Coupled Eulerian-Lagrangian Simulation of Indexable Drilling

This paper presents finite element simulations of indexable drilling of AISI4140 workpieces. The Coupled-Eulerian-Lagrangian framework is employed and the focus is to predict the drilling torque around the hole axis, thrust force, temperature distributions and chip geometries. The cutting process is modelled separately for peripheral and central insert. Then, the total thrust force and torque are predicted by superposing the predicted result for each insert. Experiments and simulations are conducted at a constant rotational velocity of 2400 rpm and feed rates of 0.13, 0.16 and 0.18 mm/rev. While the predicted torques are in excellent agreement, the thrust forces showed discrepancies of 12 - 20% to the experimental measured data. Effects of the friction modelling on the predicted torque and thrust force are outlined and possible reasons for the thrust force discrepancies are discussed in the paper. Additionally, the simulations indicate that the tool and workpiece temperature distributions are virtually unaffected by the feed rate.

Determination of technological heredity when machining holes in parts of gas turbine engines

Calculation of parameters that determine technological heredity during drilling and the ability to control the process of technological heredity. Keywords: drilling, cutting force, drift, hole axis, depth and degree of hardening, technological heredity. [email protected]

Application of hole axis alignment at drilling pipes of different purpose

A plant ensuring control of cutter parameters during deep drilling pipes of a different purpose to increase effectiveness of deep hole machining in parts of “pipe” type is considered. The plant allows controlling the following parameters: tool rotation, feed, parts rotation, runout on the outer surface of a part and its wall thickness.

The method of calculation of the deviation of the tool axis when machining small diameter holes

The article is devoted to an important parameter that characterizes the accuracy of the shape and location of the hole after machining — the displacement of the hole axis. When designing operations for drilling small-diameter holes with a large depth (the ratio of the hole depth to its diameter is more than 10), a method for predicting this parameter is necessary to improve the accuracy of work. The article considers the causes and methods of eliminating this negative impact on hole machining using the example of a small-diameter drill axis runout. Recommendations are given for reducing drill runout: to reduce cutting modes; to perform the drilling operation while rotating the workpiece, which can stabilize the drill position during machining; to use drills made of hard alloy or obtained by powder metallurgy methods, which increases their rigidity; before drilling the workpiece, to center the hole with a more rigid drill.

Methods of Measuring Over-Piston Clearances of Automotive Diesel Engines in Operating Conditions

На современных автомобильных дизельных двигателях предусмотрены конструктивные мероприятия, позволяющие выдерживать оптимальные надпоршневые зазоры в цилиндрах при их сборке на заводе-изготовителе. На двигателях отечественного производства зазоры достигаются разбивкой поршней на группы, в зависимости от размера между осью отверстия и днищем поршня, а также применением стальных прокладок газового стыка различной толщины. В процессе эксплуатации, при ремонте двигателей ЯМЗ и КамАЗ, в большинстве случаев указанные зазоры не выдерживаются в оптимальных пределах из-за отсутствия информации о методах их замеров. Это обстоятельство в конечном итоге приводит к тому, что двигатели после ремонта имеют повышенные расход топлива и дымность отработавших газов. Рассмотрены простые и нетрудоёмкие методы определения надпоршневых зазоров и способы их регулирования для достижения оптимальных значений, рекомендуемых заводами-изготовителями. Structural measures that can withstand optimal piston clearance in the cylinders when they are assembled at the manufacturing factory are provided on modern automotive diesel engines. On engines of domestic manufacture clearances are achieved by breaking down the pistons into groups depending on the size between the central hole axis and the piston top and also using steel gaskets of the gas-tight joint of various thicknesses. During operation and the repairing of Yaroslavl Engine Plant and KamAZ engines in most cases these clearances are not maintained within optimal limits due to the lack of information about the methods of their measurements. This circumstance in the last analysis leads to the fact that the engines after repair have increased fuel consumption and smoking at the exhaust. Simple and labor saving methods for determining the over-piston clearances and methods for their regulation to achieve optimal values recommended by manufacturing factories are considered.

Experimental research on the deep-hole boring of pure niobium tube

In the deep-hole boring process on pure niobium tube, there exist some problems including serious tool wear, tough chips, and poor surface quality. In order to bore high-quality deep holes on rolled niobium tube, the cutting tool structure and boring process parameters suitable for machining rolled niobium tube were designed and two experimental schemes were proposed. The results showed that the geometric parameters of the cutting tool and process parameters have important influences on the tool wear, chip morphologies, hole-axis deflection, and hole surface roughness. By adjusting the geometric parameters of the cutting tool and boring process parameters, reasonable geometric parameters of the cutting tool and boring process parameters were obtained.

EXPERIMENTAL DETERMINATION OF THE HOLE AXIS DEFLECTION WHEN WORKING WITH A COUNTERSINK WITH CARBIDE BLADES

This article discusses the developed mathematicalmodel that takes intoaccount the errors of sharpening and assembling the cutting blades of a countersink tool with carbide blades. This allows you to determine the actual area of the cut sections of the allowance for each blade and calculate the cutting forces acting on them. The resultant cutting forces leads to lateral displacements of the axis of the tool during machining of the hole. The mathematical model makes it possible to determine the errors of processing holes (axis retraction, split and shape accuracy) with a countersink with a carbideblades. To check the adequacy of the mathematical model, fullscale experiments were performed on blanks madeof various materials. The method of conducting a full-scale experiment was developed. Recommended cutting modes and a countersink with three blades are selected. Processing was performed at the MM800 Fanuc processing center. Using modern automation tools – the Renishaw system and additive technologies using the Range Vision Spectrum 3D scanner, the drift of the hole axis was measured after processing with a vertical drill with carbide blades. This device allows you to get the desired result in a very short time. A compact sensor was used to measure the deflection of the hole axis, allowing for very accurate results. Substituting the part processing data into the mathematical model, the calculated values (theoretical) of the hole axis withdrawal during processing for the prototypes are obtained. The theoretical results and the results of the field experiment are compared. Comparing the obtained theoretical results – the results of a mathematical model, and the results of a full-scale experiment, it was concluded that the developed mathematical model is adequate and can be used in production by technologists in the development and computer debugging of technological processes.

The accuracy of holes drilled in the side surface of plywood

Dimensional accuracy of machining translates into susceptibility to defects in assembly of furniture elements. In the initial drilling phase, the tip of the drill may slip due to the properties of the workpiece, which may result in inaccurate machining. Taking this into account, it was decided to investigate this phenomenon for drilling in the side of the plywood board. Samples for testing were made of 18 mm thick, 13 layer birch-alder plywood, covered with melamine film, glued with phenol-formaldehyde glue. With the use of an industrial dowel drilling machine, 30 holes in each of three examined layer were made. All holes were made parallel to the layers – on the side of the plywood board, and their axes were located in three adjacent layers: the birch veneer layer, the adhesive layer, and the alder veneer layer. Two types of geometric accuracy of holes were analyzed: the distance between the real center of the hole and the nominal position and also the inclination of the hole axis from the nominal axis. The holes made in the adhesive layer showed approximately twice larger deviations compared with the holes made in two adjacent layers of veneer. There was no significant relationship between the deviations of the angle of holes axis and the inaccuracies in the position of their centers. Main conclusion: When drilling in the side surface of the plywood board, less accurate holes are obtained if the hole axis is located in the adhesive layer, and there is more accuracy if the hole axis is located in the veneer layer.

ACCURACY OPENING OF HOLES AFTER DRILLING

At enterprises of building materials, various large-scale technological equipment is used, which in the process of operation is subjected to various types of repair, requiring the use of appropriate equipment and technology. Mills used for grinding raw materials have flanged connections that are attached with precision and fastening bolts to ensure the tightness of the connection. The precision bolts of the flange connections perceive the entire load of the equipment; therefore, high quality requirements are imposed on the holes for them in the flanges. Precision holes must be machined according to technology that meets their requirements. This article presents a study of hole machining by countersinking, ensuring the accuracy of holes after drilling in shape and spatial deviation. The results of experiments related to the machining of holes using portable devices with a sliding spindle and a movable drilling head are given. The deviations of the holes, which are obtained after drilling on portable devices, are set out, and the dependence of the deviations on various factors, which is expressed in breaking down and leading away the hole axis, is established. The influence of technological heredity after drilling on the accuracy of the hole when countersinking is established. The dependences give the opportunity to predict the accuracy of holes machining using portable devices after drilling and after core drilling, to establish the actual depth of cut for core drilling taking into account the rigidity of the technological system and independent variables.