C.A.S.E. Isotropic Superfinishing
C.A.S.E. (chemically assisted surface enhancement) is a two-stage process consisting of shot peening followed by vibratory superfinishing. The fatigue enhancement properties of shot peening are complimented with a mirror-like surface finish.
Applications that require both residual compressive stress and excellent surface finish include precision gears and airfoil blade geometry. Depending on the application and customer finish requirements, the valleys of peening dimples can be retained for lubricant retention.
Depending on customer requirements, a component may be super finished as a standalone process or shot-peened followed by super finishing, which is the C.A.S.E. process.
How Isotropic Superfinishing Works
Isotropic superfinishing consists of immersing parts in a vibrating bowl charged with properly sized media. A weak acid is used to soften part surface so that contact with vibratory media removes asperities such as grinding and machining lines while retaining low spots for lubricant retention.
The process continues to progressively remove asperities while leaving valleys until the desired surface finish is achieved. Before completing the process, parts are neutralized so the acid has no detrimental effects.
C.A.S.E. Isotropic Process
The “peak to valley” of the shot peened finish is ~ 2.9 microns. After isotropic finishing, performed as part of CASE, this improves to ~ 0.6 microns
Applications for Isotropic Superfinishing
- Transmission gears and shafts
- Cams and followers
Benefits of C.A.S.E Vibratory Superfinishing
- Reduced surface roughness to mirror-like finishes
- Improved contact/surface fatigue strength of gearing
- Reduction in transmission noise & lubricant temperature
- Prevents micro and macro pitting
- Rounding of sharp edges for ease of assembly