Example Problems: PRO-E 2D Modeler: Remote Positioner

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*Example Problems*	PRO-E Modeler: CHAPTER 6: TUTORIAL--REMOTE POSITIONER
Home : Example Problems : Pro-E 2D - Modeler - Remote Positioner

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CREATING THE ASSEMBLY DRAWING

The first few steps of 1) setting the display, 2) defining DRF's and feature datums, and 3) defining joints has been completed for you so that we may continue with the new modeling elements - open loop design specifications. The assembly should appear as in Figure 6-1.

Figure 6-1. Remote positioner with DRF's, datums, and joints defined.

With the DRF's, feature datums, and joints defined, design specifications can now be applied to the assembly model.

DEFINING A PARALLELISM SPECIFICATION

Design specifications allow limits to be placed on assembly dimension variations to ensure the assembly functions properly. The parallelism of PART 5 with respect to PART 1 is critical to the remote positioner's function. The parallelism specification constrains two parts to be parallel. PART 1 of the remote positioner must remain parallel to PART 5 to within 0.100 inch to assure accuracy of the parallelogram linkage. The .100 inch tolerance refers to the width of a tolerance zone parallel to a datum line on PART 1 and in which a specified datum line on PART 5 must be contained. A tolerance "bandwidth" such as this is also used for the relative orientation specification.

Creating a parallelism specification.

Select Specification from the TOL-2D main menu.
Select Create from the SPEC menu.
Select Parallelism from the SPEC TYPE menu.
Pick the APNT where the DRF for PART 1 is located to be the first reference location.
Pick the APNT at the right tip of PART 5 to be the second reference location.
Pick the top surface of PART 1 to be the surface that the first point is on.
Pick PART 1 as the part associated with the specification.
Select the DRF for PART 1 to define the specification.
Pick PART 5 as the second part associated with the specification.
Enter 22 as the length over which the tolerance zone applies (in inches).
Select the feature datum and the DRF associated with PART 5 to define the specification.
Enter .1 as the maximum tolerance.
Enter -.1 as the minimum tolerance.

All tolerances, characteristic lengths, bandwidths, etc. must be in the same units (inches or millimeters).

DEFINING A POSITION SPECIFICATION

The position of the tip of PART 5 with respect to the Ground is also critical to the remote positioner's function. The tip of PART 5 must be at its nominal position within a circular tolerance zone with a diameter of 0.2 inches.

Creating a position specification.

Select Specification from the TOL-2D main menu.
Select Create from the SPEC menu.
Select Position from the SPEC TYPE menu.
Pick the APNT at the Ground DRF as the first reference location.
Pick the APNT at the right tip of PART 5 as the point of interest that the variation will be measured at.
Pick Ground as the first part associated with the specification.
Select the Ground DRF to define the specification.
Pick PART 5 as the second part associated with the specification.
Select the feature datum and DRF associated with PART 5 to define the specification.
Enter .1 as the maximum tolerance.
Enter -.1 as the minimum tolerance.

DEFINING LOOPS WITH THE AUTOLOOP GENERATOR

Four loops are required for analysis of the remote positioner - two open loops for the two open-loop specifications, and two closed loops. All four loops can be created with the Autoloop command for creating loops.

Creating loops with the Autoloop command

Select Loops from the TOL-2D main menu.
Select Create from the LOOP menu.
Select Autoloop from the LOOP TYPE menu.

The loops will automatically be generated and drawn in place on the assembly model, as shown in Figure 6-2.

Figure 6-2. Remote positioner with all loops defined.

MODIFYING LOOPS

Two or more unique vectors in a vector loop that go between the same points on an assembly should usually be equivalenced to give them identical variations. Equivalent vectors occur in three different locations in the vector loops that were generated for the remote positioner.

Between the DRF of PART 5 and revolute joint between PART 2 and PART 5. Between the DRF of PART 5 and feature datum on PART 5.
Between the feature datum on PART 5 and the parallelism specification endpoint on PART 5. Between the feature datum on PART 5 and the position specification endpoint on PART 5.
Between the DRF of PART 3 and revolute joint between PART 2 and PART 4. Between the DRF of PART 3 and feature datum on PART 3 (on top of the revolute joint).

Since two equivalent vectors occur at the same location on an assembly model, the Query Sel option of the GET SELECT window should be used to select the hidden vectors. After selecting Query Sel and picking the area of the hidden geometry on the assembly model, the user can toggle through the hidden geometries at the specified location with the Next and Previous commands in the CONFIRM window. Each feature has a feature number that is displayed in the message window. The user can ensure selection of different vectors at the same location for vector equivalencing by selecting vectors that have different feature numbers.

Equivalencing Vectors

Select LOOPS from the TOL-2D main menu.
Select Modify from the LOOP menu.
Select Equiv Vect from the VECT DESC menu.

The message window will prompt for a dimension vector and an equivalent dimension vector. Use the Query Sel or Sel By Menu command to select the first set of two vectors. The two vectors will then be equivalenced.

Select Equiv Vect from the VECT DESC menu.

Again use Query Sel or Sel By Menu to select the second set of two vectors. The two vectors will then be equivalenced.

Select Equiv Vect from the VECT DESC menu.

Use Query Sel or Sel By Menu to select the third set of two vectors. The two vectors will be equivalenced.

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