Projecting Countersunk Hole pattern to Surface

[patl1]

I am designing a 3D guitar bridge and need to project the pin hole pattern of 6 countersunk holes onto the crowned top surface of the bridge. I want to keep the holes all perpendicular to the Z axis so I can CNC them on a 3 axis router. I was able to project the hole locations onto the crowned/3D surface by creating an offset surface of .000 distance from the modeled surface of the bridge and then projecting the hole locations down to the new surface from the flat X/Y plane I created on the top of the bridge with the hole pattern on it. Next I created 6 individual offset planes at each of the projected hole locations on the 3D surface so I could make the 6 countersunk hole at the projected positions. This all worked fine until I parametrically changed the hole pattern angle as I was refining the design and the projected holes lost their reference to the projected locations (which did in fact move with the new parameters) and the holes did not move to the new positions as expected. I hope all of this makes sense and someone can help me figure out what I am doing wrong.

[TheCADWhisperer]

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

[patl1]

Thanks for the reply. Here is the file. Since I am being paid to program the Bridge, it is rather proprietary. The file as saved has the "surface feature" suppressed along with the sketch that projects the hole pattern to the 3D surface (since it was not working as intended). I also have deleted the individual planes parallel to the X/Y plane and offset to each projected point that I discussed above since it was not working for me. Currently the file has the countersunk holes using the points on the flat X/Y plane and am living with the shallow countersinks it produces on the 3D modeled surface when the cnc machines them

[laughingcreek]

an approach. did the attached before you uploaded the file.  i'll have a look now and see how close I was to guessing right.

add just these dims to change gross spacing and angle.

[patl1]

Sorry, the version I just uploaded had the projected point deleted. Here is a version with the points on the 3D surface (when "unsupressed")

[laughingcreek]

i mean, you could just bodge it by press/pulling the charmfer face to about the right size.

[patl1]

True, but if I understand your proposal, I believe I would lose the benefit of the parametric design to change on the fly as I change the crown radius of the bridge. 

[laughingcreek]

then go with the first proposal

[laughingcreek]

or (palm slap)use a chamfer-

[patl1]

Thank you, I'll take a look at it to make sure I understand what you did and see if I can make it work.

[patl1]

laughingcreek.....I ended up taking your 1st suggestion since it doesn't seem possible to project to the surface and have it remember the link

[patl1]

I think the chamfer is a very good solution. Wish I would have thought of it instead of going down the "countersunk hole" rabbit hole

[TheCADWhisperer]

---

@laughingcreek wrote:

or (palm slap)use a chamfer-

@laughingcreek 

@patl1 

Uhm, be careful about that "solution" - will only work if 3D printed (or perhaps with hand finishing).

Will not reproduce the same geometry using standard rotating cutter process on a milling machine (or drill press).

Let me know if you need an example that conclusively illustrates the issue.

[patl1 · Accepted solution]

OK, Thanks for the heads up. I ended up modeling and machining it using the chamfer approach and it is giving me a satisfactory result given the situation. By that I mean since I am creating a countersink on a curved surface. I used a drilling toolpath and thankfully there was an option in the "heights " tab to set the bottom as the "chamfer width". Without that setting, I probably would not have been able to accomplish what I needed. That approach kept the tool (90 deg V bit) moving on the centerline of the hole and limited its z travel as intended to the top surface of the material where the chamfer met it (I think). In any event, it will serve the purpose for the pins in the guitar bridge application. Thanks for the dialogue. Now I have 2 workable approaches for what I needed to do