"breaking" planes and non-intersecting bodies

Hello,

I have been using Sketchup Web for quite a while for simple Floor plans etc. But as I have started 3D Modeling for printing, I am using it more intensively. I keep having one recurring problem, which is being constantly frustrating and often causing me to be “creative” in order just to being able to print parts at all.

I will try to describe my issue: In this current project, I have drawn a basic 2D-Shape, used “Offset” and “Push-Pull” to create a 3D-Shape. Altough I have been paying attention to using the Snap and Alignment guides, I keep getting “broken” planes on the top of my 3D-Model. Where I would like it to intersect with other objects (e.g. extrude a Circle into the object for creating a Screw-Hole) it doesn’t. Also, even if I try to at least make it work “somehow” while using creative (but not clean) methods, the 3D-Slicer identifies these issues as being wrong and eliminates a part of my model.

I somehow have the feeling that Sketchup Web is in my case somehow drawing less accurate than it is posing to do and therefore resulting in inconsistent planes and Endpoints. Maybe this has to do with those accuracy-settings?

For some reason, I can not upload any files. Maybe it is because I just recently joined the Forum.

You will probably be allowed to upload a file after posting another reply or two. Or, you could upload an example model to a site such a DropBox, make the file public, and then post a link to the file here.

All variants of SketchUp are extremely precise in terms of 3D coordinates for geometry (much less than a millionth of an inch). I’m guessing that geometric accuracy issues in your models are caused by using unintended inference points (e.g., using the wrong one of two closely-spaced inferences), or possibly because SketchUp’s evil “Length Snapping” feature is enabled.

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You will probably be allowed to upload a file after posting another reply or two. Or, you could upload an example model to a site such a DropBox, make the file public, and then post a link to the file here.

Thank you! I just realized this. Here is my example where I encounter this problem currently:

And this is the Sketchup File:

While it looks okay now, the top Part which is extruded from the Base seems to have issues with planes not perfectly “understood” by Sketchup. I must say, I have already (poorly) tried to fix the issues so it might already be more of a mess than when I had done the actual mistake.

All variants of SketchUp are extremely precise in terms of 3D coordinates for geometry (much less than a millionth of an inch). I’m guessing that geometric accuracy issues in your models are caused by using unintended inference points (e.g., using the wrong one of two closely-spaced inferences), or possibly because SketchUp’s evil “Length Snapping” feature is enabled.

Yes, thank you! I kind of realized this. My mother language is not English so please excuse my inaccuracy. I more meant that what looked to me as being aligned (especially: aligned in one plane) and also displayed by Sketchup as such turns out to be not so.

There does seem to be a mess in this model. Some of the surfaces are divided but those coplanar edges can be erased. There’s a bunch of internal geometry and what looks like some important stuff embedded in the rest as if maybe this should be two separate pieces that have become intersected due to lack of use of groups or components. The bulk of what I see “wrong” with the model I would attribute to your modeling workflow.

How thick are the sides of this thing supposed to be?

Thank you for your answer. I realize I am probably making 10 mistakes at a time so it might be difficult to help.

First of all, what I did not mention: I inserted one existing part from thingiverse, which is the small part in the top with the triangles.

However, because I have already had my share of frustration, I had saved a backup before going into merging them together:

Here with the SKP File:

At least from my understanding this should have been the point where still everything was fine. At least I had this impression. In the subsequent steps I always discovered that on the top part of the model, those planes start behaving strange and not being “planes” anymore. What I mean: I could not intersect them, whole parts of my object kept being deleted when I just wanted one plane to disappear.

How thick are the sides of this thing supposed to be?

Basically 3mm but I had scaled up the whole model by a factor, as I have previously run into the issue that on a mm-scale some small arcs with small diameters where not possible to be drawn anymore.

So that’s typical of importing .stl since they are always triangulated. For something as simple as that object is, I would be inclined to use it as a guide and create a new version of it that is correct and clean.

The intersection thing appears to have a problem due to the already triangulated geometry in the imported object.

I would suggest trying to do the modeling at meters so the wall thickness would be 3 meters. The .stl file you export will have no units so if your slicer will allow you to define import units as millimeters, you don’t need to scale down before exporting.

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Okay this is interesting! I did not know there is something like a “reverse” face. I did not know that faces do have “front” or “back”. Or did I misunderstand you? Apart from this: Yes, you are right, I do not have a “workflow”, I just do :slight_smile: . But to my excuse: These internal structures are usually eliminated by the slicer software anyway.

To give a bit of context. What I am trying to do is a variant of this: Electricity meter - AI-on-the-edge (Less support is needed, also closer to the Meter) by DerpyDoom - Thingiverse

Thank you for your analysis!

There are issues with both parts before the merge. In the bottom part (which you should make into a component), there are internal faces where the top meets the sides. You can see them in the image below where I hid the top face first. The easiest way to get rid of them is to erase the edges that separate the middle of the top from the sides (without hiding anything). These faces are coplanar, so they don’t really need to be separated anyway.

The top object imported from thingverse is a component, but is somewhat of a mess. If you select it, you will see in entity info that it is not a SketchUp solid. The core problem isn’t all those diagonal lines (which are messy but can be erased with no impact in SketchUp because they aren’t needed - probably arose when the object was modeled in stl format, which uses only triangles). The issue is that there is a tiny hole at the location highlighted in red in the image below. There are actually three edges there, where there should only be two: there is a long one running the whole length, and two shorter ones for the top and bottom sections. I found that if you erase all three as well as the diagonals leading to the middle vertex (faces will disappear) and then redraw those parts using the rectangle tool in SketchUp, the flaw will be healed.

Now when you place the top object overlapping the bottom one, you can open each for edit, select the areas that overlap, do Intersect Faces with model, and the erase the extra edges and faces where they overlap. It can be helpful to use x-ray view or to temporarily hide outer faces, because most of the extras are concealed inside the objects. This process is much easier in the pro version because you can use solid tools to do the tedious work automatically.

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oh wow!

I must say you managed the full solution in the amount of time it just takes me to rage out about single problems within the process :smiley:

But seriously, thank you for this explanation as I can now see how this approach leads to a much more clean process to reach the goal. I have the feeling the choice of a smooth workflow is also a matter of practice and foresight a few steps ahead.

The issue is that there is a tiny hole at the location highlighted in red in the image below.

Okay right. It makes even more sense now to create objects like these myself when I see a pitfall like this one.

I will take some time to go through this step by step. It is great to see that there is this amount of helpfulness and structured thinking here as I was already starting to give up on Sketchup. Thanks so much!

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