Time & Power Mode is faster to set up for initial feasibility trials when you are still learning how a new material behaves. Understanding the thermal requirements of your material determines which mode is appropriate and what your target parameters should be.
Pebax (polyether block amide) is the dominant material in micro-invasive interventional catheters because it offers an unusually wide hardness range — from 25D for ultra-soft distal tips to 72D for stiffer proximal support sections — within a single material family. That flexibility is also what makes its processing parameters non-trivial.
The glass transition temperature of Pebax is approximately 250°C, but effective tip forming occurs well below that. Lower durometer grades (25D) are formed at lower die temperatures to preserve the soft polyether segment structure that gives the tip its suppleness and atraumatic character. Higher hardness grades (72D) tolerate and benefit from more energy, promoting crystallization in the nylon-rich hard segments that provide pushability and kink resistance.
One of the most critical but underappreciated variables with Pebax is moisture. Pebax is highly hygroscopic, and material that has absorbed moisture will degrade hydrolytically during forming — producing surface defects, bubbles, reduced mechanical properties, and inconsistent tip geometry. Drying before forming is not optional; it is a fundamental process step. For neurovascular applications calling for 25D–45D Pebax tips, the goal is a soft, atraumatic geometry that will navigate tortuous anatomy without damaging vessel walls. Getting there consistently requires stable die temperature, proper slide insertion speed, and adequate cooling time — all parameters that ONEX RF systems record and store in recipe form, allowing up to 40 distinct product configurations on one machine.
Nylon, or Polyamide — with a glass transition temperature around 120°C — is the go-to material for catheter proximal support sections where torque transmission, pushability, and abrasion resistance take priority over flexibility. Nylon 12 is particularly common in catheter shafts due to its combination of mechanical properties and processability.
Like Pebax, Nylon is hygroscopic. Moisture absorbed during storage will lead to processing defects — silver streaks, surface splay, and reduced structural integrity — if the material is not adequately dried before forming. Thorough drying at appropriate temperatures before any heat-forming operation is a non-negotiable step.
Multi-durometer catheters often combine a Nylon proximal section with a softer Pebax distal section. In RF tip forming, the interface bond between dissimilar materials requires careful control of both temperature and insertion mechanics. If the die temperature is too high or the slide advances too quickly, the bond zone can be compromised. ONEX RF systems provide adjustment of insertion force via a load cell, insertion depth and speed via a servo-controlled motor — all of which contribute to consistent, strong interface bonds on multi-segment catheter designs.
Thermoplastic Polyurethane (TPU/PU) is versatile — covering a hardness range from 60A to 85D — and biocompatible, making it a widely used material for catheter shafts and balloon components. However, PU is thermally sensitive in a way that demands careful die temperature control.
The glass transition temperature of Polyurethane sits around 150°C, but degradation of the polymer's ester or ether linkages can begin at much lower temperatures if the material is wet or if the die is too hot. Exceeding the degradation threshold results in rapid property loss — reduced elasticity, pinholes, or discoloration. This is why closed-loop temperature feedback matters so much for PU forming: you need to know the die is at the right temperature, not above it.
For PU balloon-to-shaft bonding, the temperature differential between the two components being joined is a key variable. A large thermal gradient at the bond interface leads to weak fusion that can fail under pressure. ONEX RF's Soft Tip Bonding system (STB-807) is specifically designed for this application, using external heated molds and support mandrels to produce consistent bond geometry across a range of catheter sizes from 3 to 36 French.
PEEK (Polyether Ether Ketone) occupies the extreme end of the catheter polymer spectrum. With a glass transition temperature of approximately 300–350°C and a Shore D hardness of 85D, it is the material of choice for demanding applications — radiofrequency ablation catheters, high-pressure delivery systems, and structural components that must resist deformation under load at elevated temperatures.
Forming PEEK requires a system capable of reaching and sustaining high die temperatures. ONEX RF catheter tip forming systems can achieve die temperatures up to 500°C, which is more than sufficient to form PEEK. Processing below the required temperature threshold produces incomplete forming — the polymer chains do not adequately disentangle, resulting in uneven material flow and poor tip geometry.
Cooling strategy is equally important for PEEK. Because the material has significant crystallization behavior, rapid or uncontrolled cooling can introduce internal stresses that compromise dimensional stability and compressive strength. A controlled, gradual cooling approach — which the ONEX RF air-cooling system facilitates through programmable cooling time parameters — allows for optimal crystallization and stress relief in the finished component.
PTFE (Polytetrafluoroethylene, or Teflon) has a glass transition temperature of approximately 230°C and is prized for its extremely low coefficient of friction — critical for inner liners of guide catheters and introducer sheaths where smooth wire or device passage is required. PTFE does not melt and flow the way thermoplastics do; it sinters. This means tip forming of PTFE components requires careful attention to die temperature range and forming pressure. ONEX RF systems' dual pressure control, which maintains constant forming pressure and speed throughout the cycle, is particularly valuable for consistent PTFE tip geometry.
HDPE (High-Density Polyethylene) has a glass transition temperature around 210°C and is used for structural catheter layers and protective outer jackets. It is cost-effective and highly moldable, with lower melt viscosity than many engineering polymers. HDPE's forming window is relatively forgiving compared to PEEK or PTFE, but melt uniformity and controlled cooling remain important to achieve consistent crystallinity and dimensional stability in the finished tip.
The catheter polymer is only one half of the equation. The die material — and how it responds to RF induction heating — determines how efficiently and uniformly heat is delivered to the tube. ONEX RF manufactures catheter tip forming dies in three primary materials: stainless steel, nickel, and carbide. Each reacts differently to the RF field and requires different power settings to reach the same target temperature.
The die and coil are housed together in a cassette, which can be swapped as a complete unit when changing from one product to another. This cassette-based architecture means switching from a Pebax tip forming application to a PEEK application — with very different temperature requirements — takes minutes rather than hours, and the new recipe is simply recalled from the system's stored parameters.
Knowing the general thermal requirements of a material is the starting point. Establishing a validated, reproducible process parameter window for a specific catheter design — with a specific die geometry and a specific tube lot — is the actual goal of process development. At ONEX RF, we offer three levels of process development (PD):
Feasibility PD demonstrates that the material can be formed and that our system is capable of the application. Basic PD produces good-quality catheter tips and delivers nominal process parameters — the starting recipe a manufacturer can use in production. Advanced PD delivers a full Design of Experiments (DOE), documented process parameter windows, IQ and OQ support, and guarantees that tips meet customer dimensional and quality specifications. Advanced PD typically requires 2–4 weeks, depending on the complexity of the specification.
Process development is completed at our Duarte facility before the system ships to the customer. This turn-key approach means the manufacturer receives a forming system that already runs their product — not a machine they have to spend months qualifying from scratch. Process parameters are stored in the recipe system, process limits are configured to prevent operator error, and the system arrives production-ready.
No matter how well a process is initially developed, production consistency depends on whether the forming system can maintain those parameters cycle after cycle, shift after shift. ONEX RF systems use closed-loop RF power feedback and closed-loop die temperature feedback via a thermocouple welded to the die. These are not just monitoring features — they are active control elements. If the die temperature drifts, the control system adjusts RF power to correct it. If reflected power changes (which can happen when the coil-die relationship shifts), the system detects and compensates.
Every forming cycle is logged. The system records die temperature, RF power, slide position feedback, forming time, and cooling time for every part produced. This data collection supports the machine learning-based process optimization described in ONEX RF's Data Collection Mode, and it provides the production records that medical device manufacturers need for traceability and process validation documentation.
Password-protected operator access levels prevent unauthorized parameter changes, while the calibration module — which connects between the controller and tipping station — allows in-house verification of thermal and analog I/O calibration without sending the system back for service.
Catheter material selection is a clinical and mechanical engineering decision. The manufacturing consequence of that decision is a specific set of forming requirements — temperature range, heat delivery rate, insertion force, cooling time, and moisture management — that the tip forming system and process must accommodate. A system without closed-loop temperature control cannot hold the tight temperature window that differentiates a good Pebax tip from a degraded one. A system without programmable forming pressure cannot produce consistent bonds across a multi-segment Nylon-Pebax catheter.
ONEX RF catheter tip forming systems are engineered from the ground up to handle the full range of catheter polymers in commercial use — from PVC and Nylon at the lower end of the temperature spectrum to PTFE and PEEK at the high end. The Air Tipper and Servo Tipper platforms support catheter sizes from 2 to 36 French, run on standard 110–240VAC/15A/80PSI utilities, require no water cooling, and fit in a 2-foot by 1-foot floor footprint. They are built in Duarte, California, carry a 1-year manufacturer's warranty, and have a field failure rate of less than 1%.
If you are developing a new catheter design or scaling an existing one and need to understand how your material's properties should shape your forming process, ONEX RF's process development team works with customers at every stage — from initial feasibility through full IQ/OQ validation. Reach us at +1.626.358.6639 or visit www.onexrf.com.