Client: Various Major Manufacturing Firms (John Deere, Eaton, GM)
Abstract: This case study summarizes the results of a systematic investigation into the Cascade Finishing Process and its ability to improve surface finishes. Primarily used for deburring and cleaning castings and machined parts, the Cascade System has demonstrated significant improvements in surface roughness under optimal operating conditions.
Introduction: The Cascade Process (CP), developed by Iowa Engineered Processes Corp. (IEP) of Independence, Iowa, employs a combination of burnishing, shearing, and peening actions to deburr, clean, and finish metal parts. Using abrasive media, the CP can produce smooth, matte surfaces with Ra values as fine as 0.27µm Ra. The process involves setting parts in a fixture within a work chamber, where media and liquid cleaning compounds flow over and through the parts while the fixture vibrates at high frequencies.
Experimental Procedure: A series of nine designed experiments were conducted to analyze the effects of various factors on surface finish, including run time, vibratory frequency, media type, and surface orientation. SAE 1018 cold-rolled mild steel blocks were used as test specimens. Four different media types were tested: case-hardened steel pins, small and large case-hardened steel balls, and triangular ceramic media.
Results:
1. Surface Finish Improvement:
- Directional Surface: Abrasive media produced directional, matte surfaces similar to ground finishes, with surface roughness values reduced significantly under optimal conditions.
- Cratered Surfaces: Vertical surfaces subjected to peening action achieved smoother finishes than standard shot peening, with Ra values ranging from 1.5µm to 0.59µm.
2. Media Type Effects:
- Steel Balls vs. Pins: Steel balls produced more intense peening action, while pins generated irregular divots. Larger balls provided smoother surfaces on initially rough profiles, while smaller balls achieved finer finishes on smoother surfaces.
3. Run Time and Frequency:
- Significant Factors: Run time and vibratory frequency were critical in determining the extent of surface smoothing. Higher frequencies resulted in more aggressive finishing actions, while longer run times were needed for substantial surface improvements.
4. Fixture Clearance and Initial Surface Finish:
- Minor Effects: Fixture clearance had minimal impact on surface finishing action, while initial surface roughness influenced the degree of smoothing achievable.
Benefits:
- Environmental Impact: The Cascade Process reduced the need for toxic chemicals and waste, aligning with sustainable manufacturing practices.
- Operational Efficiency: The CP provided consistent, high-quality finishes with reduced run times, enhancing overall production efficiency.
Conclusion: The Cascade Finishing Process has proven capable of significantly improving the surface finish of machined parts under optimal conditions. Continued research and refinement of the process parameters can further enhance its effectiveness and broaden its industrial applications. The CP offers a viable alternative to traditional finishing methods, providing environmental and operational benefits for major manufacturing firms like John Deere, Eaton, and GM.
Acknowledgments: This study was supported by the D.O.Ed. as a Fellow of Concurrent Manufacturing at Iowa State University.
References:
- Gillespie, L., et al., (1976), “Deburring by Centrifugal Barrel Tumbling,” Government Document BDX-613-1559, pp. 1-82.
- Loersch, J.F., and Neal, J.W., (1986), “Simultaneous Peening and Smoothing of Part-Surfaces of Aerospace Applications,” Impact Surface Treatment, Elsevier Applied Science Publishers, New York, pp. 173-184.
- Verpoort, C.M., and Gerdes, C., (1991), “Influence of Shot Peening on Material Properties and the Controlled Shot Peening of Turbine Blades,” Shot Peening Theory and Applications, IITT International, Gourney Sur-Marne, pp. 11-70.
