At the moment, many parameters can be set to zero / negative while Laserweb complains about the parameter is in wrong range with red flag
Bitmaps:
Laser Diameter
Passes
Cut Rate
Gamma
Vectors:
Line Distance
Laser Power
Passes
Cut Rate
Segment (A Axis)
i.e. negative laserpower doesn´t make sense 
+Peter van der Walt you get it right. It does warn, thats right. But in many cases negative values just dont make sense.
It helps eliminating possible wrong user inputs when not allowing numerical inputs which never will lead to something useful.
Like negative laser power or negative laser diameter.
Warning if zero is great. I like that.
But on the same time letting the user do wrong inputs is the same as let him choose zero without a warning 
User shouldn´t be able to go the wrong way.
Why not clamp/prevent? Makes user experience feel more trustful imho.
(btw: does that sound like a beginner mode with warnings / hints and an expert mode without?)