Solidworks Motion Final
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Transcript of Solidworks Motion Final
SolidWorks Motion21 July 2011 Professor Erik Spjut, Engineering Clinic Director, HMC Ayyappa Vemulkar, HMC 2013
ObjectiveBy completing this tutorial, you will learn to model, simulate and analyze the motion of mechanical parts in SolidWorks, using the Motion add-in.
IntroductionSolidWorks motion 2010 is an add-in module that comes with SolidWorks 2010. Apart from being a 3-D CAD Design Software, SolidWorks also allows you to evaluate and analyze your design in motion prior to moving on to the prototyping stage. It allows you to determine specific aspects related to design such as the interference of moving parts; power consumption of motors; sizes of springs, dampers and motors; and the forces related to surfaces in contact. SolidWorks Motion allows one to analyze two major types of problems pertaining to the motion of solid bodies. The first is kinematic, which refers to the study of the motion of a rigid body without considering the forces that result in the motion of the body. The second is dynamic, which refers to the study of the motion of a rigid body as a result of the applied external forces on the body. SolidWorks motion allows you to answer the following questions: 1. 2. 3. 4. 5. Will the various assembled components of your design move as you intended? Will the various assembled components of your design collide when in motion? How much force or torque would you require to drive the system? What are the magnitudes of the forces between two parts in contact with one another? What is the path followed by a particular end or joint?
Before you beginAs most people with experience with SolidWorks will agree, it is important that you create a single folder (preferably on Charlie) to save all your parts and assemblies to. Also consistently saving your document will help save time and effort if SolidWorks crashes unexpectedly. What is very important with using SolidWorks motion as a tool is that it is only a tool. You must already understand how you expect the parts of your assembly to move, prior to using motion. It is also imperative that you verify the results output by SolidWorks Motion.
The Analysis ProcessIt is advisable to break up the analysis of motion into three main sections, namely creation of the model, analysis of the motion, and verification of the results. Starting a Motion project Prior to analyzing the motion of your design there are two components of the design process that need to be taken care of. First begin by drawing the various parts associated with the design. Second create a New Assembly and assemble the various parts of the design. It is important to assemble the parts using particular mates that allow for specific kinds of motion of certain parts (more on choosing the right mate options will be stressed later on in the tutorial). Once the parts have been assembled, you are ready to begin motion analysis. Select Tools Add-ins SolidWorks Motion. Checking the box on the left opens the SolidWorks Motion module for your current session, checking the box on the right however opens SolidWorks motion permanently for every session you begin.
User Interface and Common Tools/Terms The interface for SolidWorks Motion is similar to that of SolidWorks itself, with one or two added toolbars for motion analysis, as seen in Figure 1: SolidWorks Motion user interface.
Figure 1: SolidWorks Motion user interface
When SolidWorks Motion is activated there will be a tab, normally titled motion 1 on the bottom left end of the screen. This tab allows you to toggle between the assembly and the motion
model you wish to develop. Hovering your mouse over a button gives you a brief description of the function of that button. There are certain terms or entities one must keep in mind prior to beginning a motion project. They are: 1. Ground Part: Refers to the part of the assembly that will be considered as the fixed reference frame for the motion simulation. It is usually the first part you place on the assembly. 2. Moving Part: Refers to the parts of the assembly that will move during the motion simulation. 3. Constraints: Refers to a joint or contact that restricts the relative motion between two parts. Note that SolidWorks Motion directly converts Mates into Joints or Constraints. 4. Degrees of Freedom: Any unconstrained body has six degrees of freedom, three translational and three rotational. When mates are created as parts of an assembly, constraints are imposed that restrict relative motion between the two mating surfaces, often restricting motion to one degree of freedom. For more information on how SolidWorks Motion calculates degrees of freedom of moving parts based on the mates placed in an assembly, refer to Motion Simulation and Mechanism Design with SolidWorks Motion 2009 by Kuang-Hua SolidWorks motion ignores redundancies in degrees of freedom for kinematic analysis but asks the user to verify redundancies in degrees of freedom when computing dynamic calculations. 5. Forces: In SolidWorks Motion, motors, springs, dampers or gravity produce forces. When creating a force using the Force tool force or a torque. 6. Results: In SolidWorks Motion, one may analyze different aspects pertaining to the motion model one develops through animations, graphs and reports. , you will have the option of creating a linear
Tutorial The tutorial will be divided into two parts. The first will be an introductory set of examples that you will work through to understand the environment of and tools available in SolidWorks Motion. The second will require you to understand problems present in a model of a singlecylinder, two-stroke combustion engine, and fix them as directed. Part 1: Introductory examples: applying forces and studying the motion of rigid bodies To begin this part of the tutorial, download and open the file labeled SolidWorks_Motion_Tutorial_2010.pdf from the SW Motion folder in the clinic folder. The tutorial was developed by the higher education department of the McGraw-Hill companies. Apart from guiding you through the SolidWorks Motion environment, the examples aim at introducing you to three main tools in SolidWorks motion: 1. Simulation tools, such as Forces, Gravity, Friction and Rotary Motors 2. Analysis tools, which allow you to graph results and write data to spreadsheet files 3. Mating tools, which allow you to control the motion of parts in an assembly The tutorial also emphasizes the importance of following the analysis process outlined earlier. Complete the tutorial mentioned before moving on to the next section. One major concept to take away from this section is the use of SolidWorks for dynamic analysis, i.e. the motion of a rigid body as a result of the applied external forces on the body.
Things to keep in mind: 1. Try and save all the parts you create and assemblies in one folder, this will make searching for them while building assemblies easy. 2. Remember to start drawing all parts in the front plane. 3. Many of the plots and results are directional. Thus when the tutorial asks you to determine a certain result regarding the Z Component and you receive something unexpected, remember to check the other directions. 4. Remember which plane you start drawing your part in. It may come in handy for mating and arranging parts in an assembly, particularly for the roller on the ramp. What to turn in: 1. Did you get the same graphs as depicted in the tutorial? 2. Did you get the same trace path as depicted in the tutorial? Part 2: Debugging errors in design by simulating motion
The goal of Part 2 is not to give you step-by-step directions on the process, but to show you how you would use SolidWorks to debug a design and make sure things work. If the instructions ask you to do something, and you dont know how, first check the SolidWorks help, and then ask a proctor or Professor Spjut. To get started, first copy the folder labeled SWmotion_part2 from the clinic SW Motion tutorial folder to the folder you created for this tutorial. To begin this section open the assembly labeled OneCylEngine and when prompted to find parts for the assembly, agree to do so and remember that they are in the SWmotion_part2 folder. The assembly should appear as that in Figure 2.
Figure 2: Initial Assembly
The assembly is a simplified model of a single-cylinder four-stroke internal combustion engine. If you dont know how an internal combustion engine works review the Wikipedia article on it http://en.wikipedia.org/wiki/Four_stroke_engine. Part of modeling is deciding what does and doesnt need to be modeled. The current model is useful for looking at the timing and the relative motion of the parts, but it doesnt model the force and energy dealing with the air intake,
compression, combustion, or exhaust output. While approximations for these four steps could be added by adding time- or position-dependent forces, this particular model wasnt designed with those analyses in mind. It doesnt have and exhaust or intake manifold or a carburetor or fuel injectors. The current model also does not have friction, but it does have models for the mass and moments of inertia of the components, and the behavior of the valve springs and the timing belt. Friction can be added relatively easily by suppressing some of the mates and adding contact pairs in their places. There are three issues with the current engine that you want to fix: 1. The compression ratio is far too high. A reasonable value for a modern car engine is 8:1. 2. The intake and exhaust valves are not opening and closing at the correct time, and the valve throw may be too long. 3. The valves exhibit float at far too low a speed. You are to fix the three problems and turn in a report explaining how you fixed them and the values of the parameters you used. If you have time and desire, you can also modify the model to account for friction and report on how muc