Strain Relief Options and Considerations
One feature of a medical cable assembly that is important to both the electrical and mechanical performance is the strain relief. Connectors are typically rigid and the strain relief provides a transition from the stiffness of the connector to the flexibility of the cable. A good strain relief prevents force applied to the cable from being transferred to the electrical connections in the connector, which could lead to failure.
Example of custom overmolded
solid strain relief
Pre-manufactured or Custom
Strain reliefs can be either pre-manufactured or custom designed and overmolded. Pre-manufactured strain reliefs typically slip over the cable before the connector is terminated. After the cable is terminated to the connector, the strain relief is screwed or glued onto the connector. Pre-manufactured strain reliefs are available in a variety of sizes to match common cable diameters. In virtually every instance, an overmolded strain relief will offer better flex life, tensile strength, and moisture protection performance than a pre-manufactured strain relief.
Example of pre-manufactured
slip-on strain relief
Flex Life and Tensile Strength Performance
Besides the raw cable or wire, flex life performance is influenced by a number of factors, including: design of the strain relief, the type of material the strain relief is made of and also the hardness or durometer of the material. Typically, softer materials give greater flex life performance, but do not offer as high of tensile strength. Some materials adhere better than others. As an example, a polyurethane strain relief overmolded onto polyurethane cable offers better adhesion and higher tensile strength than some other materials.
If additional tensile strength is needed, a band can be clamped to the cable or wire prior to molding. When the clamp is imbedded into the mold material, it greatly increases the tensile strength of the strain relief.
Segmented or Smooth
Overmolded strain reliefs can be segmented or smooth. A segmented strain relief typically offers the greatest degree of flexibility, but can be more difficult to clean. Smooth strain reliefs are easier to clean, but generally do not offer quite as much flexibility as a segmented strain relief. An overmolded strain relief can also provide a moisture-resistant seal, important for medical cables that will be cleaned regularly.
A well designed segmented strain relief will feature walls and spaces designed to allow the bend radius to increase a greater distance from the connector. The size of the solid sections and the size of the gap between solid portions are varied to achieve the desired bend radius. Segmented strain reliefs are generally designed so that the segment closest to the connector closes first and the segment furthest from the connector closes last. This provides the greatest amount of bend relief, protecting the wire terminations within the connector.
Bend starts at connector
Bend completes at segment
farthest from connector
reducing stress on connector
The length of a strain relief also contributes to the performance. Generally, the longer the strain relief, the better the bend and tensile strength performance. However, there is a possibility that long strain reliefs may make the cable more difficult to coil for storage.
Custom Overmolded Strain Relief
The only drawback to a custom overmolded strain relief can be the cost for tooling. At Affinity, we typically design and fabricate two tools, one for the inner and one for the outer strain relief. During manufacturing, the inner mold is formed using a hard material such as polypropylene. This inner mold holds everything together and gives the assembly a great deal of strength. To improve aesthetics and tactile feel, the inner assembly is then overmolded using a softer material such as TPE (Santoprene) or TPU (polyurethane). This combination of inner and outer molding yields a strain relief with excellent mechanical and electrical performance.
Inner hard mold provides
Finished solid overmolded
strain relief and connector body
Custom segmented strain
relief molded onto
A well designed strain relief will improve the performance of medical cables and wires. Whether smooth or segmented, for cable or wire, when it comes to strain reliefs, we’ve “done it.”
Affinity Medical Technologies has the experience and expertise to assist you with custom medical cable assemblies, including effective strain reliefs. Let us become part of your team. Contact Affinity Customer Care at 949-477-9495 or email to firstname.lastname@example.org.
Suzann Sitka joined Affinity Medical in September 2004 after spending 13 years with Baxter CVG and Edwards LifeSciences. She brought a wealth of experience in marketing and international trade to Affinity.
At Affinity, Suzann is part of our Customer Care team, being the single point of contact for her customers. “I handle orders, inquires, quotes, and all correspondence from my customers. I try to make sure they are always more than satisfied with our level of service and commitment to them. If a shipment is delayed or there is a problem with an order, I let them know right away. I feel it is important to keep my customers informed at all times and do whatever I can to meet their expectations.”
Suzann staffing Affinity booth
at 2007 MD&M Exhibition
One of Suzann’s responsibilities at Affinity is participating in new product development meetings for her customers. She takes notes and then publishes the meeting minutes to everyone involved which become part of our project documentation.
Suzann is from Chicago where the rest of her family still resides. She graduated from Western Illinois University with a degree in Communications. She has spent the majority of her career in sales and marketing in the medical field in addition to a six-month gig as a nightclub singer!
Suzann began entertaining when she and her sister produced and participated in talent shows for their friends. This led Suzann to tour the United States performing with the USO for active and recovering servicemen and at various missile bases in the Midwest. “On Friday evening, they would pick us up in a big, brown Army bus and take us to a “secret” location to put on a variety show for the soldiers,” said Suzann. “I still support the USO and think it is a wonderful organization.”
Suzann likes to sing, plays piano and drums and is a professionally trained dancer. She also has acted in many theatrical productions and participated in local Orange County Community Theater. On occasion, you might also find her singing at a well known piano bar in Newport Beach.
Away from the office Suzann says, “I am an avid sports fan and watch football, basketball, tennis, NASCAR and golf.” She also is an active member of the Red Hat Society and enjoys foreign films, dancing, roller skating, live music and theater; a well rounded person! Suzann lives in Mission Viejo, California but enjoys visiting the California wine country and traveling to exciting destinations whenever possible.
Custom bulkhead connector
with wiring harness
A Bulkhead Connector is an essential molded component needed to enable total connection from the main electronic device to various patient monitoring connections. Whether you require a standard or custom bulkhead connector for your medical device, Affinity Medical Technologies offers numerous solutions for many current applications including invasive and non-invasive blood pressure, temperature monitoring, cardiac output, ECG, and Pulse Oximetry to name a few.
Working with our medical device partners, Affinity Medical has designed and manufactured a variety of unique custom bulkhead assemblies. Designing both the device connector and the cable assembly in tandem allows great flexibility and offers the potential of cost savings and timeline reduction.
Custom bulkhead connector
with circuit board
Custom bulkhead connector
with 5 safety sockets
Our specialty is working with OEMs from concept to product development to final production. When used with the Affinity mating cable assembly, this method ensures a high quality patient monitoring connection system.
Affinity Medical booth design
for MD&M West show
Medical Design & Manufacturing
(MD&M) West Preview
Once again, Affinity Medical Technologies will exhibit at MD&M West in Anaheim. The exhibition runs Tuesday January 29th through Thursday the 31st. MD&M West has grown to be the world's largest medical OEM event.
Affinity’s booth will be located in Hall D, booth number 1979. We are “opening-up” our booth by eliminating the front display table that we have used in the past. We want to welcome our friends into our exhibit even if it is just to say hello.
If you would like to schedule a meeting please contact Candy Golding at email@example.com or call her at 949-477-9495.
Suzann Sitka and Candy Golding
the Affinity Customer Care team
Affinity Customer Care - Hours of Operation
Affinity Medical Technologies customer care specialists are available from 7:00 A.M. until 4:00 P.M. Pacific time.
Affinity Medical Technologies
1732 Reynolds Ave
Irvine, CA 92614 USA