Fort Wayne Metals

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Flat Wire

Manufacturing Techniques

Flat wire, often referred to as ribbon wire, is commonly used in devices designed to reduce catheter profiles or increase available lumen size. Typical applications include safety wires in a catheter guidewire, helical coils in a catheter guidewire and braiding wire. Fort Wayne Metals uses two manufacturing techniques to yield different types of radius edged flat wire: rolled flat wire and drawn flat wire (see illustration below on the left).


Flat Wire Comparisons

Both products exhibit a smooth bright surface finish and tight size tolerances. However, each has its advantages. Rolled flat wire has a larger cast, less camber (see Straightness), less stress induced in the wire and a lower cost versus drawn flat wire as the width/thickness ratio increases. While drawn flat wire has the advantage of improved size tolerances (see Standard Tolerances), it’s often specified for applications requiring more consistent and tighter dimensions.


Size Availability

The maximum available width for both types of flat wire depends on the thickness and the alloy. The maximum width/thickness ratio of rolled flat wire is approximately ten to one, alloy allowing. Rolled flat wire is available as thin as 0.0003". Drawn flat wire is available as thin as 0.0015". Standard tolerances for each wire type are described below. Depending on width, thickness, alloy and width/thickness ratio, both drawn flat wire and rolled flat wire may be offered.


Drawn Flat Wire

Thickness Tolerance:

±10% of the thickness rounded up to the next 0.0001", with a minimum of ±0.0002".

Width Tolerances:

±10% of the width rounded up to the next 0.0001".

Width or ThicknessTolerance
OverIncludingPlus or Minus

0.0000"

0.0080"

0.0002"

0.0080"

0.0120"

0.0003"

0.0120"

0.0240"

0.0004"

0.0240"

0.0330"

0.0005"

0.0330"

0.0440"

0.0008"

0.0440"

0.0010"

 


Tensile Strength

The tensile strength of flat wire is determined by manufacturing techniques. Tensile strength ranges from annealed to spring temper in most alloys. The maximum tensile strength is a function of both the alloy itself and other requirements of the specified wire, such as cast.


Cross-Sectional Area Calculation

When determining tensile strength, it’s necessary to properly calculate the cross-sectional area using the flat wire conversion factors (see chart below). Because both rolled and drawn flat wire have full radius edges (see illustration above), necessary adjustments to remove the corners of the rectangle from the area calculation must be determined. Accurate calculation is vital because minute differences in cross-sectional area can make significant differences in tensile strength.


Flat Wire Conversion Factors

The first column is width divided by thickness. The factor is to be used to calculate cross-sectional area (i.e. 0.010" ÷ 0.003" = 3.3; look up 3.3 to get 0.984; 0.003" x 0.010" x 0.984 = 0.0000295; this is the cross-sectional area).


Flat Wire Conversion Factors

Width ThicknessFactorWidth ThicknessFactor

1.1

0.836

3.0

0.981

1.2

0.867

3.1

0.982

1.3

0.890

3.2

0.983

1.4

0.907

3.3

0.984

1.5

0.920

3.4

0.985

1.6

0.930

3.5

0.986

1.7

0.939

3.6

0.987

1.8

0.946

3.7-3.8

0.988

1.9

0.952

3.9-4.0

0.989

2.0

0.957

4.1-4.2

0.990

2.1

0.961

4.3-4.4

0.991

2.2

0.964

4.5-4.7

0.992

2.3

0.968

4.8-5.0

0.993

2.4

0.970

5.1-5.5

0.994

2.5

0.973

5.6-6.0

0.995

2.6

0.975

6.1-6.9

0.996

2.7

0.977

7.0-8.1

0.997

2.8

0.978

8.2-10.00

0.998

2.9

0.980

>10.0

0.999

 


Secondary Cleaning Capabilities

Fort Wayne Metals uses various techniques to improve the surface cleanliness of flat wire. These include heat cleaning, solvent wipes and hot alkaline or ultrasonic-cleaning, used on their own or in various combinations.


Straightness: Cast and Camber

If straightness is critical to the flat wire application, then a minimum cast and/or maximum camber may be specified. Cast is measured by cutting a three foot piece off the spool and laying it on its edge on a flat surface so it forms a circle or an arc. The size of the circle or arc is the cast. To determine camber, a short length of flat wire is cut. Next it is placed on its width rather than its edge. Then, by holding the wire in the middle against a straight line, the distance that the free ends extend from the line is measured as camber.

 

Stock Program

Small amounts of flat wire are available through our stock program.