Joint origins and midplane joints

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Joint origins and mid plane joints.

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In this video, we’ll create a revolute joint using between two faces.

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Create a slider joint, edit joint limits, create a joint origin and explain the differences and similarities between joint options.

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In Fusion 360, we want to get started with the supplied dataset air cylinder and mount.

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When we take a look at this, you'll note that we have a couple different McMaster-Carr components.

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These are brought in from McMaster-Carr and you'll notice that these are bodies inside of a top level component.

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These are for an air cylinder as well as an air cylinder mount.

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Let's expand all of these and make note that the air cylinder mount contains multiple brackets.

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We have a left hand, a right hand side as well as a pin with clips but everything is free to move.

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So to get started, the first thing I like to do is go to Inspect and turn on Component Color Cycling,

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which will help me understand which components are together and which ones are isolated.

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Next I'm going to go into my browser and go to Bracket L, right click and ground it.

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This will keep this bracket in position and then I can go to Assemble and create a rigid group between it and the right hand side as well as the pin.

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Now my mount is going to be fixed in place inside of my 3D workspace.

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The next thing I need to do is figure out how to create those joints inside of the air cylinder.

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But remember the air cylinder is comprised of multiple bodies.

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There's a Nose Nut, Body 2, Air Cylinder Body, The Nut at the Tail and the Shaft.

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Because we don't need all of these bodies, we're going to first select by holding down the control or command key the Nose Nut, Body 2 and Nut Tail,

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we're going to right click and remove them.

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Remove places a feature in the timeline that allows us to roll back at any point in time or bring them back if we simply delete this feature.

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However, we only need to focus our attention on the Air Cylinder Body and the Shaft.

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As soon as we move either of these, they'll move together because currently they’re just a single body.

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So the first thing I want to do is select both of them, right click and create components.

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Now we have our air cylinder and the shaft.

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Now I can make use of an as-built joint for the shaft and the air cylinder body.

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We're going to select as-built joint and set the type to Slider.

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We’ll select the air cylinder body and the shaft,

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and then we'll select a cylindrical reference on the outside and allow it to move back and forth and say, OK.

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Next we want to place the back of the air cylinder on the shaft of our bracket.

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When we do this, we're going to go to assemble and select joint.

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The motion type we're going to use is revolute,

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and for the position we have a couple different modes, Simple, Between Two Faces and Two Edge Intersection.

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One thing that we can do if this is going to be centered is hover over the inside diameter of the back of our cylinder,

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hold down control or command and navigate to the middle of that selection.

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Because we also have a shaft on the back side, we can do the same thing.

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This will automatically place it in the correct position for us.

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I'm going to select Cancel.

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And if for some reason we didn't have the pin and we only can move between the left and the right brackets,

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let's take a look at how we would accomplish this.

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Once again we'll use Joint,

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again with mode we're going to start with Simple hovering over the inside diameter and holding down control or command so we can select the mid.

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For the second one, we're going to select Between Two Faces.

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We're going to select the inside face but notice that it doesn't allow us to select the face on the other side of the bracket.

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And this is because they're not the same body.

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This option between two faces only works if they belong to the same body.

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In order to make this work, we have to create a joint origin.

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We can do this by going to Assemble and select Joint Origin.

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Using this Between Two Faces option will allow us to select multiple bodies or components,

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and then we can determine a snap location which is going to be the center diameter of the bore.

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We're going to say OK and now we've created a joint origin which will allow us to go to Assemble, Joint,

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once again, we can snap to the center position and then we can snap to that center location.

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We also need to give it an axis of rotation.

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Notice in this case how the air cylinder doesn't actually fit between the brackets, they're a little too close together.

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The Fusion 360 is only taking into account our orientation, a location.

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Let's go to motion and make sure it's set to revolute and we'll say OK.

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Now if we zoom out, you notice that we can rotate the air cylinder, we can move the shaft inside and out but it's under constrained.

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Let's revert our position and go to a back view.

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In the Joints folder, notice that we only have Rev1 because that's between the two components.

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If we want to take a look at the slider joint that we created, we need to expand the joints folder that's inside of the air cylinder component.

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We're going to right click and edit the joint limit.

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We're going to set this to a minimum and a maximum value.

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As we begin to drag these out, notice that it's moving the air cylinder and in this case, that's going to be okay.

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We know that the travel of this air cylinder is going to be 5.5 inches.

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So we're going to set the minimum and the maximum values accordingly.

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When we take a look at this because it's a negative value, our minimum is minus 5.5 inches and the maximum is 0.

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If we had an air cylinder that had say a spring return in it, we could set the rest position to a fully closed position or fully opened position.

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We'll say OK and as soon as we begin to move this, you'll notice that it automatically pops back out to that rest position.

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Now we're able to rotate the air cylinder as well as move the rod in and out.

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We can always go back and edit that joint limit and for example, remove the rest option,

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which would allow the air cylinder to stay in whichever position it's in.

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We can always revert back to go back to its original position.

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So just a quick recap, we want to make sure that we understand the differences between an as-built joint and a joint.

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The functionality of the motion between these two are identical.

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However, applying an as-built joint makes use of the current position of your components,

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while the joint will allow you to select the location as well as the type of joint.

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We can create joint origins between multiple bodies to enable easier selection whenever we're creating those specific entities.

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In this case, an air cylinder between two brackets.

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And last, if we have multiple components that are stuck in the same position or bolted together,

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we can use a rigid group to make sure that they stay fixed.

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I'm going to bring the pin back temporarily, go back to a home position and make sure I save this before moving on.