Why don't my extrusions work? (Follow Me tool)


#1

Sketchup is driving me NUTS.

I am trying to create a design that involves what is in effect a tubular question mark with curves where the circular top semi-circle joins the vertial. However Sketchup’s “Follow Me” is refusing to go around corners!

Here’s what I did.

  1. I started by creating a circle,

  2. I used the Line tool to remove the unwanted section of the circle.

  3. I drew a line from the base of the circle down/away from the center of the circle.

  4. I then used the “2-Point Arc” tool to make a radiused corner

  5. I then deleted the unwanted parts of the corner.
    ==> We now have a question mark shape.

  6. I add a circle whose center is at the base of the question mark shape

  7. I then select all 3 sections of the line using select tool

  8. But when I click on the Follow Me tool it either soon stops and the end of the straight section OR it moans that the line is on a path or something similar.

I have tried rebuilding the above about 5 times, using slightly different techniques but still it fails to work.

What am I doing wrong?

e.g. Is there something I need to do to make the question mark line formally become a single line?

Honestly I go from loving Sketchup - all is so easy in the tutorials - to wanting to kill someone.

(OK before you call the cops, no not literally.)

PS Does it matter whether I extrude from the white or the dark side?


#2

for this type of question it’s best to add the skp to your post…

john


#3

Done.

Sketchup_v001a_real.skp (1.1 MB)

P.S. And when I try to extrude using a circle from the other end of the “question mark” line, with the Follow Me tool the circle just disappears!


#4

The main problem is that your model is too small and is running afoul of SketchUp’s tolerance for creating small geometry. Here’s what I got by scaling everything up by a factor of 100 before doing the followme (by the way, you can select a bunch of segments for the path using either a drag box or by ctrl-clicking multiple parts):


#5

Looks promising. Thanks. OK so would it be sensible for me to work in metres instead of mm and simply reduce in scale by x1000?

Edit: Apparently yes. (Answered in my other thread)


#6

That is one common approach. Wait until your model is complete and then scale the whole thing down by 1000 before export.


#7

slbaumgartner OK many thanks


#8

Wait - I have a new, but related problem… (btw, should I start a new thread?)

Nothing I do seems to allow me to create “solid” groups. Is there some trick to getting all the surfaces to seal up?


#9

It’s probably the path lines left inside the crook.

Shep


#10

I have tried building the crook / question mark shape about 3 different ways.

How can I fix the problem?


#11

There are several ways to fix the problem. Edit the group, switch to wireframe face style and delete the crook shape is one way.

Another way is to not put the path inside the extrusion in the first place so you can easily delete it when you’re finished with it.


#12

Another thing to consider is whether you really need so many segments in your circles and arcs. Due to them followme is creating a tremendous number of very small edges and faces (I got 40834!), probably much smaller than will have any use in your final model.


#13

Yes, it was simply the fact that the original path was still inside the volume of the 3D shape that screwed up its ability to make a 3D object. [Another quirk of Sketchup!] Thanks.

Probably not - I have no idea!

My plan will be to 3D print the final object which will include a piston of radius c.5mm with a cylinder going up and down it. Fwiw, I am now working at a scale of meters and will shrink the model by x1000. I will need an accuracy of say 0.05mm in the model. How many sides to my circles would seem reasonable? (The default 24 doesn’t look to me like it will be enough!)


#14

The easy definition of a solid group or component is that every edge must be shared by exactly two faces. No more and no less. The path you drew for Follow Me was a series of edges that were shared by zero faces. Obviously if there are holes, the faces surrounding the hole will have at least one edge which is shared by only one face and thus the shape would not be “solid”.

24 probably isn’t for the application at hand but I’d bet the numbers you’ve chosen are much higher than they need to be. You might compare the length of the resulting edges with the resolution of the printer.

While learning how to use SketchUp, it would be less frustrating if you keep your models simpler.


#15

Ultimately, the results you get from your 3D printer will tell you, though that’s a time and expense-consuming experiment. I think @jimhami42 has somewhere provided an extension that will calculate the deviation between a true arc and SketchUp’s segmented representation for a given radius and number of segments, though I can’t find it now. I believe @TIG may have done something similar. Or you can work out the math yourself if you are adept at geometry.


#16

My current model has circles with 64 rather than 24 sides.
How much does it matter if my geometry has too many faces & edges?
I mean it will obviously run a bit slower when rendering to screen. But will it make the 3D printing slower too?

PS What is the point of grey(inside?) and white(outside) surfaces? Does it matter whether the white or the grey surface is on the outside of an object? (I seem to be able to create Solid Groups with grey on the outside…)


#17

Actually the more ROUND it is the easier for the 3D printer to make as it does not have to make changes for each face just make a circle and fill in the area . So 360 faces makes it almost round . . . Like in CNC programming a G03 r 2.00 or something like that been long time since I was a CNC Programmer GEEZ almost 30 years ago WOW I am OLD . . haha still ride a motorcycle though ! Kawasaki Vulcan 900 Classic . . 2007 version
Back to answer the radius is the center of the extruder nozzle not the edge of the layer or where the circle is . . That is why it takes longer to make a 2 inch radius base 1/4 inch thick and fill in than the 2 inch radius with a say 1/4 inch wall by 1/4 inch tall . . This also depends on FILL IN mine is set to 90 % for really nice looking surface , , And it depends on the material also the ABS takes a bed temp of 110 and PLA only takes temp of 60 . .


#18

Every SketchUp face has a front side and a back side, or, in the context of a solid, outside and inside. Technically, the normal to the face points out from the “front” surface, which matters to anything that does math or interpretation based on the orientation of the face. For example, a renderer will choose what a surface looks like based on the orientation of the normal. The orientation can matter a lot in a surface comprised of multiple faces, because if adjacent faces don’t have their fronts the same way across the edge that joins them, there is a confused notion of which side of the surface is which.

Sometimes a SketchUp operation can’t deduce which way you thought was meant to be “outside”, especially as you assemble an object in multiple steps. This may cause SketchUp to orient adjacent faces inconsistently. Because the inconsistency can confuse downstream usage of the object, SketchUp does not consider it to be a “solid” unless the faces are all oriented consistently with their neighbors.


#19

A simple way of looking at it.
Place a cube within a cube.
White face big cube out, small cube white faces in,(so blue faces facing each other) print result will be a cube with a cube void within.
Big cube white faces out, small cube white faces out, print result will be solid cube with solid cube inside, in other words a solid cube.


#20

Ship 69, with no problem
I drew the ? first without using the arc tool for the rounded corner and it extruded no problem. Then I used the arc tool and it failed to extrude. the line was broken into three segments, so I using the weld tool I made it one segment and it extruded