This paper presents a semirigid (SR) bonnet tool which has the advantages of high efficiency and determinacy for material removal on optical elements and also has the potential to be used on aspheric optics. It consists of three layers: a metal sheet, a rubber membrane, and a polishing pad, from inside to outside. It inherits the flexibility of a normal bonnet but has a higher stiffness. Finite element analysis was performed to determine that the stainless steel is the best-suited material for use as the metal sheet. An SR bonnet with a stainless-steel metal sheet was fabricated and tested. Its tool influence function (TIF) is Gaussian-like, and the TIF stability is more than 90%. The peak-to-valley of its uniform removal area is less than 0.1λ. Tool ripples are highly depressed and the surface profile is well preserved in the prepolishing test. In 12 min, ∼36 mm3 of material is removed.
Bonnet polishing system is mostly used in rough polishing and fine polishing because of its own features. Due to
different aims of polishing stages, optimal ranges of key parameters are different in various polishing stages. Simulations
in ANSYS are present in order to get optimal ranges of key parameters including inner pressure P and compression of
bonnet H in different polishing stages, firstly, the reliability of simulation of bonnet polishing using ANSYS is verified
through a series of simulation about fine polishing stage, on the condition of using ranges of key parameters got by
former researchers from polishing experiment; secondly, simulations about rough polishing were carried out, and optimal
ranges of key parameters were found, which have reference value in future work.