§ Sharp corners limitation:
Sharp corners are impossible to be obtained in pocketing of internal cavities, but these sharp corners can be reduced to very small fillets using small diameter bits.
§ Shape limitation
Surfaces that have a surface of material above it can’t be milled (directly and simply). In some cases reorienting the shape may make the shape surfaces accessible to milling tool
§ Tool length limitation
Tool bit is restricted to be short and can’t be too long, because too long tool bit will be exposed to high bending moments which may break the tool bit.
§ Spindle limitation
Spindle (or axis assembly) and tool dimensions both in combination make limitations in some cases. The main limitation in z direction is heavily related to short tool lengths.