Medical Device Link.

ENGINEERING INSIGHT

Harland Medical Systems uses precision spray valves developed by EFD Inc. to apply a UV-cured coating to urinary catheters without the risk of clogging two small openings at the tip.

Medical coating processes require a high degree of precision and process control. As today’s hydrophilic, antimicrobial, and other biocompatible coating chemistries become increasingly sophisticated, the challenge becomes finding the most efficient and cost-effective way to apply them. Harland Medical Systems (Eden Prairie, MN, USA) faced just such a dilemma when it needed to develop a catheter-coating system that would enable more-precise process control than the conventional dip coating technique.

Harland Medical Systems specializes in developing automated modules that can be linked together in different configurations to handle a range of coating applications. The company says this modular approach gives device makers a cost-effective alternative to outsourcing a custom coating system or fabricating one in-house. “Essentially, we can provide device makers with the performance of a custom coating system, but without the [associated] high cost or long lead time,” says Drew Summerville, vice president of marketing. “That can be a huge advantage when building products with short life cycles or introducing a new product when time to market is critical.”

Harland recently assembled a modular coating system for a manufacturer of urinary catheters. The UV-cured coating specified in the process had a tendency to bridge over the two small openings at the tip of the catheter, however, and Harland needed to find an alternative to the dip coating process that is often used for high-volume catheter production. “With dipping, the sheer volume of fluid can plug small openings, especially on devices with complex geometries,” Summerville explains.

Harland opted for a spray-based coating system that would allow the user to refine the amount of coating that is applied to the catheter. Specialized valves from EFD Inc. (East Providence, RI, USA) are one of the keystone components of the system. Unlike traditional spray valves, EFD’s 781-series valves feature a low-volume, low-pressure (LVLP) design that uses extremely low nozzle pressure to apply a fine, even coating with minimal overspray.

Process System Benefits

The Harland system moves, via an overhead conveyor, a pallet containing 48 catheters into the spray module. The pallet stops above a rectangular opening that has four EFD valves positioned along each of the longer sides. As the module’s software actuates the valves and they begin to spray, the catheters are lowered and raised at a controlled rate while the coating is applied. At the same time, the catheters are rotated to ensure a uniform coating thickness.

Harland’s new system will allow its customer to clean, coat, and cure a batch of 48 catheters every 3 minutes. Moreover, the valves have virtually eliminated the possibility of the UV material webbing or bridging over the small openings. Another advantage is that the coating material is supplied to the valves from closed tanks, which simplifies changeovers and eliminates downtime.