Create motion with assembly joints

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Create motion with assembly joints.

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After completing this video,

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you'll be able to

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create a joint origin,

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apply all joint types,

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control joint limits,

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and create rigid groups.

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To get started in Fusion,

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we want to open the supplied dataset Advanced Joint sample.

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F3D.

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This design contains a component called PA that's currently grounded,

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and then we've got a component called knob,

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a block component that has two subcomponents,

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a ring as well as a ball.

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We're gonna revert them back to their original

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positions and talk a bit more about joints,

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as-built joints,

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and some of the advanced options we need to understand.

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When we're thinking about mechanical motion and assemblies,

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we need to think about how we're going to create that motion,

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and we're gonna replicate that by using as-built joints or joints.

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In some cases we may find the need to use things like contact sets.

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If a joint can't be used to represent

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the mechanical motion and contact sets are needed,

01:02

that's important to understand,

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but also keep in mind that contact sets will increase the compute processing power

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that's needed in order to calculate this motion.

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So contact sets should only be used in certain

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situations where an assembly joint can't be used.

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The first thing that we want to understand is the differences between joint

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and asbuilt joint.

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An Abelt joint and joint will apply the

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exact same joints to create the mechanical motion.

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However,

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an Abelt joint makes use of the current location of a component.

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For as-built joints,

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we simply need to select the two components,

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in this case,

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the ring and the plane.

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And then we need to decide the motion type.

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In this case,

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we can select the motion of revolute if we want the ring to spin around that base.

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We can also use things like cylindrical.

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A cylindrical will allow it to rotate by selecting a revolute reference,

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but it also allows it to move up and down.

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Because in reality,

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the ring is just placed on the plate,

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using this type of joint is likely going to be

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the most ideal or the most practical because the ring is free to move up and down.

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Keep in mind that if we were using something like contact sets,

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because there is a difference in diameter,

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it would allow it to float around as well.

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Another thing that we want to consider is that

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if we don't have components in the correct location,

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we need to use a joint.

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And when we do that,

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we need to pick the locations of the components.

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For example,

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if we want to move this knob to the slot,

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we first need to pick the location on the knob.

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This can be by selecting an edge or a cylindrical reference.

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Then we need to pick the location on the slot.

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It's important to identify the joint origins on

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the screen when we're making our selections.

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Then we want to select the motion type.

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In this case,

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pin and slot is going to be the ideal motion.

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This allows for one degree of translation,

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as well as one degree of rotation.

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The difference between cylindrical and pin and slot is

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simply that the degree of translation is different.

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Cylindrical will have the degree of translation with the rotation axis,

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while pin and slot uses a different axis altogether.

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We're going to select OK,

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skipping over the fact that we have joint motion limits in the dialogue

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directly because we're going to talk about those in just a little bit.

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The next thing that we want to identify is when we're creating a joint,

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there are options for the origin mode.

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In this case,

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between two faces may be used when we've got two individual blocks.

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However,

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this only works if the selection is part of the same solid body.

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In order to use a joint origin between these two,

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we would need to pre-select and create that.

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Another thing to keep in mind is that these

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blocks are individual components inside of a top-level component.

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This means that each one has its own origin,

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and there's an origin at the top level.

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Because of this,

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we could do an as-built joint to make them rigid with each other,

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but this would still allow them to move inside the block component.

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So a more ideal situation is to create what's called a rigid group.

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A rigid group allows us to select the top

04:10

level component and automatically include all the children.

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We can also select more than two components,

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which in a joint or an as-built joint,

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you can only have 2.

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So in this case,

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we can select OK.

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Then go to assemble and manually create a joint origin between two faces.

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This origin will support the use of multiple bodies or components.

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So we're gonna select plain one.

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And then we'll select plane 2.

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Then we need to select the snap location.

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I'm going to pick the bottom center location.

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However,

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the coordinate system's not pointing in the right way.

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So we're going to use reorient and manually pick a

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Z orientation as one of these vertical edges and say,

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OK.

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Now,

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when I go into create a joint,

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I can select my joint origin,

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which represents these two components.

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Then I can select a joint origin on my plane.

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For the motion type,

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we want to make sure that we set this to planar,

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allowing these blocks to freely move.

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Once you say,

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OK,

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the blocks can now freely move along that plate.

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I'm gonna put them over here in the corner and capture their position.

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Another thing that we may want to take a look

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at is the advanced options inside of these joints.

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When we go to a joint.

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May be easy to select the type of joint first,

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such as ball joint.

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Then when we select the position,

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we'll select the center of this ball

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and the center of this

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ball socket.

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As we begin moving and rotating these around,

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we may find that we want to dictate these limits.

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This can be done by using the joint limits directly inside of the joint,

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and they're going to be found on the motion tab.

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When we do this,

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we want to pick each axis individually,

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then we want to set the minimum and maximum values.

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The minimum and maximum values will be displayed on the screen.

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So we can see here that we've got

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And we've got

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Then we'll select another axis and begin using those as well.

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For this instance,

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I'm going to select OK,

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only limiting one axis of rotation.

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Keep in mind that with a ball joint,

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the motion is fairly free because we've got 3 independent axes of rotation.

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So this can be a very tricky one to fully define.

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Keep in mind that fully defining these joints isn't required.

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The motion limits are not a requirement of each joint,

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it's just optional and something that does help

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when we're talking about defining our assemblies.

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Another thing that we do want to consider is the use of contact sets.

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Contact sets can be helpful,

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especially with a joint like this,

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where it's free to rotate and move up and down.

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Under the assemble menu,

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we can enable contact sets for all components,

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but this can oftentimes cause problems and increase calculation times.

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So a more common approach is to enable contact sets,

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then right click and manually create a new contact set just between two components.

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Now,

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this means that the ring can move up,

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but it won't be able to move down through that plate.

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Keep in mind once again that contact sets will increase the calculation needed,

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especially for complex assemblies.

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So oftentimes you may want to do no contact

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and temporarily disable it,

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that way the calculation times are reduced.

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Keep in mind,

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however,

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that if you're creating an assembly,

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a joint doesn't mean that the motion is OK.

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In this case,

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you can see that the diameter of the base of our knob is too large for the slot.

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And while our joint

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lets us look at this and see that it moves freely,

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in reality,

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those two components wouldn't fit together.

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So you do still need to pay close attention

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to how your components are created,

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any tolerances or gaps that are required

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in assigning them or putting them together.

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If you want to go back and modify joint limits at any point in time,

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you can simply find the joint,

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in this case pin slot,

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right click,

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and edit the motion limits.

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In this case,

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I don't care about limiting the rotation,

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but I do want to limit the slide.

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I'm going to set the minimum at 0

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and the maximum value should be about 8 inches.

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We can do this on screen by manually dragging,

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or you could enter it here.

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We could also set a rest position,

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let's say 4 inches right in the middle.

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When we do this,

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as we begin to drag,

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it's going to stop at either end,

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and once we let go,

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it'll snap to that middle position.

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I'm going to go ahead and capture this position.

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Once again,

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this allows us to freely rotate and have it snap back to that center position.

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Keep in mind that the rotation is not fixed,

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so each time you will need to capture the position or revert back.

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There are many other options that we haven't covered in this video,

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things like tangent relationship,

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the drive joints option,

08:53

or creating motion links.

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These are all things that you should be familiar with and explore,

08:58

but keep in mind that on the topic of our certification,

09:02

we really want to make sure we understand

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the differences between joints and asphalt joints,

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the degrees of freedom of the various joint types,

09:09

rigid groups,

09:11

manually creating joint origins,

09:13

as well as understanding how we can define

09:15

and drive the joint limits.

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Playing around with all of these different aspects is going to be

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an important step in understanding how they work for your own designs.

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Once you're done,

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make sure that you do save this before moving on.