Quality Assurance of 3D Models Using Solid Inspector

At Boots Industries we often use SketchUp to create 3D models that are ready for print.  In this article, we’ll introduce the use of a SketchUp plug-in called “Solid Inspector” created by Thomas Thomassen. This plug-in is so effective that it’s now used every time we design a part in SketchUp.

An important step in producing high-quality models is to ensure that they are “watertight”. What does watertight mean? Essentially, it means that there are no holes in any of the shapes and that if you were to trap water inside the model it would have no way to escape. Creating watertight models is vital in order to ensure that your slicer software is able to properly interpret the model and print it without any unexpected results.

Still not convinced? Let’s look at a simple example so that you can see what could happen if your model is not watertight. Let’s start with a hollow cube.

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This cube is watertight and when we bring it into our slicing program we obtain the expected result in the 3D preview window.

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Now, let’s voluntarily introduce a small pinhole in the model and see what happens when we slice the model. We’ll exaggerate the pinhole and make it obvious for the sake of this demonstration, but, when dealing with complex models, some small holes and discontinuities can be quite hard to see.

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This time when we slice the model and look at the preview we can see that the slicer could not properly interpret the model and has filled the hollow part of the cube.

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Now, had we used the Solid Inspector, it would have alerted us immediately to the pinhole and would have allowed us to correct the model before slicing.

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In order to use the Solid Inspector, you must first “group” the shapes of your model. This can be done by right clicking the model and clicking on Select, then All Connected and then right clicking again and selecting Make Group.

Selecting an entire object

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Select the model (it will become blue when selected) and simply press “I” to run the Solid Inspector. Alternatively, you can go into Tools and then select Solid Inspector. You will find that if your model is fine, nothing will happen and that when there is a problem there will be a visual indication. Red indications sometimes refer to water tightness problems.

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So far we have focused on water tightness, but another important feature of this plug-in is that it allows you to quickly identify and remove unnecessary components in your model. This is what we call the “cleanliness” of the model. It’s good practice to make sure that your models do not carry useless edges or faces.

It’s a fact that sometimes after a long night designing parts we sometimes forget to remove a useless edge. By applying the Solid Inspector we can quickly find these unnecessary components and remove them. You probably noticed on the last image that there is also a yellow indication. This indication marks a useless component, i.e. one that does not form a useful volume in the model.  In this case, I simply drew a random line on a face of the model and Solid Inspector determined that it’s not really useful in my model. If I remove it, the yellow indication will disappear.

Typically, we work with the Solid Inspector to solve one problem at a time. Then, we inspect again to see if the problem has been solved. It’s not uncommon to solve a problem and see new problems appear in models that are complex. Simply go through and eliminate each problem one by one until you have a clean model.

To get you started we’ve included additional examples of typical problems you will encounter when making 3D models.

A possible problem is when you have a useless face inside a model that does not contribute to the overall volume. In this case we also receive a red indication and the entire perimeter of the face in question is highlighted.

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If we take a closer look at the model by using a section pane (click on Tools and then select Section Pane) we can clearly see that a face exists inside the model. In this case all that is left to do is remove that inner face and re-assess the model using Solid Inspector.

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Another problem you might encounter is an error where there doesn’t seem to be anything abnormal with the model. This can occur when some aspects of the geometry are “hidden” from view.

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In this case it’s useful to go into the View options and select Hidden Geometry to show the hidden features of the model. Once the culprit has been revealed you can select and delete as normal.

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In conclusion, this plug-in is fantastic at quickly evaluating the water tightness and cleanliness of a part before production, but it’s also a great learning tool. Indeed, as you spend more time designing you will learn how to anticipate where and how errors occur in typical models.

To help you better understand we’ve also included a SketchUp model with the examples used in this article.

Download it now!

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