Gear Metrology. Requesting help in processing raw XYZ, PLY or STL data from a point cloud files in order to obtain gear geometry in the form of a gear report.

I have measured gears via the optical focus variation method with a confocal microscope, and I have collected point clouds. I can provide the data in either STL, PLY or simple XYZ coordinates (as well as a drawing and possible CAD model). Normally, on a coordinate measuring machine (CMM) the gear report would be created automatically from the collected XYX coordinates via standard gear software. Gear software is not available for the microscope, so I am hoping that this can be done in Matlab. I am now looking for someone who has knowledge or experience in creating a gear report from raw data. I am a basic MATLAB user, but I believe that this should be possible (can anyone advise please?).

[Udit06]

Hi Denis,

MATLAB offers several functions for reading and preprocessing 3D data. To assist community members in providing better support, it would be beneficial if you could share a sample data file along with the expected format of the gear report.

Thanks

[Denis Sexton]

Thank you so much. The files are quite large so I attach a link. Data for MATLAB

Answer 1

[Ayush]

Hi @Denis Sexton,

I understand you want to create a gear report using MATLAB.

As the link for the sample data is not accessible, I am using a sample data which I generated using the following script. This is an example demonstration to use MATLAB for 3D data processing.

% Generate sample gear-like point cloud data
theta = linspace(0, 2*pi, 100); % Angle for full circle
radius = 10; 
tooth_height = 2; % Tooth height
tooth_width = 2; % Tooth width

% Generate points for the gear body
x_body = radius * cos(theta);
y_body = radius * sin(theta);
z_body = zeros(size(x_body));

% Generate points for teeth
num_teeth = 10;

for i = 1:num_teeth
    angle = (i-1) * (2*pi/num_teeth);    
    x_tooth = [0, tooth_width, tooth_width, 0] + radius * cos(angle);
    y_tooth = [0, 0, tooth_height, tooth_height] + radius * sin(angle);
    z_tooth = [0, 0, 0, 0];
    hold on;
    plot3(x_tooth, y_tooth, z_tooth, 'k'); % Plot teeth
end



% Save the points to an XYZ file
xyz_data = [x_body', y_body', z_body'];
writematrix(xyz_data, 'sample_gear.csv’);

Now, using this sample data, you can create the gear report using the pseudo code given below:

% Load the sample data
data = readmatrix('sample_gear.csv');

% Extracting x, y, z coordinates
x = data(:, 1);
y = data(:, 2);
z = data(:, 3);



% Create a point cloud
ptCloud = pointCloud([x, y, z]);



% Visualize the point cloud
figure;
pcshow(ptCloud);
title('Point Cloud of Sample Gear');
xlabel('X'); ylabel('Y'); zlabel('Z');



% example: Try to Fit a plane to find the base of the gear
model = pcfitplane(ptCloud, 0.01); 
fprintf('Plane Model:\n');
disp(model.Parameters); % Displaying plane parameters



% Calculating pitch diameter (example calculation)
pitch_diameter = 2 * (radius + tooth_height);
fprintf('Estimated Pitch Diameter: %.2f\n', pitch_diameter);


% Create a report
reportData = table();
reportData.Parameter = {'Pitch Diameter'; 'Number of Teeth'};
reportData.Value = {pitch_diameter; num_teeth};

% Save the report to CSV
writetable(reportData, 'gear_report.csv');

Here are the required documentation links which you can access to get more information:

1. “pcfitplane” function: https://www.mathworks.com/help/vision/ref/pcfitplane.html
2. Point cloud: https://www.mathworks.com/help/vision/ref/pointcloud.html
3. “pcShow” function: https://www.mathworks.com/help/vision/ref/pcshow.html

Hope this helps!

[Denis Sexton]

Hi Ayush, many thanks for your reply. I will have a play with this next week......cheers