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PART MODELING ASSIGNMENT 6: Lofted Solids

Objective:

The aim of this assignment is to understand the lofting technique and use it to create

some objects. Creating these objects by any other method would take longer and

involve more effort. Therefore lofting comes handy for modeling some non-prismatic

solids. We begin our study by creating a tetrahedron first.

PART I Tetrahedron

Procedure:

1.  Draw an equilateral triangle using the polygon command on the workplane.

Let the circumcentre of the triangle be at the origin and the side length be50mm.

2.  Calculate the vertical height of the 4th point where the other three edges of the

tetrahedron will be connected and create a 3D point taking z equal to the

calculated height.

3.  Loft Command: Next we make use of the loft command to create a solid

from the triangular base to the vertical point we created in the last step.

4.  To verify the newly created edge length: Measure the length of any one of

the newly created edges to check your calculations are right.

Figure 1: Lofted Tetrahedron

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Exercise 6a: Transit ion solid having three different cross sections

The following solid has to be modelled using lofting method. We have a pentagonal

 base to begin with. The diameter of the circumcirlce of the base is 30mm. The second

hexagonal section is at 30mm from the base on the z-axis. The diameter of the

circumcircle of this hexagon is 50mm. At the top we have a circular section at 30mm

from the previous section with diameter 70mm.

Figure 2: The I-DEAS loft command

Figure 3: The lofted tetrahedron

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Hint: We need to create the three sections along a path; it could be a coordinate axis

also. We may need the following command to create these sections.

Sketch on Path Command:

Use this command to designate a path on which a reference plane is created. You can then sketch

wireframe on this plane.

There are several methods (available as MB3 options) for controlling the orientation of the reference plane:

•   Normal to Path keeps the Z axis tangent to your path, and the X axis is determined by a rulethat minimizes spin about the Z axis.

•   Normal to Plane keeps the Y axis parallel to the fixed direction. The software projects thefixed direction onto the section plane.

•   Normal to vector  keeps the Z axis parallel to the selected parallel plane.

•   Revolve about Axis keeps the hinge line always on the section plane, and the section planerevolves about the hinge line. The Y axis is always parallel to the hinge line.

Figure 4: Lofting with multiple sections