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.

How to open the Point-Cloud dialog

To open the Point-Cloud dialog:

1.Double-click a Point-Cloud FB in the graphics-area

See How to open a dialog

The Point-Cloud dialog is now open.

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)