Doctor Walt s Tips and Tricks 1

Doctor Walt s Tips and Tricks 1

I find that many KeyCreator users do not understand the difference between a collection of surfaces and a solid. To explain I use the concept of a child s inflatable beach float created by using multiple vinyl sheet pieces that are sealed together. The float is then inflated with a bycicle pump. If the vinyl patches completely enclose a volume of space with no gaps such that they hold air, you have the equivalent of a collection of surfaces that make up a solid. Solids to Surfaces to Solids If there is a gap at any spot on the surface, air escapes and the float is useless. You can think of a solid object in the same way. In this exerxcise we ll take a simple solid and unstitch it into multiple surfaces. We ll then replace one of the planar surfaces with a more complex one and stitch all of the surfaces back together. This will bring us full cycle from a solid to individual surfaces and then back to a new solid. A copy of this part is available for download as SfPart1. We ll start with a new file in View 1. Click on the CREATE BLOCK Icon. A Dialog Box appears. We ll use the Key In Option. Type 2 for the Width, 3 for the Length, and 1.5 for the Height. Use the Cursor Option to place the block anywhere on the screen. Doctor Walt s Tips and Tricks 2

Now, switch to the Isometric View. Click on the TAPER FACES Icon. A small Dialog Box appears. Type 25 for the Taper Angle. Select the About an Edge Option. You can use the Preview and Modify Faces Interactively. Select the front face of the block. Then, click on the top edge of the front face and hit the ENTER Key to confirm that you are done selecting faces. You are prompted to indicate a taper reference vector. Select the Line Option and click on the lower end of the left, front edge of the block. If you are working interactively you ll see a ghost representation of the taper surface transformation. You could play with the part, adding or reducing the slope of the face but for this exercise, just click on the DONE Button. Doctor Walt s Tips and Tricks 3

Now, we could use the Constant Radius Blend tool to soften the corners on this part and get an end result like the one illustrated to the left. (Don t actually do this right now.) But let s suppose that we need a more elaborate part design with an amorphous front surface like the one on the block to the right. That s actually quite easy to do if you use some simple surface modeling. First, click on the UNSTITCH FACES Icon. A Dialog Box appears. We ll use the Faces of Solids Option. Click on the Unhook Edit Type and the One Body per Face Result Option. Click on the All DSP Option and then on the ALL OPTION. Then, hit the ENTER Key. Doctor Walt s Tips and Tricks 4

You now have a collection of six sheet bodies on the screen where the solid used to be. Delete the sloped, front face (sheet body) on the part. Your screen should now look like this: Click on the CREATE LINE BY ENDPOINTS Icon. Using the CtrMid Option, click on the top edge and the bottom edge of the opening at the front of the part. You will now have a line at the exact middle of the opening. Next, establish a construction plane on the part by clicking on the left end of the bottom edge of the opening and the bottom end of the line that you just made. This gives you a construction plane with the Z Axis pointing outward from the part. Doctor Walt s Tips and Tricks 5

Now, click on the XFORM DELTA JOIN Icon. Select the line that you just created and type 1 for the Number of Copies. Hit the ENTER Key twice, type 0.4 for dzc and hit the ENTER Key again. You now have a rectangular grid that will be handy for creation of a guide curve for the new surface that we're about to develop. Establish a new construction plane on the rectangle that you just created. Click on the CREATE ARC BY THREE POSITIONS Icon. Create a curve that runs from the center of the bottom edge of the opening to the center of the top edge of the opening. The midpoint will lie on the midpoint of the top edge of the rectangular grid that you just created. (You ll find that this is an extremely convenient way to create cross curves that can be used to give a surface cross curvature at a controlled radius.) Doctor Walt s Tips and Tricks 6

Now, click on the CURVE MESH SURFACE Icon. A small Dialog Box appears. We ll use the default Curve Fit Tolerance. Make sure that there is NO check on the Chain Select Option. Click on the bottom edge of the left side of the opening, the bottom edge of the new arc that you made, and the bottom edge of the right side of the opening. Then, hit the ENTER Key. Now, click on the left end of the bottom edge of the opening and the left end of the top edge of the opening. Hit the ENTER Key. You will now have a new surface to close up the front of the part. (Note: I was specific about picking at the same end for each curve. This eliminates introducing twist into the surface.) Click on the STITCH SHEETS Icon. Click on the ALL DSP Option and then on the ALL Option. Hit the ENTER Key. Doctor Walt s Tips and Tricks 7

You will now have a complete solid body with a more exotic front face! Click on the CONSTANT RADIUS BLEND Icon. First create 0.4 radius blends on the top, front edge and top, rear edge. Your part should look like this: Note the front constant radius blend looks quite exotic because the new front surface rises abruptly from the edge at the midpoint. This changes the included angle that the blend runs through, thus creating the constriction! Wrap up the job with two 0.25 radius blends on the left and right edges. You ll find that combining solid and surface modeling tools gives you a whole new range of possibilities in your designs. To learn more about more complex modeling, I recommend my Doctor Walt s KeyCreator8 Hybrid Modeling Book. Doctor Walt s Tips and Tricks 8