Zero thickness Geometry error Solidworks
What it is, Why it happens and how to fix it.
What is Zero Thickness error?
Zero thickness geometry error occurs because the software can not calculate whether material should be placed in a certain point or not. This is a common problem that occurs in many different CAD programs. You may have heard the term ‘non-manifold geometry’, which is defined as ‘A 3D shape that cannot be unfolded into a 2D surface’. It is known, in solidworks, as ‘zero thickness error’. Both are very similar and are fixed in the same way.
If you search ‘zero thickness error’ the information google offers is niether a definition or a solution. Solidworks help has a page on zero thickness geometry. My post will elaborate in fine detail on each example of non-manifold geometry (generic industry term for zero thickness geometry) in its different forms.
Why does it occur?
In order for me to communicate why this happens, I will sketch out a basic square in solidworks. I will then add a circle that is tangent to one of the outside lines. Finally, I will attempt to use the extrude boss feature and be greeted by this error message (picture above).
The purple space represents areas where Solidworks will add material. The zoomed in image shows the exact point where the circle and the line meet. As you can see in the middle there is a point at which, technically material does and does not exist at the same time. To Solidworks coded language of 1’s and 0’s, the problem lies in this: it is both a 1 and a 0. And yet at the same time it is neither of them. For a mathematical programme this simply does not make sense. Therein lies the problem.
Zero thickness Error – Fix!
A Solidworks tutorial
A great video for beginners as it is not too long and it is easy to take in. Also a nice visual addition to this blog, in which, I will go into more intricate detail below.
Different types of zero thickness errors
If you are new to Solidworks, you may be sitting there scratching your head as to how to fix this problem. Above all, you need to tell solidworks if there is material at the point at which the two bodies meet (or don’t meet). Solidworks can work in tiny fractions of a mm. Therefore, all you need to do is make sure that the point is not touching.
One can achieve this by moving the sketch line away from the circle’s edge by 0.001mm. In terms of manufacturing this is a neglegable distance. As most manufacturing processes handle minimum features as low as 0.1mm. (For example, a FormLabs 2 SLA printers minimum layer height is 0.025mm). A gap of 0.001mm would not affect any model. Also you are telling Solidworks that there is material at that point. However, you can also achieve this by moving the shape over the line, or point. This will tell the software that there is not material. All Solidworks needs, is a definitive answer.
Below i will outline some common occurences of zero thickness geometry error and how to fix each one.
Edges tangent with straight lines
Also speaks for any edge of a shape that becomes tangent or touching a line. Zero thickness is located at the point at which the circle touches the line.
The two pictures show how this can happen when you ‘boss extrude’ (above) and ‘extrude cut’
So you know that we need to tell Solidworks whether the material on the line of the zero thickness exists or not. Achieved by creating a very small (0.01-0.001 gap). In terms of manufacturing this is a neglegable distance. As most manufacturing processes can handle features as low as 0.1mm, this will not affect the model during manufacture.
You must start by removing the tangent relationship between the circle and the line. Afterward, you then draw a centerline from the edge of the circle (or the center is fine) and either add or subtract 0.01mm to create the gap. Finally, select the boss extrude or extrude cut and then confirm. Sorted!
Can count for any pair of geometric shapes, where the edges are touching. The zero thickness is located at the point they touch.
Here you can see how this happens with ‘boss extrude’ and ‘extrude cut’.
So of course by now you know that we need a create a small gap at the point at which both shapes meet but here is how to do it.
After you have seen the error message, you need to edit the sketch of the second shape. Then you need to get rid of the coincident relationship of the point. consequently, drag either edge of the rectangled (horizontally or vertically) away from the point. Then draw a centerline between both points. Finally, you can proceed to define your centerline with a 0.01 – 0.001mm gap. And there you go, the sketch will look identical to the naked eye. Also, solidworks will be happy too.
Counts for any vertices (a point at which 2 or more lines meet) that touches another vertices or edge. The zero thickness occurs at the point at which the vertices (or corner point) touches another vertices or edge.
Here is an example of this using ‘boss extrude’.
Our final example is the most complicated geometry we have seen so far. However, it is the most basic to fix. No removing your existing sketch relationships here. Simply subtract 0.01 – 0.001 mm from the boss extrude direction 1 dimension. In the context my dimension was 20mm. so i changed this to 19.99 and it works just fine.