He is the storty: My friend ordered PVC board (pre-cut) from Malaysia for his desk top CNC machine assembly. He already assigned the factory the blue print of each cut with precise dimension. He actually make one of those by using another CNC machine to make sure that everything was well calculated. Those PVC boards supposed cut by CNC router but somehow those guys did it by using laser without consideration some drawback from using laser machine. It ended up that those boards he received all came with some a gap, far enough causing headache for user. The cutting supposed to be perfect and solid once they put together. With the offset (space), it's now losing the back to back force when being attached.
We all know that laser cutting is simply doing 'melt' things off. So, it must create some soft of offset. If you're trying to cut a square from a piece of epoxy, say 100mm x 100mm. I bet the resut would be 99.9mm x 99.9mm or 99.5mm somewhat with offset. If you're trying to make a box without consideration of the offset, you're in big trouble.
Now back to the subject. What is a parallel offset mean? Now, smart you folks. I don't think I need to explain what it is and you can come up the idea. Yes, it let you to 'expand' or 'shrink down' the orignal image by the amount you set in outward or inward.
Taking the 100mm x 100m square cut as an example. If the machine follow exact route from the drawing, ideally it will cut 100mm x 100mm. But since the laser is doing "melting', so, it will end up a square of 99.5mm x 99.5mm (note, it's just my assumption for that amount). So, let's now set the "Parallel offet" by 0.5mm Outer. It will do 100.5mm x 100.5mm cuting. After minus the burned off, you will get 100mmx 100mm perfect square! Isn't it a good features!
Worth a cup of coffe for the tips
Marco