When I was laying out my workshop building for woodworking/metalworking I used an on line tool from Grizzly (tool mfr.)
Shop Tools and Machinery at Grizzly.com
Its free for one thing - and you can save your design on-line. They have templates for power equipment of various sizes - you can use those for your shop equipment such as grinders, lathes, tool chests or tables - and then can create other objects or use objects from their library. They've even got a model for a shop dog, cat, fireplace and other furniture.