Remove internal faces in obj files

[nicobousquet]

Hi guys,

I would like to remove all the internal faces in my obj files in order to print it.
For example, have a look on this image:

This figure is just the junction of two polygons. In red, we can see the internal faces I want to remove.
Do you know if there is a way to it ? Or a way to just take the contour of my mesh ?
I give you the obj file in attachment.

Thanks in advance.
angle.zip