超声振动辅助三尖钻钻削皮质骨的研究

在临床中,使用医用麻花钻给骨钻孔是常见的治疗手段,但医用麻花钻通常存在定心能力差的问题,骨大多都是曲面,所以在骨钻削中极易造成孔位的偏离、孔形不圆、孔直径偏大等现象。针对这一问题,改用定心能力更好的三尖钻并施加超声振动对皮质骨进行钻削研究。通过研究发现三尖钻超声振动辅助(UAD)钻削不仅改善了给骨钻孔时定心能力差的问题,而且与三尖钻普通(CD)钻削对比发现,UAD三尖钻钻削在轴向力、钻削温度、孔内壁表面粗糙度均比CD钻削有大幅度减小,钻孔直径精度则有大幅提高。三尖钻UAD钻削大幅度提高了孔的表面质量。     

印刷电路板超细微孔钻削加工及其关键技术

基于PCB板业的发展现状,全面阐述了PCB板孔加工的基本情况,分析了国内外在PCB微机械加工的加工过程、钻削力与加工质量、钻头设计、钻头磨损与折断、机械钻孔孔位精度与机床动态性能等方面的研究现状。指出超微细孔其钻削加工尺寸属于介观尺度,多层PCB基材材料性能呈非线性且各向异性明显,钻刃磨损规律及刀具失效形式较为复杂,加工质量评价体系特殊等加工特点。提出目前亟待研究的关键理论问题包括PCB钻削去除机理、钻头失效机理、表面创成过程建模与质量控制、钻削系统工艺优化、钻头的优化设计与制造等方面。     

深孔麻花钻横刃修磨对切削性能的影响

采用自行设计的10支不同内刃圆弧半径、内刃前角和过心量的深孔麻花钻对45#钢进行钻孔加工试验。通过分析钻孔时的轴向力、扭矩和被加工孔精度等因素,研究了横刃对钻削过程的影响,为提高深孔麻花钻寿命、钻削生产效率和孔加工质量提供了指导意义。     

钛合金微小孔钻削试验研究

应用自行研制的TiC涂层和类金刚石（DLC）涂层硬质合金钻头以及市售硬质合金钻头（WC-Co）对钛合金材料进行微小孔钻削性能对比试验,研究了进给速度与切削力和扭矩的关系,分析了刀具的磨损特征以及孔的表面质量和孔入口处的毛刺情况。结果表明：DLC涂层硬质合金钻头比普通硬质合金钻头和TiC涂层硬质合金钻头更适合加工钛合金材料微小孔。     

基于径向力的可转位浅孔钻加工孔径误差研究

为研究可转位浅孔钻在切削过程中的钻孔孔径误差,基于可转位浅孔钻的理论几何模型,并利用经典斜切理论得到浅孔钻的径向力、力矩关于刀片几何参数和切削参数的计算公式。选取常用切削参数组合,将计算得的径向合力及力矩作为边界条件,通过ANSYS有限元分析刀体挠度,得出相关钻孔孔径误差的理论值。利用统计学回归方法建立相应数学模型,并通过切削试验验证数学模型的精确性。基于建立的数学模型,通过调节切削参数,可预测并控制孔径误差值,实现浅孔钻在半精加工中对孔径余量的精确控制,有效拓展可转位浅孔钻的应用范围。     

Finite element and experimental investigation of temperature changes on a twist drill in sequential dry drilling

The drilling process is highly non-linear. Coupled with a thermo-mechanical machining, localized heating and temperature increases in the workpiece are caused by the rapid plastic deformation of the workpiece and by the friction along the drill-chip interface. The cutting temperature at the tool-chip interface is an important factor which directly affects workpiece surface integrity, tool wear, and hole diameter and cylindricity in the drilling process. In this study, the effects of sequential dry drilling operations on the drill bit temperature were investigated both experimentally and numerically. Drill temperatures were measured by inserting standard thermocouples into the coolant (oil) hole of TiN/TiAlN-coated carbide drills. Experimental studies were conducted using two different workpiece materials, AISI 1040 steel and Al 7075-T651. The drill bit temperature was predicted using a numerical computation with Third Wave AdvantEdge finite element method (FEM) software, which is based on Lagrangian explicit. The results obtained from the experimental study and finite element analyses (FEA) were compared. Reasonable agreement between the measured and calculated drill bit temperature results were found for sequential dry drilling.     

Modeling transverse motions of a drill bit for process understanding

A model for drill bit transverse motions is proposed that identifies process conditions affecting hole quality and helps in the interpretation of drilling signal patterns produced during the hole-making process. A two-dimensional model of a drill rotating in a hole with clearance is presented. The simulation results, drilling force signal patterns, and hole geometry were found to be in close agreement. Drill rotation speed, drill stiffness, structural damping, drill hole clearance, and amplitude modulation of the forces acting on the drill appear to have a significant effect on drill bit transverse motions and on hole quality.     

Tool life evaluation of CFRP drilling with three kinds of drill

Serious tool wear in CFRP drilling is one of the key problems to be solved urgently. Firstly, a suitable indirect evaluation index of tool life is selected according to the literature. The critical delamination force was obtained by blind hole pushing experiment. Then, tool wear experiments were carried out with double point angle drill, stepped drill and reverse edge compound drill to analyze the variation rules of the thrust force, exit burr, exit delamination and tear with tool wear. Threshold values of exit delamination, tearing and critical thrust force were compared with each evaluation index one by one to study the causes of drills failure. The results indicated that the maximum tool wear position was the outer corner. Among the three types drills, the thrust force, delamination factor and burr angle of the reverse edge compound drill are smaller. The double point angle drill fails due to the excessive thrust force, while the stepped drill and the reverse edge compound drill fail due to the hole exit delamination exceeding the threshold. The number of drilled holes of the reverse edge compound drill is 100 % and 25 % higher than that of the double point angle drill and the stepped drill, respectively. Therefore, the reverse edge compound drill is suitable for drilling CFRP.

     

Effects of different cooling conditions on twist drill temperature

In the past, many researchers have studied wear developed on drilling tools mainly due to the high temperatures generated which accelerate thermally related wear mechanisms and thereby reducing tool life. This paper deals with an experimental investigation on the effect of an internal coolant approach (for different air pressure) on drill bit temperature, comparing it with an external coolant approach and dry cutting. Drill temperatures were measured by inserting standard thermocouples through the coolant (oil) hole of TiN/TiAlN-coated carbide drills. Experimental studies have been conducted using Al 2014 alloy materials. In the drilling tests, cutting conditions had different spindle speeds, coolant approaches and feed rate values. The settings of drilling parameters were determined by using the Taguchi experimental design method. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) were employed to analyse the effect of coolant approaches and drilling parameters. The objective was to establish a model using multiple regression analysis between spindle speed, coolant (air) pressure and feed rate with the drill bit temperature. Mathematical models for drill bit temperature are proposed that agree well with the experiments.     

CORRELATION BETWEEN DRILL GEOMETRY AND MECHANICAL FORCES IN MQL CONDITIONS

This article deals about the determination of the suitable cutting tools for the machining of a large welded frame in low carbon steel. Various drill technologies are used in the drilling process such as solid carbide drills, solid carbide modular drills, which consist of coated carbide edges and a sintered steel body or indexable drills. The effects of the drill technologies and the lubricant conditions are compared with taking into account of the cutting conditions and forces. The objective is to link the cutting forces and it distribution along the cutting edges to the cutting parameters the drill geometry and the cooling conditions.     

用国产 BTA 深孔钻头加工奥氏体不锈钢管板深孔

本文介绍用国产 BTA 深孔钻头在进口奥氏体不锈钢上加工深孔的情况。文章以直径25.65mm 的钻头在不锈钢管板上加工直径25.7_(-0.10)~(+0.05)mm 的孔为例,分析了加工中出现的问题、产生问题的原因及解决办法,还介绍了刀具几何参数等问题。     

Analysis of temperature changes on the twist drill under different drilling conditions based on Taguchi method during dry drilling of Al 7075-T651

In this work, effects of drilling parameters (drilling depth, feed rate, and spindle speed) on the twist drill bit temperature and thrust force in the dry drilling of Al 7075-T651 material were experimentally investigated. During dry drilling experiments, drill bit temperature and thrust forces were measured. Drill temperatures were measured by inserting standard thermocouples through the coolant (oil) hole of TiN/TiAlN- coated carbide drills. The settings of drilling parameters were determined by using the Taguchi experimental design method. An orthogonal array, the signal-to-noise (S/N) ratio, and the analysis of variance (ANOVA) are employed to analyze the effect of drilling parameters. The objective was to establish a model using multiple regression analysis between spindle speed, drilling depth, feed rate, and drilling method with the drill bit temperature and thrust force in a Al 7075-T651 alloy material. The study shows that the Taguchi method is suitable to solve the problems with a minimum number of trials as compared with a full factorial design .     

The effect of starting hole geometry on borehole quality and tool life of twist drills

This paper reports about the relationship between starting hole geometry and twist drill performance, which is determined by the location error and diameter of the drilled borehole as well as the tool life of the employed twist drills. The experimental results lead towards the conclusion that the type of starting hole has a significant effect on borehole quality. This, however, is not as commonly assumed attributed to a variation in the location error of the different starting holes themselves, but to how a starting hole allows the subsequent twist drill to engage in the cutting process. Although twist drills that drill straight into the workpiece material achieved the longest tool life due to a gentle engagement, a deep starting hole (‘pilot hole’) results in the most satisfying overall twist drill performance.     

CrAlTiN梯度涂层高速钢刀具的切削性能研究

用闭合场非平衡磁控溅射离子镀PVD涂层工艺在高速钢麻花钻上沉积了CrA lTiN梯度涂层。在干式切削条件下,对45#号钢和30CrMnS iA钢进行了钻削试验。通过涂层与未涂层钻头的寿命、磨损和切削力等试验比较,表明CrA lTiN梯度涂层钻头的切削性能远优于未涂层钻头,是一种极有发展前途的刀具涂层。     

玻璃钻孔的试验研究

本文讨论了用切削法进行玻璃钻孔中所使用的钻头、钻削过程及钻削用量等问题。采用三种不同的硬质合金钻头在一定的切削用量范围内进行玻璃钻孔,试验结果表明：本文所用的钻头结构简单、钻孔效率较高、加工质量较好、成本较低,可在生产实践中推广使用。本文还推荐了一些常用的切削用量。     

钎焊套料钻钻削碳纤维增强复合材料层合板出口撕裂缺陷的成因分析

针对碳纤维增强复合材料钻孔时钻头寿命短、易产生加工缺陷等问题,将钎焊金刚石套料钻应用于碳纤维增强复合材料的钻削加工中。为更好地说明钎焊金刚石套料钻的加工性能,选取了复合材料钻削中常用的金刚石涂层麻花钻进行比较,并选择了实际加工中严重影响加工质量的出口撕裂缺陷进行成因分析。通过检测与分析出口处加工质量,得到以下结论：对于不同结构形式的钻头,仅依靠轴向力及扭矩并不能判断是否产生撕裂缺陷;在相同工艺参数下,钎焊金刚石套料钻的轴向力及扭矩均小于金刚石涂层麻花钻的轴向力及扭矩,使用钎焊金刚石套料钻更有利于减少撕裂缺陷,提高加工效率。     

地震勘探钻机的设计

针对我国地震勘探钻孔技术的现状和存在的问题,研制了适合我国国情的用于山地、丘陵、戈壁滩、森林地区钻进用的JSWS-30型山地钻机、JSWL-30型砾石钻机、JSWT-50型土层钻机、JQWS-30型森林地震勘探钻机,重点介绍了各种钻机的结构及性能特点。通过钻机在现场的试验,证明钻机具有良好的使用性能。     

Design and experimental study of an end effector for robotic drilling

This paper presents the development of a drill end effector for use on industrial robots. The end effector has low weight and high rigidity. The drill end effector is fully programmable and will realize different drilling mode. The real-time force feedback can detect dull or broken bits, drill to breakthrough, and plot thrust force while drilling. Additionally, the end effector can also be equipped with a coolant/lubricant device. Based on the drill end effector, an experimental study on dry drilling of Ti-6Al-4V alloy and 7075-T6 alloy bimetal stacks was performed by using an uncoated cemented carbide drill. The hole quality (hole size, surface roughness) and thrust force were evaluated at various spindle speeds, feed rates, stacking sequence, and clamp force. This study indicates that the spindle speed and feed rate have an effect on the hole quality and thrust force by means of changing the temperature and plastic deformation of cutting zone. The results show that drilling 7075-T6 alloy firstly would be most efficient because of the high hole quality and the low thrust force. It was also found that high clamp force is helpful to improve the hole quality.     

薄板钻孔加工方法的改进

对薄板钻孔容易钻扁孔、钻头易折断的问题进行了探讨，分析了钻头的受力情况，并提出了薄板钻孔的改进办法。     

MINIMUM QUANTITY LUBRICATION (MQL) APPLICATIONS IN AUTOMOTIVE POWER-TRAIN MACHINING

ABSTRACT

Minimum Quantity Lubrication (MQL) is a near-dry machining method that may be applied to reduce coolant usage in operations such as drilling, which cannot be performed completely dry. Although significant research has been reported on MQL, relatively little information on production applications and experience has appeared in the technical literature. The most common high-volume production application for MQL is cross and oil hole drilling on steel crankshafts. This paper reviews MQL test results for deep hole drilling of forged steel and cast nodular iron under conditions similar to crankshaft oil hole drilling. The results show that MQL can yield tool life equivalent to gun drills at higher penetration rates under these conditions. This result is consistent with production experience with steel crankshafts, and shows that MQL may also be useful for cross and oil hole drilling of cast crankshafts. Limited test and production data for MQL machining of aluminum prismatics is also described. Significant areas for future research and development, including chip management, air quality, capability and robustness, and cost are also discussed.