The Third Design

In looking over these modeling strategies, these two can be changed such that the model created is exactly the same, but with different values to locate the part with respect to the origin. This is extremely beneficial in this model, as there are no standard places to put the origin. It varies from designer to designer, and even from use to use. It depends greatly on how the part is being used, and what other geometry is being used as a reference.

To this end, a third method was created. In this third method, the only change necessary to move the part with respect to the origin is to change the named parameters X_Offset, Y_Offset, and Z_Offset. No locations have to be changed in this model. In the previous two methods, three separate locations would have to be changed. This allows the designer greater flexibility when using these parts. This method has the default (all the Offset variables equal to zero) origin at the bottom left corner, with the flange along the X axis, and the web along the Y axis.

Another change was made at this point. All references to -Draft were changed to Draft_Negative. It was discovered that using -Draft caused some problems with the regeneration due to the software forgetting that the angle originally entered was negative. This would cause the regeneration to fail, since it changed the shape of the curve. This normally only occurred when the angle was changed to zero, the model regenerated, and the angle changed again. The change was an attempt to prevent this problem from occurring while parts were being generated in general use.

Four stages of construction for this design are shown in Figure 4.13. These pictures show the model after the first, fourth, fifth, and final steps.

Construction:

1. Insert Line Free Ref Loc [0,0,0] Dxyz X_Offset Y_Offset Z_Offset Dy Fl_Th Xangle Draft Dx Flange_2 Xangle
   Draft_Negative Dx Flange_2 Dy -Flange_Th Dx -Flange
2. Join Pcurve Chn (select previous Line)
3. Duplicate Entity (select previous Pcurve) Mirror Plane Y Ref End (either line at the bottom left corner) Dy Web_Ht_2
4. Insert Rectangle Height Web_Ht Width Web_Th Center Ref End (either line at the bottom left corner) Dxyz Flange_2 Web_Ht_2 0
5. Union Profile (select all curves)
6. Break Pcurve (select new profile)
7. Insert Fillet Radius Fillet (select each of four corners to be filleted)
8. Insert Fillet Radius Round (select each of four corners to be filleted)
9. Join Pcurve Chn (select curve)

Figure 4.13: Steps in Creation of the Beam, Third Design

Variables:

Variable - description                  Type    Value From
Draft - draft angle on inside of beam   const   table
Draft_Negative - negative of draft      free    eqn
Fillet - radius of corner fillets       free    table/eqn
Flange - width of flange                const   table
Flange_2 - half of width of flange      free    eqn
Fl_Th - thickness of flange             const   table
Min_Radius - min allowable radius       const   constant
Round - radius of inside rounds         free    table/eqn
Web_Ht - height of web                  const   table
Web_Ht_2 - half of height of web        free    eqn
Web_Th - thickness of web               const   table
X_Offset, Y_Offset, Z_Offset - offset from origin
                                        free    free

Equations:

Flange_2 = Flange / 2
Web_Ht_2 = Web_Ht / 2
Fillet >= Min_Radius
Round >= Min_Radius
Draft_Negative = -Draft

Last Modified: Wed Aug 28 14:41:29 EDT 1996