Some of you might have noticed that a few days ago we launched problem visualization for non-manifold models. This is a tool to help you guys upload your models easier. It allows you to actually see on Shapeways what the issue is with your model.
If you upload a model that is non-manifold then we send you an email telling you that you have a non-manifold error. You can click a link in that email and this link will take you to a part of your my designs page, there you will see a log of your non-manifold errors. These are kept for 14 days.
You can then click on the model name and you will be taken to the analysis page. On this page you can see where the non-manifold areas are in red. You can use the viewer to spin your model around and look at it in 3D and then go back to your 3D app to repair it. In actual fact it is an online 3D mesh analysis tool. You can probably guess where were going with this?
A little background: Every shape that can be 3D printed has to be 2-manifold, so each edge has to be shared by two faces(no more, no less). A model can be non-manifold if it for example contains two cubes that share one edge as you can see below. The edge itself is shared by four faces, so the resulting shape is not 2-manifold. For a little more detail about non-manifold you can check out this link.