Hello all,
(This is very long and probably only of interest to the poor person on the development team being hit over the head with the Loft Command complaint noodle.)
As have many others, I am finding the Loft command somewhat ... unreliable ... problematic ... twitchy. On occasion it will work for me and then, later, something else comes along and Loft becomes a source of complete frustration. I am providing a link below to a sample problem drawn from my real efforts demonstrating Loft Command's difficulties.
The basic problem is to provide a horizontal rib from the top of the side frames to the central beam (spine) rising from the aft end of this locomotive bed:
The rib section is supposed to be trapezoidal, tapering from ~2.5" thickness at the frame to ~0.875" at the beam, but as this section shows in this past attempt (as in the current one), I had to settle for a Press/Pull of the frame's 2.5" profile which was then appropriately trimmed and joined to the model.
I could, of course, have used the Draft command to obtain some taper, but, given the curvatures in the plan view, this would have resulted in a somewhat kludgey appearance.
From this "real world" situation I have developed this isolated rendering of the Loft problem:
The lavender (?) curves represent the Loft rails along the central beam (nearer curves) and the side frame (farther curves). These particular curves were developed from repeated Intersection Curve commands which resulted in numerous (apparently meaningless) warnings (signaled by a yellow highlight of the sketch in the timeline). I also developed similar curves using the Project to Surface command, but these faired no better in subsequent Loft attempts. The closed sketches for the Loft profiles are also shown.
The Loft rails were developed from these 2-D sketch curves:
The two lower curves are the plan view of the central beam and the side frame while the three upper curves are the lateral elevations of these elements. Note that the central beam and the side frame share the same top lateral elevations since the joining ribs have horizontal tops. The other two lateral curves simply reflect the different thicknesses of the ribs from the side frame to the central beam.
Some partial lofts could be obtained. For example,
While usable, this loft was not obtained without complaints -- mainly that a loft rail did not touch all the profiles. Chain Selection seems to have difficulty recognizing what is, in my reality, a smooth 3-D curve from top to bottom. Occasionally, when selecting a rail, Chain Selection does not recognize a rail all the way through to the final selected profile. Sometimes selecting the next segment of that rail works, sometimes it doesn't. Sometimes Loft will refuse to even highlight a curve segment for selection.
Some lofts are just not going to happen:
Here it was convinced the lower rail did not touch all three profiles. I know that rail touches, at least to the best of my ability to make it so. I did an Include 3D Geometry of the needed points or curves in each of the profile sketches. I got the Coincident constraint to work on each corner of the sketched trapezoid. Fusion 360 just seems to want something more, or different, or something.
As my final grasp for the brass ring, I tried making a series of evenly space ribs parallel to the YZ plane. This got as far as Sketch 21:
Here the inner, upper rail has been included as 3D geometry in the sketch, but the Coincident Constraint simply refuses to connect the end point of the line to the curve. I gave up there and decided to go with the Push/Pull workaround again.
If this is all my incorrect use of Fusion 360, I (and I am sure a multitude of others) would be delighted with an enlightening exposition on the subject. For now, lunch awaits.
Public link: http://a360.co/1oxWVIv
Regards,
Bill
