I use a modeling program at work called Solidworks and have begun to use it to create props for poser and such. Now the problem is that when converted form a Solidworks to a Obj. the file size increases substantially. For instance I have a P90 submachine gun its file size after converting to almost 20 mb. Considerably slow in poser when imported.  Now is there a way to trim down this file size? I have allot of weapons, tanks, and props I would like to use and even put up on the market place, but there’s no point if the file size is so huge.

Perhaps you may try to reduce the number of polygons.

Attached Link: http://www.okino.com/proe_tut.htm

If you have a VRML exporter, it should have different levels of compression and I've had decent luck with the middle level of compression.  

There should be a way to turn interiors into solids before exporting.  The advantage to this is that it deletes a lot of interior details that aren't needed. For example, your submachine gun probably has interior moving parts that do not need to be seen in Poser--eliminating that level of detail decreases the polygons that will be exported.

The real problem is that 3D CAD programs aren't modeled with polygons and, when converted to polygons, tend to blow up drastically in size. There are some high end programs that are supposed to reduce the filesize efficiently while not reducing the level of model detail, but I haven't tried them. I've provided a link to a site I found a few years ago when I was looking into the matter:

Have you tried feeding it into UVMapper or Stomp they both have the ability to remove normals from obj models, now I'm no expert at modelling but I know normals aren't used by poser & increase the size of models a lot, worth a try anyway :D

Thanks for the responses. Ill try out everyone’s method. Oh and as  rreynolds probably knows when the files are converted, poly count and shape are ugly and I see why they take file size increases. Which makes it hard to reduce the poly count on some models. But it might work with some.