How to avoid removing outer perimeters when removing support?  

t

Unless you have changed some of the settings, outer perimeters shouldn't disconnect from the infill (which is what I understand you're seeing). However, the default settings for support create supports that are in fact hard to remove. A well-regarded set of parameters for support settings is:

0.25mm z distance

3mm pattern spacing

4 interface layers

75% xy distance

0.2mm interface layer spacing

RE: How to avoid removing outer perimeters when removing support?

Thank you. I guess I should have mentioned that the outer-most perimeter got disconnected from the 2nd outer-most perimeter rather than from infill. An example is removing the support on the surface of a circular disc or a square which has 3 perimeters. As I tried to remove the support, part of the outer-most perimeter of the object (i.e.  the edge) got separated from its immediately neighboring perimeter (the 2nd perimeter).  What caused such problem and what settings should I change to prevent that from happening again?

For future reference, is the set of parameters you mentioned good for any type of filaments? 

t

Thanks for clarifying. I suspect what you're seeing is caused by the supports being too tightly attached to the outmost perimeter, so the settings I sent you earlier should work. I've used them successfully for pretty much any type of filament. I only change the distance a bit when I go to different layer heights, eg 0.2 mm z distance for 0.1mm layer height.