Mohammad Malekian

Bio: Mohammad Malekian is an academic researcher from University of Calgary. The author has contributed to research in topics: Machining & Rake angle. The author has an hindex of 8, co-authored 10 publications receiving 729 citations.

Modeling of dynamic micro-milling cutting forces

Abstract: This paper investigates the mechanistic modeling of micro-milling forces, with consideration of the effects of ploughing, elastic recovery, run-out, and dynamics. A ploughing force model that takes the effect of elastic recovery into account is developed based on the interference volume between the tool and the workpiece. The elastic recovery is identified with experimental scratch tests using a conical indenter. The dynamics at the tool tip is indirectly identified by performing receptance coupling analysis through the mathematical coupling of the experimental dynamics with the analytical dynamics. The model is validated through micro end milling experiments for a wide range of cutting conditions.

A New Mechanistic Approach for Micro End Milling Force Modeling

Abstract: This paper investigates the mechanistic modeling of micro end milling forces, with consideration of the effects of plowing, elastic recovery, effective rake angle, and flank face rubbing. Two different mechanistic models are developed for shearing- and plowing-dominant regimes. Micro end milling experiments are conducted to validate the model for Aluminum 6061; and, the model appropriately predicts force profiles for a wide range of feed rates, and prediction of the root mean square (RMS) values of the resultant forces is, on average, within a 12% error. The study of the model shows that plowing and rubbing force contributions are significant, especially at low feed rates. The edge radius is found to have a significant effect on plowing and rubbing force components and the effective rake angle, which indicates that it is important to maintain a low edge radius to reduce micro end milling forces.

A review of surface roughness generation in ultra-precision machining

Abstract: Ultra-precision machining (UPM) is capable of manufacturing a high quality surface at a nanometric surface roughness. For such high quality surface in a UPM process, due to the machining complexity any variable would be possible to deteriorate surface quality, consequently receiving much attention and interest. The general factors are summarized as machine tool, cutting conditions, tool geometry, environmental conditions, material property, chip formation, tool wear, vibration etc. This paper aims to review the current state of the art in studying the surface roughness formation and the factors influencing surface roughness in UPM. Firstly, the surface roughness characteristics in UPM is introduced. Then in UPM, a wide variety of factors for surface roughness are then reviewed in detail and the mechanism of surface roughness formation is concluded thoroughly. Finally, the challenges and opportunities faced by industry and academia are discussed and several principle conclusions are drawn.

Size effect and minimum chip thickness in micromilling

Abstract: This paper compares the size effect behaviour in micro- and macromilling by applying Analysis of Variance on the specific cutting force (kc) and relating it with the tool edge radius (re), workpiece roughness (Ra), cutting force and chip formation when cutting slots in AISI 1045 steel. Size effect is observed in micromilling through hyper-proportional increase of the specific cutting force for feeds per tooth (f) lower than endmill edge radius, reaching levels of grinding process (∼70 GPa) when f≅re/10. This particular milling condition does not produce chips. The minimum uncut chip thickness (hmin) varied between 22% and 36% of the endmill edge radius. This range was determined by proposing a curve (kc/Ra versus f/re) where specific cutting force becomes amplified (size effect) due to workpiece roughness association. In addition to the minimum uncut chip thickness, there is a cutting thickness between hmin and re that optimizes workpiece surface integrity and not only forms the chip completely. This thickness may be as important as hmin. Besides this, a relation between deformation mechanisms during chip formation and cutting force oscillations is proposed for micromilling and also related to tool tip radius (re). This cutting force behaviour enables the determination of certain characteristic chip thicknesses including hmin. Finally, it is concluded that minimum uncut chip thickness varies practically from 1/4 to 1/3 of tool cutting edge, regardless of workpiece material, tool geometry, mechanical machining process and technique used for measuring or estimating hmin, i.e. numerical, analytical or experimental.