Open Design Optimization Platform (ODOP) - Coil spring design app; mechanical springs; compression spring, extension spring, torsion spring
If you want to avoid dealing with the ODOP:Spring "factor of safety" approach and design a spring in a more traditional "design to specific stress" approach, this is possible.
A method of getting ODOP:Spring to find a design with a specific working stress is presented here. Another approach that allows the user to have complete control over the allowable stresses that are used in the factor of safety calculations is presented in the MATERIALS section.
First, it will be necessary to free the various FS_ constraints so that they are no longer active. This is accomplished by removing the checkmark in front of the specified MIN and MAX constraints.
For compression springs: For extension springs:
FREE FS_2 FREE FS_2
FREE FS_CycleLife FREE FS_CycleLife
FREE FS_Solid FREE FS_Hook
Next it will be necessary to tell ODOP:Spring to find a solution with the desired stress (substitute your desired stress level for xxxxx below).
FIX Stress_2 xxxxxx
Finally, enter the rest of your problem's FIX and constraint information, then go to the Search menu item (Action : Search menu) to have ODOP:Spring find a design with the requested stress level at the second working position.
Note that as with the "factor of safety approach" it may be desirable to use the Seek menu item (Action : Seek menu) to find a spring of minimum weight.
Also, while it is likely not a significant concern, remember that fixing any Dependent Variable (like Stress_2) will increase the difficulty of the search problem and thus potentially increase the time required to execute the search.
The value of Prop_Calc_Method controls how material properties and allowable stresses are determined and used.
Prop_Calc_Method = 1 - Use values from material table indicates values come from materials table; allowable stresses will be calculated as a function of Wire_Dia.
Prop_Calc_Method = 2 - Use Tensile & %_Tensile_... indicates Tensile and allowable %_Tensile (%_Tensile_Endur and %_Tensile_Stat) are supplied by the user; allowable stresses (Stress_Lim_Endur and Stress_Lim_Stat) are calculated. There is no dependence on wire diameter.
Prop_Calc_Method = 3 - Use Stress_Lim_... indicates that allowable stresses (Stress_Lim_Endur and Stress_Lim_Stat) are supplied directly by the user. There is no dependence on wire diameter.
Refer to additional discussion in the MATERIALS section.
The easiest way to design a hot wound spring is to open a start point that is already set up for hot wound. Sample compression spring hot wound startup designs supplied with ODOP:Spring (marked "[ReadOnly]") are:
HotWound - U.S. customary units (inches, pounds)
HotWoundMetric - metric units (mm, Newtons)
Each of these files are pre-configured for a material type (Eg. 5160H) that carries an appropriate value of HOT_FACTOR_KH, an end type of TAPERED_C&G, and starting values that are closer to the solution point of a typical hot large wound spring than the values in the default startup design.
Alternately, select a material from the table that indicates it is "hot wound", select an appropriate end type (Eg. TAPERED_C&G) and then adjust Wire_Dia, OD_Free and Force_2 to start with a realistic approximation of the desired result.
The value of HOT_FACTOR_KH is used to reduce the effective modulus of elasticity and torsional modulus in the design equations.
For normal cold coiled materials, the value of HOT_FACTOR_KH is 1.00. Thus, it has no effect on the modulus. For materials designated as "hot wound" in the materials table, the value of HOT_FACTOR_KH is automatically established as appropriate (generally 0.96 for centerless ground materials and 0.91 for not centerless ground materials).
PROCESS MATERIAL HOT_FACTOR_KH
COLD_COILED 1.00
HOT_WOUND CENTERLESS GROUND 0.96
HOT_WOUND NOT CL GROUND 0.91
It is possible to set a different value for HOT_FACTOR_KH by using PROP_CALC_METHOD = 2 or 3. This will permit any desired value of HOT_FACTOR_KH to be entered into the Advanced View Calculation Input entry field.
Make permanent changes in these values by altering the appropriate materials file. For additional information, refer to: