Hydraulic Excavator Source Part 10/28/2018

The completed source part model is displayed in four images below.  Notice that edges of the model have sharp corners that should be rounded.  The reason?  Best practice for associative copy in Nx Ideas, is to avoid 3D fillets in source parts and put them in target parts (copies).  All rounded-corner geometry in this model are created within extruded 2D cross sections.

This image shows the current history tree of the source part.

This is a more detailed view of the tree with notes and highlighted steps.  I photoshoped together images and notes to convey information about the model process.

There are three branches to this tree.  Starting from lower left, the first branch creates a solid model of the upper structure and cab.  The second branch, starting at the lowest left tree step shown, creates another solid volume of material within 3.5mm of exterior surfaces, except the saddle shape surface of the counterweight, where it is about 30mm thick.  Until the panels (except side rails and counterweight) become sheet metal parts, this will be panel thickness.  There are also rectangular-strips and rounded-quadrilateral shaped features sticking out of the model to shape gaps between panels, frame part outlines and cab windows.  Where the branches converge, branch two cuts out branch one.  The next nine steps complete frame side rail parts and the last step cuts a characteristic Deere-Hitachi smiley face on the saddle surface.

The next, four images are an assembly of the cab and upper structure.  This assembly is made from target-part copies of source-part surfaces.  Target parts have 3D fillets to indicate their appearance after they become sheet-metal parts.  The actual sheet metal parts will have material thickness, and fillets, louvres, with other stamped features.  Also note, that frame side-rail parts are missing from this assembly.  They are exterior features, and from the source part, but target copies of side-rail geometry are in the frame assembly.

The rest of the 150-something screen-shot images on this page show history tree steps to create the source part.  On the left side of (most) images, the history tree is displayed with highlighted step(s).  On the right side, results of CAD operation or cross-sectional sketch from operation may be shown.  Some are just better detail images of previous cross-section sketches.

This one sketch (left) creates many excavator features, because the sketch curves become reference curves, as shown.  Reference curves can be re-used in Nx Ideas.

The sketch on the right is used to make all tool box features currently in the source part.  A real 250D backhoe excavator has a headlight assembly in the toolbox lid.  I am not sure if that feature could be made entirely with sheet metal or if the source part model will also change.  I would rather not add to the complexity of this model, where possible.

This is the last step to create source part solid material.

History branch steps in the following images create a model of material removed from solid upper structure to make body panels.  The final thickness of panels (in assembly) will be determined by sheet metal material properties and shelling operations, but gaps between panels are controlled in the source part only.

The next four images display an effort not to cut out material in desired location of frame side rails.  (rectangular sections in the sketch below)  This allows complete side rail parts to be modeled in subsequent steps.

One issue I have with bushy history trees is that reference curves, coordinate systems and reference geometry from one branch are not available in separate branches.  For example, the first excavator profile sketch (42nd images up) is created within the first branch of the history tree and cannot be used in the (cutter part) branch of the tree.  So, I had to make another sketch of the excavator to re-create profile shaped geometry in this branch, as shown.  After tree branches join together into a trunk, everything described above becomes available.

One mistake I made, was sketching both profile curve sets in the same plane.  They should be in parallel planes with (perhaps 50mm) space in-between.   That way, they are not on top of each other in the updated part, and would be easier to distinguish them.  This can be fixed next time.

Last step to create the cutter part.

All the images below, except last two, illustrate steps to creating frame side rails.

Detail views of side rail cross-section.

Side rail part surfaces are completed below.

The last step creates the Deere-Hitachi smile on the counterweight.