simple loft driving me crazy!

[charlieuk]

Im trying to do a simple loft but for some reason even when using rails the loft profile seams to distort when I do It. I have re done the drawing multiple times and tried it various way but can not figure why it keeps doing it! any ideas?

edit: it only seams to do it when I do the loft as a create new body if I do it as a join it (looks) ok

http://a360.co/2D3eWXm

many thanks

[davebYYPCU · Accepted solution]

Yep some weirdness happening to me ....

Crashed A360 when asking to download the file. 

Crashed F360 again when attempting to move a mapping point.

Can't say for sure, but likely to be Sketch 1, you don't have the straight lines fully constrained, and of 5 spline attachments, only two are tangent, and they are at the area of distortion.

I presume that all five spline attachment points would be tangent.

Could be a simple as that sketch is not fully constrained.

Sketch 2 is fully constrained but has one more sketch article 8 as against sketch 1, has 7 articles.

Sketches 3 and 4 look ok, splines are constrained to the horizontal and or tangent, but may need to change the bottom rail to be two in a vee, creating your own mapping point count to match

Sketch 1 distortion appears with no rails selected, in preview, 

However when I joined the loft, the top worked out ok, but the bottom surface of the loft showed a temporary mismatch, almost as if it was a surface, near 6 o'clock on the sketch 1 position.

only saw this on one test, wasn't repeatable.

Some things to look at, in Sketch 1,

can you make arcs for the splines? 

There is no mirror with in the sketch, 

no canvass, 

no dimensions

recommend two point splines with constrained handles, adjust handles that are tangent for shape.

if fixing up Sketch1 doesn't do it,  would refer this one to the Lofting gurus.

Might help....

[TrippyLighting · Accepted solution]

This is a LOD (Level of Detail) graphics glitch only. Your geometry is fine.

Objects need to be tessellated in order to be displayed in the viewport. When deciding how fine it needs to tesselate a body Fusion 360 takes the overall size of objects into account. For long, thin objects, this tends to lead to such issues where the body is not tessellated fine enough and that results in such screen artifacts.

If you right-click in the browser on the body in question you can select "Display Detail Control" from the pop-up menu and set it to fixed/high. That will correct the situation.

[charlieuk]

ok great many guys thanks changing the Display Detail Control does seam to correct it. perhaps I need to look at the things you mentioned also dave, it was a little trick drawing it as its a part that I have had to try and replicate the shape of the real part with only very few dimensions and there was a lot of trial and error using the 3dprinter to see if I had it accurate.