Loft difficulties

Chris_S_2018

I am trying to do some what I believe should be simple lofting between a circle and an ellipse.  When I try to apply a guide or path constraint sometimes I can get them to work and sometimes I can not.  I keep getting the "loft path must pass through all profiles or their paths." error.  I have tried to make sure all my points are coincident between the planes and guide curves/paths.

For the guides/paths I want to use a spline, but to simplify things I have switched to a straight line. 

I have been through many tutorials online.  None of the tutorials appear to explain the differences between guides and paths.

I need to know not what is just wrong with this error, but more importantly how I can use guides consistently.

JDesilets

 Chris_Shearer

Hello Chris!  Can you share your example as public and paste the url into the forum? Thank you in advance! 

bradley_sauln

Have you taken a look at the help documentation on lofts yet? There is a section that goes over guides vs paths: https://cad.onshape.com/help/index.htm#loft.htm?Highlight=loft

Tony_C_

Split the circle and ellipse and then match vertices.  

michael_watson

I am having similar difficulties with the loft feature. I have two guide curves but only one will actually allow a successful loft. The two curves are built in same manner with same overall dimensions just slightly different profile. But if you use Sketch 4 instead of Sketch 1 as the guide in the loft, it will fail. I am at my wits end on this and have rebuilt the curve a dozen times over the last couple of days. i just dont get why one sketch works and the other doesn't. Appreciate any help.

https://cad.onshape.com/documents/d6947a8c6e1a6ae034cec202/w/dd91caac1c5cecba868037f1/e/6b3e91ddecb7c1c1ddc2f758

NeilCooke

@michael_watson add 2 sketch fillets to remove the sharp corners in sketch4

michael_watson

@NeilCooke oh wow... are you kidding me - two days on that... thanks. works now. 

bruce_williams

That is a great learning moment for me and what a cool feature loft is. Nice job OS team!

owen_sparks

NeilCooke said:

@michael_watson add 2 sketch fillets to remove the sharp corners in sketch4

Nice Neil

I'm still seeing some weirdness.

***Edit, please note that the numpty that wrote this didn't read the instructions properly 

(a) Doing as Neil suggests and then selecting the whole "sketch4" from the feature tree as the guide works fine.
(b) As above but selecting the individual sketch4 entities in the graphics area fails to loft
(c) Selecting the same entities to make a composite curve and then using the new curve as the guide works fine also.

Linky

Confused.com

Owen S

bruce_williams

@owen_sparks - So your method (b) is tricky.  Reading help on Loft I found "To select tangentially connected curves as a single guide, click the down arrow next to the selected guide to open the field for more selections. "   So the two clues are "tangentially" & "click the down arrow".

You selected each curve segment as a new guide curve.  Instead click the > at guide to expand it and then select all segments into one guide.  Now that is (my favorite word...wait for it....)  ESOTERIC.

Thanks for hammering on that Owen; now I learned even more!

michael_watson

@owen_sparks & @bruce_williams this is some great stuff, guys. Appreciate the informative posts.

owen_sparks

Thank you sir, I'm glad my ineptitude helped you out!

@bruce_williams, at least one of us is prepared to RTFM.

Now you mention it I remember thinking "that's clever" when OS released it.  Doh.

"To select tangentially connected curves as a single guide, click the down arrow next to the selected guide to open the field for more selections. Make additional selections:"  In my pedantic defence it only turns into a down arrow after you've clicked it, before then its an across arrow 

Ooops.  Then again if I'm dull enough to get it wrong presumably others will too.  OS is there an opportunity to make this a bit more obvious from an UX point of view, some sort of anti-numpty methodology?

I'm going to give up thinking until the new year, I've clearly lost all aptitude for it.

Cheers all,

Owen S

michael_watson

@owen_sparks  Ha - you got it to work with composite curves - I did not. So you are firing on more cylinders than myself. I realize now I was selecting the composite curve from the Features and not the Curves and it would never accept it as a guideline. 

In any case, I just learned more about how to properly do lofts in this conversation than I understood from the ~10 videos, the manual, and various other loft-related posts that I have looked at for the last two days. Appreciate the walk-thru and easy to follow explanations and the picture that shows how to select the individual components to make a guideline.

owen_sparks

Sure thing!

This is a pretty friendly forum to bounce ideas around in so feel free to keep asking questions.

If you've got an Extrude question I might even be able to answer it correctly.

Cheers Owen S.

bruce_williams

@owen_sparks

You did well with that question!

owen_sparks

Love it @bruce_williams, made me feel much better, thanks

Owen S

chris_8

A point that I picked up from an OS video several months ago:  coincident is not the same as intersect.   The loft function prefers the "intersect" constraint for the points where guides meet profiles.

This seems obvious to some I'm sure, but it took me a while to realize the word "intersect" was being used in those how-to-loft videos for a reason

Chris_S_2018

I appreciate all the feedback. I finally figured out that the trick to using a single spline as a guide was to draw the faces for the loft first.  Than I draw a spline that is on an orthogonal plane.  As I click each control point for the spline I put it close to the edges of the loft faces.  Than I go back and use the pierce command to put the spline control point on each face.  Than I use the split command on the spline and split the spline close to each face.  Finally I use the pierce command again to pierce the split points on the faces of the loft.  I can then loft between each face one at a time and use the split segments of the spline as a guide.  

chris_8

Chris_Shearer said:

 Finally I use the pierce command again

Yes Pierce is the word I should have used instead of Intersect.  I'm glad loft is working for you now.