A Heidenhain 430 can calculate a circle center from three probed points even when the available software cycle expects four points. Build a parameter program that calculates the three probe locations, captures each measured coordinate pair, and passes the resulting six values to the controller's three-point circle-calculation Q function.
Three-point measurement strategy
Place the three nominal probe locations 120 degrees apart. From an estimated center, calculate each target position with sine and cosine: X(i) = X(est) + R(approach) × cos(A(i)) and Y(i) = Y(est) + R(approach) × sin(A(i)), where A(i) identifies each probe angle. The evidence does not specify whether the feature is an internal or external circle, so select the approach direction and clearance for the actual geometry.
Three distinct points define a circle only when they are not collinear. A 120-degree distribution provides broad angular separation and avoids concentrating measurement error in one region of the circumference.
Capture the probe results
- Calculate the X and Y approach position for each of the three angles.
- Use a touch-probe cycle that supports angular probing. The available evidence does not identify the cycle number, so verify the correct cycle in the Heidenhain 430 manual.
- After every probe operation, copy the measured point coordinates into dedicated Q parameters. Do not allow the next probe operation to overwrite an earlier result.
- Arrange the six stored values as three X/Y coordinate pairs in the order required by the circle-calculation function.
Run the Q circle calculation
The Q-function circle calculation accepts either three or four points. For a three-point calculation, specify the first input parameter; the function automatically consumes that parameter and the following five parameters. The four-point form similarly consumes the first parameter and the following seven. Confirm the required coordinate order in the control manual before execution because the evidence establishes the contiguous parameter count but does not provide the function identifier or its formal argument layout.
| Calculation | Input storage | Result |
|---|---|---|
| Three points | First Q parameter plus the next five | Center X, center Y, and diameter in three parameters |
| Four points | First Q parameter plus the next seven | Center X, center Y, and diameter in three parameters |
Verify the calculated circle
Inspect the three result parameters containing center X, center Y, and diameter. Check that the diameter is plausible for the feature and that the calculated center lies within the expected workpiece region. Then compare the radial distance from the calculated center to each captured point; the three distances should agree within the measurement tolerance established for the part. If they do not, review the copied coordinates, parameter order, probe approach directions, and whether each probing result was stored before the next cycle.
FAQ
Can a Heidenhain 430 calculate a circle center from three points?
Yes. Store three measured X/Y point pairs in six consecutive Q parameters, then use the Q-function circle calculation configured for three points.
How many Q parameters does the three-point circle calculation use?
It uses the specified first parameter and the following five parameters, for six input values total. The calculation returns center X, center Y, and diameter in three parameters.
How should the three circle probe points be positioned?
Calculate three target positions with sine and cosine and distribute them 120 degrees apart. Use an angular touch-probe cycle, then preserve each measured coordinate pair before probing the next point.
