Let’s say you run two line tests. Both with THC off. On the first test you let IHS set the cut height. On the second test you manually set the cut height. If you get poor cut quality on the first test, it’s due to IHS setting the cut height too high or too low. You’ll need to compensate for this by either reducing or increasing the cut height in your g code.
IHS will set an incorrect cut height for two reasons. One is to compensate for spring back in the material. The torch and slide has weight which will cause the material to deflect (obviously worse for thin material). This has the tendency for the actual cut height to be lower than the programmed cut height. Second, there is some backlash in the z axis lead nut which must be compensated for. If it was not compensated for, it would have the tendency for the actual cut height to be lower than the programmed cut height. The backlash is the same whether you are working with sheet metal or thick plate and is built into the post processor of Sheetcam. I believe it’s .020”.
Let’s say that you program your cut height to .060”, but find that in reality your actual cut height is .080”. You need to set your cut height in Sheet CAM to .040” in order to guarantee a .060 cut height.