Pocketing Odd Shapes

[kisolre]

In my understanding (please someone correct me) what is passed to he OCC kernel to make the Pad is not a list of vertices and then edger in the form of (edge from vertex1 to vertex2) but a list of edges in form of edge1(v1,v2); edge2(v3,v4); arg(c, r, v5, v6);... So edge connection is not derived from passed data. You can have edge vertices that are coincident without a constraint applied. For example if you use snap to grid or create sketch by converting connected Draft wire. And this will pad at first. But as soon as you move something it might fall. Coincident constraint forces the sketch solver to move those edges so their vertices are close together within tolerance accepted by the kernel. There were several posts recently where the solver failed to do so and despite the applied coincidence the sketch will not pad.
Hope that makes sense

[kisolre]

Did some modifications in constraints of your sketches. Construction lines for arc centers. Tangency between arcs where it looked like it was intended.

[dave_w]

Did some modifications in constraints of your sketches. Construction lines for arc centers. Tangency between arcs where it looked like it was intended.

There are so many things to learn about FreeCAD... In the few things I have pushed into my brain, I've now forgotten when my wife's birthday is.

Construction lines: What a great concept. I will study...

I had expectations that when you fix a point on a target and when you create a tangent constraint, the 2 objects would be joined. I believe that to be true with fixing a point, but can see how that doesn't apply to tangent constraints. The 2 unconnected points in my sketch were tangent constraints originally, but I believe I eventually fixed the points on the arcs. ???

And again, I expected that having a fully constrained sketch would mean I could pad (which I did) without having to validate the sketch (which I didn't, and had errors).

I've now forgotten when my birthday is.

Now going back to the scale and pad issue. Your previous post was way above my head. But I suspect the reference is to scale and pad. Not sure how this fixes it though. This will most likely will cause me to forget my anniversary.

Thanks kisolre!

[chrisb]

Tangents come in 3 flavors.
- line-line, as known from school geometry where two lines just touch, e.g. from an arc and a line
- point-line with the additional condition that the endpoint lies on the other line
- point-point with the additional condition that the endpoints are made coincident.

If you want the latter use the latter and don't try to achieve it by using other constraints.

Fully constrained has nothing to do with paddable. It means (roughly) that nothing can be moved. Paddable means you have a closed polyline where all points are connected. You can have one such inner polyline which must not cross the outer.

[kisolre]

Now going back to the scale and pad issue. Your previous post was way above my head. But I suspect the reference is to scale and pad.

With that file what would you like to offset? To make something like an indent in the face? What is the final goal? looks like a fidget spinner...

[dave_w]

Tangents come in 3 flavors.
- line-line, as known from school geometry where two lines just touch, e.g. from an arc and a line
- point-line with the additional condition that the endpoint lies on the other line
- point-point with the additional condition that the endpoints are made coincident.

If you want the latter use the latter and don't try to achieve it by using other constraints.

Fully constrained has nothing to do with paddable. It means (roughly) that nothing can be moved. Paddable means you have a closed polyline where all points are connected. You can have one such inner polyline which must not cross the outer.

Thanks Chris. Makes sense.

[dave_w]

With that file what would you like to offset? To make something like an indent in the face? What is the final goal? looks like a fidget spinner...

Hey, great idea! Anyone have a fidget spinner design?

As I'm learning more and more about the enormous capabilities and complexities of FreeCAD, I'm looking ahead to the final goal of this project. I have an antique lamp that has a bracket that is somewhat shaped like that 3 lobed pattern. The bracket is made from pot metal and is broken. It's not possible to either repair it (I've tried) or replace it. The lamp is so old that I may not be able to remove the old bracket without destroying the lamp. So I'm thinking of making a slightly larger replica which I can pocket to the size of the original and just slip the new part over top of the older, broken part.

Long story to say that I would like to pad that 3 lobed shape to about 7mm then pocket it by about 4mm to the scale which is the size of the original.

Thanks!

Dave

[dave_w]

Forgot to say: You guys are AWESOME! I can't express my gratitude enough!

[kisolre]

I think you should then first design the part that you already have and then decide how to enlarge it. 3D offset mentioned up can help.

[dave_w]

I think you should then first design the part that you already have and then decide how to enlarge it. 3D offset mentioned up can help.

Thanks kisolre. I believe that's what I'm trying to do. Once I figure out how to do that, I'll start from scratch and design my final part.

This is an enormous learning process for me, so I don't mind going through the process many times.

Experience is recognizing you've made the same mistake before. And making mistakes is a valuable tool to learning and gaining experience.

Dave