Open Design Optimization Platform (ODOP) - Coil spring design app; mechanical springs; compression spring, extension spring, torsion spring
Alerts specific to extension springs.
Alert entry #E201
The force at operating point 1 (Force_1) is greater than the force at operating point 2 (Force_2).
Extension spring forces are ordered from the smallest (free condition) to Force_1 to Force_2 to the largest (Max Safe). The Extension Spring Force - Deflection Diagram provides more detail on this point.
Resolve this alert by reducing the value of Force_1 below the value of Force_2.
It should also be possible to confirm that Force_1 is in Free status, confirm that the constraint L_Stroke MIN is enabled with a greater-than-zero constraint level and then use the Search feature (menu Action : Search or Search button).
See also:
Alert entry #E202
In an extension spring, having the current value of Force_1 less than the current value of Initial_Tension is ambiguous. Calculations for L_Stroke and Cycle_Life may not be valid.
Where practical, change these values in the direction specified:
| Increase | Decrease | |
|---|---|---|
| Force_1 | Initial_Tension |
Alternatively, confirm that the Force_1 MIN constraint is set to the (FDCL) value of Initial_Tension and use the Search feature (menu Action : Search or Search button).
See also:
Alert entry #E203
The manufacture of springs with insufficient Initial_Tension is said to be "Difficult to control". This alert indicates that the current value of stress generated by initial tension (Stress_Initial) is below the lower limit indicated by Stress_Init_Lo. Increasing the value of Initial_Tension should clear the alert.
Initial tension in an extension spring is limited by a number of factors. Beyond things like the material selection and heat treatment, the primary factors are spring index and the torsional stress caused by initial tension.
The Calculation input SI_Range provides user control over the default constraints on Stress_Initial. When set to "Readily_Obtainable" or "Special Request" and a known ferrous Material_Type is in use, the values of SI_Lo_Factor and SI_Hi_Factor are obtained from the built-in materials table. The software calculates the dependent variables Stress_Init_Lo and Stress_Init_Hi to form a range of attainable stress. These values are then applied as MIN and MAX constraints on Stress_Initial.
Also, if the Stress_Init_Lo and Stress_Init_Hi constraints are in place, the Search feature will work to generate designs that fall within the preferred range of Initial_Tension.
Before finalizing a design that has this alert outstanding, check with the spring manufacturer regarding capabilities and costs.
See also:
Alert entry #E204
The manufacture of springs with high values of initial tension is said to be "Difficult to attain". This alert indicates that the current value of stress generated by initial tension (Stress_Initial) is above the upper limit indicated by Stress_Init_Hi. Decreasing the value of Initial_Tension should clear the alert.
Initial tension in an extension spring is limited by a number of factors. Beyond things like the material selection and heat treatment, the primary factors are spring index and the torsional stress caused by initial tension.
The Calculation input SI_Range provides user control over the default constraints on Stress_Initial. When set to "Readily_Obtainable" or "Special Request" and a known ferrous Material_Type is in use, the values of SI_Lo_Factor and SI_Hi_Factor are obtained from the built-in materials table. The software calculates the dependent variables Stress_Init_Lo and Stress_Init_Hi to form a range of attainable stress. These values are then applied as MIN and MAX constraints on Stress_Initial.
Also, if the Stress_Init_Lo and Stress_Init_Hi constraints are in place, the Search feature will work to generate designs that fall within the preferred range of Initial_Tension.
Before finalizing a design that has this alert outstanding, check with the spring manufacturer regarding capabilities and costs.
See also:
Alert entry #E205
Given the selected end type:
and / or
In order to clear this alert, where practical, change one or more of these values in the direction specified.
| Increase | Decrease | |
|---|---|---|
| Wire_Dia | Coil_Dia | |
| FS_2 | Force_2 | |
| FS_Hook | L_Stroke | |
| Spring_Index |
Alternatively, use Advanced View to enable the minimum constraint on FS_Hook with a constraint level of 1.0 or greater, enable the maximum constraint on Stress_Hook (defaults to the FDCL of Stress_Lim_Bend) and then use the Search feature (menu Action : Search or Search button). It will likely be necessary to clear some or most seemingly unrelated constraint violations in order to achieve no violation on the FS_Hook constraint (and thus achieve a design considered to be feasible).
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Alert entry #E206
The material property data SI_Lo_Factor and SI_Hi_Factor necessary to compute an appropriate range for stress induced by initial tension in non-ferrous materials is not in the internal material table.
In order to clear this alert:
or
It may be helpful to consult with the supplier of the non-ferrous material under consideration.
See also:
Alert entry #E207
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 #E208
The first operating point (point 1) has less than 20% of maximum safe deflection. End effects and other factors may cause some inaccuracy in forces and deflections for this point.
Even if the application requires that this design operate outside the range of 20% to 80% of available deflection, the inspection (acceptance) criteria should be specified within this range.
Helical coil compression, extension and torsion springs that have the properties of uniform pitch and cylindrical shape follow Hooke's Law in that they provide a nominally linear relationship between force and deflection. However, in the real world there are limitations.
When extension springs are extended less than roughly 20% of safe deflection various factors such as deviation from perfect coil straightness (cylindrical form) and any lack of perfect form in the ends will become a factor in the real (as opposed to theoretical) force-deflection relationship. Thus when operating within the first 20% of the available deflection expect forces to be somewhat lower (or deflections to be somewhat greater) than the linear behavior predicted by the equations.
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