Problems with a basic loft

[jo_sluddeng]

Hi guys

I am tryingto execute a simple loft from a circle to a slot. I've tried sketching the slot in various ways:

1. As a slot, using the dedicated command for this

2. As a rectangle with circles on each end, then trimmed to the same shape as the slot

3. As two parallel lines, joined with a semicircular arc at each end

In all cases when I loft between the two profiles Inventor connects the ends of the straight line sections of the slot to two (seemingly random) points/nodes of the circumference of the circle. This results in an uneven loft shape.

I cant't find a way to control these point on the edge of the circle, or remove them.

I've attached the part file and a screengrab to try to illustrate the issue

Any ideas?

[-niels-]

@jo_sluddeng Turn off "automatic mapping" on the transition tab to get control over the vertices

It might help if you add some points to the circle as start points for those lines.

[jo_sluddeng]

I have tried that already - I can't move the points on the circle manually and when I delete/remove the point sets the loft just fails

[-niels- · Accepted solution]

Then i think it might be easier to "split" your sketches in half and mirror the resulting shape.
Loft has a hard time defining points on a circle that has no clear start or end, so if you have half a circle then it should be more predictable.

[jo_sluddeng]

Thankyou - that works as intended. 

I still don't understand why I get the issue - I have used the same model with my classes in previous years, actually with the same version of Inventor (2019) without encountering this before.

Anyway - thankyou for the solution. Appreciated

[-niels-]

It's a bit weird, if i set it up in IV2018 i can control the vertices reasonably well.
(if i set them to 0 or 1 they all converge on the same point on the circle, 0,5 for the other side)
Not sure what's going on, but manually trying to find the smoothest transition isn't that easy anyway so i'm glad my workaround helps.

[jo_sluddeng]

It's possible there is a setting somewhere that has been applied as a default during a software update, or reinstall (which is done by technicians remotely).

I can tinker at my leisure now to find a more general solution for similar parts now that I have a workable solution to this particular model.

Thanks again