CAD Forum

I had no initial problem using the Lofted Cut feature's 'Start Constraint' > 'Normal To Profile' with 'Apply to all' unchecked so I could set constraints from an 8 segmented circle to an 8 segmented rectangle.

But when I tried the same process on a 2nd identical object (in a different location) the Lofted Cut keeps automatically setting ONLY the 'Start Constraint' settings as if 'Apply to all' were checked although it was NOT (i.e. I set 8 constraints individually and can confirm so before final OK/check, but after the processing is done the result shows all 'Start Constraint' settings as 1 equal setting as if 'Apply to all' had been checked - which it was NOT).

I've tried deleting the Lofted Cut and even the sketches and redoing them several times with the same results.

What puzzles me is that the first execution of the feature has no issues and shows clearly the individualized Start Constraints. If my initial attempt did not work I would not be so puzzled, but the first iteration is still in the part as a glaring example that I had not done something that was 'unsolvable'.

Why is SW only allowing me (during the 2nd attempt) to have only 1 setting for all 8 segments of the Start Constraints in the results, even though the 'Apply to all' option is UNCHECKED and SW allows me to edit each constraint individually during the editing process? BTW, the individual constraints on the End Constraints function fine (even more puzzling), its just the Start Constraints that will only allow 1 setting for all. What am I missing???

Thanks in advance!

What da...?! It just now processed the 'Start Constraint' as I'd set individually! Hmmm...

The only difference I noticed was that my computer wasn't full blasting its fan suggesting that previously when the processing was executed with the fan at full blast, the system might have been under heavy load thermally and/or memory wise.

I wonder if such system loading either thermally and/or resource wise can cause SW to have brain farts?! LOL

This will be hard to diagnose without at least some screen shots of the geometry. If you can upload the model, that would be best.

Below are screen shots of the Lofted Cut feature's 'Normal' operating condition, and the so called 'Brain Fart Condition'.
The circle has 8 segments which are set as 'Start Constraints'.
The pair of 'Start Constraints' at the top(11/1 o'clock) and bottom(7/5 o'clock) were set to "0.3",
and the pair of the segments on the left(8/10 o'clock) and right(2/4 o'clock) were set to "0.7".

When the Lofted Cut was initially executed, the results reflected the original settings without issues.

When I moved onto the second iteration of this object at another location(different plane, angle etc.), the 'Start Constraints' would only be processed as if 'Apply to all' had been checked (it was NOT). Sometimes all the constraints would be 0.3, and sometimes all would be 0.7, even though I meticulously set them differentiated by segments according to the initial settings mentioned above.
Note in the image above, the '5 o'clock' constraint would be set to "0.3" but after processing it would be set to 0.7 along with all the other constraints of the Start Constraints.

After a day, several reboots, and the system at a steady pace (not full blast fan state), the Lofted Cut processing succeeded smoothly. I'm now wondering if thermal loading and/or system resource loading(memory) could cause such 'Brain Farts'? LOL

The vertices selected in the two images are not the same. Here they are side by side:

Yes, I was trying to show in the 2nd screenshot that I'd input a different value 0.3 instead of 0.7 for a different vertex set but the result(after processing) would show all vertices the same value and length (0.7), as opposed to the 1st screenshot in which the different values set were processed with their respective values and lengths (notice some are short and some are long in the first screenshot). Please note, as I could not recreate the issue at will, I had to improvise and use one screenshot(the 2nd one) to describe both the preprocessing input and the post-processing modeling result (pardon me).

I sincerely appreciate you even considering this matter. Thank you!

If there isn't a known bug regarding this or similar matter, I'm currently thinking that my computer's limitations might have contributed to this issue (I'm running SW on a VM in a 2011 MacBook Air with only 4GB RAM - this is a temporary setup, I'll certainly be getting a more sufficient machine with a lot more RAM and a Quadro GPU etc. soon). The screenshots only show a minute bit of a much larger recumbent bike frame single part, and without suppressing most of the part while editing, the system gets pretty heavily loaded.

But if anyone else has encountered a similar blip, I'd certainly like to hear about it. Thanks.

Use guide curves, sometimes, even on simple lofts it will do weird things if you don't. Also, if you have a constant thickness use a shell instead of a lofted cut.

I tried adjusting the normal to length on a sample part and it let me set each one, you can see from the preview the different lengths on each vertex

Thanks for the pointer TTevolve.
Indeed in hindsight using Guide Curves in combination with the Shell feature would be a better method giving me more direct control of the curves, and certainty of equal thickness throughout (currently I think the areas where there are complex "S" shaped curves on the sides, the thickness is not uniform).

I thought the Loft/Cut would be simpler (thinking that I could just use the same input values for constraints in the Loft and Cut), but it's actually harder to control the point where the "S" shaped curves get positioned as the curves are indirectly manipulated when using constraints - some constraints in the Cut may require a smaller value than in the Loft, resulting in much fiddlin'. It also seems to require more processing resources to compute/mediate between the 2 opposing constraints into a complex curve.

I'm also considering adding one or more planes for adding intermediate sketches as 'ribs' in between the ends to more accurately model an actual bike's pinched chain stay and seat stay for mating with rear dropout tabs. Currently the model looks more like a USB plug! LOL

Cheers~!

With lofts the more intermediate sketches and guides curves you use the better you can control it. from the looks of your picture above you should do a straight extrude for the back half, and then only loft the front section where it actually transitions. Also, I don't think you want normal to on the end, try using none while using a guide curve to control the ends

Without guide curve With guide curve

TTevolve wrote: ↑Tue Dec 13, 2022 8:14 am Use guide curves, sometimes, even on simple lofts it will do weird things if you don't. Also, if you have a constant thickness use a shell instead of a lofted cut.

When I have relatively complex lofts (I go months without needing to use a loft at all) I often have decent results by lofting a surface first, then thickening it to create a solid, instead of lofting the solid.