Modeling a finger; attempting a loft and having an issue with creating a guide line

scott_lake

I am wanting to 3D print a splint for my little finger.  I have an injury that the doctor called a "Swan's Neck Injury" where the flexor tendon(s) have been injured.  The Dr. office hand-made a splint out of a material called 'Aquaplast' which works pretty well, but I want to make a more nerdy version which has some smoother shapes and optimized strength with a little tighter bend at the 2nd joint from the tip of the finger.

The modeling approach I was going to take was to measure the bend angles I want for the joints, measure the length of the phalanxes (sp?) and model the diameter of each section with an ellipse, then loft from ellipse to ellipse, shell the loft, then apply some subtractive tools across the back side of the 2nd joint.

I should have looked more deeply into guide lines before I modeled the x-section ellipses because the guide line I did make was the center of where I laid out the ellipses on planes normal to that guide line.  You OnShape pros know that the guideline can't be a centerline.

I thought it would be no problem to make a new guideline by connecting to the ellipses on an outer edge of each ellipse, where they intersect the plane where I laid out the centerline.  Well, I can't make that work for whatever reason.  I can't get a point to lay out where the 3 different ellipses intersect the plane where the centerline is laid out, and as a result, I can't force a line to connect to those ellipses.

Any clues?  Link to my file is here:  https://cad.onshape.com/documents/d002c2baef598dc443f902a1/w/2ca82884d4cd6b1e036a917d/e/9655c4bbbfe163b62062e001

bradley_sauln

Also, make sure to use the "pierce" sketch command, when creating your guide curves https://cad.onshape.com/help/#sketch-tools-pierce.htm?Highlight=pierce

owen_sparks

Hi, your link is view only so can't edit for you.

Have you tried the new 3d curve spline tool?  You have a point at the top of each circle, I'd try a spline through those for the guide.

Brilliant project BTW

Owen S.

bradley_sauln

Also, make sure to use the "pierce" sketch command, when creating your guide curves https://cad.onshape.com/help/#sketch-tools-pierce.htm?Highlight=pierce

scott_lake

owen_sparks said:

Hi, your link is view only so can't edit for you.

Have you tried the new 3d curve spline tool?  You have a point at the top of each circle, I'd try a spline through those for the guide.

Brilliant project BTW

Owen S.

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Owen, I put those points there but I can't seem to pick them for points on the guide line.

scott_lake

bradley_sauln said:

Also, make sure to use the "pierce" sketch command, when creating your guide curves https://cad.onshape.com/help/#sketch-tools-pierce.htm?Highlight=pierce

YES!  That was it.  At least to generate the guide line, but I get an error when I try to loft, something like this "Loft did not generate.  Guide should intersect each profile in the loft".  Well, I thought by forcing the guide to follow where the ellipse/sketch interface was using the pierce, that this would guarantee the guide line would also intersect the profiles.  I'm still doing something wrong.

scott_lake

OK, I went back in and tried the 3D spline and I was able to make a guide line that connected all the ellipses.  I now have a file that I'm going to try to print.  Our local library has some crude 3D printers we can use and just pay for the material.

Ben_Misegades

"Phalanges"