Metalworking fluid selection for grinding process: Coolant or lubricant? How it can be selected for a given condition?
How about a single (or unique) parameter for predicting the extent of grinding process responses?
How the micro grinding tool topography information can help us to predict the worksurface topography?
For which micro-manufacturing processes, micro grinding can be considered as an alternative?
*Only recent works informed here (since 2018)
Click on the images to see the magnified version
1. How to classify the micro grinding tools according to their topography?
A method has been proposed to characterize electroless plated micro grinding tools using an optical measuring device. Abbott Firestone curve characteristics, such as height distribution, void volume, and material volume obtained from topography measurements, were used to define “volume ratio.” This parameter distinguishes the micro grinding tools according to their planar grit density. As a result, micro grinding tools can be classified in a manner similar to conventional grinding wheels.
Schematic of planar grit density variation of different tools (above and below the mean height plane)
volume ratio = grit volume above mean height plane/chip space volume below mean height plane
volume ratio ∝ planar grit density
Volume ratio values: dense structure → 0.45 – 0.35, medium structure → 0.35 – 0.25, open structure → 0.25 – 0.15
2. Kinematic simulation of material-dependent pile-up behavior in single grit scratching
Scratch tests are useful techniques to gain insight into the material removal mechanism of abrasive machining processes. In most of the scratch tests, the uncut chip thickness value is either constant or varies from zero to maximum. However, in abrasive machining processes, the uncut chip thickness value ranges from either zero to the maximum or vice versa. Moreover, regular scratch tests are conducted at very low speeds, in which either the indenter or the workpiece is stationary. Because of these limitations, the knowledge obtained from the existing scratch test results is not valid for most of the abrasive processes. Hence, in this work, the influence of chip thickness variation, speed ratio, and depth of cut on the pile-up behavior of AISI 1015 steel and 2017A-T4 aluminum alloy surfaces were investigated. The workpiece having the comparable thermal diffusivity value with the grit has shown a significant difference in its pile-up behavior. Through a better understanding of chip thickness influence on the pile-up ratio, a mathematical model was developed for kinematic simulations. Using the developed model, kinematic simulations were done to visualize the scratch surface topography and material pile-up by considering the grit trajectory path and chip thickness variation.
Schematic of experimental and simulated scratch surfaces with the pile-up nature
3. How the micro channel geometrical deviations are related to micro grinding tool topography?
In micromachining processes, achieving the required accuracy and surface quality in the first attempt is of utmost importance. Because it is challenging to perform a secondary operation in a microscaled structure due to re-positioning inaccuracies. In the micro grinding process, geometrically deviated structures are common due to the low depth of cuts compared to the size of abrasive grits. In this case, the abrasive grits located at the tool bottom surface highly influence the quality of the component produced. A simulation study has been performed for the micro grinding process to understand the influence of tool topography on the microchannel geometrical deviations, especially when the depth of cut is less than the size of the grits. Simulation results showed the importance of the number of grits, protrusion heights, and radial positions on the tool bottom surface at small depths of cuts to minimize the geometrical deviations.
Channel geometrical deviations related to grits radial positions and protrusion heights
4. How the micro grinding process is different from the conventional grinding process?
Micro grinding is an emerging technology for producing structured surfaces on hard and brittle materials. A micro pencil grinding tool (MPGT) consists of a layer of superabrasive grits, bonded to a solid cylindrical surface. Randomly distributed and geometrically undefined grits interact with the workpiece surface at random positions. These random grit positions and protrusions lead to a difference in the size of undeformed chips. An analytical method has been developed to understand the undeformed chip geometry, that considers grit kinematics. Kinematic simulation of grit trajectory paths in longitudinal direction showed a reduced number of active grits in micro grinding with an increase in speed ratio and with reduced tool dimensions. The influence of maximum radial height grits on surface generation in micro grinding has been verified experimentally for up and down grinding modes. Microscopic observations of ground surfaces have shown the distinct differences between up and down grinding modes, which are similar to the surface generation in milling processes. Moreover, the formation of linear grooves with uniform depth and width unlike conventional surface grinding at lower speed ratios indicated the influence of individual grits on surface generation. Trajectory path simulation results have also shown the same observation.
Schematic outline of grits trajectory and scratches produced over the ground surface in conventional and micro grinding
conventional grinding - needle-shaped scratches, micro grinding - linear scratches
feed per grit/contact length ratio controls the scratches pattern
feed per grit/contact length < 0.33, a higher probability for linear scratches