Materials Science Forum Vol. 723

Abstract: In this paper, the effects of cutting parameters and tool geometry parameters on the damaged layer were investigated with precision cutting of high strength alloy experiments. The mechanical and thermal effects on microstructure of sub-surfaces in precision turning high strength alloy are studied with a scanning electron microscope (SEM) analysis. A thin disturbed or plastically deformed layer is distinguished by the presence of grains that are elongated and rotated in the direction of cutting. No significant heat affected layer and phase transformation is found below the machined surface in all the tests. It also implies that mechanical deformation plays a larger role during precision turning.

Abstract: The microstructure and mechanical properties of samples were examined, and the relationship of structure and mechanical properties for VC/Fe composite sintered at different holding time were studied. Holding time can influence the mechanical properties, with the holding time rising, when the holding time is 80 min, the hardness is Max, it’s 10.71 GPa, the enhancing range is 37.66%; The relative density changes slower from 60 to 100 min; when the holding time is 60 minutes, fracture toughness and bending strength of material is 16.17 MPa•m ^1/2 and 1070 MPa, it’s better than before.

Abstract: In this paper, it is described the vibration problems in machining the impeller blades of high temperature alloy and some Solution about Vibration Problems at present.Then in allusion to vibration and low efficiency in machining the impeller blades of high temperature alloy, a new and stiffness adjustable damper is designed according to extrusion mode. And we compose the performance of magnetorheological elastomers and the operating mode of magnetorheological elastomers. Then we experiment on the damper which we have designed using the test systems which has been erected. The experiments show that we can suppress the vibration through changing the current. And when the coil windings of magnetorheological elastomer damper are set as current, the stiffness of magnetorheological elastomer damper is adjusted and the vibration is suppressed. Therefore,we can suppress the vibration through changing the current. And the magnetorheological damper can meet the design requirements.

Abstract: This work presents an experimental investigation on micro-milling of fully sintered Zirconia (ZrO₂) by diamond coated tools. The experiments were conducted on a Kern MMP 2522 micro-milling centre and WC micro end mills, diamond coated by chemical vapour deposition (CVD) and of stiff geometry were employed as cutting tools. The effects of cutting parameters and milling time on tool wear were investigated. The results revealed that the tool wear characters included diamond coating delamination and wear of substrate WC. Both cutting forces and machined surface quality were affected by tool wear with the progress of milling.

Abstract: Micro cutting is a promising technology to manufacture the micro parts. The shear mechanism of micro cutting is different from the conventional cutting due to the round cutting edge. The ratio of uncut chip thickness to cutting edge radius plays an important role on the micro cutting process. This paper investigates the size effect phenomena of micro cutting. Firstly, the cutting force and size effect of specific cutting energy depending on the ratio of uncut chip thickness to cutting edge radius are analyzed according to the experimental results. Then, the size effect of surface roughness due to the size effect of specific cutting energy is explored. Lastly, the size effect of the exit burr height is depicted and the potential reason is analyzed. The paper supplies a good understanding of how to get the best surface integrity and minimize the exit burr height for micro cutting.

Abstract: In micro cutting field, the micro-cutting tool technology is one of the key technologies. Some new types of PCD milling tools have been designed and made. This paper presents an experimental investigation on micro-cutting pure tungsten to estimate PCD tool performance. Compare to commercial tungsten carbide helical tool, PCD tool can be used for micro-milling with wider ranges of processing parameters, and the material removal rate could be improved. The PCD tool worn mildly, and had longer tool life.

Abstract: Based on microscope and image processing, a method of auto tool setting for micro turning was innovated. Firstly, real-time images of tool setting were obtained by high pixel CCD camera, then specific image processing method and algorithm were applied to these images and the deviation between the tool point and target position was calculated. Based on the gap value, tool feeding increment value was adjusted and image processing operations were executed. These steps were repeated until the gap was zero, which means that tool setting was finished. Moreover, a reliability analysis was performed. Result indicated that the precision of tool setting is satisfactory.

Abstract: The downscaling of the cutting process into micro dimensions poses some new problems compared to machining in macro dimensions, which is called size effect. In this paper, a mathematical model of ideal turning surface roughness and a turning surface roughness experiment was done, trying to find out whether the theory roughness equals to the real roughness by the influence of size effect.

Abstract: The effect of cutting tool geometry has long been an issue in understanding mechanics of cutting process. Tool geometry has significant influence on chip formation, heat generation, tool wear, surface finish and surface integrity during cutting process. This paper presents the actually geometry of milling tool involved in cutting process based on mathematics analytical methods including matrix translation and rotation. Results show that according to the different helix angle and tool fluted, the geometry of cutting tool involved in cutting is different. For two or three-fluted mirco-milling tools, no mater helix angle is 30 or 45, the actually geometry involved in cutting is sphere. Different cutting tool corresponds to different sphere radius. Experiments were set up to validate the effect of cutting tool geometry on cutting forces. Results show that the smaller of the sphere radius of cutting tool, the lower of the cutting force; the larger of the sphere radius, the higher of the cutting force.

Abstract: Cutting force is one of the most important parameters in the drilling process of FPC (Flexible printed circuit board). It has a directly affect on the micro-drills’ life and the micro-holes quality. It causes the FPC delamination, pulling of the plastic, the burr of exit hole and other processing defects. In this paper, some experimental investigations of cutting force of high speed micro-drilling are carried out to improve the drilling quality of FPC. The results indicate that the drilling parameters(spindle speed, feed speed and drill-bit diameter) have significant influence on micro-drilling thrust force. The thrust force of drill copper foil is larger than the thrust force of drill adhesiver layer and the thrust force of drill PI layer is the smallest. The larger the thrust force is, the bigger the exit burr is.