IF you remember to wind the scale up BEFORE trying to preview the pattern you can get away with a few minutes of down time, but if you leave the scale at 1 its goodnight! It would be nice if Inventor could warn you (a bit like it does if you foolishly opt for a huge part array) becasue not only do you lose your inventor files but also any other unsaved app data as in my case my Dell M6500 PC just dies as all available memeory just gets swallowed up. The problem seems to be with more complex patterns (I'm using a stone wall type hatch - mountainledge.PAT is a prime example) and I think the issue is related to the scaling factor used. Importing a new hatch pattern more than often than not results in Inventor winding up the memory usage on the PC to bursting point as it runs through 'Calculating containment of profile areas' that seems to be called when previewing a hatch pattern. See atatchment I've got a recurring problem with using hatch patterns on 2013.
