Technology

Expanding Technology™

A Commitment to Innovation and Quality

Expanded metal is made by a process of slit and stretch. A precision die slits and stretches the material in a single operation. The material is then processed through a set of rollers which adjusts the final thickness. The shape, form and number of openings are dictated by the particular tool used (See Die Chart for discussion on available dies).

The Tool selected dictates the Long Way of the Diamond (LWD), whereas the strand width and the Short Way of the Diamond (SWD) is machine adjustable and is selected based on the needs of the customer.

The expanded metal process.

How Expanded Metal

White Papers and Technical Documents

Dexmet precision expanded metal and expanded plastic products are used in batteries, electronics, aerospace, aircraft, medical, packaging, filters, fuel cells, heating elements, resistors, load banks, food & drug products, automotive and wherever mesh and perforated foils, metals and plastics with high precision characteristics are required. They are available in most metals and polymers, or we can work with your proprietary materials. Metals we regularly produce include: aluminum, brass, copper, Monel™, nickel, steel, stainless steel, and zinc.

A range of standard diamond mesh sizes is available. As many as 9,000 openings per square inch can be achieved, with an open area from as much as 95% to as low as 10%. The variable open area facilitates lamination with a variety of other materials, including those which expand, contract and flex.

We will engineer a precision expanded foil, expanded metal or expanded plastic with unique characteristics for your particular application. Dexmet’s proprietary manufacturing methods can accommodate a host of process variations.

Technical References

  1. Mesh Per Inch (MPI)

    EMI RFI Shielding Grid

    Measure one inch and count the number of meshes (or openings – between two nodes) along the SWD direction. We generally refer to MPI in the SWD direction and not the LWD direction. See Standard Product Range for the mean MPI count for each Mesh Designation.

  2. Openings Per Square Inch

    EMI RFI Shielding Grid 2

    Double the product of MPI and LWD mesh count. Openings per square inch = (3.5 x 2) x 2 = 14

  3. Product Code Nomenclature

    Product Example: 3 Ni 5-077

    • Original Foil Thickness: 0.003 in.
    • Metal or Alloy: Nickel
    • Strand Width: 0.005 in.
    • – LWD: 0.077 in.

  4. Coverage Area Calculation

    (Accurate to ±10%)
    Coverage Area = 2 x MPI x Strand Width
    Product Example: 2 x 24 x 0.005 = 0.24 Coverage Area = 24%

  5. Open Area Calculation

    (Accurate to ±10%)
    Open Area = 1 – Coverage Area
    Product Example: 1 – 0.24 = 0.76 Open Area = 76%

  6. Weight Per Area Calculation

    (Refer to Density of Materials Chart)
    Grams per square inch = metal weight (Lbs per cubic foot) ÷ 12 x original foil thickness x 2 x MPI x strand width x 3.1416
    Product Example: 554.688 ÷ 12 x 0.003 x 2 x 24 x 0.005 x 3.1416 = 0.10456 grams/sq. in.

  7. Total Surface Area Calculation

    A = Coverage Area
    B = 85% of Original Foil Thickness
    C = B/Strand width
    D = Total Surface Area = 2A (1+C)
    Product Example: A = 0.24

    B = 0.85 x 0.003 = 0.00255
    C = B/0.005 = 0.00255/0.005 = 0.51

    Total Surface Area = 2 x 0.24 x (1+0.51) = 0.7248 sq. ft. of Surface Area per sq. ft. of MicroGrid®

  8. Resistivity and Conductivity

    See Resistivity and Conductivity Chart

Physical Testing of Expanded Metal Foil

The first rule in testing expanded metal and expanded plastic is the need for new rules. The standards of Ultimate Tensile, Yield Strength and Elongation do not necessarily apply. Simply establishing the area to be considered becomes a point of discussion. The solution is to eliminate the questionable areas and concentrate on what we know to be true. The tests are simple and do not generally require expensive equipment, so quality may be verified by our customers.

Tensile Testing

Tensile Testing to failure (Ultimate Tensile) is usually more of a shear test than a tensile test. Tensile Testing rips rather than pulls the strands apart. Depending on the configuration of the product, pulling the mesh may actually change it from one form to another. For example, a flattened metal foil will revert to its expanded configuration before failing.

Bend Testing

Dexmet has established a simple yet effective test that utilizes the elasticity of the material. As the material is annealed, its elasticity, or spring-back, decreases. Relative stiffness can therefore be translated into degrees of anneal. A history has been developed that tells us whether we have accomplished a complete anneal. Feedback from our customers has also provided the specific numerical hardness requirements for a variety of processes. We know that certain rolling mill practices can adversely affect the ability of material to function in our process as well as in our customer’s applications. Testing has also shown that stress relieving will make the material feel softer and lay flatter but will not affect the bend recovery.

Pull Testing

Pulling to within a small percentage of what would result in permanent deformation gives a reasonable measure of the force the material can tolerate without undue stretching. However, if stretching must be avoided entirely, pulling to the same distance a second time will result in the amount of force that the material can withstand without permanent deformation. This information can be very useful to the machine designer.

Salt Solution Plating Tests

The immersion of a sample of Nickel plated steel mesh in a bubbling 2% salt solution is an excellent test for plating quality. There is sufficient air to readily oxidize the nickel, but it is controlled. Salt Solution Testing remains one of the best methods for evaluating the post plating process. Exposure time provides a means to quantify the results.

Standard Product Range

The chart below shows a sampling of dies that are available at Dexmet. We produce over 100,000 configurations and can design a die to suit your particular application.

The unique, single-unit structure of MicroGrid provides many real advantages. First and foremost is its uniformity of electrical conductivity, which surpasses that of discreet metal fiber and wire cloth open materials. Woven wire cloth strands can unravel and contact resistance between the strands can vary. MicroGrid’s unitary solid foil structure offers uniform and better conductivity. The proportions between the length and width of MicroGrid’s openings can be developed to produce specified conductivity. MicroGrid is light and fantastically flexible. It can be bent, shaped and laminated with a variety of flexible materials. A square foot of raw material when expanded can produce two to three times or more of open area material without scrap. Stamping or etching creates open area by removing material that becomes scrap resulting in higher material costs.

PolyGrid provides a similar range of open area patterns and flexibility to customers. PolyGrid is manufactured utilizing ductile polymers including Teflon, polypropylene, polyethylene and others. These metal foil and plastic film products are available from .001″ (25 microns) think, up to 60″ (152.4cm) in width from 1 to 9,000 openings per square inch (14/sq.mm).

Pattern Shown Pattern
Designation
LWD
inches
(mm)
SWD
inches
(mm)
Orig. Mat’l
Thickness
inches
(mm)
Strand
Width
inches
(mm)
Openings
per sq. in.
500 Metal Mesh 500 .405 – .506″
(10.25 – 12.75)
.143 – .279″
(3.6 – 7.1)
.003 – .04″
(.075 – 1)
.007- .07″
(.175 – 1.775)
15-22
275 Metal Foil 275 .215 – .289″
(5.4 – 7.4)
.107 – .200″
(2.7 – 5.1)
.003 – .035″
(.075 – .9)
.005- .055″
(.125 – 1.4)
33-77
190 Metal Foil 190 .180 – .190″
(4.5 -4.8)
.056 -.143″
(1.4 – 3.6)
.002 – .030″
(.05 – .75)
.005- .045″
(.125 – 1.1)
79-166
125 Metal Foil 125 .112 – .160″
(3.0 – 4.06)
.055 -.115″
(1.4 – 2.92)
.002 – .026″
(.05 – .7)
.004- .04″
(.1 – 1.10)
114-253
100 Metal foil 100 .093 – .112″
(2.4 – 2.8)
.038 -.091″
(.97 – 2.3)
.002 – .025″
(.05 – .61)
.005- .026″
(.125 – .66)
253-353
077 Metal Foil 077 .075 – .080″
(1.91 – 2.03)
.032 -.053″
(0.82 – 1.35)
.001 – .018″
(.025 – .46)
.004 – .020″
(.1 – .51)
493-780
050 Metal Foil 050 .050 – 06″
(1.27 – 1.5)
.021 -.041″
(0.53 – 1.04)
.001 – .015″
(.025 – .381)
.004 – .015″
(.1 – .381)
809-1814
031 Metal Foil 031 .03 – .04″
(0.78 – 1.02)
.021 -.029″
(0.53 – 0.74)
.001 – .005″
(.025 – .127)
.004 – .012″
(.1 – .31)
1789-2942
020 Metal Foil 020 .020″
(0.51)
.011 -.014″
(0.28 – 0.36)
.001 – .002″
(.025 – .050)
.004 – .006″
(.1 – .152)
8500-11000

LWD

(Long Way of the Diamond), measured from the center of the joint to the center of the adjacent joint. This dimension is built into the tool, and is always parallel to the width of the coil and corresponds with the diamond dimension.

SWD

(Short Way of the Diamond) is the length of the short axis way of the diamond, measured from the center of the joint to the center of the joint. For each fixed LWD dimension, there is a range of SWD dimensions available as shown above.

Ductile Metals:

Aluminum, Brass, Cadmium, Columbium, Copper, Gold, Inconel, Lead, Magnesium, Nickel, Nickel Alloys, Phosphor Bronze, Platinum, Silver, Stainless Steel, Low Carbon Steel, Tantalum, Titanium, Zinc, Zirconium, etc.

Plastics:

Nylon, Polypropylene, Polyethylene, Mylar, Teflon, Tefzel, etc.

Explanation of Product Code:

Example: 3 Ni 5-077

First number represents nominal original thickness
3 = .003″ (.076 mm)

Letters are chemical symbol for material
Ni = Nickel

Number immediately following letters represents strand width
5 = .005″ (.127 mm)

Last number indicates the long way of the diamond
077 = .077″ (1.96 mm)

Variations to many of these standard MicroGrid® products are described in the previous section. In addition, each mesh size offers a wide range of tools for your desired results. We can help design precision expanded foil to meet your specialized mechanical, electrical, or heat transfer requirements. Call for material/mesh samples and engineering assistance.

Below sample images are for reference only.

  • Metal Sample LG 2
    3 Brass 10-125
  • Metal Sample LG 1
    20 Al 20-416
  • Metal Sample LG 3
    10 Cb 20-284

Contact Us

Phone: (203) 294-4440
Fax: (203) 294-7899

sales@dexmet.com

22 Barnes Industrial Rd. So.
Wallingford, CT 06492
United States of America

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