Open Access Thesis
Molding (Founding)--Technological innovations; Rapid tooling;
This study was completed to address the problem of determining what effect selected cutting conditions have on tool wear and tool life in robotic sand milling (RSM) operations. The purpose of this study was to analyze the tool wear mechanisms and characteristics that govern the RSM process. The purpose was also to establish an experimental methodology that may be used in future studies to assess tool life when examining various tooling materials and designs, as well as additional sand workpiece materials. Completing this research allowed the machining process to be optimized by analyzing differences in tooling cost with variable values of the observed cutting conditions.
End milling paths were executed with a pre-determined selection of cutting conditions to remove material from a pre-formed block of silica sand bonded with the phenolic urethane no bake (PUNB) resin system. Twelve experimental trials were completed during the study which consisted of a variable feed rate and variable cutting speed series utilizing solid carbide and high-speed steel (HSS) cutting tool materials. Data collection for the experimental trials was conducted by measuring the observed width of flank wear present on the cutting edge of the cutting tool at each machining interval. The width of flank wear was determined by measuring the tool diameter with a digital micrometer, and monitoring the change in tool diameter
The tool wear plot results showed that the HSS cutting tools reached the established flank wear limit in less than one minute of machining time, and the solid carbide cutting tools did not reach the flank wear limit after a minimum machining time of sixty minutes for both the feed rate and cutting speed experimental series. The observed tool life values for the HSS cutting tools ranged from 0.23 to 0.65 minutes based on cutting condition values used during the experimental trials. In comparison, the extrapolated tool life values for solid carbide ranged from 82.37 to 135.67 minutes using the same selection of cutting condition values during the experimental trials.
The tooling cost analysis plots demonstrated that increasing the selected feed rate decreased tooling cost, and increasing the selected cutting speed increased tooling cost. The lowest tooling costs were observed to occur at a cutting speed of 1275 SFM and a feed rate of 300 in/min. It was also observed that solid carbide was significantly less expensive to use as a cutting tool material than HSS on the basis of cost/ft3 removed. Linear regression analysis found that cutting speed and cutting tool material type were considered to be statistically significant factors in the tooling cost analysis. Analysis of Covariance (ANCOVA) was used to determine that the parallel model was the preferred model, which indicates that the cutting tool material type categorical variable has a significant impact on tooling cost.
Abrasive wear was determined to be the primary tool wear mechanism in the RSM process, and flank wear was identified as the dominant tool wear failure mode. Tool wear was found to increase as the cutting conditions of feed rate and cutting speed increased. Cutting speed was identified as the cutting condition parameter with the greatest contribution to tool wear. Cutting tool material type was found to have the greatest impact on tool life of all the factors observed in this study, and solid carbide was determined to be a more suitable cutting tool material for RSM than HSS.
Year of Submission
Master of Science
Department of Technology
Scott Giese, Chair
1 PDF file (ix, 72 pages)
©2020 Craig Ertl
Ertl, Craig, "The effect of cutting condition selection on tool life in sand milling" (2020). Dissertations and Theses @ UNI. 1066.