Due to the fact that this is the first 2010 article, I wanted to do something useful to most everyone, especially newbies. There is not much new in the way of Projected Geometry and Cut Edges in 2010.  I did run across some new issues however.

I spend some of my time redesigning parts and especially tooling so that the design intent can be achieved, on more limited machinery than the original design permitted.  In this case I was working with an indexable endmill using square inserts, greater pitches, and limited by a 3-Axis mill.  The next few articles will be pulled from what I learned on this particular part.

What I was doing

During the redesign, I decided to approach it from an axis orthogonal view, using trig to offset sketch planes.  In this case the key factors are the Flute plane, and the Insert Pocket plane.  The angular relationship is variable to the Z-Axis, both Radially, and Axially.

The offset sketch planes would receive the projected geometry to calculate an edge, and then I would hinge the respective Flute and Pocket planes at those projected edges (the axial relationship).  Then more sketching and cut extrusions.

The Problem

The problem lies with Projecting Geometry onto a sketch that lies on plane that varies in it’s orthogonal relationship to the plane the geometry was projected from.  It’s fine until you change the angular relationshipYou won’t notice it until something is dependent on that projection.  THEN it becomes a problem.  If you don’t vary the angular relationship until after building off that projected edge, and it’s continued dependencies, it becomes a disaster.  The whole thing lights up like a Christmas Tree.

Oddly enough, when you return the plane to it’s original angle, everything goes back together.

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Above: The flute plane is Orthogonal and aligned to the Z-Axis.  No problems in the browser.

 

Now, Let’s change the Axial relationship to 5°.

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Above: Axial 5° – Notice the pink disconnected geometry.  The detail shows how the constrained intersection has come loose from the pink geometry as well.

I tried everything.  Cut edges work great, but I could not always generate the relationships I needed.

The Solution

  • Cut Edges
  • Surfaces
  • Projecting Sketch Geometry
  • Work Features

The solution was found while completely STARTING OVER.  Since my original Trig equations were very long, and took forever to proof, I decided to do half my planning radially. You can also bet I didn’t go far without testing that angle.  I worked farther without the Solid using the list above.

You can project anything EXCEPT Solid Features, and cut edges related to Solid Features.

It appears as though the Projected geometry in this scenario (Axial Relation) is stored, but cannot update properly.  The geometrical relationship is often held, and then rotated with the plane.  Here is a better example on a test part.

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Notice the highlighted sketch.  It is cut 8° off of the Z-Axis.  Sketch 7 was created on the plane, and Cut Edges applied.  Then Sketch 8 Created on the same plane, and projected the Sketch 7 Cut edges, then constrained the 2 dimensioned sketch geometries to those projections.

Now we can turn the plane to 0°.

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The Cut Edges are fine, but once again the projections from those edges are blown.  See how it mimics what was created at 8°.

Cut Edges – Work fantastic especially when a work surface can be the object being cut

Surfaces – Flawless in every test I did, especially when coupled with Work Features

Projecting Sketch Geometry – Worked very well in this scenario

Work Features – The Kings of stable relationships in the model

My rebuild included interpolating to a surface, intersecting planes and Axis with the surface, and projecting all of the above.

It was hard to decipher, but the end result was NEVER, and I mean NEVER, constrain or reference Project Geometry from a Solid Object, or anything related to the Solid Object when the plane you are sketching on will change its angular relationship to the Projected Object.

I’m sure Flayler and a few others will actually have some aged documentation of this fact.  Please post your comments and thoughts.