Abstract
Micro-milling is a promising technology for micro-manufacturing of high-tech components. A deep understanding of the micro-milling process is necessary since a simple downscaling from conventional milling is impossible. In this study, the effect of the mill geometry and feed per tooth on roughness and indentation hardness of micro-machined AA6082 surfaces is analyzed. A solid carbide (SC) single-tooth end-mill (cutting edge radius 670 nm) is compared to a monocrystalline diamond (MD) end-mill (cutting edge radius 17 nm). Feed per tooth was varied by 3 μm, 8 μm and 14 μm. The machined surface roughness was analyzed microscopically, while surface strain-hardening was determined using an indentation procedure with multiple partial unload cycles. No significant feed per tooth influence on surface roughness or mechanical properties was observed within the chosen range. Tools’ cutting edge roughness is demonstrated to be the main factor influencing the surface roughness. The SC-tool machined surfaces had an average Rq = 119 nm, while the MD-tool machined surfaces reached Rq = 26 nm. Surface strain-hardening is influenced mainly by the cutting edge radius (size-effect). For surfaces produced with the SC-tool, depth of the strain-hardened zone is higher than 200 nm and the hardness increases up to 160% compared to bulk. MD-tool produced a thinner strain-hardened zone of max. 60 nm while the hardness increased up to 125% at the surface. These findings are especially important for the high-precision manufacturing of measurement technology modules for the terahertz range.
Highlights
Miniaturization of metallic components brings advantages such as space savings, lower energy consumption or improved behavior of high-frequency components.Manufacturing of such parts on industrial scale requires the ability to reliably produce micro-scaled structures
Embedded tungsten carbide particles can be distinguished in the cutting edge
The electropolished Al5N sample is the weakest with H IT ≈ 240 MPa, while this value increases at lower indentation depths due to the indentation size effect (ISE)
Summary
Miniaturization of metallic components brings advantages such as space savings, lower energy consumption or improved behavior of high-frequency components (transmission, reflection, etc.). For OFHC-Copper, the tool cutting edge radius of 2 μm, hmin is proposed to be 0.25 times the cutting edge radius They proposed that the micro-milling size-effect is caused by material behavior at the micron level. It can be stated that the interplay of the undeformed chip thickness and hmin which is mainly influenced by the cutting edge radius is critical for surface strain-hardening. These factors are supposed to be most relevant to the current study. The effect of tool geometry (cutting edge radius, cutting edge roughness) and undeformed chip thickness (via single tooth feed) on surface roughness and strain-hardened zone have been investigated. The surface hardness is determined by instrumented indentation with indentation depth from approx. 200 nm to more than 9 μm
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