Updating Alignment Points in BuildIT Projector
Overview
These retro-target positions are often on a tool that warp after being used for a long time, due to various manufacturing procedures. The position of the retro-target may shift and so it may be necessary to update these positions to regain the projection accuracy initially achieved. In other cases, target positions need to be moved elsewhere due to a tool redesign.
Measuring New Target Positions
Depending on whether you are updating for slight warping, or for a redesign, the procedure differs slightly:
Slight Warping
- Load the part containing the datums to which target points are aligned.
- Measure the position of each retro-target.
- One way is to measure the pin hole and to then offset a hole’s endpoint by the retro-target’s offset of 0.5in.
- An easier way is to use a 0.5in pin nest, which will place your hard probe right where the center of the retro-target will be.
- Measure the datums of the part.
- Align your device to the datums of the part. This will align new targets to the datums of the part.
- Clean up your file:
- Save a separate BuildIT file with just the updated alignment point positions.
For example: new_target_positions.buildit - Delete every except the new alignment points.
- Make sure the alignment point names are the same as the original.
For example: Point1, Point2, ... Point 8.
- Save a separate BuildIT file with just the updated alignment point positions.
Redesign
In this scenario, the new and old set of alignment points share at least 3 point positions. These points that do not move are what will allow you to align the new set of point to the old set of points.
- Load the old set of alignment points.
- Measure the position of each new retro-target position.
- Measure the position of the retro-targets that are not moving. There should be at least 3 points.
- Align your device to the by best-fitting measurements to the old positions. This will align the new targets to the old targets, and by extension, the projected part itself.
- Clean up your file. (same as above)
Update Projection Plan
You'll need: A separate BuildIT file with just the updated alignment point positions. Make sure the alignment point names are the same as the original.
For example: In a file named new_target_positions.buildit, have it contain Point1, Point2, ... Point 8 which have been recently measured by the CMM, and aligned with respect to the previous point locations.
- For the BuildIT file you wish to update, export the projection plan in a BuildIT format.
- Delete the projection plan
- Delete alignment points in the model using the Manager tab. You may use the Search bar to easily find the alignment points.
For example: Search for all objects that contain the word "Point", select Point 1 to Point 8 and then press delete:
- Import the new point positions.
Example: Go to File > Import Model, and then select new_target_positions.buildit and click Import. - Import the Projection XML exported in step 2. It will use the new point positions as the coordinates for the alignment points.