3D Scanning 3DT2
Scanning with st600
Our Lab is equiped with a Scantech st600 scanner. This scanner uses a laser measuring distance to record a 3d point in space (where laser hits the object being scanned). Two modes of scanning are possible: Cylindrical and Relief. Cylindrical scans Hold the Laser head in Y-axis, and spins the W-axis. The laser starts at a X-Axis position and records points while spinning the W-Axis, the moves up in X a specified amount. Rinse and Repeat. This mode is only appropriate for object with a definable central axis of rotation - things that are cylindrical or spherical in nature. Eccentric rotation of objects will result in distortion because the object is "moving" in relation to the laser. Distortions can be cool". Scanning something "wrong" is not bad if your aim is not just accuracy.
For Relief scans we mount the aluminum Jig to the W axis. In this case we don't want to rotate W axis at all, the object is stationary, and the Laser moving in X&Y to collect a grid of points. The scanner outputs Scantech propritary file formats .SRF for relief scans and .CYL for cylindrical scans. We need additional Scantech software to view these files and save out an .STL file - common Mesh file format. It can also be set to output a and ASC ascii file with the point coordinates. We use that. I have written a Rhino 4 command which on the scanner PC which translates teh point data to a mesh surface in Rhino. Use that. The command is called View_Scan.
A quick overview of steps
Please Read the manual printed in color and hanging above the scanner before operating. Consult the manual for more info on each step listed here.
Turn on the Machine - Turn red knob + hit green button.
Remove any platforms or objects from the scanner!
Start st600 software- machine will Initialize axes.
Check the machine speed and set to a safe number
For a cylindrical scan
Find The center of rotation - place the calibration sphere (red box below scanner- be gentle) on W-Axis holder and jog machine to approximate center of sphere.
Click System/Find Axis of Rotation - the machine will scan the sphere and calculate the center of rotation and set the Y axis to the position.
Place platform and object on W axis.
Slowly move Z-axis until highest point on the model model is within starting range (10mm)- see manual for details.
Go to bottom X axis and click enter.
Move to top of scan and click enter.
Click the Run Perimeter button to check the perimeter is set.
Set the scan to Cylindrical Mode.
File/ save - Create file name, choose location. and most importantly set file output type to ASC
Change the speed for scan
Set the X-axis step and points per revolution
For a relief scan - Same as above except:
Use the Aluminum platform.
Use the laser range reading to square the platform to the laser -- or not, be creative! See manual for details.
Make sure your speed is slow before rotating the platform. We don't want to wack the Laser module!
Set the left bottom corner point.
Set the top right corner point.
Run perimeter to check.
Set Scan to Relief Mode.
When you are finished - Close St600 application and turn off machine - Red Knob on side. Please don't leave the laser running!
Using cage and cage edit, I created control points to distort the apple in different ways. I made a cage that had 4 points in each axis. It also asked me to specify degrees, and suggested '3 degrees', but I'm not sure what that means. After dragging the control points, I used bounding box to find the dimensions of the apple. Its about 55x61x60 mm.
For this manipulation of the egg carton I used reduce mesh and twist. The original mesh had over 260,000 polygons, but I reduced it to 4600. Then I twisted the form 90 degrees around a fairly central axis, and a second time at 270 degrees around an axis that was farther to the left. The dimensions are about 176x169x130 mm.