Author Topic: Fillet edge/corner  (Read 334 times)

Dr PR

  • Hero Member
  • *****
  • Posts: 5379
Fillet edge/corner
« on: August 05, 2016, 08:42:39 AM »
One thing that DesignCAD really needs is a smart 3D fillet function that will filet edges and corners.

For example, suppose you have a rectangular box solid. It would be nice to start the fillet function and then click on multiple edges to select them, and then click "OK" to start the function. All edges would be filleted according to the number of facets, etc. Any corners common to the selected edges would also be filleted.

Note: A corner of a solid can have more than three common edges.

In the "Filleted edges" image I gave filleted three edges on the red boxes. The result is a sharp corner where the three edges meet. What I would really like to happen is to created a filleted corner like you see in the green box with rounded edges.

This should be extendable to incorporate edges that have already been filleted. Suppose I have filleted an edge that extended to a corner, but didn't fillet any other edges at that corner. Then I might select the other edges that extend to that corner and fillet them. In this case the corner should be redrawn to incorporate the original filleted edge and the newly filleted edges.

The examples above use "outside" edges like the corners of a rounded box. The fillet function should work for inside edges as well. See the "Filleted edges and corners" image.

There are two types of corners:

1. All outside edges.
2. Outside and inside edges.

The current fillet edges function fails when both inside and outside edges are involved.

Ideally, the fillet edge/corner function would resolve all cases to produce correctly filleted corners in all cases.

****

It is possible to create these complex filleted corners now, but it isn't easy. It involves sweeping quarter circles, slicing spheres with "Solid Subtract" or drawing a bunch of template arcs and using the "Surface Patch" function to create the rounded corner. Sometimes I create a bunch of rounded boxes, explode them, and reassemble the pieces to get the desired edges and corners.

NOT PERFECT!

Phil
DesignCAD user since 1987

adriank

  • Sr. Member
  • ****
  • Posts: 423
Re: Fillet edge/corner
« Reply #1 on: August 08, 2016, 04:51:12 AM »
I'd vote for that!
Currently anything that involves filleting round multi-faceted corners I have to draw a line on the edges to fillet, make a 'tool' plane attached to the line, extrude that 'along a curve' (which is not a curve, BTW), and subtract the resulting solid from the original solid.


Dr PR

  • Hero Member
  • *****
  • Posts: 5379
Re: Fillet edge/corner
« Reply #2 on: August 08, 2016, 07:38:28 AM »
I have been doing this by extruding segments curves to create the filleted edges and either sweeping curves for corners or using "Surface Patch." In some cases I create a sphere or hemisphere and slice away parts until I get the desired corner.

Sometimes I start with a box with rounded corners and slice away parts. Or I just explode the solid and use parts to build up what I want. For really complex fillets I just draw dozens of template lines and use "Surface Connect." PITA!

The really obnoxious constructions involve filleting edges between corners with different radii. The edges are not sections of cylinders but are sections of truncated cones.

I have attached some images showing some complex filleted edges. Virtually every metal casting has rounded edges. Even though these are very common in the real world they are very difficult to model in DesignCAD. I would say this is the program's greatest shortcoming.

Phil
« Last Edit: August 08, 2016, 09:19:09 AM by Dr PR »
DesignCAD user since 1987