Open Design Optimization Platform (ODOP) - Coil spring design app; mechanical springs; compression spring, extension spring, torsion spring
Alerts common to all round-wire coil springs
Alert entry #S51
This situation creates numerical difficulties. In mathematics, this is sometimes referred to as a "pathological" case.
To resolve this Alert, increase the value of OD_Free and / or decrease the value of Wire_Dia. To achieve a feasible design, continue increasing OD_Free and decreasing Wire_Dia until Spring_Index achieves a value within the range of manufacturability.
With round wire helical coil springs, the case where coil outside diameter (OD_Free) is exactly twice the wire diameter (Wire_Dia) creates numerical problems. In this situation, the inside diameter (ID_Free) is exactly zero and the spring index (Spring_Index) is exactly one. That value of Spring_Index results in a divide-by-zero problem in the calculation of the Wahl curvature correction factor (kc). The result of infinity then propagates through dependent equations. Subsequent operations like subtraction of infinities create values of NaN (Not a Number) which propagate to additional dependent equations.
The Search feature may or may not be successful in finding a solution when its start point has such numerical difficulties.
See also:
Alert entry #S52
This situation creates numerical difficulties. In mathematics, this is sometimes referred to as a "pathological" case.
To resolve this Alert, increase the value of OD_Free and / or decrease the value of Wire_Dia. To achieve a feasible design, continue increasing OD_Free and decreasing Wire_Dia until Spring_Index achieves a value within the range of manufacturability.
With round wire helical coil springs, the case where coil outside diameter (OD_Free) is exactly equal the wire diameter (Wire_Dia) creates numerical problems. In this situation, the mean diameter (Mean_Dia) and spring index (Spring_Index) are both exactly zero, creating a divide-by-zero problem in the calculations. The result of infinity then propagates through dependent equations. Subsequent operations like subtraction of infinities create values of NaN (Not a Number) which propagate to additional dependent equations.
The Search feature may or may not be successful in finding a solution when its start point has such numerical difficulties.
See also:
Alert entry #S53
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 #S54
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 #S55
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 #S56
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 #S57
A warning alert is produced whenever the current design has less than one active coil.
As long as Coils_A is greater than zero, 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.
Values of Coils_A less than or equal to zero will trigger the associated validity alert.
Alert entry #S58
Spring_Index is the ratio of Mean Diameter to Wire Diameter. Specifically: Mean_Dia / Wire_Dia.
To resolve this alert:
If Spring_Index is less than Spring_Index MIN: decrease Wire_Dia or increase the variable controlling coil diameter (OD_Free, Mean_Dia or ID_Free).
If Spring_Index is greater than Spring_Index MAX: increase Wire_Dia or decrease the variable controlling coil diameter (OD_Free, Mean_Dia or ID_Free).
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.
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 with Spring_Index outside the range of easy manufacturability, 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.
Alert entry #S59
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).
Note:
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 #S60
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.
Note:
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.
Recommendations:
Change inputs such that stress at working point 2 (maximum operating load) is reduced.
| Increase | Decrease | |
|---|---|---|
| Wire_Dia | Force_2 or M_2 | |
| OD_Free |
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 #S61
This is an information alert. No action is required.
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 thus the current cycle_Life value is not supported by published data.
See also:
Alert entry #S62
To clear this Alert, remove Fixed status from either OD_Free or ID_Free by unchecking the checkbox immediately to the right of the value field.
With a helical coil spring, having both outside diameter (OD_Free) and inside diameter (ID_Free) in Fixed status raises a concern that the design may be unintentionally over specified. In this situation, there is only one possible value of wire diameter (Wire_Dia) that will permit a feasible solution. That value is not likely a standard wire diameter. As this may not be the designer's intent, this alert is intended to bring attention to the situation.
See also:
Alert entry #S63
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:
A lower constraint on deflection at the first operating point (Deflect_1) prevents Search from generating negative values for force and deflection at point 1.
Constraints on Spring_Index insure that designs produced by the software are within the range of manufacturability. For custom springs, consult your manufacturer regarding capabilities and costs.
Constraints on factor of safety at the second operating point (FS_2) insure that stresses are in an appropriate range.
Disabling FS_2 MIN allows Search to return a highly over-stressed design and declare it as "feasible".
Disabling FS_2 MAX allows Search to return a under-stressed design and declare it as "feasible". If a relatively heavy, low-stress design is desired (an "over-design" situation), increase the value of the FS_2 MAX constraint.
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 #S64
The value of Tensile strength is close to or less than zero. Check that it is correct.