A ‘Trial and Error’ Approach to Micromolded Parts

After losing four babies, Jamie McDonald was overjoyed to learn she was expecting twins. But her happiness abruptly ended when she gave birth to the tiny pair at 24 weeks. “We felt pretty positive we were never going to bring them home,” she recounted to “The Doctors” syndicated talk show.
 
McDonald’s babies—Everly and Maverick—weighed 1.9 pounds at birth and both were diagnosed with patent ductus arteriosus (PDA), a potentially life-threatening congenital heart condition triggered by an opening between two cardiac blood vessels. The sixth most common defect, PDA occurs in 5-10 percent of all children born with congenital heart disease, and is twice as likely to occur in girls than boys.
 
The condition is treatable with therapy, minimally-invasive catheter-based interventions, and minimally-invasive surgical solutions. Doctors chose the latter option for Everly and Maverick, implanting a pea-sized wire mesh device between their pulmonary arteries and aortas to prevent blood from mixing and straining their tiny hearts and lungs.
 
The device, made by Abbott Laboratories, is inserted through a small leg incision and guided to the afflicted cardiac vessels. Manufacturing such a diminutive object most certainly entailed micromolding, a type of injection molding that produces extremely tiny parts, often with micron tolerances. The process uses special equipment that can produce intricate designs and details.
 
Medical Product Outsourcing’s October feature, “Little Big Parts,” addresses the latest trends and challenges shaping the fast-growing medical micromolding market. Raghu Vadlamudi, chief research and technology director at Donatelle, was among the various experts interviewed for the story. His full input is provided in the following Q&A.
 
Michael Barbella: What market forces are fueling the need for micromolding technology and services?
Raghu Vadlamudi: As the use of implantable pulse generators is expanded to other branches of medicine, such as neurology and ophthalmology to cardiology, the demand for smaller and smaller parts increased. Medical devices in these fields are much smaller in comparison to the peripheral devices. Even in cardiology, transitioning to leadless pace makers necessitated the design of micro parts, or in some cases parts with micro features.
 
Barbella: How is the need for smaller, more complex medical devices/components challenging micromolding suppliers and providers?
Vadlamudi: While there is quite a bit of information available for reference regarding macro parts, when it comes to micro parts, the micro molding suppliers are on their own to come up with solutions by trial and error. The need for innovation among service providers is very high. The stringent requirements in the medical device industry makes it more difficult when it comes to injection molding, as it is considered as a “special process” and has to be validated. Validating the injection molding process of a micro part is a herculean task due to the tiny feature sizes. Establishing a measurement system is not easy when the parts weigh around a tenth of a milligram, and it’s difficult to fixture the part. There are no systems readily available to facilitate manufacturing of micro parts.
 
Barbella: What factors must be taken into consideration in designing tooling for micromolded parts?
Vadlamudi: Tooling for micro molded parts needs to be precise. There is very little room for error or missing the target. The tooling needs to be designed to accommodate the entire manufacturing process from molding through packaging. 
 
Barbella: Should micromolding tooling design be outsourced? Why or why not?
Vadlamudi: This would depend on how the micromolding services are provided. It is advantageous to have mold design and building capabilities in-house for a micro molder. Understanding the injection molding process and maintaining the tooling in-house plays a critical role in meeting the customer’s expectations. Outsourcing the design of tooling might extend the project time lines and result in miscommunication of requirements.
 
Barbella: What are customers demanding or expecting in their micromolded products?
Vadlamudi: Customers expect consistency in their micromolded products, in addition to being cost conscious. In reality, micro molded parts tend to be costly because of the need for state-of-the-art equipment, technology and skilled man-power. 
 
Barbella: How are minimally invasive and point-of-care applications affecting micromolded device design and development?
Vadlamudi: These applications are demanding innovation in every aspect of the micromolding process.  Service providers are inventing the technologies to suit micro-manufacturing, as the situation demands.
 
Barbella: What new micromolding technologies (if any) are on the horizon?
Vadlamudi: There is not much innovation beyond the “micromolding after screw over plunger technology” that a couple of injection molding machine manufacturers came up with a couple decades ago. Most advancements are happening in the part handling systems. One notable technology that entered the micromolding industry uses ultrasonic energy to melt plastic. This technology claims no material degradation during molding in addition to energy savings.