PCS Example #8

Plane - Intersect Lines - Bisect Points - Circle

In this exercise we will combine two constructed features to create the secondary datum. These constructed features are derived from two lines intersected and two 2D points bisected. The following example assumes the part is placed on your CMM where the cylinder of the GeoWidget is pointing in the -X direction.

figure 1, Datum target layout	figure 2, Completed PCS

Step 1

Request a -Z plane <b>, if auto-direction is not activated, you will be prompted for the probing direction which you should select as -Z. You will then be prompted to "Measure -Z Plane", (if auto-direction is active "Measure Auto-Dir Plane"). Capture points A-1, A-2, A-3 and A-4 as shown in figure 1.

Step 2

Select Orient <j>. The orient command will create the primary datum on the axis that is most normal to the machine coordinate system. In your PCS Setup Guide, the Z Axis will be signed off.

Step 3

Select Origin <l>. This will establish the Z origin which is determined by the normal direction of the -Z plane.

Step 4

Request a Line feature <m>, You will then be prompted to select the probing direction, enter -X (if auto-direction is not active). The prompt will update to display "Measure -X Line" (or "Measure Auto-Dir Line"). Capture points B-1 and B-2. When the points have been captured, you will be asked which projection plane to use, select XY. A secondary request may be made to determine the pierce axis, select X, see Measured Features→Line for more information.

Step 5

Clear the current mode by pressing the < Esc > key. Request a Line feature <m>, You will then be prompted to select the probing direction, enter +X (if auto-direction is not active). The prompt will update to display "Measure +X Line" (or "Measure Auto-Dir Line"). Capture points C-1 and C-2. When the points have been captured, you will be asked which projection plane to use, select XY.

Step 6

Select the Intersect <d> command. This command will take the two projected lines and solve for the intersect between them. The result will be a 2D XY point.

Step 7

figure 3, Select PCS Base Plane

Select a 2D XY Point <5 + 2>. The selection of a 2D point requires two commands. The first command is activated by pressing the < 5 > key, 2D and 3D point selection, which will then prompt which current base plane you will project into, see figure 3.

After the selection has been completed, Geomet will prompt you to "Measure XY Point". Capture points D-1 and E-1.

Step 8

Select the Bisect <a> command. This command will take the two projected XY points and solve for the bisect between them resulting in a 2D XY point.

Step 9

Select in the report display feature number 7 by left-clicking on it (2D point formed by the intersect command). Right-click your mouse and select from the popup menu, <Recall Feature>. This will recall the feature and create new feature number 11.

Alternatively you can recall a feature by pressing the Recall Feature <h> command from the keyboard. In the control labeled "<- Enter Feature No. to Recall" , enter 7 and press the <Ok> button or the <Enter> key on the keyboard.

Step 10

Select Align <k>. Your ICS will update to include the secondary datum which is derived from the recalled 2D XY point and the previous 2D XY point created from the bisect.

Step 11

Select Circle <z>, if auto-direction is not activated, you will be prompted for the Circle type: ID, OD, IR, or OR, choose ID. Capture the four data points identified as F-ID/4, see figure 1.

Step 12

Select Origin <l>. the Circle, which is 2D, provide two directions when establishing an origin. In our example, the circle can be used for the X and/or the Y direction. The origin command will prompt you whether to use the X and then the Y. For our example you should answer Yes to both requests. Upon completion, you will have established PCS 1, see figure 2.

In this exercise we had combined features to create constructed features which are then used to create part coordinate system components. In part production we will find numerous cases where one or more part coordinate system datums are symmetry lines or points where no features exist.

figure 4, Final Inspection Report

When performing constructions in a ICS, it is important to remember the established projection base planes that are valid. For example, in this exercise it would not have produced acceptable results if we established 2 ZX point, one each on the top and bottom surfaces of the GeoWidget and then performing the bisect. The resulting 2D point would be projected into the alignment of the machine coordinate system and therefore would not represent a valid point feature for the part coordinate system.

Related Procedures:

Download PCS Example #8 (.zip)
Go to PCS Examples: prev 1 2 3 4 5 6 7 8 9 10 11 12 next

Orient, Align, Origin, Plane, Line, Circle, 2D Point