Feed Force and Sawdust Geometry in Particleboard Sawing

The measurement of cutting forces permits building of physic-mechanical cutting models for a better understanding of the phenomena observed during cutting. It also permits the design and optimization of processes, machines, tools, and wood preparation. Optimization of cutting conditions of wood-based materials can decrease the cutting forces, which directly relates to the energy consumption and surface quality. The sawdust analysis may serve for analysis of cutting kinematics and occupational health risk. The aim of the study was to estimate the correlation between the feed rate and both feed force and sawdust particle size produced during particleboard circular sawing. A saw machine type K700 was used in experiments. There were three feed rates of 12, 18, and 24 m/min executed by a horizontal pneumatic actuator fixed to the sliding side table of the saw machine. Based on the results of the experiments, a positive correlation was observed between the feed rate in a circular sawing process and feed forces and an unexpected particle size distribution depending on the feed rate.

Experimental Evaluation of Cutting Kinematics and Chip Evacuation in Drilling With Low-Frequency Modulation-Assisted Machining

Modulation assisted machining (MAM) superimposes a low-frequency oscillation onto the cutting process. The otherwise continuous cutting is transformed into a series of discrete, intermittent cutting events. A primary benefit of this process is to form discrete chips of small sizes and hence to improve chip evacuation. For applications in drilling the ability to control the chip size offers a direct route to improving process efficiency and stability. In this paper, the MAM process is evaluated for drilling applications via systematic experiments in drilling copper and Ti6Al4V with a two-flute twist drill and a single-flute gun drill. Based on the measurement of thrust force and examination of chip morphology, the continuous cutting and intermittent cutting regimes of MAM are determined experimentally in the normalized frequency and amplitude parameter space. The results are compared with those predicted by the kinematic model of MAM. Furthermore, the results clearly demonstrate the effect of chip morphology control on chip evacuation and process stability in drilling. The modulation conditions leading to the best performance in chip evacuation are discussed. The study shows that MAM is a promising process for enhancing the efficiency and stability in drilling difficult-to-cut materials and/or holes with high length-to-diameter ratio.

Efficient Machining of Microdimples for Friction Reduction

In order to improve the tribological properties of thermomechanically highly stressed surfaces such as cylinder liners, microdimples are produced by fly-cutting kinematics along the functional surface. The structures are used to hold back lubricant but also to increase the hydrodynamic pressure, which is built up between the sliding friction partners. For that, machining strategies for the pattern generation in cylindrical components are developed as well as a mathematical model of the microdimple arrangement and distribution. The tribological performance of the machined microdimples is analyzed by means of ring-on-disk experiments. At low sliding speeds the friction coefficient can be decreased clearly by microdimples. This indicates the potential for low-speed or reciprocating tribosystems like cylinder liners. This potential is quantified by motor driven experiments and the comparison between structured and nonstructured cylinder liners. A honed (fine) liner with additional microdimples along the interstice area shows friction losses up to 19% compared to standard honed nonstructured cylinder liner.