Sketching on a surface not on a plane

Can I do different sketch planes then connect them with lines or splines?

I drew several circles on different sketch planes. I double tapped on the bone surfaces and drew the circles in place of the screw holes. They ended up on the bone surface, so can I connect them with a line or spline to finish the bone plate which will be close to the bone surface. Then I can extrude the sketch planes from the side facing the bone and the side away of the bone. After doing that I can subtract it from the bone to be perfectly fitting on the bone surface


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Hey @zsurgeon, I’m back!

Regarding my idea with the scale tool… well, I had to think about it again. The difference between the inner and outer surfaces is so big that my idea was not useful at all. Sorry for that. Nevermind, here is another one that I can prove with a video :smiley:

After aligning the body to be parallel-ish with the coordinate axes, I just created a simple body that will be a tool in the next steps. If you remove the scanned data from that body, the body will accurately follow the scanned data along the face they are intersecting. Moving this tool away from the scanned body will maintain a constant thickness for any implants you design. Please have a look at this video and feel free to share your feedback:

Connecting the holes to answer your second question is a different topic. One way would be to create a 3D spline along with the center points of the circles and then make it a rib, but that is fairly complex. Instead of that please extrude the circles away from the mesh body and simply merge them together with additional modeling elements.

ps.: in the video, I struggled with the boolean a lot. It is a common problem when working with mixed CAD and mesh files even if there is a clear intersection. In many cases moving one of the bodies just a few mm solves the problem.

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Dear KPeter

I could not connect the different circles together as every one of them is a different sketch not on the same sketch plane. My idea was to draw the circles that would represent the screw holes with each one of them on the surface of the mandible then connect them together with a spline or line in the shape of the bone plate arm. If I could,
the arm connecting two circles will be in close contact with the surface of the mandible. After that I extrude it bi directional and subtract it from the mandible. I prepared a video for that but it was too big to attach it I will prepare another on shorter and post it

Hi,
Yes, I see, simply connecting the circles would require 3D sketching. Please have a look at this video where I connected some random cylinders with the Loft tool, I think it can be a solution for your case too:

ps.: Please note that the only reason for being able to sketch onto the model is because you sketch on a plane of a polygon. It is not possible to sketch on real curved faces.

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Dear KPeter

Thank you a lot for your help

I am now sending you a picture of simulated surgery for moving the upper jaw forwards and upwards then designed a plate to fix the upper jaw in the new position

I united the postoperative models. The plate was modeled then subtracted from the united postop. I then scaled the post op to 104% then made an intersection from the subtracted plate

I will try the loft and send you pictures