Staying Connected - February 2008

Mating and Retention Force for Non-locking Medical Connectors

Threaded locking connector
often used on small portable
devices because safety
disconnect is not necessary

Medical connectors can be divided into two broad groups: locking, also referred to as latching, and non-locking.  Each offers advantages and disadvantages.  This article primarily addresses non-locking connectors.

Locking vs. Non-Locking

Many early medical cables used connectors borrowed from industrial or military electronics.  These were often metal connectors with threaded coupling systems.  Once “screwed down,” this connector would not come loose inadvertently.  While this type of connection met the requirement that the connection not be broken unintentionally, they were somewhat difficult to use and provided no safety disconnect.

RJ connector – If “jerked”,
locking mechanism can be easily
broken requiring cable replacement

A more up-to-date example is an RJ type connector.  RJ connectors commonly include a locking mechanism.  If enough force is applied to the cable, the locking mechanism typically breaks.  Once the locking mechanism breaks, the plug is so poorly retained by the receptacle that the cable is generally discarded.

Medical cables, particularly those that connect between a patient and a stationary device, typically need a safety mechanism that will allow disconnection without harm to the patient or damage to the device or cable.  The need to ensure a reliable connection to the device, yet allow for safe, inadvertent disconnect is a design challenge that we at Affinity like to tackle.

Non-Locking Connectors

The very nature of medical cables requires a positive connection between the plug and receptacle.  Any looseness in the connection will usually cause intermittent contact and poor signal quality.  This may make diagnosis or therapy difficult, if not impossible.  How firmly the connector is held by the receptacle is known as retention force and is almost completely controllable in the design process.  Pin and socket selection as well as the physical design of the plug and receptacle allow almost complete control over both insertion and retention force.

What Makes Up Retention Force

Retention force of a connector pair, plug and receptacle, is nominally made up of the sum of the retention force of each socket and pin as well as any friction between the plug insulator and the receptacle walls.  For connector pairs with few contacts, friction between the insulator and receptacle wall may be the largest factor in determining the total retention force.  For units with a larger number of contacts, little or no friction may be needed between insulator and receptacle wall.

Custom non-locking in-line
connector with 21 sockets

Custom non-locking male mating
connector with 21 pins – 5.5 lbs
retention force for pair

An additional factor to be considered is that in a connector with more than a few contacts, the total retention force is greater than just the sum of each pin to socket retention force.  This phenomenon is detailed in a paper by Robert S. Mroczkowski, Sc.D “The Mating Game” in Connector Specifier magazine, December, 2001.  Mroczkowski states that “mating force will always be greater than that value (if all contacts mate at the same time) because of tolerance and housing interaction effects.”

Retention Force Specification Established Early

Custom 17 pin non-locking connector
achieved specified retention
force using tool-safe design

At Affinity, one of the specifications we attempt to establish with our OEM partners early in the project is the retention force of the plug to receptacle.  Once established and documented, we design tooling in a “tool safe” manner.  This means that the tooling is specifically designed to produce parts that have retention force below the specified level.  By removing metal from the tool, the connector becomes larger and retention force is increased.  This is done in very small increments which allows us to “dial in” almost any desired amount of retention force.  It allows our OEM partners to actually experience insertion and retention force before production parts are manufactured.


Over the past year at Affinity, more often than not, our OEM partners are specifying non-locking connectors.  Affinity Medical Technologies has the experience and expertise to assist you with custom medical cable assemblies, including both locking and non-locking connector systems.  Let us become part of your design team.  Contact Affinity Customer Care at 949-477-9495 or email to

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Meet Janett Lopez – Affinity Medical Administrative Assistant

Janett Lopez –
the friendly voice you hear
when you call Affinity Medical

“Thank you for calling Affinity Medical.  This is Janett. How may I help you?”   This familiar greeting is the first voice you hear when calling Affinity Medical.  Janett’s pleasant voice and friendly personality is heard every day by customers, suppliers and Affinity Medical team members. 

Before joining Affinity, Janett was employed in the product returns area of a major cosmetic manufacturing and distribution company in Orange County.  The company valued her skills and abilities so highly, she was sent to their Midwestern headquarters for extensive training in operations.  However, after the company relocated, Janett decided to find work closer to home that would allow her to spend more time with her family.

Janett was hired by Affinity Medical three years ago.  After only one year in production, she was asked to join the front office staff as Administrative Assistant.  She quickly adapted to the busy environment assisting our president and CEO, Mary Phillipp, as well as the entire management team with projects, presentations, file maintenance, employee handbooks, the Quality Manual and both internal and external audits.

Janett at
Affinity 10 year
anniversary picnic

Janett’s excellent bi-lingual skills are frequently used by our human resource manager and production supervisor when interviewing new hires or to answer questions from the production staff about insurance or other company matters.  Always willing to help, Janett is always enthusiastic, efficient and reliable.  In fact, Janett Lopez helps everyone at Affinity Medical Technologies at one time or another!

When asked what she likes most about her job, Janett replied, "I really enjoy helping to organize our company events such as the yearly Christmas luncheon and our recent 10 Year Anniversary party.  It is worth all of the extra effort to know everyone has a good time and is pleased with the outcome."

Janett lights candles
on cake for monthly
birthday celebration
at Affinity

Janett handles catering needs during customer visits, audits and vendor presentation meetings as well as our monthly employee birthday celebrations.  She works closely with sales and customer care in helping with customer inquiries and preparing for medical shows.  Janett also supervises several mass mailings to customers and prospects throughout the year.

Janett moved to Southern California as a child and is a former high school cheerleader.  She enjoys dining out and going to the movies with her husband, Arturo and two sons, Ivan and Steve. Janett is an excellent Salsa dancer and occasionally accompanies her husband to functions where he DJ’s. The entire family travels frequently to Sonoma in the California wine country to visit relatives.  The family enjoys frequent visits to Disneyland where Arturo is a long time employee.

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Lunch and Learn - A New Resource from Affinity to Help You

Our Lunch and Learn program is another way we can stay connected and help our friends and customers.  Choose from one of our three programs and gain additional insight and perspective about custom medical cable assemblies and connectors.

Our programs last about thirty minutes, with the time divided between learning and lunch.  Affinity will provide lunch; sandwiches, pizza, or some other “fast and easy” food of your choice.  There is no cost or obligation, other than your commitment for three or more of your team members to attend.  Each of your team members that attend will also receive a copy of the training material and a certificate.

  • Off the Shelf or Custom Medical Connectors – A discussion of three connector options: off-the-shelf, custom, or hybrid.  We’ll discuss the advantages and disadvantages of each including performance, cost, and availability.
  • ANSI/AAMI EC53 Compliance – the basis for establishing medical cable and leadwire specifications.  We’ll discuss the standard, its intent, and how it can be applied to medical cable design and connector design.
  • Strain Reliefs – A discussion of how strain reliefs affect both electrical and mechanical performance of medical cables.  We’ll show samples of off-the-shelf and custom strain reliefs and discuss the advantages and disadvantages of each.

Lunch and Learn sessions are offered free of charge when we are in your area.  For more information or to schedule a Lunch and Learn session, contact Hank Mancini at 949-477-9495 or

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Announcements and Information

February 14th is Valentine's Day. Although it is celebrated as a lovers' holiday today with the giving of candy, flowers, or other gifts between couples in love, Valentine’s Day originated in 5th Century Rome as a tribute to St. Valentine, a Catholic bishop.


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.

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Affinity Medical Technologies

1732 Reynolds Ave
Irvine, CA 92614  USA
Phone: 949-477-9495
Fax: 949-477-9499