Open Design Optimization Platform (ODOP) - Coil spring design app; mechanical springs; compression spring, extension spring, torsion spring

View the Project on GitHub thegrumpys/odop

Spring Alerts  

Alerts common to all round-wire coil springs

On this page:

Alert entry #S51

Wire_Dia > ID_Free

The wire diameter (Wire_Dia) is greater than the coil inside diameter (ID_Free).

Most spring wire is not sufficiently ductile to be wound this tightly.

Resolve this alert by increasing the value of the variable controlling coil diameter (OD_Free, Mean_Dia or ID_Free) or decreasing the value of Wire_Dia.

Alternatively, confirm that the Spring_Index MIN constraint is enabled at a constraint level of 4 or greater and run Search (menu Action : Search or the Search button).

Before finalizing a design that has this alert outstanding, check with the spring manufacturer regarding capabilities and costs.

Alert entry #S52

Material properties for this Wire_Dia may not be accurate.

This message is provided to warn the user that the current value for wire diameter is well outside the anticipated range for the selected material type and the material properties from the internal table may not be completely accurate.

Specifically, the ODOP : Spring software uses an interpolation / extrapolation mechanism to calculate a new value of tensile strength for each new wire diameter that is evaluated. The specific numbers involved change with each different material in the materials table. In this case, the current value of Wire_Dia requires an extrapolation significantly outside the range covered by values in the materials table. Thus, the corresponding values for tensile strength may not be completely accurate.

If possible, select a standard wire size.

Alternatively, obtain the appropriate value of tensile strength for the wire material and wire diameter in use and then modify the Calculation Input Prop_Calc_Method to a value of either 2 or 3 so that the material table is not used and it is possible to enter the more accurate value of tensile strength.

See also:

Alert entry #S53

FS_CycleLife MIN is not set.

A more restrictive Life_Category has been selected but the corresponding constraint on FS_CycleLife is not enabled.

Selecting a Life_Category gets a corresponding value of %_Tensile_Endur from the internal material table. This value is then used to calculate Stress_Lim_Endur. The MIN constraint on FS_CycleLife must be enabled in order to have Search achieve designs that do not exceed the designated Stress_Lim_Endur.

Suggest enabling the FS_CycleLife MIN constraint.

See also:

Alert entry #S54

Over-design concern

The term "over-design" implies that this design may be too conservative. Its Factor of Safety at operating point 2 exceeds the maximum constraint (FS_2 MAX).

Try investigating a smaller wire diameter. One approach is to run Search (menu Action : Search or Search button) with Wire_Dia in Free status.

Later, when ready to finalize the design, investigate design variations with the nearest standard wire diameters. Select and Fix the nearest smaller standard wire diameter. Run Search. Select and Fix the nearest larger standard wire diameter. Run Search. Compare the results. It may be necessary to accept a small amount of over-design in order to utilize a standard wire diameter.

Alternatively, increase the FS_2 MAX constraint or disable that MAX constraint. This action will allow Search to produce a very conservative (heavy) design and consider it to be feasible.

See also:

Alert entry #S55

Coils_A is less than 1

A warning alert is produced whenever the current design has less than one active coil.

This is not an error that will block operations like Search, Seek and Trade. As less than one coil may not be the intent, the warning is intended to bring the situation to the designer's attention.

Alert entry #S56

Spring Index manufacturability concern

Spring_Index is the ratio of Mean Diameter to Wire Diameter. Specifically: Mean_Dia / Wire_Dia.

The presence of this alert indicates that the current design is outside the range of constraints Spring_Index MIN to Spring_Index MAX. This design may be difficult to manufacture.

Spring index less than 4 is considered "difficult to manufacture". Spring index greater than 25 is considered "difficult to control".

Ideally, spring index should be in the range of 6 to 12 in order to easily achieve spring industry standard tolerances. Reduced coiling machine speeds, specialized fixtures and other tooling may be required outside this range. For custom springs, check with the spring manufacturer regarding capabilities and costs.

The value of Mean_Dia can be controlled in the Advanced View and appears in Report 3.

To resolve this alert:

Alternatively, confirm that either (or both) Wire_Dia and the variable controlling coil diameter (OD_Free, Mean_Dia or ID_Free) are in Free status and (re-)run Search.


Alert entry #S57

Cycle_Life calculation is not available

The Cycle_Life variable (Modified Goodman calculation) is available only for materials contained in the internal materials table. The current setting of Prop_Calc_Method indicates that material properties are user supplied, thus there is not enough information available to directly calculate cycle life.

The FS_CycleLife variable (Soderberg calculation) remains as a way of gauging cycle life for user defined materials (Prop_Calc_Method = 2 and 3).

In this case of user supplied material properties, if Cycle_Life is Fixed or has either MIN or MAX constraints enabled, Search is not likely to find a solution that is judged to be FEASIBLE.

In order to continue with user supplied material properties, disable constraints on Cycle_Life and enable constraints on FS_CycleLife.

See Also:

Alert entry #S58

Cycle_Life not defined beyond yield

The load specified in the current design is sufficiently large to cause the wire to yield. The notion of cycle life does not apply.

More specifically, the current design has a Factor of Safety at the second working point (FS_2) that is less than 1.0. This means that the current set of inputs have resulted in a stress at point 2 (maximum operating load) that exceeds the maximum allowable stress. For this design, the wire is at or perhaps even beyond its yield point. In this situation, the direct cycle life calculation (Cycle_Life variable - Modified Goodman calculation) is not meaningful.

In this case of unrealistically high stress at point 2, if Cycle_Life is Fixed or has either MIN or MAX constraints enabled, Search is not likely to find a solution that is judged to be FEASIBLE.

Change inputs such that stress at working point 2 (maximum operating load) is reduced.

Increase   Decrease
Wire_Dia   Force_2 or M_2

Perhaps the best approach is to to confirm that one or more of these variables is in Free status and then run Search.

See also:

Alert entry #S59

Cycle_Life value is extrapolated

The built-in material table provides allowable stress information derived from published s-n (stress versus number of cycles) data that covers the range from 10,000 to 10,000,000 cycles. In order to facilitate proper operation of the search algorithm, the allowable stress data has been extrapolated outside this range and is not supported by published data.

See also:

Alert entry #S60

Default constraint not enabled

Disabling default constraints is not recommended. Adjust the constraint value instead.

This alert is produced when constraints enabled by default are disabled. This alert can be also be produced for designs created and saved with older versions of the software. Specifically, constraints on Spring_Index were not enabled by default in older designs. If this alert is associated with Spring_Index on an older design, it may be ignored. Better yet, clear the alert by enabling MIN and MAX constraints on Spring_Index.

The default constraints guide Search to "good" spring designs. The Seek and Trade features utilize Search internally and thus those results are also guided by the default constraints.

For example:

In summary, while it may be reasonable to adjust the constraint values of a default constraint, disabling a default constraint entirely is not recommended.

Alert entry #S61

Value of Tensile is suspect

The value of Tensile strength is close to or less than zero. Check that it is correct.