Ultra-fine shaped wire, frequently as thin as one-tenth of human hair, is the basis of critical components in applications ranging from aerospace and integrated circuits to automotive and, especially, medical instruments. Minute defects in such wire can lead to serious problems in the precise applications in which they are utilized. This micro-thin wire must meet exact tolerances and specifications. Manufacturers seeking ultra-fine wire have come to depend upon California Fine Wire Company (CFW) of Grover Beach, California.

CFW has been producing fine wire for a worldwide customer base since 1961. Most of the company's manufacturing is done for medical device OEMs who require microscopic wire drawn to fine diameters and shapes from hundreds of metals and alloys including stainless steel, aluminum, copper, nickel, nitinol and other precious metals.

Fine Wire and Medical OEMs
CFW-produced wire is used in applications such as cochlear hearing implants, heart probes and telemetry devices. Medical OEMs use fine wire to make microsurgical catheters and the tools attached to them. They use ribbon-shaped wire to make the outer shape of the catheter, winding the ribbon on an edge to make it extremely flexible, so it's easier to maneuver inside the human body's cardiovascular system.

While the ultra-fine shaped wire may itself be one-tenth the thickness of a human hair, the dimensional tolerances of its features are measured in millionths of an inch. Products made from shaped fine wire normally require Six to Eight Sigma consistency and ultra close tolerances. “Our internal standards include tolerances that are within 0.000025 in. Not very many instruments can even make such a measurement,” says Mike Greenelsh, President of CFW.

Starrett Bench Micrometers
CFW uses Starrett bench micrometers to check ultra-finished (polished) wire measuring 2-ten thousandths in diameter with a tolerance of 25-millionths of an inch. Inspections occur at critical stages of processing, for example checking incoming wire, at the shaping and coating stages, after manufacturing and final quality checks. “Meeting our customers' exacting specifications means measuring tolerances that stretch the capabilities of inspection devices,” explains Jorge Jacobs, Quality Assurance Technician at CFW.

While the 11 Starrett bench micrometers on the CFW shop floor are fully capable of accurately measuring the fine wire, their analog gage amplifiers could not consistently resolve at the tightest tolerances. CFW started a search for the necessary resolution. “Some of the gage amplifiers were producing different readouts due to the resolution limitations of the amplifiers,”
Mr. Jacobs recalls. “The last digit was rounding up so we knew we needed a 6-digit readout.”

Starrett Gage-Chek Bench Amplifier
We looked into various methods to solve the problem, For example, we tried laser micrometers but found the fine, airborne dust from our grinding operations interfered with the laser beams. Besides, the problem wasn't really the bench mics which our inspectors preferred, but getting the resolution we needed out of our amplifiers. That's when we tried the Starrett Gage-Chek bench amplifier which allowed a resolution of .000001 inch when measuring to 5 millionths accuracy.”

Starrett and Metronics provided an application program formula for the Gage Chek that counted revolutions of the Starrett bench micrometer to achieve the 6 digit resolution. Inspectors at CFW found the Starrett Gage-Chek 776 amplifier was the answer to the “case of rounding at five digits”, and key to restoring confidence in their QC inspections.

At CFW, Starrett 776 Series LVDT probes (linear variable displacement transducers) are attached to the bench micrometers. The micrometer contacts the wire and measures the variance from acceptable wire. Users orient the wire in the mic, contact the work and view the value on the Gage Chek. If required, users can press a print button to record the inspection. The Starrett Gage Chek 776 has a three-color, microprocessor-based display, allowing even the most inexperienced inspector to visually make quick, easy decisions on part quality.

Starrett Gage-Chek 776
The Starrett Gage-Chek 776 is a versatile amplifier that combines the simplicity of go/no-go gaging with the power of a microprocessor. Although CFW uses one probe sensor, the 776 accepts up to 8 direct probe outputs. The probe readings can be algebraically and mathematically combined for dimensions such as thickness, flatness, angles, length and heights with the choice of a numerical or graphic display.

The readings can be archived for process studies such as simple X-Bar and Range charts. Trigonometric formulas can convert linear measurements into angular measurements. Other formulas can also be created for TIR (total indicator runout), volume, angles between features and more. The unit also interfaces with PCs and/or other devices for data collection, reports, and other forms of documentation. SPC functions are integrated in the 776 Gage-Chek, so operators are able to ensure a process is corrected before out-of-tolerance work is manufactured or shipped.

Reducing Waste & Increasing Productivity
The Starrett Gage Cheks are doing their part to boost productivity and reduce waste at CFW. Presently, 6 Starrett Gage-Chek amplifiers are on the job but future plans call for 5 more to accommodate all of the bench micrometers on the production floor and set the stage for implementing a 100% SPC program. “Now material is flowing smoothly throughout the shop” says Jacobs. “And we are not wasting time running down conflicting readouts”.

“Upgrading to the Starrett Gage Chek amplifiers has increased our productivity by thirty percent,” states Jacobs. “They have helped us reduce our re-work of bare wire and minimize the amount of insulated wire that must be scrapped. Scrapping micro-thin wire and ribbons, especially when they are made from precious metals like gold and platinum, is a significant expense.

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