Oven with slotted doors for potting distal end of imaging
catheters
Intravascular Ultrasound (IVUS) catheters have imaging
elements arranged in a circular array mounted on the distal end. They are used for
real-time viewing of artery and veins to help diagnose conditions.
Process: Drying and Heating of Imaging Catheters.
The distal tip of imaging catheters is filled with liquid resin to seal and protect the
elements. The resin is preheated prior to the potting process to allow the mixture to flow
better. Once the catheter tip is filled with resin it is cured in an oven.
Problem:
Since only the tip of the imaging catheter needs curing the oven must be able to receive
just the tip of the catheter to avoid unnecessary heating of the rest of the catheter.
Consistent and repeatable temperature is critical for getting reliable potting results.
The customer was having difficulty achieving uniformity with their existing oven solution.
The ovens had an open void in the chamber that resulted in heat loss near the opening. And
the solid bottom trays they were using to carry the catheters was restricting airflow. Air
flow needed to be precisely directed over the top portion of each tray in order to achieve
the correct process requirements and horizontal flow. The trays did not extend all the way
to the back side of the ovens, so maximum air flow to the work area was not achieved. That
led to inconstant performance and a 4% failure during the curing process. An unacceptable
amount for such an expensive component, and time and energy consuming process.
Solution:
The solution Despatch provided was a modified, 18 cubic foot LBB model lab oven with slots added to the doors of
the oven to allow the customers trays to be inserted without opening the oven. Silicone
flaps cover the slotted openings to prevent heat from escaping. Despatch engineers
investigated ways to improve air flow characteristics. The first step was eliminating the
open space caused by asymmetrical loading of the oven. This led to the addition of a
partition that would meet with the inserted trays, blocking off a portion of the oven
chamber. This area still received warm enough air to help maintain uniformity, and it
redirected a larger portion of the air movement over the work area. The second step dealt
with the problem of the restricted horizontal flow. To address this, adjustable louvres were
placed in locations that would direct the air over the top of the customer’s tray design.
Performance results:
The results were an air flow that spread evenly over each work tray and afforded an
unobstructed path to the area between the 2 vertical rows of trays on return to the
circulation fan. An oven chamber uniformity certification was provided and testing in
Despatch’s Innovation Center proved the concept.
Process failure was kept to a minimum, increasing output and profitability from catheter
production. Energy use was reduced by being able to fulfil manufacturing quotas with fewer
process cycles.