Only Tangent Mate Available

I have an imported .step file that I am trying to use in an assembly. I have tried various ways of importing the file (multibody part or not). When I try and mate the part or assembly my only option is for a tangent mate. Does anyone know how I can fix this?

2 Answers

Generally, only two planer surfaces can mate in coincidence. If any of the surface is not a planer surface then mating can happen only in tangent. Most probably, the surface of the step model is not a planer surface. Please see the attached file to get the way to know whether the surface is planer or not

Your surface is not planar, therefore you cannot use anything other than a tangent constraint. Try removing the surface and replacing it with a planar surface. This will give you the mate and flush constraints.