Tooling Advice

Prior to the prototyping stage, design review ensure the original requirement of the part are achievable. An available resource is Advance Technical Products services including the material selection, technical service and free sample submission.

Alloy selection - With more than 200 strip metals listed by the Copper Development Association (CDA), paring those down to a handful with the proper attributes is useful to connector design engineers.

Design Assistance - Advance Technical Products has the resources to perform simple stress calculations as sanity checks as well as in-house capability to perform more complex Finite Element Modeling.

Formability
The formability ratio or R/t is the ratio of the bend radius (R) to the strip thickness (t). This value defines the sharpest forming radius allowable prior to failure. A 90 degree bend test using a "vee" block and die generates formability data . An R/t value of 0 defines a material that can form a very sharp bend without failure. Larger R/t values indicate reduced formability. Formability is dependent on the material's yield strength with formability decreasing for higher strength and harder tempers.

The ability to make a sharper bend improves as the strip width decreases at constant thickness. For large width to thickness ratio ( >8 ), a plane strain stateexists producing reproducible and conservative estimates. When width to thickness ratio decreases below 8, the deformation mode changes from plane strain to plane stress. More localized or necking strain is available ot assist forming in the latter before fracture ensues. Thin strip is formable to tighter minimum bend radii than suppliers' published minimum bend ratios. However, parts formed with this ratio are more sensitive to edge conditions and damage associated with stamping. Additional information is available in the Brush Wellman TechBrief "Formability of Beryllium Copper Strip."

Longitudinal versus transverse forming
The directionality of strip properties is a result of cold rolling. Formability is a function of the bend orientation relative to the rolling direction in a heavily cold rolled product. The formability in the longitudinal direction, good way bend, is usually better than that present in the transverse bending
direction.

Formability
Formability
Rating
Specific
Formability
Alloy
and Heat-
treatable
Temper
R/t Ratio
for 90o Bend
Alloy and
Mill
Hardened
Temper
R/t Ratio
for 90o Bend
Direction of Bend
Direction of Bend
L
T
L
T
Excellent
Used for deep
drawn and
severely cupped
or formed parts
25A
0
0
 
 
 
As formable as
the annealed
temper but
easier to blank
25 1/4H
0
0
290 TM00

290 TM02

0

0

0

0

Very Good
Used for
moderately
drawn or cupped
parts.
25 1/2H
0.5
1.0
190 AM
174 1/2 HT
190 1/4 HM
60 3/4 HT
3 AT
290 TM04
0
0.5
0.5
0.7
1.0
1.0
0
0.5
0.5
0.7
1.0
1.0
Good
Formable to a
90o bend around
a radius less
than 3 times the
stock thickness
25H
1.0
2.9
190 1/2 HM
60 HT
3 HT
190 HM
290 TM06
0.5
1.5
2.0
2.0
2.5
1.0
1.5
2.0
2.0
2.0
Moderate
Suitable for light
drawing; used
for springs
 
 
 
174 HT
190 SHM
290 TM08
190 XHM
1.2
2.8
3.5
4.0
5.0
3.2
3.0
5.0
Limited
For essentially
flat parts;
forming requires
very generous
punch radius
 
 
 
190 XHMS
5.0
10.0

Note : Formability ratios are valid for strip up to 0.050 inch thick. Strip less than 0.010 inch thick will form somewhat better than shown. Values reflect the smallest punch radius that forms a strip sample into a 90o "vee" -shaped die without failure.

R = punch radius t = stock thickness