Ultra-precision turning method efficient for optical freeform surfaces with a hybrid slow-fast tool servo

Area of Science:

• Manufacturing Engineering
• Mechanical Engineering
• Materials Science

Background:

• Machining large steep freeform surfaces presents challenges for conventional Slow Tool Servo (STS) and Fast Tool Servo (FTS) methods.
• STS methods struggle with accuracy and efficiency on large, steep surfaces.
• FTS methods are limited by stroke length, restricting the manufacture of surfaces with significant sag.

Purpose of the Study:

• To develop a hybrid STS-FTS method for efficiently machining large steep freeform surfaces.
• To address the limitations of individual STS and FTS techniques in freeform surface manufacturing.
• To improve both the accuracy and efficiency of freeform surface machining.

Main Methods:

• A hybrid approach combining STS and FTS was developed.
• Freeform surfaces were decomposed to enable simultaneous machining by both STS and FTS.
• A variable feedrates tool path strategy was implemented to optimize machining efficiency.
• Experimental fabrication of a saddle surface was performed to validate the method.

Main Results:

• The hybrid STS-FTS method significantly improved processing efficiency by 47.5%.
• Achieved excellent surface roughness with an arithmetic mean (Ra) of 2-4 nm.
• Obtained low peak-to-valley (PV) values: 0.4780 µm at hollows and 0.3884 µm at swells.

Conclusions:

• The proposed hybrid STS-FTS method effectively machines large steep freeform surfaces.
• This approach overcomes the limitations of standalone STS and FTS systems.
• The method offers a viable solution for high-efficiency, high-precision manufacturing of complex freeform geometries.