Abstract: The factors which lead to the surface delamination existing in milling carbon fiber reinforced plastic (CFRP) with PCD tool have been studied. The surface delamination is summarized by analyzing the experiment results based on studying cutting velocity and cutting feed. Experimental results show that the increasing cutting feed leads to the increment of cutting force which in turn causes the increasing delamination of CFRP materials. Moreover, the delamination initial reduces with the increasing cutting speed from 6000 to 10000r/min but subsequently raises when the cutting speed vary from 10000 to 15000r/min with the same cutting feed of 0.08mm/z.
Abstract: Magnetorheological (MR) fluids can transform from fluid to solid and back to fluid rapidly in magnetic field. It is a novel intelligent phase transition material. In this study, MR fluids are filled inside a thin wall spherical shell as phase transition material to improve the workpiece stiffness. A fixture structure based on MR fluids for the thin wall spherical shell precision machining is designed. The fixture stiffness can be controlled and the MR fluids can be used many times. The MR fluid as strengthening material is developed and the amount of metal powder in MR fluids is 52% by volume and the performance of MR fluids is measured. Based on electromagnetic principle, a special magnetic field is designed and the magnetic field distributing is analyzed and optimized. The thin wall spherical shell using the designed fixture is turned in CK7820B lathe. The cutting experiment result shows that the fixture based on MR fluids can improve the workpiece machining precision.
Abstract: The random errors exist in measuring with touch trigger probe. These errors are directly introduced into workpiece coordinate system with conventional alignment method. An enhanced measuring method is proposed in this paper to improve the accuracy of alignment for five-axis CNC machine tools. By using the method of least square, an error reference frame is constructed, and the relationship between the alignment parameters and the error reference frame is derived. An example of aircraft structural parts is presented to validate the presented method.
Abstract: Polycrystalline diamond (PCD) tools have been obtained increasing application in aluminum alloy processing industry due to the excellent surface finish and tool life comparing with other traditional tools. Investigation of the wear mechanism of PCD milling tool for machining Al-Si alloy at cutting speed of 5000m/min (n=12732r/min) has been performed. The wear morphology of tool has been studied by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Results show that PCD milling tool suffers from abrasive wear and diffusion wear on the flank face and adhesive wear on the rake face in the machining process.
Abstract: Large quantities of coolant-lubricants are still widely used in metal working industry, generating high consumption and discard costs and impacting the environment. An alternative to current practices is to use biodegradable cutting fluids that doesn’t pollute environment or require new setups. In current study, biodegradable base oils, synthetic ester and castor oil, are chosen and compounded into cutting fluids which correspond with the national standards. The tests have been performed to high speed turn AISI 1045 steel in ester-based fluid, castor-based emulsion, kerosene and dry condition. The results indicate that the application of cutting fluids is inevitable in metal machining and can not be replaced by dry machining. The lubricating and cooling properties of the ester-based fluid and castor-based emulsion are better than kerosene and can wholly replace mineral oil.
Abstract: This paper studied how to improve motion blur on the image obtained while a micro mill is rotated at very high speed. Vision technology is capable of extracting the information of a rotating micro tool such as tool offset, breakage and runout by video analysis. Distinct images are necessary as the input for such vision based tool inspection system. However, the spindle speed of a high precision machining center is usually very fast. It is a real challenge to capture clear images. Stroboscope is an economic solution to overcome motion blur. In this paper, a customized stroboscope was designed and an on-machine experiment was conducted to test its performance to capture the image of micro cutters. The diameter of a micro end mill is 0.9mm. The spindle rotation speed is 120,000rpm. The motion blur is about 2 pixels if pulse duration of the stroboscope is set as 2 µs. The distinct images of the rotating cutter can be obtained. The result shows that stroboscope is effective to improve the motion blur dramatically for micro milling tools.
Abstract: An experimental investigation on the unique reaming behavior of aluminium cast alloys (AlSi12) by using PCD (polycrystalline diamond) tools has been studied. The torque has been monitored in real time during reaming process and the average values of torque were calculated by using FFT (Fast Fourier Transform) filtering. The optimized cutting parameters are provided in terms of analyzing the cutting torque, hole diameter and cylindricity. Results show that the torque initial increases with the rising cutting speed but subsequently decreases when the cutting speed reach to 6000r/min. It is also notable that the optimization of machining parameters basing on cylindricity are that when the cutting speed is under 6000r/min, smaller cutting feed is recommended, while when the cutting speed is over 6000r/min, higher cutting feed is appropriate.
Abstract: The performance of a spindle is critical for high precision machining. In this paper, the spindle error motion in a high precision milling center was measured. The spindle is driven by air turbine with rotation speed of 120,000rpm. The radial and axial error motion of the axis of rotation was measured. The capacitive displacement sensors with nanometer resolution were mounted against the master gauge pin through the dedicated setup. Tlusty method was adopted to synchronize angular position of the spindle and data sampling. The measured radial and axial error motion of the spindle were 2.73μm and 2.59μm respectively. Despite of motion errors, the better machining accuracy still can be achieved. It seems that cutting force may improve the rotation performance of a spindle with aerostatic bearing.
Abstract: Based on non-contact 3-D on-line measurement technology, the article studies the aviation structures’ machining deformation on-line measurement technology. The technology provide a effective way to measure the machining deformation, and the accuracy of the system can reach 0.05mm in 2000mm. Use the on-line measurement technology to get the 3-D shape of the structures after machining, and then compare the measurement result with the theoretical model to get the machining deformation. The deformation results provide the basis for the improvement of machining process.