MechDesigner Reference & User Interface > Dialogs > Dialog: Function-Block: Point-Cloud

Point-Cloud FB

Do two steps in the Point-Cloud dialog:

STEP 1: Import-data (TXT file-type).

For example, import the X,Y coordinates of a cam-profile which you have measured with a Coordinate Measurement Machine (CMM).

STEP 2: Fit-a-Curve to the data

We fit for you a smooth Curve to the data that you import, with a Fourier Harmonic-Series.

You specify the accuracy you want, and edit the number of harmonics until the error between the curve we create and the original data is less than the accuracy.

Point-Cloud dialog

STEP 1: Import Data

STEP 2: Fit Curve to Data

STEP 1: Import Data

Do A, B, and C.

Import and Browse buttons

Example File Format

A. Browse...

Click the Browse... button to find a data-file.

The data-file must by an ASCII, or TXT file-type.

The file-name you select shows in the Data-File (read-only) box.

A preview of the data in the file is in the box below.

B. Edit File-Format

Any Header in the data-file is not imported.

The data should be rows of data-points - see Data-Points below

You can remove extra data from columns/rows with the Edit File-Format box. See File Formats below.

C: Import button

When the File Format is correct (see below), click the Import button to import the Point-Cloud data-file.

We plot for you the Point-Cloud on the Part to which the Point-Cloud FB is a child.

The Point-Cloud plot is a continuous line in the graphics-area.

Data-Points

The File Format must include at least these terms:

•(x) (y) : if each data-point is an X and Y coordinate

•(Radius) (Angle) : if each data-point is a Radius and Angle coordinate.

Characters that are ignored in the data-file:

•Header lines, when entered as text.

•ASCII characters that are NOT : . , -, 0–9, in all lines.

Optional: Data Offset and Scale option

Options:

x , y

When you add a Point-Cloud, you select a Part. The Part has an origin - its start-Point - where its XY coordinates are (0,0)

If the origin of the Point-Cloud has an offset relative to the origin of the Part, you can remove the offset. Enter -X, -Y, the negative of the offset.

Or, to offset the Point-Cloud, by (X,Y), enter (X,Y) values.

File Rotary Units ; File Linear Units

Select the units that match those of the original Point-Cloud data-file.

File Formats:

Pre-Select a File Format

To help you with the formatting, you can use the Pre-Select a File Format from the drop-down list-box.

MD-Dialog-PointCloud-PreselectFormat

When any of these formats do not represent the format of the data in your data-file, then edit the format in the Edit File Format box directly.

Example: Data-Files and File-Formats and Enter File Format.

Example 1: Data-File:

Example data-file to import as a Point-Cloud

Enter File Format: () () (x) (y)

Why?

Line 1	Is Not imported - text only (A, B, C, ... Z)
Line 2	Is Not imported - text only (A, B, C, ... Z)
Line 3: Column 1 and Column 2:	Are Not imported because of () () in the File Format () () (x) (y) removes these two Columns
Line 3: Column 3 and Column 4	Are Imported because the (x) (y) in the File Format () () (x) (y) identify that these Columns as x, y data
Lines 4, 5, 6, ...	Equal to Line 3

Example 2: Data-File

Data Format: N100 G00 X10 Y25 Z27

Enter File Format: () () (x) (y) ()

Why?

N100 G00 X10 Y25 Z27	Letters - not imported (A, B, C, ... Z)
N100 G00 X10 Y25 Z27	Column 1, Column 2, and Column 5 - not imported - the () in the File Format () () (x) (y) ()
10 25	Imported - the (X) and (Y) in the File Format () () (x) (y) ()

Feedback Messages:

STEP 2: Fit Curve to Data

When you import Point-Cloud data, the chart shows the Points, the Curve, Nothing, or Points + Curve

In the chart below, the Continuous Curve does not follow the Point-Cloud data - it is planned and to see the different charts ONLY.

The two charts show as one chart after you successfully Fit the Continuous Curve to the Point-Cloud data when you increase the number of Harmonics.

Point-Cloud dialog > Fit Curve to Data tab

Parameters

Original Data Accuracy

This is a judgment you must make. Start with 0.1 then reduce it to approximately 0.001 - but see Original Data Accuracy for more thoughts.

Auto-Fit check-box and Fit Curve button

Usually, click the Auto-Fit button to make it active - see options

Increase the # Harmonics

Edit the # Harmonics

The difference between the Continuous-Curve and the Imported Data decreases as you increase the # Harmonic.

Fit-Quality =0 >> 1

When Fit Quality Traffic Light is Green, ...

When the number in the Fit-Quality Number box is near to, or equal to, one(1), ...

... STOP - do not increase the number of Harmonics.

Display Options

Click one of the four radio-buttons

○Show Nothing

○Points only

○Points and Curve

○Curve Only

The view of the Continuous-Curve and the Point-Cloud in the graphics-area match the P, V, or A button.

Steps to do in Fit Curve

A.Edit the # Harmonics

☑Auto-Fit Check-box

The Curve updates immediately when you edit the number of harmonics: # Harmonics

❑Auto-Fit check-box is clear.

The Curve only updates when you click Fit Curve

B.Repeat A

Increase # Harmonics until the Fit-Quality =~1, and the Traffic-Light is Green or Orange.

We recommend the maximum # Harmonics < number of Data-Points in the Point-Cloud / 3.

Velocity and Acceleration Graphs and Filter Width

We plot the Point-Cloud and the Curve as a Position graph. If you want to plot them as Velocity or Acceleration (), then click the V or A icon.

Even if the Fit Quality = 1, you can continue to increase # Harmonics to improve the fit of the Velocity and/or Acceleration Curve to the Point-Cloud.

However, we recommend the Maximum # Harmonics = # Points in the Point-Cloud/3.

If the plot of the Velocity or Acceleration data is noisy you can smooth the noise (remove the noise) with the Filter-Width. This may help you identify the original Motion-Law.

Original Data Accuracy

Thoughts:

•Consider an Original Data Accuracy of 0.1, then reduce it to approximately 0.001.

•Do not enter a value that is more accurate than the original accuracy of the data. For example, if the data is to 2 d.p., then 0.05 OK, and 0.001 is a minimum sensible value. However, experiment, as you may find that more accuracy gives you better results.

•Is the skill of the person that measured the Cam-Profile a factor?

•Is the Cam-Profile clean? Is the Cam-Profile worn? Is the Cam-Profile damaged?

Machine Measurement Accuracy Approximations: per 100mm Diameter of Cam Diameter:

•Temperature-Controlled (18-22ºC) CMM approximately 0.2 - 2µm

•Non-temperature-controlled CMM approximately 2 - 10µm (~h4 for a 100mm shaft)

•Portable CMM approximately 5 - 20µm (~h5-h6 for a 100mm shaft)

•Test Rigs are variable, but you should aim for approximately 20 - 100µm (~h8-h9 for a 100mm shaft)