10 Ways Expert Device Engineers Create Quality, Repeatable Tube Bonds

Featuring 3 Catheter Tube Bonding experts, with over 60 years of cumulative experience in Laser, RF and resistive heating tube bonding, this webinar will cover topics including Material Selection, Configuration, Manufacturability and Testing. Our experts will teach techniques and the critical steps used to create quality repeatable tube bonds.

WHAT PARTICIPANTS CAN EXPECT TO LEARN:

Material Selection
Configuration
Manufacturability
Testing

LAP JOINT HIGHLIGHTS:

This method is used when similar and dissimilar materials need to be welded together.
Applications include high to low durometer thermoplastic, braided to non-braided, dissimilar polymers or thermoplastic to metal.
Process requirements include coated mandrels, protective sleeves, tooling and radial compression.
Split die bonding and hot air bonding are both suitable methods depending on the desired application, cycle time, product handling.
Split die bonding provides focused heat to deliver heat right where it is needed.
Hot air bonding is ideal for thick walled materials or when a wide range of product sizes are desired.

How to prep materials for a lap joint?

To select an appropriate mandrel, then flare one material or neck the other for insertion. Measure the OD and select appropriate FEP.

Where is the temperature measured and how do you maintain a stable process?

Within .050” of the material. Autotuning maintains stable temperature.

What bond sizes are possible and how to size the die?

Split Die Min/Max width (1mm min. -3cm max.) Split Die Min/Max diameter (.031” Min OD .375”OD max)
Hot Air Min/Max width (.040” – .50” W) Hot Air Min/Max diameter (.031 OD to .500”OD)

BUTT-WELD HIGHLIGHTS

This method is joining the square cut ends of two tubes together to form one continuous tube.
Polymers require similar melting point, wall thickness and durometer to form a strong weld.
Application include braid to non-braid, single or multi lumen tubes, tapered bonds and can be done in a single step with tip forming in some cases.
Butt weld tooling is designed for the maximum tolerance dimension of the tube OD.
Avoid using large solid metallic mandrels when possible as the mandrel will act as a heat sink.
Tensile tests and flex tests are common test methods. Carefully consider product handling and other fixturing to ensure repeatable test methods.

What are the critical considerations for braid to non-braided tubes?

The braid moves when the polymer around it is heated. Vante RF technology and tooling is designed to minimize the width of the heating zone to prevent braid exposure. Annealing the braid and high-quality end cuts also improve bonding results.

What are the effects of using lubricants in the bonding process?

Lubricants can impact the process both positively and negatively. Lubricants aid in enhancing flow of the plastic, but by their nature inhibit strong bonding forces. For some applications a PTFE sleeve or non-stick coating can be designed into the tooling design to achieve higher strength bonds.

Why is a clearly defined, straight line a bad visual characteristic for the interface between the two welded tubes?

Good flow of plastic and higher push forces results in products with higher bond forces, but visually there will be blending of the plastics. Tubing sizing, concentricity and clean cuts can support a better bond strength with less blending.

LASER WELDING FOR BALLOON BONDING HIGHLIGHTS

Heating of the material is done with laser energy with a spot size can be as small as 0.5mm
C02 laser wavelength is close to the resonance frequency of polymer groups which makes is possible to weld clear polymer materials.
Applications include balloon bonding, soft tip attachment, distal weld and tip forming in a single process.
Laser bonding requires a heat shrink material to confine the melting plastics. Polyolefin, RNF100, polyester or flor-polymers can be used. Heat shrink properties to consider include material, shrink ratio, absorption behavior, transparency and peelability. Good fit is essential.
A good bond is an interplay between laser power, laser duration, travel speed, spot size and rotation speed. A good strategy is to start with a low energy take up and work your way up.
For applications where the product can not be rotated consider the BW Tec model 1530.

Is it better to have larger or smaller focus point?

Spot size is defined as the energy density being delivered to the product. The laser can be mechanically adjusted to make the beam bigger or smaller. The further away I’m with the Focal point, the bigger the spot size gets and the lower the energy density is.

What is the impact of alignment or bent mandrel in the process?

Misalignment of the product to the laser will impact the process. As straight mandrel is a critical input for a consistent process. Consider the Machine Solutions MS1000 mandrel straightener for high volume production environments. It is definitely better if they’re straight, but also with a bit of a wobble you’re still able to get decent welds. The only thing which changes is that you get less acurate regarding the size of the weld.

Does colorant effect energy transfer from the laser?

I assume colorant from the material? No this should not have an effect, CO2 Laser have such a long wavelength the energy is absorbed on the surface of the material . This is also the reason why we’re able to weld transparent materials, respectively why we can use transparent shrinking tubes.