Why Error Thicken surface
why error sufvace sir
The surface that you are trying to thicken is not properly knitted or joined. There will be curve or an element which will be highlighted in blue. You have to rework on it. Try knitting those surfaces again it will work. Due to the low quality of the image I won't be able to tell you which element is defective. Try reducing the thickness value sometimes due to intersections this error also occurs.