Manifold issue creation

I am looking for advice on how to avoid the manifold issues I am creating on the attached model. I have made and printed this part successfully twice with some minor manifold issues. Whatever I changed created a corrupted print. I started over and have the base part provided and clean, but when I add the single support spoke it creates the issue, and I am unclear why it is not seeing the faces or edges correctly. I don’t know if the pic below comes thru yet, but the .SKP appears to have. Any assistance is kindly appreciated.

Focus Wheel Cap V7.skp (131.9 KB)

You’ve got multiple problems. There are reversed faces on that center part.
Screenshot - 5_22_2023 , 3_15_15 PM
The other part isn’t complete. You’ll need to create a face across the end of the spine and erase the face under the spine.

What steps did you follow to make this thing? How will it be used?

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You made the top part a group but left the rest as raw geometry. It created some internal faces and that’s why you were having slicing problems.

Here’s a revised version:
Fixed Focus Wheel Cap V7.skp (131.9 KB)

Even ran it through Cura and found no printing issues.

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NP beat me to uploading but since I redrew your model as a single solid component I’ll share it. Your original is still in the model. I drew the cross section of the cap and used Follow Me to make the initial part of it. Then I just trimmed away what wasn’t needed and add in the spine.

Focus Wheel Cap V7dr.skp (210.1 KB)

Thanks to you both pointing out the basics I miss while learning to drive. I wondered about mixing grouped/components and raw. Also I seem to miss when I create reversed faces and thought I had rotated to check for that by looking for white faces. I’ll take all this and finalize and review your versions to learn for the next round!

I’ll repeat what you did here to learn as it is likely a much better approach.

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The short version is I create the bottom disk and then raise up the edge ring. I didn’t make into a comp or group obviously. Then I separately created the hub and made a comp. Then moved to sit on the face at the center of the disk. My revision was to add the spokes to add support as these parts warped as I thought they might with sun exposure out of PLA. Still stress relieved. I am going to print in PETG to see if that is enough. Anyhow I am sure in some attempts I have added lines for all edges on the spokes to make sure I have an enclosure but clearly missed on this example. I noticed closing that one face against the hub it not enough to create a solid. I will learn how to view so I can see there are all faces and I think by making these grouped or comps and lifting to see from the other parts like the disk.
This is a center wheel cap for a Ford Focus and then I glue on separately printed items that contrast. Fun and a way to replace the ever breaking OEM parts.

I’m still not sure how to see which faces are reversed but I’ll rotate it to see if any remain grey. Is there an easier method to check, or avoid when I am cutting segments out of a solid using lines an push?

Your method sounds like a lot more work than it needs to be. Even if you were going to make the disc and the center part separately, it would be easier to make the disc part and make that geometry a group or component (I prefer the latter) and then model the center part in place on top of it. Saves a bit of work and reduces the chances of inducing errors.

As for the back faes, you’ll just have to get in the habit of orbiting around to look for them. If you were using SketchUp Go or SketchUp Pro you could edit the style to make the back face more obvious.

Thanks. I have made separate sub-items comps before and merged them. I will make that a habit. I think I would still have created a problem when I added the spokes, my way, but I’ll look at your suggested and follow me. I just fixed mine by raising what I could of the spoke, making it a solid and component, and lowering into place. that worked. I will now try to copy n times to see if I can easily repeat it around and not one for each placement. I did create some blank int he inner OD wall, so ended up with some lines but that wouldn’t occur if I do this from the start.

You’re in luck. I found a short video from our own Aaron on YouTube just yesterday (it’s a short, so I can’t embed it here, but I’ll do my best approximation. This should work in the free version of the web browser, but apologies if it isn’t so.
Go to the Styles tab on the right hand menu.

Click on “Edit Style” (the little pencil).
Then go to the “Back Edges” and click on the little square.

You’ll get a color selector, complete with a convenient little hex code for reference. Simply pick a bright, contrasting color like pink or yellow.

Now all of your reversed faces will stand out as you pan around.

Alternatively, if you can’t edit the style, there’s other color sets available you could quickly switch to.

Aaron’s video was done in the desktop version and this works for SketchUp Go but SketchUp Free doesn’t have the facility to edit styles. Using one of those funky color sets would work although I’d find modeling with them annoying.

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I’d be curious to see how well PETG would hold up in the application you’ve described. Although it’s a lot more durable than PLA, it’s still hygroscopic and could break down over time depending on the environment. As much as I hate it with every ounce of my being, you may want to consider ABS. It’s the type of plastic most car parts are made of in the first place, and it’s meant to handle the elements as it doesn’t absorb moisture like PLA or PETG.

Right you are, Dave, on both fronts. If I ever use one of those high contrast styles, it’s purely for when I export to a 2D graphic. I’m normally a big fan of dark mode, but something about SketchUp makes it feel weird to work in an environment like that. Maybe it’s the whole “cutting foam core” aesthetic SketchUp is built on.

The free version can use a style from another model, so if you can make one in a trial or get one from the warehouse that suits you can set that as a template.


Thanks to all three of you. I’ll explore the ideas resented for face views I can use in the free cloud version, and I will forever more make all my designs using components that merge and/or use sections to trace around using follow me.

As to PETG, I am trying that to see how it performs now that I have the part sorted out. I had printed my first in that material but that was with my manifold error and it caused quite the mess backing up around the print head and out everywhere as the z axis was not incrementing! I can always use a clear coat to help with moisture absorption once I get them to survive sun exposure. Unexpectedly the heat from the brakes are a minimal cause as I don’t see any difference in warping from the front to rear wheels.

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