Every time I move a curved objects face vertically it ends up "bowing"

advice

#1

I have a pretty simple curve that is a 41mm half-circle, extruded so it has 3x3mm sides. I want to move the one face up so it’s the start of a ramp (essentially) but every time I move the face up, the half circle bulges out instead of staying at the 41mm that it started out. I am moving the face directly on the Y axis (up arrow on the keyboard). The screenshot shows that the Radius of the circle expands to 55.6mm instead of staying at 41mm. How can I contrain the half-circle so it keeps the dimensions?

I also tried doing a “line version” put when using the “follow me” tool the end-point face is skewed and tilted compared to the face I originally start the follow me tool with.

I hope this makes sens but I can clarify if needed. Thanks for nay help.


#2

It’s not unusual to wind up with distorted geometry when you do something like that. I would use Upright Extruder with the profile and a rising curve for the path. You can get Upright Extruder from the Extension Warehouse.


#3

Sigh I so hate this forum software…Meant to reply to DaveR but it won’t let me re-port as a reply…

I installed the plugin but it doesn’t work the way I would have expected well, or hoped.

If I make a flat path and make a 3x3 square face for it to follow the plugin works as intended. However, If I try to take the single face and move it up, it gets distorted because a bunch of faces “stick” to the ground. No idea idea how to solve that.

If I make a path that is already curved like the one shown below:

It makes the shape but has a bunch of faces missing (which is fixable) and it’s still bowed out (because the curve path is bowed out once I move it up.

So, I am stuck again trying to get rid of this bowing effect.


#4

How about uploading the SKP file?


#5

upload2.skp (41.0 KB)

1st shows that I am starting with a standard circle, second shows just simply moving the one edge up and the 3x3 face I used for the upright extruder plugin. 4th shows why I am saying it’s “bowing” I want this to hug the half-cylinder.

The end result I am trying to go for is to carve that 3x3 piece out of the cylinder and I suspect I am going at in a completely un-sketchup-like way. I have also tried using the “tools on surface” plugin which feels more intuitive but also has it’s own issues.


#6

There’s issues with the path you are creating because it becomes elliptical in plan view when you move the end of the arc up like that.


At the bottom left of the screenshot, above, is my version. You can see it maintains the circular shape.

upload2.skp (79.9 KB)

I used the Helix tool in the Curve Maker extension to create a half turn helix with a pitch of 100. (50 for the half turn) and then I used Upright Extruder to extrude the square.


#7

That is EXACTLY what I needed! I didn’t even know such a plugin was needed or existed. That solves all of my issues! Thank you!