Measure Surface Flatness

Description

This Step is used to measure the flatness of a specified surface region.

Workflow

The process of configuring this Step is shown below.

measure surface flatness

  1. Configure the input. Connect the ports manually or select the input(s) under Input in the parameter configuration panel.

  2. Determine whether to use feature region.

  3. Set other parameters.

  4. Select the desired output(s) under Output. For an expandable output item, click ▶ and configure the Min and Max values of the acceptable range.

  5. Run the Step and view output.

Parameter Description

Use Feature Region

Feature region defines the processing area to facilitate fitting the optimal plane. Once this parameter is selected, only data within or outside the feature region will be processed.

Default setting: Unselected

Instruction: Please set the parameter according to the actual requirement.

Feature Region Mode

Once Use Feature Region is selected, this parameter is used to set the mode of the feature region, i.e., to choose whether to use the data within the feature region to fit the plane and calculate the flatness, or to use the data outside the feature region to fit the plane and calculate the flatness.

Options: Include data in Region, Exclude data in Region

Default setting: Include data in Region

Instruction: To use the data within the feature region to fit the plane and calculate flatness, select Include data in Region; otherwise, select Exclude data in Region.

For other parameter settings of the feature region, please refer to Set the Feature Region.
Global Flatness Mode

This parameter determines which points on the surface are used to calculate global flatness.

Options: All points, Single average point

All points:

When no feature region is set, all data points on the surface will be used to fit the global plane and calculate flatness.

  • When a feature region is set, the global plane is fitted and flatness is calculated according to the feature region.

    • Single average point: Use the average of data points inside or outside the feature region(s) to fit the global plane and calculate the flatness.

      This option is only available when at least three feature regions are set, or else the Step will fail.
Data Filtering Mode

This parameter specifies the data filtering method. Filter the data points according to the actual Z values before fitting the plane and calculating flatness.

Options: None, Local percentile, Global percentile

  • None: No data filtering is performed.

  • Local percentile filters data according to the feature region; Global percentile filters global data. In both cases, percentiles must be set to define the range of Z values of data points. Data points outside the range will be filtered out.

    • High Percentile: the percentile corresponding to the upper limit of the Z value of the data point.

    • Low Percentile: the percentile corresponding to the lower limit of the Z value of the data point.

      When no feature region is set, both Local percentile and Global percentile indicate that the global data will be filtered.

Output Description

Select the output item(s) according to the actual measurement requirements. Then, the corresponding data will be output after the Step is run.

If you select an expandable output item, you must expand it by clicking ▶, and then set the Min and Max values to determine the acceptable range. If the output value falls within the acceptable range, the measurement item is judged as passing (OK), or else it is judged as failing (NG).
Output Item Description

Global Min

The minimum distance from the data points involved in global plane fitting to the fitted global plane.
The distance is positive for points above the plane and negative for points below the plane.

Global Max

The maximum distance from the data points involved in global plane fitting to the fitted global plane.
The distance is positive for points above the plane and negative for points below the plane.

Global Flatness

The flatness of the globally fitted plane, which is the difference between Global Max and Global Min.

Global Min Point

The point representing Global Min.

Global Max Point

The point representing Global Max.

Global Average Point

The average point of all data points involved in global plane fitting.

Global Median Point

The median point of all data points involved in global plane fitting.

Global Plane

The fitted global plane.

Local Min

The minimum distance from the data points involved in local plane fitting to the fitted local plane.
The distance is positive for points above the plane and negative for points below the plane. The number of output Local Min matches that of fitted local planes.

Local Max

The maximum distance from the data points involved in local plane fitting to the locally fitted plane.
The distance is positive for points above the plane and negative for points below the plane. The number of output Local Max matches that of fitted local planes.

Local Flatness

The flatness of each fitted local plane, which is the difference between Local Max and Local Min.

Local Min Points

The points representing Local Min.

Local Max Points

The points representing Local Max.

Local Average Points

The average point of data points involved in the fitting of each local plane.

Local Median Points

The median point of data points involved in the fitting of each local plane.

Local Planes

Fitted local planes.

Troubleshooting

Invalid Type

No. Error Possible Causes Solution

1

Invalid data filtering mode

The data filtering mode is not selected properly.

Adjust Data Filtering Mode.

Invalid Parameter

No. Error Possible Causes Solution

1

Improper setting of the percentile for data filtering

The value of Low Percentile is greater than that of High Percentile, or either of them is not within [0, 1].

Reset the percentile to ensure that the percentile is within [0, 1] and that the value of Low Percentile is lower than that of High Percentile.

2

Failed to fit the global plane

  • The number of points in the feature region is less than 3 and Global Flatness Mode is set to Single average point.

  • The number of points in the feature region is less than 3 and Global Flatness Mode is set to All points.

  • Adjust or add feature regions to ensure that the number of points in the feature region is equal to or greater than 3.

  • Adjust the feature region to ensure that the number of points in the feature region is greater than 3.

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