pylfrm RE: free state 3DDave (Aerospace) 5 Mar 16 01:05 I would think the designer needs to know if the envelope principle applies before the first part is made, and the inspector needs to know without knowing any details of the manufacturing process. Do you get a pass on the envelope principle because the part was subject to free-state variation? Is the customer going by happy when they inspect it? For all they know, you bought stress-relieved material and just machined it curvy.

The geometry and material are such that the part is still very stiff. The feature of size now violates the envelope of perfect form at MMC by ten times the tolerance.

You remove the clamp force, and the part is now distorted due to the internal stresses released by material removal.

Everything is within tolerance, including envelope principle. That interpretation doesn't sit very well with me.Īs an example, imagine you clamp an incomplete part in a vise and machine away a bit of material, completing the part and creating a feature of size in the process.

Flatness drawing symbol