Page updated: 2002/06/12
'StCAD6 was created on 2002/03/30.
patch61.zip supersedes all patch6*.zip.
'StCAD' allows users to create and manipulate assemblies, which are collections of 3D parts. The parts are 3D solids, which can be connected by joints, constraints, contacts, actuators, springs, dampers or forces. The parts and connections define the structure or mechanism that the assembly is meant to represent. Animation is possible, if the user can provide time series of position and orientation data for the parts.
Users can also obtain output data in the form of plots and tables. XY plots can be zoomed and set to equal scales. Data series available include linear and angular displacements, velocities, accelerations and other user generated data.
'StCAD' has been used to create a freeware called 'freeCAD' which is a
3D CAD with Motion Simulation. The parcel 'StMbD' has been included to provide
a functional demonstration, but its source code is hidden. For more information
Users need to provide the domain to simulate the behavior of the system.
Simulation progress can be animated and stopped any time. After simulation,
the computed solution can be used for animation or frame by frame analysis.
Full 3D pan, zoom, tilt and rotate is available during simulation and animation.
Users can also obtain output data in the form of plots and tables. XY plots
can be zoomed and set to equal scales. Individual parts can be saved into
files and reinserted into any assembly repeatedly. Assemblies can be saved
in binary or tab delimited text format with textual notes and simulation
data for later reload. The text format allows pre and post processing of
assembly and simulation data by other programs. 'StCAD' runs on Windows,
Macintosh PPC, Linux PC and other Unix's. Assembly data are unchanged across
To try 'StCAD' in VisualWorks 5i.4:
Create a directory, say, C:\vw5i4nc\stcad6 for the downloads.
Download stcad6.zip (2.11MB, 2167KB, 2218630 bytes).
Download patch61.zip (3.68KB, 3776 bytes).
The files should be good on all platforms supported by VisualWorks.
Unzip stcad6.zip into the same directory.
Unzip patch6*.zip into the same directory. Let it overwrite other files.
Save a new image in the directory and launch it from you operating system.
Load parcel C:\vw5i4nc\stcad6\stcadstart6.pcl.
Click 'Yes to All' for all prompts.
Launch 'freeCAD' with doit 'StCAD.Editor open', if it is not already launched.
Inside 'freeCAD', click Explain/Quick Test/ and Explain/Quick Start/, to find instructions and tutorials.
Quick test 'freeCAD':
Make sure that the example assemblies (*.asm) are in the directory of the image.
Click File/Open/Assembly/ to get list of example assemblies.
Choose one, say, fourbar.asm
Click View/Tilt Rotate/ to center the model. Drag the handles to tilt and rotate the 3D assembly.
Click Simulation/Animation/ to get the animation dialog. Click Play to start animation.
You can click any View menu item and drag handles, even during animation.
Please report any problems to
Click Explain/Quick Start/ to learn how to build a model from scratch. Together, the tutorials demonstrate the available features in 'freeCAD'.
Inside 'freeCAD', documentation are collected in a series of menu items labeled 'Explain'. Click on them anytime. Click Explain/Quick Start/ for a list of examples on projectiles, circular motion, relative motion, pendulums, spring-masses, four bar linkages, piston crank, gyro, cam follower.
The motion simulation theory is in the journal paper:
Koh, A-S., and Park, J-P. "Object Oriented Dynamics Simulator," Computational Mechanics, Jun 1994, 14(3) 277–287.
More Example Assemblies
Right clicking on some mice does not bring up the correct menu. Try right clicking while holding the ctrl key down.
On Windows 98, the help dialog for motion and force-torque dialogs will not close when the X button is clicked. Close with ESC key.
On machines with low memory, desktop icons may become white when 'freeCAD' exits. Reboot to recover. Internet Explorer 5.5 seems to be the cause. Upgrade to Internet Explorer 6.
If resizing the window is very slow to repaint, disable 'Show window contents while dragging' found in Start/Settings/Control Panel/Display/Effects.
'Out of Memory' error at startup. The probable cause is having too many fonts. Execute with the following command to start freeCAD
./visual -h10M visualnc.im
Please report problems to
To pose a question, submit it to the newsgroup comp.lang.smalltalk. Prefix the question with [StCAD] to distinguish it from other questions in the newsgroup.
Finally, you can email:
For more information, please contact A-S Koh at email@example.com
Copyright (C) 2000-2002, A-S Koh, All Rights Reserved.