Simple CATIA Kinematics Block/Base Tutorial with Law

Simple DMU Kinematics Prismatic Tutorial and Applying a Law

Lets make this block slide along the base!

Two very simple parts need to be designed which are the block and the base. Video part 1 shows a quick way to create them along with the dimensions. For simplicity make the block the same width of the base. Once the parts are constructed then they can be brought into a product and constrained properly. A coincidence constraint is applied to the edge of the block to the edge of the base and then the bottom face of the block to the top face of the base. 

Part 2 shows the block being constrained to the end of the base for its starting point in the simulation and the base being fixed because the block will do the moving. Once the constrained are done then move over to the DMU Kinematics workbench and fix the base allowing you to create a new simulation. In the specification tree under application you will now see there is a mechanism. Under the fix part you will see the base you selected. To make adding the joints easier, drag and put the compass on the block to move it off the base (This will go back to how it was constrained when updated). Now you can add your first joint. Lets select the prismatic joint and select the first line to be the bottom edge of the block and the other line to be the top edge of the base. The plane will the bottom face of the block and the top face of the base. As you can see your mechanism still has one degree of freedom that needs to be taken care of. 

A mechanism needs at least 1 command to be simulated and the command will take away 1 degree of freedom. So now we can add a length driven command to the prismatic joint we made. When adding a command a blue arrow will show up showing which way it will translate or rotate. When you have 0 DOF's and your joints are done correctly you will receive a message that you can simulate your mechanism. Congratulations. 

Click simulate with command and drag the cursor on the bar to watch the block slide along the base until the end length which was added. The length can be modified by clicking on the joint if your block is coming up short or going off the end of the block. 

Under edit simulation, click the mechanism you created and insert a new simulation. Change it to a continuous look and change the speed to 0.01 to slow it down. 

Note: If your simulation does not move, drag the cursor on the simulate with command to the end before you click insert and it will work. 

Part 3 shows adding a law to your length command. This is done by adding a formula and then clicking your mechanism to show the parameters it can be added too. Lets add a velocity of 1mm per second we want the block to travel. Since we are in a kinematics simulation we need to relate this velocity to the kinematics time. This can be done by going under parameters under time and selection Mechanism.1/KINTime and multiplying it by your formula. Apply the formula and add a sensor to the block and the base. The reference product would be the base (which is your fixed part) and the part we want to get data from is the moving block so lets select a vertex on the block. 

Part 4 shows how to simulate your mechanism with a law. Select the simulate with law tool behind the simulate with command and add the number of steps. The number of steps is the amount of times CATIA is collecting data within the amount of seconds the simulation will be ran. The seconds can be changed by clicking the three dots and entering a new amount of seconds. The more steps the longe the simulation will take. 200-500 is usually a good range of steps for accurate data depending on the complexity of the simulation. 

Note: Make sure to clear history each time the simulation is ran even when sending it back to the start point to ensure accurate data and graphs. 

Under selection is where you can select sensors you would like to observe. They can be activated by clicking on them. Units can be changed under CATIAs options. Once you have the sensors you want selected you can clear your history and run the simulation. 

Clicking graphics allows you to view your graphs. Under options you can create custom graphs that allow you to control the data you would like to see by selecting the axis's of the graph. 

Note: Custom graphs will not save and will have to be entered each time the simulation is open. So screenshot your graphs if you would like to save them. 

Comment with any questions or problems you encounter. Thanks!

CATIA V5-6R2015 DMU Kinematics

Description of different joints in the DMU Kinematics Workbench of CATIA V5-6

Kinematics is the motion of objects without regarding forces.
Kinetics is forces that cause motion and acceleration which is the result of the motion. 

Planar Joints have 3 degrees of freedom which are translation in the x-direction and y-direction and rotation about the z-axis. Example is a block sliding on a flat plane. 

Prismatic Joints have 1 degree of freedom which is translation in an axis direction. Example is if a block was sliding along a flat plane but with the edges coincident allowing no rotation. 

Cylindrical Joints have 2 degrees of freedom which are an angle of rotation and a translation along a direction. Example is a the axis of a pole translating along the axis of a hole. 

Spherical Joints have 3 degrees of freedom which only allow for rotations. There are no translation capabilities. Example of a spherical joint would be a ball joint. 

Revolute Joints have 1 rotational degree of freedom. Two lines and two planes are required. The plane can be offset from the other plane but must be normal to the axis. 

Gear Joints are made up of two revolute joints and allow for a gear ration and direction of rotation. They have 1 degree of freedom and do not need actual teeth for simulation. 

Rigid Joints have no degrees of freedom and simulates a part being fixed. The parts are locked together and do not have to be in contact. 

Rack Joints are a gear joint were the radius of curvature of the gears is infinite. They are made using a revolute and a prismatic joint. The direction of rotation can be specified and it has one 1 degree of freedom which can be either translation or rotation. 

Universal Joint consists of two shafts constrained in its axis with a revolute or cylindrical joint. The angle of the shaft will be driven by the angle of the other shaft. 

Screw Joints are either translated along an axis or rotated about an axis. The pitch of the screw needs to be specified along with the axis. 

Point Surface Joints have 3 degrees of rotation and 2 translation degrees of freedom. The point has be actually on the surface before the joint is applied. 

Point Curve Joint has 3 degrees of rotation and 1 translation degree of freedom along a curve. The point needs to be actually on the curve before the point is applied. 

Slide Curve Joint consists of 2 curves that remake in contact but allows one curve to slide along the other curve. The curves must be coincident and tangent at a given point before the joint is applied.  

Roll Curve Joint allows two curves to stay in contact. The curves must be coincident and tangent at a given point before the joint is applied.  

Cable Joints can be used to simulate a cable and pulley. They can be thought of as two prismatic with a pulley in between. There is no friction required for this joint.

Other Tools that are often used: 

The Assembly Constraints Conversation Tool will automatically make joints that CATIA sees are needed based on the constraints. This is very handy once you understand the kind of constraints that each joint will make and you can make them before going into kinematics. If you constrain the product properly in the assembly then the tool should make all the joints for you. This tool is also helpful if for finding what other joints are still needed if you are doing a complex simulation and still have many degrees of freedom left. TIP: Do all the basic/obvious joints first, pay attention to how your constraining it and this tool will do most of your work for you.

The Speed and Acceleration Tool is for adding a sensor to a specific point on a part with a reference to another part (usually the part that is fixed). This allows you to track the acceleration, velocity, and displacement on a specific point of the simulation.

Mechanism Analysis is a tool that will show you the data of your mechanism. You can visually see joints which is useful for complex assemblies. You can also see the joints you created are valid and having an effect on the degrees of freedom. 

CATIA V5-6 FEA Tutorial Bearing Load with Adaptive Mesh

Dassault Systèmes CATIA V5-6 FEA Tutorial

Applying a Bearing Load to Part as well as adding an Adaptive Mesh

1. In this tutorial we will be making a simple part and applying a bearing load to the hole in the front of the part and clamping the back. 
2. First make the part, the dimensions are shown in the beginning of the video or feel free to make up your own. When switching from the part design workbench to the generative structural analysis toolbar and select the static analysis. An OCTREE Tetrahedron Mesh is added to this part as well as a 3D property. When choosing a mesh size select it to be parabolic because parabolic meshes have more nodes and work better for circular and curved surfaces. Parabolic meshes also have 3 points on each edge of the tetrahedron. 
3. To view the mesh size you have selected simply right click on Nodes and Elements and choose mesh visualization. Make sure to deactivate the mesh.1 in the tree by right clicking on it before continuing the tutorial. 
4. A bearing load is then selected as the load being applied to the part. For this case select 100N and apply the bearing load to the inside face of the hole. The angle setting allows you to decide which way the force will be applied. Simply adding a negative sigh to your force will flip the force in the direction in which the sign is added. 
5. Add a clamp restraint to the rear face of the part. 
6. Check mesh size to ensure it the proper size you desire then compute. After the part has computed click the static case solutions. Select Deformation, Von Mises Stress, and Translational Displacement. Notice when selecting the Translational Displacement that it comes in as vectors, simply click a vector and change the selection to average ISO. 
7. Use the Images Layout tool to move apart the static case solutions so they can all be viewed together. 
8. Then we are going to compute with an adaptive mesh. Note that you have to compute normally before you can compute with adaptivity. 
9. Select the Adaptively Tool and select mesh you want to use. Add desired % error goal. Compute normally first then compute with additivity. Give the number of iterations and minimum mesh size. 
10. To view the static case solutions as an animation use the Animation Tool located by the Images Layout Tool. I prefer to slow down the animation by increasing the number of steps to the max of 50 and then selecting my own duration which 1s works well.