Hi, everyone.

We make thermoforming molds which often require dozens or hundreds of tiny holes to draw vacuum through.  We generally backdrill with a larger drill, then use a very small drill to poke through the remaining material to hit the mold's top surface.

We are looking for a way to bore/drill a hole to a depth which is an offset from a surface (the offset is the red arrow in the image below), then drill a second smaller hole the rest of the way - the length of the smaller hole would be approximately the same for any location on the 3D surface.  We can place points on either the top 3D surface or on the bottom planar surface (green circles) - either would work.  I've struggled to find a way to make the hole wizard work, but the counterbore depth is always fixed.  I've also tried modeling a single hole (with the hole wizard or with extrude cuts), and then using the sketch driven pattern to create the rest of the holes, but that doesn't work - the patterned holes have the same geometry as the initial hole, so they don't follow the varying contours of the top surface.

We really need to make this point driven because of the huge number of holes needed, and sketching circles just isn't practical.  Dropping a bunch of points in the hole wizard could work, but a 3D sketch with all the points representing the hole location would be ideal.

The other option we're looking into is to not model the holes at all, but to use the points in our CAM package (Hypermill) directly, and work offsets with that.

Any ideas of how we can do this easily would be greatly appreciated!

Cheers.

Len