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Alibre Design Assembly and Alibre Motion

Welcome, this tutorial is based on Alibre Design version 12.1. For any additional information such as installation, registration or upgrading, Please contact CADDIT.net via email. In Australia a free trial download for Alibre Design Professional is available HERE.

To start with assembly make sure that all the part design models have been checked and that all parts have be constrained correct within the model. We start be creating a directory for all the part of the assembly in one location. This allows for the ease of access of the parts when needed as well as the editing of each part when necessary change are to be made. To create the working directory simple gather all the parts required for Alibre Design, create a new folder where the assembly design is going to be saved and copy the parts to that working directory.

Alibre_design_assembly_save.bmp

Once you have done that, proceed to creating an assembly model in the home window and select the middle icon which says combine multiple parts into a finished design. A new window will open and click on the save icon and rename the assembly accordingly. Here in this example below I have select the middle icon in the home window and save the file extension as tutorial _assembly.AD_ASM.

Now we will introduce parts into the assembly one at a time. Alibre Design will allow you to use multiple parts in a single assembly and are introduced one part design at a time. This will make sure that you can use the other features such as linear pattern to your advantage by limiting the amount of time required to assemble a design together with few clicks.

To do this we will select the insert part or assembly which is located in the far right hand corner of the workspace screen indicated by this icon. Otherwise by going to the insert menu and selecting insert part/assembly option (shortcut key to this is Ctrl+Shift+I) will open a window explorer dialogue box where you can choose where you are getting your parts from.

Alibre_design_insert_assembly__msg.bmp

Once you have selected the design part and clicked okay, you will return to the workspace window and with the part attached to the mouse cursor on the screen. To place the part down in the workspace, simply click the design where you want the part to be orientated and the part will placed in that orientation. Once you are satisfied with where the part or parts have been placed clicked finish on the open dialogue give you this message or alternatively press the esc to finish. 

Alibre_design_parts_floating.bmp

As shown here, I have selected the parts I required from the explorer window and have placed the multiple parts that require for this assembly. Note that the positions of each of the parts are fair distance away from the main design part. This makes sure that you have all the correct parts available for the assembly and also that you do not have overlap in the assembly design.

 

The next step in this process requires that the main component or main design part is locked down and secured in place. The reason for this to be done is that when editing the parts for constrains that the main component doesnft move everywhere and provide an anchored point where you can see the motion of the assembly part later on. After anchoring the main component, the additional parts now can be added to the design or constrained onto the design. By using the constrain tool located in the middle of the right hand side toolbar in the workspace window indicated by this icon here, you can add various constraints on to the model design to complete the assembly. As mentioned before in tutorial two, constraints provide parametric control on the location and positioning of the part in the assembly process. This step is vital if the assembly is to be presented correctly and show in motion at the end step of design process.

Alibre_desgin_assembly_constraints.jpg

Using the parts in the previous example, I will be using the constraint options of align and mating. Note that offsets can be used if desired to the design and also if the icon is not present in the toolbar on the right hand side, you can go to the menu > tools > assembly constraint. Here you will get another dialogue box open up and provide you with the options in adding constraints to your model.

Alibre_design_parts_constraints_example.JPG

            In the image, you see that have added mating constrain between the two faces added here which results in the next image shown. Now that parts have been constrained, it is best if you add at least three constraints to make sure that the model is properly positioned later when you need to us Alibre motion to replicate the movement of the parts required. Once you have completed this with the first two parts continue with remaining parts for the assembly until you have completed. It is worth noting that parts which are being constrained have a separate design tree section noted as constraints. If you have applied more than one of a similar constraint to a model you will receive an error in which you would need to edit from here.

Alibre Motion

This part of the tutorial we will be looking at Alibre Motion. Before we start there are few concepts in which need to be understood before continuing. In Alibre Motion, there are two types of motion constants that are used. One is prescribed motion which described by constant rotation using degrees per second or velocity in feet per second. Prescribed Motion does not take into account the forces in which are causing the motion itself, just shows that the motion is happening,

The second way in which you can describe motion in Alibre Motion is using Forces. For this to applied you will need to describe the motion which is to take place in a linear motion in torques or foot pounds.

Note: You define all motions directly onto assembly constraints. If your assembly does not have any constraints, or does not have the appropriate types of constraints, you will be unable to define motions.

With all of that in mind, the Alibre Motion simulation has two types of motion analysis Kinematic and dynamic. The one in which the user will choose depends on the motion defined in the simulation and its outcome. The two motions are described as follows:

Kinematic - Kinematic simulation excludes the consideration of any force or mass during analysis. For example, a force such as gravity or a torque definition would be ignored during a kinematic analysis. With this type of analysis, you must use the prescribed motion definitions mentioned above.

Dynamic- Dynamic simulations include all constant and oscillating torques, linear forces, springs, dampeners, and masses when analyzing.

This tutorial assumes that you are already familiar with sketching, modeling, and assembly techniques in Alibre Design. If that is not the case, please review the beginning of this tutorial before proceeding.

In tutorial, we will be using out an assembly model of a v8 engine to demonstrate in between each step on how to setup for Alibre Motion and running the simulation. Firstly we start out by opening the assembly required for this tutorial. Ensure all the constraints of you assembly has been set correctly otherwise you will get some strange motions from your assembly as the simulation is running. Now we will got to View and disable all the options in the display of referencing geometry to help us see the simulation better and improve the performance of the simulation. Note to also enable shaded and visible edges if you havenft done so already.

Now make sure that you have Alibre motion installed, and go to the drop menu you motion and select the motion explorer. This will switch your views on the model and you will notice that your design explorer has changed to motion explorer.

Note: Some assemblies will get errors in this stage popping up. This is due to the user either not setting any material properties for the parts or that the density is too high or low for this simulation to give out accurate numbers.

Toggling the Motion Explorer option will display or hide the Motion Explorer. There are also tabs at the bottom of the Explorer on the left side, allowing you to transfer between the Design Explorer and the Motion Explorer.



The Motion Explorer is very similar to the Design Explorer. The Motion Explorer is a data tree that contains the applicable data of the assembly model, constraints and simulation information The Config section at the top of the motion explorer allows you to define several simulation scenarios, similar to Design Configurations you would use for a part or assembly. Fixed Parts shows you all of the parts in your assembly which cannot move. Note that this does not mean "may not move during a simulation". This more or less means all the parts that you have anchored.

Moving Parts show all of the parts that can move. This does not mean that they all will move since the user will be defining all the movement themselves. If your motion definitions do not end up affecting some parts during a simulation, those parts will not move even though they are in the Moving Parts section. The Constraints section shows you all of the applicable constraints that can be used to define a motion. The Actuators, Springs, and Dampers will show you what kinds of motions you have defined. Until you define motions, these will be empty. Gravity option will tell you whether or not you have enabled gravity. If it is grayed out, gravity is not enabled. To enable, simply right click on the word and click "enable". The Measurements section shows you what dynamic measurements you have set up. For example, if you have set up a measurement to follow the angular velocity of a part, the definition of that would show up here. Traces section will show you all of the motion traces you have assigned to the simulation. For example, a position trace that follows the motion of a part would show up here.

The Motion Explorer also contains the simulation control box. Your control box will show all of the buttons inactive at this time (as in the above image) because you have not yet enabled simulation mode. Note the difference between being in the motion explorer and being in simulation mode. When you are ready to simulate your part after defining motions, you will then enter into simulation mode.

At the top of the control box is a frame scroll bar. The field on the left just under the scroll bar shows the current frame / total frames. The field on the right side shows current time in seconds / total time in seconds. Note that the total time simply represents how many seconds you have already simulated. Below that, you'll find in order from left to right: the Play in Reverse, Move Back One Frame, Stop/Pause, Move Forward One Frame, and Play buttons. The bottom row from left to right consists of the Record, Loop Playback, Show/Hide X-Y Plots, Show/Hide Interferences , and the Settings button. Note that you can also access Settings from the Motion menu on the toolbar.

            Now it is important that you select the correct settings for the simulation otherwise the simulation will skip important movements in which you wish to look at or that the simulation runs so slow that you do not get the required information. Now to setup Alibre Motion for simulation, got the motion drop menu, select settings and a motion option menu should appear similar to the one below.

You will need to set the time of the playback and the simulation periods in which Alibre Motion needs to capture the necessary information as it goes though the simulation. Now for this tutorial, the settings will be set for playback as defined, the simulation time will start a 0 with the simulation frame interval set at 0.01 and the simulation type set at Dynamic.

The Simulation Frame Interval area allows you to decide how big each "frame" will be. When you click the Next Frame button after simulating for a bit, this will be the step that it takes. Important: This does more than just control the Next Frame step. This is tightly integrated into the actual simulation. Remember that the more complex the simulation, the lower the frame interval needs to be. Complexity in this case means the number of parts, types of parts, complexity of individual parts, and the number and types of motions you have made. Simply be aware that if you are trying something very complex, you should be aware of this setting. While the effects of this setting vary depending on your computer configuration (i.e. ram, processor), it is a best practice to keep it low. Each simulation may require tweaking of this interval for the desired outcome and desired speed.

Now the simulation need to have defined source where the entire assembly can be directed to move and data can be collected based of that moition. To do this, a centre part of where the entire assembly need to be moved or driven will move all the connecting parts to move accordingly. To illustrate this, in this V8 Engine Assembly here, the Crankshaft is the main moving part that will be attached to a motor to show the data of acceleration, velocity as well as positioning of the piston head. Now, to attach a force element, expand the moving part branch in motion explorer for your design and select the required part where the motor will be attach to. This will expand into additional constraints found for that particular part. Select a alignment constraint and right click to insert the motor of choice. In the example of the V8 assembly, we have chosen the crankshaft part with the alignment constraint and then added a rotary motor to drive this part.

 Now when inserting any of the motors selected in Alibre motion, you will get another dialogue box open up with the settings for the motor. You will need to enable the motor and set the motor accordingly to what you want do in the simulation of the assembly. In the tutorial example, we will apply a specific motor torque. Next switch tabs to motor torque, and make sure that the constant torque has been set. And for this tutorial, we will apply 1 foot pound of Torque  to the motor, since we are running the simulation for the first time. Note that the amount of torque needs to adjusted accordingly to what sort of parameters that you would like to set for the simulation.


 

Click OK. A Motor will be added to the Actuators branch in the Motion Explorer. Now if you specify specific constraints in the assembly where the motor is attached to set in a locked rotation, this will allow for the improve the performance of the simulation (make the simulation run faster without loading it down with too many additional motions to consider). Now remember to enable the gravity if this is required. Gravity in the simulation will only be applied to the y axis in a negative direction.

 

Insert Dynamic Measurements and Traces

Dynamic Measurements are the outputs of your simulation results. You can collect measurements such as Position, Velocity, and Acceleration of any of your moving parts during a simulation. To do this, select the moving part in which you would like the analysis to be carried out on. Right click and select dynamic measurements. A new dialogue box will open allowing you to select the necessary settings for your simulation.

It is a good idea to name your Dynamic Measurements if you intend to collect many of them, so you can distinguish between them in the Motion Explorer. In Measurement, select Acceleration from the drop-down list. In Component, select Y. This is the direction where the measurement is to be carried out in. Check the Show in X-Y plot checkbox to tell Alibre Motion to record the data of the analysis. Click OK. The measurement appears under the Measurements branch in the Motion Explorer.

Another function in which is part of Alibre Motion is tracing. Traces enable you to see at a glance in the work area how a part moves during a simulation. These are 3D reference geometry objects that move with the model as you move and rotate it following a simulation. To enable this function select the moving part in which you would like to trace the movement part of, right click and select trace and position.

For our example, we have selected the connecting rod – 1 movement through the simulation. We have selected trace position and notice how it adds to the traces section under its parts name.


 

From the Motion main menu, select Enable Simulation Mode. You will notice that the Simulation Playback Control box now has active buttons in it, letting you know you are in Simulation Mode.To begin the Simulation, press the Play button in the Control Box . The Alibre Motion Status dialog opens. Press the Play button again to start the simulation. (If the Play button is grayed out, make sure that Enable Simulation Mode is checked on in the Motion main menu.)

Allow the simulation to collect 50 frames and then press Pause and then Stop. Click on the Loop Icon . When you press play again, the simulation will play back the 50 frame loop. You can see in the Current frames/ Total frames section when it is finished collecting the data and is simply playing back the loop of the simulation.

Press the Show/Hide XY-Plots button to bring up the Dynamic Measurements dialog, then drag the scroll bar to the end of the playback. The graph of the acceleration of the piston will be plotted. You can also open this dialog during simulation to get real time results as the simulation is running.



By clicking on the data line on the graph, you can read the values of these measurements throughout the simulation. You can also copy or export this data out of Alibre Design for reports and presentations. To do this, right-click in the graph area and select Copy or Export chart data. You can close the Dynamic Measurements box when you are finished.

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