4 Steps Toward Efficient Upgrading of Ultrasonic Welding Systems in Medical Applications

Medical devices, such as in-vitro tests, diagnostic cartridges, surgical instruments, drug-delivery and wearable devices, and many other applications, commonly require some assembly, often using ultrasonic welding systems. Annual volumes for many of these products are in the hundreds of millions, and assembly equipment is expected to run 24/7.
 
Consequently, the ultrasonic sealing equipment currently being used in your plant may have seen more than a billion cycles since installation, with attendant wear and tear as well as other problems due to lack of regular calibration and preventive maintenance.
 
When components fail on old and obsolete equipment, sourcing replacements to effect repair can be difficult, and excessive (and costly) downtime can be the result.
 
Additionally, today’s medical device manufacturing standards demand a higher level of quality as well as data collection, storage, integrity and security than even a decade ago. Dated welding equipment with analog controls and limited data retention and feedback is simply not up to the task.
 
This equipment, as well as any information that it produces, can only be controlled, monitored and managed locally — using site-based personnel. There is no way to directly communicate manufacturing or control information or to monitor or adjust equipment performance from any remote location.
 
Manufacturers may also need to improve productivity, reduce downtime or enable real-time control, troubleshooting and maintenance. And they may need to adapt to working with complex assemblies with embedded electronics or alternative materials such as bioplastics.

Components of Concern

There are three parts of ultrasonic welder construction that can be the source of major problems in outdated equipment.
 
The power supply drives and controls the ultrasonic process, monitoring the weld process and communicating with the PLC. It takes line voltage (from the wall outlet) at a nominal 240V and transforms it into a high-frequency signal that drives the welding components mentioned below. It also provides the preprogrammed weld parameters necessary to operate the actuator and ultrasonic tooling (the “stack”) that work together to actually complete welds. If a component in an obsolete power supply fails, the entire system becomes inoperable and the user will be put in a tough “line down” situation for an extended period of time until replacement parts, if available, can be found and installed. This concern is made more acute by the global chip shortage, since these supply chain disruptions are especially problematic for older printed circuit board assemblies.
 
The acoustic stack, consisting of the converter, booster, and horn or “sonotrode,” is designed to vibrate at a set frequency and amplitude, generating frictional heat and compressive force to complete the weld. Because stack components operate under mechanical stress, they can be adversely affected by material fatigue, microfractures or ordinary wear. Thus, the condition of this critical part of the welder should be monitored and carefully maintained over time to prevent catastrophic failure. In older systems, complete replacement may be warranted.
 
The actuator, which drives the acoustic stack to make the weld, has been the subject of major design changes in recent years and, depending on the application, new units can have important benefits. Traditional pneumatic actuators can be more susceptible to wear than newer electro-mechanical (servo) actuators such as the Branson GSX-E1. In addition, electro-mechanical servo actuation offers greater flexibility and precision (see Dynamic Mode below). This is not to say that pneumatic systems are outdated. Both approaches have their place depending on such factors as budget, cycle time requirements, complexity and so on.
 
Mechanically, the GSX-E1 welders offer other benefits to medical device manufacturers, including ISO class 5.5 cleanroom certification, and an optional stainless-steel actuator kit.

New Power Supply Technology

Power supplies have changed dramatically in recent years, transitioning from analog to fully digital systems that offer closed-loop feedback and control of critical weld parameters.
 
For instance, a newer power supply, such as that found on the GSX-E1 welder, takes advantage of web services and makes possible real-time control, monitoring and communication. Users can log in to connected devices and monitor and control the welding equipment. Capabilities like these enable medical manufacturers to digitally monitor the health of their assembly systems by tracking values such as frequency or power draw. Variations in these values can provide early indications of wear in the acoustic stack. Thus, upgrading ultrasonic welding systems is a proactive way to help optimize system performance, identify near-term maintenance issues, and minimize or eliminate unplanned downtime on the line.
 
In addition, the advanced data-gathering capabilities of these digital power supplies also enable users to monitor process parameters in real time, set high/low limits on weld results, and configure alarms that flag weld cycles of parts that fall outside process limits. This enables automated bad-part processing and data logging that can be indispensable for maintaining superior quality as well as the 100% traceability required under standards such as the U.S. Food and Drug Administration’s (FDA) 21 CFR Part 11, which requires manufacturers to deliver electronic records, data management and audit trails.

Dynamic Mode

Medical devices often include complex parts with very tight welding tolerances or high levels of automation. Other problematic situations involve plastic parts that are compressible or contain compressible elements that are inserted into substrates with hardness variations or structural inconsistencies, or that contain or are installed over sensitive metal or electronic components. Alternative materials like bioplastics, which require lower temperatures and an overall narrower processing window than conventional plastics to achieve a quality weld, also pose a challenge.
 
Applications like these often require something more advanced than older systems that optimize welder performance around a single factor critical to part quality such as energy (joules per weld), peak power, distance (part collapse depth), or total weld time.
 
To overcome the limitations of single-factor weld modes, Emerson has developed a new patent-pending “dynamic mode” that is available on the GSX-E1. Dynamic mode leverages an advanced servo-actuation system, combining computing power and cutting-edge algorithms with high-speed data communications to monitor, recalculate and adjust the weld process in real time and achieve an optimized “target” result.
 
When using dynamic mode, the manufacturer selects the single-factor weld mode, such as energy, distance, or time, that provides the best results in a new application. Then, the user enters two additional “scores,” which act as limits for dynamic mode activity. The first is a material “density” score that, essentially, characterizes the hardness or resistance of the material that is to receive the welded, staked or inserted part (e.g., a low density score equates to a harder, more resistant material). The second is a weld “reactivity” score, which is used to adjust the degree of variability allowed in the target result (e.g., a low reactivity score equals a more homogenous result). Then, dynamic mode monitors each weld cycle, using the density and reactivity limits to adjust the cycle in response to specific part-to-part variabilities throughout the production run.

Four Steps Toward Better Welding

As noted at the beginning of this article, if the welding equipment in your plant is seven years old or older, there is a good chance you could increase productivity and reduce downtime by replacing at least some of those systems. But how do you know for sure and, more importantly, how do you approach such a project in an intelligent, organized manner that will not disrupt your operations unnecessarily?
 
The best way is to collaborate with an equipment supplier that has the experience, global resources and defined procedures to assist you. Emerson, for instance, recommends a four-step process to help customers make these tough decisions:
 

1. Site Walkdown and Evaluation: An Emerson technical specialist will visit your facility and physically review and document existing equipment, its condition and performance.


2. Solution Identified and Tested: In consultation with you, a specific welding system will be identified for retrofitting. Depending on the age of the equipment, the system may require a total upgrade to a modern version with increased capabilities. Weld trials can be performed to build confidence that the recommended solutions will meet or exceed application and production needs. Emphasis is placed on minimizing disruption of production and evaluating potential benefits of an upgrade.


3. Strategic Plan: Based on the results of the testing, Emerson will work with you to develop a plan to bring all substandard or outdated equipment up to the level of technology required for efficient production and modern data collection and process optimization. A timeline is developed to take into account equipment lead times and avoid unnecessary downtime during installation.


4. Installation: Equipment is delivered, installed, calibrated and tested for customer acceptance. If necessary, employee training will be provided.

Avoiding Risk

When one is working in the medical device environment, risk is anathema and should be reduced whenever and wherever possible. Equipment upgrades enable superior control, real-time monitoring and reduced scrap, decreasing the chance of costly downtime. Yet equipment upgrades and replacement projects can involve their own set of risks.
 
Therefore, it is advisable to work in collaboration with a supplier like Emerson, whose global footprint ensures staff are nearby. In addition, by selecting the most up-to-date Branson products, medical device manufacturers can be certain their welding equipment will deliver efficient performance, top quality, and long-term productivity and profitability.