Blade Segment with a 3D Lattice of Diamond Grits Fabricated via an Additive Manufacturing Process

Diamond tools with orderly arrangements of diamond grits have drawn considerable attention in the machining field owing to their outstanding advantages of high sharpness and long service life.This diamond super tool,as well as the manufacturing equipment,has been unavailable to Chinese enterprises for a long time due to patents.In this paper,a diamond blade segment with a 3D lattice of diamond grits was additively manufactured using a new type of cold pressing equipment(AME100).The equipment,designed with a rotary working platform and 16 molding stations,can be used to additively manufacture segments with diamond grits arranged in an orderly fashion,layer by layer;under this additive manufacturing process,at least 216000 pcs of diamond green segments with five orderly arranged grit layers can be produced per month.The microstructure of the segment was observed via SEM and the diamond blade fabricated using these segments was compared to other commercial cutting tools.The experimental results showed that the 3D lattice of diamond grits was formed in the green segment.The filling rate of diamond grits in the lattice could be guaranteed to be above 95%;this is much higher than the 90%filling rate of the automatic array system(ARIX).When used to cut stone,the cutting amount of the blade with segments made by AME100 is two times that of ordinary tools,with the same diamond concentration.When used to dry cut reinforced concrete,its cutting speed is 10%faster than that of ARIX.Under wet cutting conditions,its service life is twice that of ARIX.By applying the machine vision online inspection system and a special needle jig with a negative pressure system,this study developed a piece of additive manufacturing equipment for efficiently fabricating blade segments with a 3D lattice of diamond grits.

Thermal residual stress analysis of coated diamond grits

Residual stresses of coated diamond grits were analyzed by a finite element unit cell model. Diamond grits coated with four types of metals, W, Mo, Ti, and Cr, were considered. The numerical results show that compressive stress occurs in the diamond particles and tensile stress occurs in the metal matrix; compressive stress is concentrated in the diamond sharp comer; interface stresses decrease by more than 1000 MPa with a metal interlayer; plastic deformation of the matrix begins near the sharp corner of diamond grits and extends toward the peripheral zone. Stress concentration dramatically decreases due to plastic deformation of the matrix. The deposition of transition metals on a diamond surface can dramatically promote the adhesion between diamond grits and the metal bond.

Micro/nano Indentation and Single Grit Diamond Grinding Mechanism on Ultra Pure Fused Silica

The existing research about ductile grinding of fused silica glass was mainly focused on how to carry out ductile regime material removal for generating very ＂smoothed＂ surface and investigate the machining-induced damage in the grinding in order to reduce or eliminate the subsurface damage.The brittle/ductile transition behavior of optical glass materials and the wear of diamond wheel are the most important factors for ductile grinding of optical glass.In this paper,the critical brittle/ductile depth,the influence factors on brittle/ductile transition behavior,the wear of diamond grits in diamond grinding of ultra pure fused silica（UPFS） are investigated by means of micro/nano indentation technique,as well as single grit diamond grinding on an ultra-stiff machine tool,Tetraform ＂C＂.The single grit grinding processes are in-process monitored using acoustic emission（AE） and force dynamometer simultaneously.The wear of diamond grits,morphology and subsurface integrity of the machined groves are examined with atomic force microscope（AFM） and scanning electron microscope（SEM）.The critical brittle/ductile depth of more than 0.5 μm is achieved.When compared to the using roof-like grits,by using pyramidal diamonds leads to higher critical depths of scratch with identical grinding parameters.However,the influence of grit shapes on the critical depth is not significant as supposed.The grinding force increased linearly with depth of cut in the ductile removal regime,but in brittle removal regime,there are large fluctuations instead of forces increase.The SEM photographs of the cross-section profile show that the median cracks dominate the crack patterns beneath the single grooves.Furthermore,The SEM photographs show multi worn patterns of diamond grits,indicating an inhomogeneous wear mechanism of diamond grits in grinding of fused silica with diamond grinding wheels.The proposed research provides the basal technical theory for improving the ultra-precision grinding of UPFS.

Deformation Analysis of Micro/Nano Indentation and Diamond Grinding on Optical Glasses

The previous research of precision grinding optical glasses with electrolytic in process dressing （ELID） technology mainly concentrated on the action of ELID and machining parameters when grinding, which aim at generating very ＂smoothed＂ surfaces and reducing the subsurface damage. However, when grinding spectrosil 2000 and BK7 glass assisted with ELID technology, a deeply comparative study on material removal mechanism and the wheel wear behaviors have not been given yet. In this paper, the micro/nano indentation technique is initially applied for investigating the mechanical properties of optical glasses, whose results are then refereed to evaluate the machinability. In single grit diamond scratching on glasses, the scratching traces display four kinds of scratch characteristics according to different material removal modes. In normal grinding experiments, the result shows BK7 glass has a better machinability than that of spectrosil 2000, corresponding to what the micro/nano indentation vent revealed. Under the same grinding depth parameters, the smaller amplitude of acoustic emission （AE） raw signals, grinding force and grinding force ratio correspond to a better surface quality. While for these two kinds of glasses, with the increasing of grinding depth, the variation trends of the surface roughness, the force ratio, and the AE raw signals are contrary, which should be attributed to different material removal modes. Moreover, the SEM micrographs of used wheels surface indicate that diamond grains on the wheel surface after grinding BK7 glass are worn more severely than that of spectrosil 2000. The proposed research analyzes what happened in the grinding process with different material removal patterns, which can provide a basis for producing high-quality optical glasses and comprehensively evaluate the surface and subsurface integrity of optical glasses.

A new diamond bit for extra-hard, compact and nonabrasive rock formation

A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can easily be exfoliated from the surface of the matrix due to weak holding-force with matrix, which made the surface non-smooth. Three Ф36/24 mm laboratorial bits were manufactured to conduct a laboratory drilling test on zirconiacorundum refractory brick. The laboratory drilling test indicates that the abrasive resistance of the bit work layer is proportional to the Si C concentation. The higher the concentration, the weaker the abrasive resistance of matrix. The new impregnated diamond bit was applied to a mining area drilling construction in Jiangxi province, China. Field drilling application indicates that the ROP(rate of penetration) of the new bit is approximately two to three times that of the common bits. Compared with the common bits, the surface of the new bit has typical abrasive wear characteristics,and the metabolic rate of the diamond can be well matched to the wear rate of the matrix.

INFLUENCE OF WHEEL STRUCTURAL PARAMETERS ON MACHINING ACCURACY OF ULTRA-PRECISION PLANE HONING

A new idea for designing wheel patterns is presented so as to solve theproblems about machining accuracy of workpiece and wear of honing wheel in ultra-precision planehoning. The influence factors on motion principle and pattern structures are analyzed andoptimization machining parameters are obtained. By calculating effective cutting length on thesurface of workpiece cut by wheel's abrasive and the orbit of one point on the surface of workpiececontacting with wheel, the wear coefficient of different kinds of wheels and accuracy coefficient ofworkpiece machined by corresponding wheels are obtained. Furthermore, the simulation results showthat the optimal pattern structure of wheel turns out to have lower wheel wear and higher machiningaccuracy.