Medical Machining

The extremely small, complex devices used in procedures to restore hearing loss require high- precision, tight-tolerance production. This company has found the right combination of machine tool technology and quality assurance to make it work.

By Chris Felix

Pardon me. I'm sorry; 1 didn't quite hear what you said.

As the body ages, a seemingly endless and continu- ously growing list of problems arises. Hearing loss stands out as one of the more obvious and frustrating issues to both the individual and those around him or her. As the baby boomer generation reaches the upper stages of middle age and health care issues become ever more prominent, medical machining is reaching full stride. The need for dentd implants, bone screws, prostheses and countless surgical instruments of amazingly high quality and p d o n have helped a relatively new industry thrive. But when it comes to requirements of such minute proportions as those in the inner ear-where a half-millimeter motion of the surgeon's hand can mean the difference between the patient hearing and not hearing--extreme precision becomes paramount.

Hear3 The Problem When the ear is working properly, sound waves are

received by the outer ear and directed through the

ear canal to the I tympanic mem-

j brane (eardrum). As thismembrane

moves, the sound energy is transferred to the ossicdar chain, a series of bones in the middle ear. The sound then continues to the inner ear fluids, which stimulate the sensory organs, which stimulate the auditory nerve, which sends the sound energy to the brain. It sounds com- plex, but resolving problems to this process is what is truly M b l e .

A number of conditions can lead to problems with the ossicuhr chain causing hearing loss. Often these problems can be remedied through the use of man- made prostheses to reconstruct the ossicular chain. One of the more common xeconstruclim procedures, a stapedectomy, is perfomled to replace or repair 1 the stapes (a stirrupghaped bone in the mid& ear), and it serves to restore the connection between the other bones and inner ear fluids. A stapedectomy can be performed in patimts who have a congenital abnormality of the stapes or have sustained a fracture from a traumatic incident. It is most often performed, however, to treat otosclerosis, a common cause of pro- gressive hearing loss involving an abnormal growth of bone in the ear. In this complex, tedious operation, the doctor

typically works through the ear with an instrument about six inches in length, approximately 3/ of an inch in diameter, tapered down to a point about a half

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millhew in d i a r n e Working with forceps under a microscope, the ductor must maintain yoga-& mcentraticm levels ta restore the patient's hearing.

While the first stapedecturny was perf&md in 1956, improvements in surgical M q u e s and the prostheses t h e d v a have allowed this prmedme to remainan important treatmept of hearing loss. In Memphis, Tennessee, Grace Medid, hc., works to continue advmcemts in this p d w , with the pmduction of I&& ALTO titanium ossicular prosthe &, a titanium device measuring as liMe as 25 mm in length and 0.24 mm in diameter.

Whwe It's Made Grace Medical manufactures medical devices that

are used in ophhhology (diagnosis and treatment of disorders of the eye) and otolaryngology [treat- ing the ear, nose and throat). The devices are made from a broad range of materials, from soft silicone compounds to strmg titanium alloys. Founded in 1996, the company employs approximately 25 people in a 20,000-square-foot facility that is certified to IS0 13485, a quality management standard for medical devices.

Because the ALTO assicuIar prosthesis is designed to interface, or connect, to the tiny ossides in the middle ear, the shape, surface finish and texture are exttemely impmbnt. These characteristics af€ect how the prosthesis interfaces with the tissue as well as the bone itself. During surgery, the physician can easily tell the difference in a prosthesis in quartefmillimeter (ten thousandths of an inch) increments. Conse-

quently, Grace Medical must mutineiy deal with toferances to * 0.002 inch and mcasionally to k 0.0002 inch or 0.0003 inch during the assembly of a

psthesis. Pot these particular parks, the company uses its Star

ECAS 20 Swiss automatic, with threeaxis capability on the back, hvo-axis capability on the front and a full C axis with live tooIing. According to Tony Presc~tt', vice president of manufacturing, "We often turn to the Star for some of our more complex pi-." He explains W e r that the company's Cincom R07 Swiss-type tumhg center seems better suited for particdxrly small parts (yes, smaller than the bucket handle stapedial), "The Citizen, being a smaller machine, allows the operator to get above the work easily and get around the work area," Tony says. For both machines, as well as an assortment of other lathes and madhing centers around the shop, mi- scopes are routinely used to check setups for workpieces that can barely be seen by the naked eye.

Machhmg such intricate parts with high preci- sion quires quite a bit of experience and patience. Machinist Andy Prescott proudly explains, "These parts are just everyday Swiss-turn for us." Because of the type of work the company nuts, quality assurance has become a top priority, and finding highly accurate ways to check the work has made all the difference in customer satisfaction.

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Reviewing The Work Accurate dimensiond measurwnent during p m

duction of these medical devices helps to ensure they function properly and are safe and effective. One way Grace Medical achieves the nec- essary accuracy is by use of a SmaxtScope Plash 200 benchtop 3D multisensor measure- ment system from Optical Gaging Products (OCP-Rochester, New York). Since imple- menting the system, the company has slashed inspection times more than tenfaid-from 10 minutes per part to 40 seconds. "And we're measuring more dimensions than we were before," Tony claims.

The company relies on the accuracy of the measurement syskm to routinely measure critical dimensions to the required 1 0.0002- inch tolerance during typical inspection cycles. Fully automated measuring capabiii-

I 4 The backet handle stgpedirl pmthmls, compared In slze bere to a mny, Is sw~lca% Immbd Into tbe middle ear In a procedure ta restore hewlag.

Medical Machining

Swiss turnlng eenbrs produce parts so small thal m l c r o w o p ~ are requlred to rnsure accurate setups. V

Today, the company's compact measuring system, with an 8 by 8 by 6-inch measuring range, is capable of checking f 0 parts per run in an automated inspec- tion routine. During inspection, the system measures critical dimensions on parts arranged in a holding fix- ture. The depths of blind holes (0.010 inch in diameter by 0.030 inch deep) are measured to the nearest 0.0002 inch. The system automatically generates inspection reports that are used in device history records. Since implementation of the SmartScope Flash, parts are measured automatically, with higher accuracy and with real-time graphic displays. "The OCP system allows operators to instantly identify visual anoma-

ties allow lights-out qualification of complex compo- nents when required. With real-time graphic display 1 of the measurements, operators can immediately - L identify potential troubie spots and respond accord- ingly. Also, automatic inspection reports document the process for critical device history records.

Prior to incorporating the SmartScope Flash system into its quality system, Grace Medical performed measurements using an optical comparator, hard gages and other dial indicators. "They required inlerpreta tion by skilled operators, which made them slow to use," Tony says. He and a QA/regulatory team initiated the search for new measurement / inspection equipment to improve compliance with FDA regulations regarding quality measurement and documentation and to increase throughput of the inspection process.

Grace Medical produces a large assortment of sxtremely smaH, somplex patts for treatment of disorders of the eye, ear, nose and throat. b

A Milan DIurd~wlc and Dlaw Holton, of Bnee Medical, visually hopect aredical device gemwfrles llging the 06P SmartScope Flash 200 multlw~lgor measllrlng system.

lies and quickly respond," says Grace Medical Qual- ity Engineer Diane Holton.

LlghtsmOut Qualification Because measurements a~ automatic, Grace

Medical also uses the m~~ system to perform lights-out qualification d components. The system warh without human interaction, so work at the Swiss machines w m a h f-d an expanding and enhandng fhe unique manufacturhg capifMlitiw. Parts with inHcate surfaces are then pduced faster, whgmethadg that are m a accurate and reprodue ible than tradipional processes.

Grace Medical utilizes advanced foe-axis capa- bilities of the inspection system to measure parts manufactwed on the Swiss machines. The system is equipped with an o p k h d MicroTheh row indexer for fodt-axis measuring and MeasureMnd 3D MultiSmsor metrology suftware with c o m p h d v e rotary axis calibration routines. These erhancemb enable the system to autom~ticdly rotate parts within a measummnt routine to easily measure mything fKnn simpL p m & c f m Po complex, freeform shapes without user interaction

Loolcfng Ahead Grace Medid c~~~ i tant ly asses8es & P-s its

machine rciutines. Because of p m c W k p r o ~ ~ m t k imphnmhd a8 a a t of the SrnwfSmp Flash system, IMkprcent dhnemhd inspwb6n is no longer q u i d . In, addition, Grace Medical continues to find new ways to use the syskmts measwments t~ reduce costs and impwe &@-.

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'%I a production envbmmitr the OGP system n ~ t o b e v i e w e d a n d ~ h k e d a s a v e f y ~ h h - ticated automated production device and not simply as a newpke of h$pe&m equipment," Tony says, uCyde times, far m.ultipIe parts t~ optimize %p fime' and quick CRanpver of impchon rou- tines and -ling need la be considered. Use of the ~ o p e m a s h ~ s y s t e m ~ t e d i n c h a n g e s i n the production flow that needed analysis, explana- tion and training to ensure that maximum benefit Is gained."

The inspection system is c u m d y used in a number af company operations, including product developmeat, enginering, productim, proms con- tror, QA, final inspection and quality training. Grace Medid's titanium implants have complex shaft georhetries on surfaces as amall as 0.008 inch in diam- eter, with core pins as small as 0.002 inch that require accurate measurement. By providing immediate, a m a t e measuremenb of dimensions such as these, h e $mart!30pe Flash 200 system helps to speed production of devices critical to patient health-while sbulW.usly impfohg quality conttol. As an aging gemratid11 hces inmasing medical

challenges, & d p n b like Grace Medical continue to step up. With the technol~gid capabjlitle availabb today, companies in the medical machining arena have heen able to deliver new, better solutions to the problems we all might anticipate facing. It is kt for all if the industry continues to age more gramftlny

t ~ n d these related articles on our Web site: Complex Angular Dental Implants Completely Maehlned

OR Multi-Axis Automatic Angular dental implants are impossible to machine on con- ventional CNC turning centers. With Tornos' model Deco 13a-for parts as large as 16 mm in diameter- manufacturers can compl&ly machine these complex dental devices in a single setup. II Want To Da MedimI Work? Sei Up TO Perlorm This Midwest manufacturer has found Its niche in machining parts for the medid Industry. Much of its success is attribut able to Its efftclent use of single-spindle CMC turning centers. For links to these articles, visit www.productionmachinIng. com/articies/OBOMl, html. For more information from Optical Gaging Products, Inc.. cal (800) 647-4243 or search.- on/lne at www.production machining. corn. 'DI more Intormatron from Grace Medical, call (901) 386-

990 or visit www.gracernedical.com.