topic Re: HELP SWEEP ALONG PATHWAY ERROR in AutoCAD Forum

HELP SWEEP ALONG PATHWAY ERROR

yasna.masye — Sat, 02 Dec 2023 11:16:34 GMT

Hi, I am currently designing a spiral with trapezoidal channel. My issue is that when I tried to sweep the trapezoid channel along the spiral line pathway, one of the sides is unable to be sweeped/error. This results in an incomplete channel with one of the outer sides missing. I read some forums regarding sweeping errors and it mostly happens due to the fact that the object is not perpendicular with the pathway chosen, with this I have tried to adjust the position but still no such luck. Please do help if possible, I attach the file below. Thank you

Here are some before and after sweep pictures for fast observation of the issue i am dealing with

I am using the newest AutoCAD 2024

Re: HELP SWEEP ALONG PATHWAY ERROR

j.palmeL29YX — Sat, 02 Dec 2023 12:44:45 GMT

Attached an attempt.

Suggestions to get this:

- join the 4 lines to one polyline

- while sweeping set Alignment to NO.

A question (because it is not very usual): Why is your profile not perpendicular to the path oriented?

Re: HELP SWEEP ALONG PATHWAY ERROR

yasna.masye — Sat, 02 Dec 2023 14:28:34 GMT

Thank you so much!

I actually tried aligning the profile to the path, but I think it didn't end up as it should have.

For future designs, any tips to make sure that it is align and if not how to fix (tool)? I apologize for asking such simple questions, I am quite new with the software 🙂

Re: HELP SWEEP ALONG PATHWAY ERROR

leeminardi — Sat, 02 Dec 2023 14:53:50 GMT

@yasna.masye If I may add to the excellent advice from @j.palmeL29YX (I was looking at your post while he ws answering it).

To get a shape perpendicular to spline do the following.

Create a UCS using the ZA option with the origin at the beginning of the spline and the second CV for the second point defing the ZA vector. For your drawing this is 0.0,-0.4850,1.5741
Use the align commad (using 3 points) to position the shape. For source and target points for the point #1 use 0,0,0 for both; for the second source point reference a point on the x axis of the shape and its target as 1,0,0; for the third source point use any point in the positive XY quadrant of the shape and 1,1,0 for the target point.
Once you have the shape aligned properly you can use the 2D rotate command to control the twist angle.

The white shape is your original shape while the green shape is aligned perpendicular to the spline's end vector.

On a related note, I needed to have more control of the twist vector for sweep on another project so I created a lisp program to positon and align tangentially multiple copies of a block along a spline. Each block could be independetly rotated about its normal. The blocks are then exploded and loft is used to create a swept shape. Let me know if you think you might have a need for it.

Re: HELP SWEEP ALONG PATHWAY ERROR

j.palmeL29YX — Sat, 02 Dec 2023 17:34:43 GMT

@leeminardi wrote:

Create a UCS using the ZA option with the origin at the beginning of the spline and the second CV for the second point defing the ZA vector. For your drawing this is 0.0,-0.4850,1.5741

.

@leeminardi

Where are these values coming from?

If I need an UCS perpendicular to the end of a spline (and don't want to use any LISP to get this) I go usually the following steps:

- Draw anywhere a small circle

- run the sweep command and sweep the circle along the spline path (MOde SOLID, Alingnment YES).

(AutoCAD itselfe rotates the circle correct perpendicular to the startpoint of the path spline.)

- run the command UCS -> Face -> ... and pick the front face of the sweeped circle.

- If necessary run the UCS command again and move the UCS to the center of the circle or the endpoint of the Spline (they should be identical)

- you can delete the circle and the sweep object. The result is an UCS whose Z-axis it tangent to the endpoint of the spline. (If you need additional you can rotate the UCS around its Z-axis).

In @yasna.masye 's dwg your coordinate given above has an distance of 0.00003554 from my Z-axis, I think it is negligible 😉

Re: HELP SWEEP ALONG PATHWAY ERROR

leeminardi — Sat, 02 Dec 2023 19:20:30 GMT

@j.palmeL29YX wrote:
@leeminardi wrote:

Create a UCS using the ZA option with the origin at the beginning of the spline and the second CV for the second point defing the ZA vector. For your drawing this is 0.0,-0.4850,1.5741
.
@leeminardi
Where are these values coming from?
!@

@j.palmeL29YX you can get CV coordinates from the properties panel. You will want the second CV or the next to the last CV for the other end of the spline (32 for this spline of 33 CVs).

I must have moved the spline in my last post as the coordinates are different when I went back and loooked at the OP's drawing.
Here's the UCS with the Z axis tangent to the start of the spline. The red rectangle lies on the UCS XY plane.

You can also get CV coordinates with the LIST command.

Re: HELP SWEEP ALONG PATHWAY ERROR

Washingtonn — Sat, 02 Dec 2023 19:36:41 GMT

My suggestion:

1. Create an OFFSET to the spline (RED)

2. Connect the endpoints of the original spline and the offset spline (GREEN) to get your starting perpendicular.

3. Create the sweep object as a closed poly line (BLUE).

4. Align it to the spline perpendicular (GREEN)

5. Use the SWEEP command to create the desired solid.

Re: HELP SWEEP ALONG PATHWAY ERROR

j.palmeL29YX — Sun, 03 Dec 2023 08:36:32 GMT

@leeminardi wrote:

get CV coordinates

Oops, at the moment I was not aware of the CV mode. Sorry for my dumb question 😉