Lesson 2: Polishing Types: High-Speed vs Slow-Speed
What You Will Learn
- Compare the processes of high-speed and pitch polishing
- understand the trade-offs between removal rate, figure control, and surface cosmetics
- Select the right approach based on geometry, material, and schedule
Two primary approaches to full aperture polishing are high-speed and conventional polishing. Each offers distinct advantages. High-speed polishing is typically performed on CNC Controlled machines where tools rotate at high RPM and high pressure. This approach enables short cycle times and high removal rates, making it attractive for production environments. The machines tool path can be programmed based on the operators’ inputs of the lens surface geometry. Machine adjustments are more precise and set ups are more repeatable between operators. Corrective actions can be applied that will assist to bring the part closer to its target figure. High-speed polishing can introduce mid-spatial frequency signatures. High speed polishing can increase the risk of cosmetic burn if slurry chemistry is not carefully managed.
Conventional polishing, on the other hand, relies on a skilled technician’s intuition to make adjustments to the machine in order to achieve the specification needed. Conventional polishing is a trade-off of cosmetic surface figure error quality over speed. The lap rotates slowly, often under the attentive guidance of an operator. This approach yields improved figure and better surface cosmetics, though at the expense of throughput. Because it depends more heavily on operator skill, the outcomes can vary, but when executed well, Conventional polishing produces exceptionally smooth surfaces.
The choice between these methods depends on priorities. High-speed polishing suits production of multiple identical parts where efficiency matters. Slow-speed polishing is often reserved for high-value optics, such as those used in lasers or aerospace systems, where performance requirements are strict and cannot be compromised.
High-speed polishing delivers faster removal but risks MSF signatures, while Conventional polishing produces smoother, higher-quality surfaces at the cost of throughput.