![\"fus-saw-frequency-400x240-2\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2017\/01\/FUS-SAW-Frequency-400x240-2-e1483642819220.png\")
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Have you ever wondered what those frequency studies are used for?\u00a0 Let\u2019s take a look at an example using the reciprocating saw seen above.\u00a0 Anytime there are moving components such as motors, there is going to be some level of vibration in the model.\u00a0 The question is whether that vibration is going to cause discomfort to the consumer or even worse, a product failure!<\/p>\n
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Fusion 360 offers a great interface for running several types of studies (Linear Static, Frequency, Thermal Heat Transfer, and Thermal Expansion).\u00a0 Let\u2019s get started!<\/p>\n
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![\"studies1\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2017\/01\/Studies1.png\")
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When working with FEA simulations on assemblies it\u2019s important to reduce the components we\u2019re analyzing to the ones we are focusing on.<\/p>\n
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![\"TheseComponents\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/TheseComponents-300x149.png\")
\u00a0\u00a0 ![\"SuppressComponents\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/SuppressComponents-300x215.png\")
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Next, we will describe how the parts are held down using constraints.\u00a0 This is where we need to be careful not to over-constrain the design or make it too rigid.\u00a0 The pin constraint enables us to constrain cylindrical faces in the radial, axial, and\/or tangential directions depending on the behavior.<\/p>\n
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![\"FaceSelections\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/FaceSelections-300x215.png\")
\u00a0\u00a0 ![\"PinConstraints\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/PinConstraints-300x233.png\")
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At this point, we have constrained the gear housing.\u00a0 What about the other components?\u00a0 Are they free to move?\u00a0 We can check this by clicking on the DOF command (Degrees of Freedom).\u00a0 This command will show in color the components that are free, fixed, or potentially fixed.\u00a0 The gear housing is \u201cpotentially fixed\u201d due to using pin constraints only.<\/p>\n
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![\"DOF\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/DOF-300x171.png\")
\u00a0\u00a0 ![\"DOF2\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/DOF2.png\")
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We can see the two covers are free to move.\u00a0 Let\u2019s create bonded contacts between the components to ensure there is no free body motion that occurs on those components during the solve.\u00a0 Fusion 360 will automatically apply these bonded contacts to faces that are coincident with each other.<\/p>\n
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![\"Contact\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/Contact-300x257.png\")
\u00a0\u00a0 ![\"Contact2\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/Contact2-300x154.png\")
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Now it\u2019s time to create a mesh of the assembly.\u00a0 Or in other words, we are going to break the models up into small pieces to be analyzed.<\/p>\n
First, let\u2019s take a look at the mesh settings.\u00a0 We are going to change the average element size to 2% of the model size.\u00a0 And check the box to use curved mesh elements.\u00a0 This setting will add a mid-side node to the element allowing it to better represent the curved geometry in the model.<\/p>\n
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![\"MeshSettings\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/MeshSettings-300x153.png\")
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Curved Mesh Elements Unchecked \u2013 Runs Faster\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Curved Mesh Elements Checked \u2013 Slower \/ Higher Accuracy<\/p>\n
![\"MeshCourse\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/MeshCourse-300x221.png\")
\u00a0\u00a0\u00a0\u00a0\u00a0![\"MeshHigh\"](\"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2016\/07\/MeshHigh-300x206.png\")
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Next it\u2019s time to run the solver which takes less than a minute.\u00a0 Taking a look at the results we can see that the blade end of the gear housing will vibrate 124 Hz if the model is excited.\u00a0 Our goal for this model may be to reach 1000 Hz for the first resonant frequency which is high enough to maintain customer satisfaction for comfort as well as increase the life of the internal components.<\/p>\n
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We can prevent this by adding tabs to the outer housing of the reciprocating saw and use them to suppress the vibration.\u00a0 We can simulate this before we spend any time creating the new 3D features in the design.\u00a0 Let\u2019s add a couple friction less constraints to the faces where the tabs will come in contact.\u00a0 The frictionless constraint only allows movement parallel to the selected face.<\/p>\n
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Now let\u2019s run the solver again.\u00a0 We have increased the frequency value for the model.\u00a0 However the center of the gear housing has a tendency to twist at 348 Hz.<\/p>\n
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<\/p>\n We will make one more modification to the design.\u00a0 Let\u2019s add extrudes to the cylindrical screw bosses which will be attached to the outer housing of the saw.<\/p>\n <\/p>\n <\/p>\n Then we will use fixed constraints on all four extrudes.<\/p>\n <\/p>\n <\/p>\n And finally run the solver.\u00a0 It looks like we have nearly reached our goal of 1000 Hz!\u00a0 At this point it would be up to the designer whether or not it is important to add more mass or stiffness to decrease vibration on the gear housing.\u00a0 As we make these changes it\u2019s also necessary to take into account the cost of making additional modifications for manufacturing.<\/p>\n <\/p>\n <\/p>\n Autodesk Fusion 360 is more than a 3D modeling tool.\u00a0 Use the simulation capabilities to solve for linear static, frequency, as well as thermal heat transfer and thermal expansion.\u00a0 Stay tuned for additional workflow blogs on other study types<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Are there moving components in your design? Find out if this is going to cause discomfort to the consumer or even worse, a product failure!<\/p>\n","protected":false},"author":957,"featured_media":5134,"menu_order":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[1],"tags":[],"coauthors":[],"class_list":["post-3039","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fusion","dhig-theme--light"],"acf":[],"yoast_head":"\n<\/strong><\/p>\n
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