Intersecting two cylinders not a solid


#1

Hello, First post:
I’m trying to create an intersection of two cylinders to make a custom replacement plastic piece for my moms 1999 Ford Ranger. It seems really simple, but I’ve found myself swearing and looking at Youtube videos for the last hour. It seems like everything I try results in a non-solid object. The picture below shows what I am trying to make. There is a cylinder, with a perpendicular intersecting cylinder. Running Solid Inspector shows that it is all jacked up. If I use “Fix All”, it simply erases the red cylinder. How do I combine these objects without ripping my hair out? I tried combining two cylinders in a fresh project and doing a solid inspector check and the exact thing happens.

Steps to reproduce:

  1. Create a cylinder.
  2. Copy cylinder.
  3. Rotate cylinder 90 degrees.
  4. Move the cylinder into the other cylinder.
  5. Run solid inspector.
  6. Fix all
    Note the cylinder disappears.

#2

Try modeling the thing at 100x scale. If it works, just scale it down to full size when you’re done.

-Gully

Edit: As I take a second look at your picture, I see that you have apparently not intersected the two cylinders. Ylu need to select them both, then right-click > Intersect Faces with Selected. Then clean all the extra geometry out of the inside of the intersection. The completed object should be completely hollow.


#3

Do model at large scale to prevent getting short edges when doing the necessary ‘Intersect’ operation(s).
In the end scale geometry down to actual size.

A SketchUp solid is a wathertight shell of faces with nothing inside. And it is grouped.

Draw a cylinder and group it.
Copy the group and rotate it into position.
Select all, right click on the selection and select ‘Explode’ in the context menu
Select all and select ‘Intersect Faces with Selection’ in the context menu
Delete internal geometry. (temporarily hide obstructing faces of the shell)
Select all and group again. The group should be a solid group now.


#4

The intersect faces got me a step closer. I ended up having a lot of faces to clean up, but it did finally work. It seems to auto-intersect with other objects for me for some reason. I understand that the arcs combining with arcs creates a complex object, though. Is there no better way to design small parts other than scaling everything 100x? I’m trying to mimic a plastic part that already exists and I’m just measuring stuff. Kind of a nuisance to have to 100x every measurement.


#5

in metric units or in inches?


#6

In inches. Not sure what else to type, but I apparently have a minimum character limit… So here’s some more text…


#7

I get that I can just multiply the top part by 100. But it’s a bit confusing when I’m looking at a sheet of paper and going back and forth. Just creates more variables and more confusion when I’m trying to match.


#8

Perhaps this, start your model at full scale, make it a component. Make a copy of this and scale it up by 100x. You can draw most of the part in the original copy but do the intersecting and cleanup in the larger one.
I hope this makes sense.

Shep


#9

Sounds like a good idea. I just did the 100x for every individual component and it seems to be functioning. The intersection didn’t require any fixing, so that’s good. I’ll have to try what you mentioned later Shep. But I would imagine that would work.


#10

Unless you are talking about very small sizes you’ll probably get away with just working with 1 inch as 1 foot. So 1 and a 1/4 becomes 1’3" or 15" and so on.


#11

You might try grouping things and exporting them without trying to perform proper intersections and cleanup. To try and mimic your project, I created a model using a 1" diameter disk and similar detail:

I grouped the top disk and central column together and then created the bottom cylinder and grouped it separately. The exported DAE file was uploaded to a 3D vendor where their software determined it was printable:

I’ve had good luck with this approach as long as the individual groups or components are each manifold and watertight and never intersect exactly in one point or share a common line. While I understand why the printer software’s scan/layer logic shouldn’t have any problem with the nested solids, I haven’t tried this with anything but DAE files and a single vendor.

It would be useful to know if this approach works for STL files or home printers, etc.


#12

I just did a version 2 of this (the item i’m trying to recreate is inaccessible, so I’m half guessing at the dimensions and testing after printing). Grouping the cylinder and then moving it into position and exporting to STL does work and the slicer successfully converted it. I’m about to go to print with v2. Thanks. Looks like that’s the way to go.


#13

Can you share the model?
Also, what version of Solid Inspector are you using?


#14

Mom_Ranger.skp (106.2 KB)
I just updated Solid Inspector2 to the latest and still the same. (Version: Solid Inspector² 2.4.3; March 17, 2015). I don’t believe this issue is caused by Solid Inspector. If you look at the attached skp, there are a few random vertexes that are being welded that don’t really make sense. As others were saying, it looks like something that is happening because of the scale of the model.
-Disclaimer: I’m half asleep right now, so this post is possibly unintelligible.


#15

Also, here is the second revision to the model using the tips above (scaling 100 times and grouping the intersection). In case you have a 99 Ford Ranger and the center console piece is broken. :wink:

Mom_Ranger_Attempt2.skp (289.0 KB)


#16

For this model the issue is that the meshes doesn’t intersect. You have faces crossing each other, but you would need to run Intersect With on them to make sure the faces split each other. In this case the intersect messed up the mesh - looks like the mesh was too small.


#17

Also here there are faces which needs intersecting so they splt each other:


#18

I grouped the two “wings” and the cylinder into one group. Opened the group and exploded the two “wings”. (The object itself needs to contain only faces and edge - no sub-instances.)

Then all the faces are properly intersected:

I can then run the Inspector:

Bob is your uncle!


#19

I can do the intersection with those faces in the model I provided because it is 100x scale. The problem came about because I didn’t know about the scale issue. (Which I’m pretty sure is a bug in SketchUp that is likely to be played off as working as intended.) But grouping the independent objects that are already solids allows slicing / printing without worrying about intersecting faces at any scale. If I try to intersect faces at the original dimensions, SketchUp projectile vomits all over my project.


#20

Actually, it’s being played off as “It is what it is–get over it and learn to multiply by 100.”

-Gully