Assuring Quality in Medical Materials
As a result of advancements in materials technology in the medical
implant and instrumentation industry, LTI has become a major supplier
of testing services for leading manufacturers of these devices. Manufacturers
have become acutely aware of the need for quality products used in human
implant materials to assure performance, durability and long-term reliability.
Through partnering with the manufacturers, LTI has become an intricate
part of the quality programs of these suppliers providing nondestructive
and destructive testing services.
Various corrosion resistant materials are tested from the raw materials
stage up to the final cleaning and packaging stages. An example of the
product form we exam is the small diameter, heavy wall tubing used in
the manufacturing of bone screws. Typical uses of the bone screws are
joint replacement and spinal column surgeries. Chemical, physical and
corrosion resistant attributes are verified on representative samples
using standard destructive test methods. Nondestructive test methods,
such as liquid penetrant and immersion ultrasonics are also typically
used.
The challenge for LTI was to develop an ultrasonic inspection procedure that would adequately and reliably detect longitudinal and transverse oriented defects as small as .004 inch in depth in heavy wall tubing, with outside diameter to inside diameter rations typically greater than 2.0 to 7.0. Using reference standards containing EDM notches from the various sized materials, LTI was able to confirm both the detectability and reliability of the ultrasonic inspection.
Further confirmation was achieved during production testing by sectioning any metallographic examination of the areas containing indications exceeding the ultrasonic reference level. Ultrasonics are also used to verify the wall thickness and run-out (TIR) of the materials, which is a critical characteristic of the material prior to threading both the inside and outside diameters. Depending on the material type, liquid penetrant examinations are performed on the tubing in the as-drawn condition and in the final machined stage by the manufacturer to further detect possible discontinuities.