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In this tutorial, we’ll look at several types of assembly spans, and go over span options and settings.
When creating assemblies, spans are the parts that run between supports, and supports are comprised of assembly components. A span can be a profile member, another component, or a sub-assembly.
The simplest type of span is a profile member. From the Samples folder choose the bench assembly, and build out a bench.
The one profile member is the bench seat, and the one component is the bench leg, composed of three objects.
There are two spans - front and back, which are the profile members that run between the bench leg components.
Each span needs to have supports, which can be selected from the components set up for the assembly. In this case there is only component - the Bench Legs. The first pattern options sets the span to run between all components, so there are Front and Back members between all legs.
As with other parts of an assembly, Left / Right and Up / Down offsets are measured from the assembly placement point to the placement point of each span.
Setback options are hidden when Auto Trim is checked. Uncheck Auto Trim to get zero setbacks, and apply changes. In X-ray view, the spans now go from center to center of the supports. This is because the origin of the bench leg component is aligned with its center. And span parts, by default, will extend between the origin locations of their support components.
Adding 1” setbacks on either side brings in the spans to fit inside the supports.
Cross Junctions is also checked, which means that spans also appear between components at the junctions: the points at which the assembly path changes direction.
Uncheck Cross Junctions for both the front and back spans and Apply, and those span segments disappear.
For another profile member span example, bring in the Railing Assembly with wires, and build it along a path that curves both horizontally and vertically.
The one profile member this time is the top rail, and the only component is the post. There are 9 spans this time: 7 wires and a bottom and top rail. All of the spans run between the post components.
The profile member curves along with the path, but all spans follow straight lines. This is because Allow Curve for each span is unchecked. Check this box for bottom rail and top rail, and apply to see those spans follow the path curve. (It wouldn’t make much sense to allow curves for the 7 wires.)
For each span, Allow Slope is also checked. Uncheck this for each of the wires, and now the wires are all horizontal, rather than following the slope of the path.
For an example of a component span, get Railing Assembly 4, and build it along the same curve.
Again, there is just one profile member which is the top rail, and one component which are the posts. There are two spans - the first being the bottom rail which is a profile member. This span is set to follow the slope but not curve.
The other span is called Inner, which is a component. Bring in one of these from the Components window; it’s the set of 12 bars that runs between each post component.
Both Scale to Fit and Shear to Fit for this span are checked, which explains how the component adjusts to fit between supports.
Open Components and change the post spacing from 3’ to 4’, and the span components will stretch to fit.
Going back to the Inner span, uncheck Shear, and the component pieces switch to horizontal and vertical. Uncheck Scale as well, and the components remain at their defined size.
For an example of a sub-assembly span, create a Railing Assembly 14.
Again there’s one profile member for the top rail, and one post component. There are three spans this time, including a profile member span for both the inner top rail and inner bottom rail. The third span is the set of two inner posts and three rails, and is a sub-assembly. Click Edit Sub Assembly to see how it’s set up.
A sub assembly is just like how it sounds: an assembly on its own, which is used as a span in a larger assembly. Draw out this assembly, which consists of one post component at start and end, and three spans for the three rails - bottom middle and top. Each of these is a profile member.
The length of the rails of the sub-assembly span, and position of the sub-assembly components, are determined by settings in the main assembly. Click the Back arrow to go back to the settings for Railing Assembly 14.
Change the 5” start and end setbacks to 10”. The inner post sub assembly narrows to accommodate.
Then go to the Component tab and change post spacing from 3’ to 4’, and remove Max. The subassemblies update once again.
For the next example, bring in the hanging chain rail and build it along a path like this, which has one 90 degree junction. The other turns are less than the minimum junction angle of 60.
The spans are sub assemblies, which consist of two repeating components: horizontal link and vertical link. These spans do not allow curves, which makes sense because this is how the chains would look if they followed the path curves:
Spans that don’t follow curves, which go in a straight line from component to component, can have sags like these chains do. The sag distance from bottom to top is 8”. Sag divisions is the number of arc segments the chain curve follows. So if you change the sag to 16” and the divisions to 3, this would be the result.
These spans are also glued to their supports.
This means that if you go back to Components and give the posts a random rotation, the chains will always connect to the posts where they should.
Without gluing, the chains would look like this.
Bring back gluing, and return the posts to zero rotation. In an actual setting, the post at the 90 degree junction would be turned 45 degrees. So change post rotation to Average to make this change.
For the last example, this rural fence assembly is based on an assembly model found in the Profile Builder 3 collection by mind.sight.studios.
Remember: if you import an assembly model from the 3D Warehouse, it must be loaded directly into your model in order to be recognized as an assembly.
This assembly has one post component and three spans.
The middle rail spans is set to repeat between each post. But you can change this to every other post, starting with the first set of posts. Also give this span a sag of 6”.
These curved rails no longer meet their posts correctly, so turn on Auto Trim.
Click Add Span to repeat this span, and this time make them alternate starting between the second set of posts. Give these spans a sag of -6” and lower the Up / Down offset. Now the rails have an alternating curved pattern.