Getting the exact shape that you want with the Loft command can sometimes be a challenge. Controlling the twist and ensuring everything lines up the way you expect often takes the additional step of adding guides. Recently, Onshape added a number of curve tools that make creating these guides much easier. Let’s take a look at them.
The Bridging Curve feature allows you to create a curve that bridges two references that you select. This command even allows you to make your curve tangent with your selection, ensuring a smooth transition between shapes. This is probably one of the easiest ways to construct a guide for a Loft as you can simply reference edges of the parts you are lofting between.
The Projected Curve command allows you to create a curve at the intersection of two sketches. This can be particularly useful when you need to create a Loft profile (or guide) that is not planar. Simply select two sketches, and a Projected Curve will be created at the intersection.
Composite Curves are a single curve comprised of several entities. They can be sketch geometry, edges, curves, or any combination of these. The Composite Curve command is useful in situations where you need a combination of entities to construct a guide. For example, do you want your Loft controlled by edges of your model plus some sketch geometry? Create a Composite curve consisting of the edges plus sketch geometry and you can use it as your guide. Composite Curves are also great when you want to bring together several entities as one Loft profile.
3D Fit Spline
A 3D Fit Spline allows you to create a 3D curve by selecting points for the spline to pass through. You can select as many points as you would like and can even control the start and end direction and magnitude.
With all of these options, there is sure to be one that meets your needs and will give you the shape you are looking for. Give it a shot!