We are aware of an issue with eSupport impacting community login. We are working on a fix and community login should be restored soon.
for some complex and large assemblies, it takes hours to create tiff files for drawings, how shall we reduce the time required to form these tiff files?
I am not sure I have understood your question 100%. Are you trying to find a fast tiff image creator library or you want to accelerate the image processing rate with same library? Hope following post can give you some information.
http://stackoverflow.com/questions/228545/on-ghostscript-fastest-way-to-create-a-blank-tif-document