Research on CNC programming and machining process based on CAD/CAM technology

A programming to make parts are CNC Programming (Computer Numerical Control Programming) for machines. An NC program consists of a sequence of instructions that control the motion and automatic sequences of an NC Machine to perform a particular processing task. In a general sense, the term NC programming refers to the creation of control data for machining workpieces on NC and CNC machines. NC programming has a decisive influence on the cost-effectiveness and profitability of NC manufacturing. The selection of a programming system is mostly guided by the need for software that is suitable for the application at hand, readily available, and as universally applicable as possible.

Introduction. The efficiency of processing on metal-cutting machines is evaluated by the reduced cost of producing a batch of parts while ensuring the required quality. In modern production, parts are usually made on CNC machines. Today the CNC program and the trajectories of the machine tool actuators match each other with high accuracy, which, however, does not yet guarantee quality and efficiency of production. The definition of the CNC program is based on the knowledge base of rational modes, tools, coolant and etc. during processing. This base reflects some averaging over the set of machines, tools and processing conditions, and does not take into account changes in the properties of the dynamic system in the process of cutting. Subject. The paper deals with the synergistic matching of external control (CNC programs) and cutting dynamics (internal control). The internal control factors can be set a priori, as well as determined as a result of the influence of irreversible energy transformations in the cutting zone. The purpose of the work is to determine the law of controlling the trajectories of the machine's executive elements in such a way that, with changing properties of the dynamic cutting system, the required surface quality of the part and minimizing the intensity of tool wear are ensured during the processing of the part. Method and methodology. Mathematical simulation of the controlled dynamic system, which properties change due to the a priori set laws of variation of subsystem parameters, as well as changes in the cutting properties conditioned by the power of irreversible energy transformation is presented. Consideration of the power of irreversible energy transformations is necessary for predicting back-edge wear, changes in dynamic coupling parameters, and evolutionary restructuring of cutting dynamics. Results and Discussion. The regularity of matching the CNC program with the changing properties of the cutting process, which allows increasing the processing efficiency while ensuring the required quality of parts, is disclosed. A number of properties of the dynamic cutting system caused by changing trajectory of the longitudinal feed rate of the tool during processing of the shaft, the stiffness change of which is given, are revealed and analyzed.

Before the introduction of automatic machines and automation, industrial manufacturing of machines and their parts for the key industries were made though manually operated machines. Due to this, manufacturers could not make complex profiles or shapes with high accuracy. As a result, the production rate tended to be slow, production costs were very high, rejection rates were high and manufacturers often could not complete tasks on time. Industry was boosted by the introduction of the semi-automatic manufacturing machine, known as the NC machine, which was introduced in the 1950’s at the Massachusetts Institute of Technology in the USA. After these NC machine started to be used, typical profiles and complex shapes could get produced more readily, which in turn lead to an improved production rate with higher accuracy. Thereafter, in the 1970’s, an even larger revolutionary change was introduced to manufacturing, namely the use of the CNC machine (Computer Numerical Control). Since then, CNC has become the dominant production method in most manufacturing industries, including automotive, aviation, defence, oil and gas, medical, electronics industry, and the optical industry. Basics of CNC Programming describes how to design CNC programs, and what cutting parameters are required to make a good manufacturing program. The authors explain about cutting parameters in CNC machines, such as cutting feed, depth of cut, rpm, cutting speed etc., and they also explain the G codes and M codes which are common to CNC. The skill-set of CNC program writing is covered, as well as how to cut material during different operations like straight turning, step turning, taper turning, drilling, chamfering, radius profile, profile turning etc. In so doing, the authors cover the level of CNC programming from basic to industrial format. Drawings and CNC programs to practice on are also included for the reader.

CNC machines allow computer programming to control the movement and actions of the machine, enabling more precise and repeatable production. However, in operating a CNC machine, good and efficient programming is essential. To optimize the use of CNC machines, it is necessary to optimize the number of NC program blocks that include the concept of macros and sub-programs. An effective CNC program, along with the proper use of macros and sub-programs, can speed up the production process, reduce human error, and increase accuracy. The research method used is comparative research by comparing using macro programs and manual programming, in this case comparing the number of solid trajectories and the number of program lines in the design using the simulation method using the Autodesk Fusion 360 application. So that the optimal number of movements will be obtained through the row value in the NC program. Macros and sub- programs allow users to easily change or modify CNC programs without having to rewrite the entire program. This increases flexibility in producing various types of products. It is concluded that optimization using macro and sub-programs provides a significant reduction in the number of program blocks in the case of the machining process for manufacturing the cover of pressure cylinder. This reduction in program blocks can help improve efficiency and sustainability in the development of modified machining processes.

Before the introduction of automatic machines and automation, industrial manufacturing of machines and their parts for the key industries were made though manually operated machines. Due to this, manufacturers could not make complex profiles or shapes with high accuracy. As a result, the production rate tended to be slow, production costs were very high, rejection rates were high and manufacturers often could not complete tasks on time. Industry was boosted by the introduction of the semi-automatic manufacturing machine, known as the NC machine, which was introduced in the 1950’s at the Massachusetts Institute of Technology in the USA. After these NC machine started to be used, typical profiles and complex shapes could get produced more readily, which in turn lead to an improved production rate with higher accuracy. Thereafter, in the 1970’s, an even larger revolutionary change was introduced to manufacturing, namely the use of the CNC machine (Computer Numerical Control). Since then, CNC has become the dominant production method in most manufacturing industries, including automotive, aviation, defence, oil and gas, medical, electronics industry, and the optical industry. Basics of CNC Programming describes how to design CNC programs, and what cutting parameters are required to make a good manufacturing program. The authors explain about cutting parameters in CNC machines, such as cutting feed, depth of cut, rpm, cutting speed etc., and they also explain the G codes and M codes which are common to CNC. The skill-set of CNC program writing is covered, as well as how to cut material during different operations like straight turning, step turning, taper turning, drilling, chamfering, radius profile, profile turning etc. In so doing, the authors cover the level of CNC programming from basic to industrial format. Drawings and CNC programs to practice on are also included for the reader.

With the development of modern manufacturing industry, complex surface parts are more and more widely used in aerospace, automobile manufacturing, the shipbuilding industry, and many other fields; furthermore, their machining demand is growing explosively, and CNC machining technology has become the mainstream machining method of complex surface parts because of its high precision and high efficiency. However, CNC machining of complex surfaces faces many challenges, especially the generation and optimization of tool trajectories. Therefore, vector field-based tool path planning methods have emerged, aiming to improve the efficiency and accuracy of CNC machining of complex surfaces. This paper focuses on the tool trajectory optimization problem in CNC machining of complex surfaces and reviews the current research status of vector field-based tool path planning for surface machining. The study explores the concept of symmetry in the design of tool paths, highlighting the importance of symmetrical vector fields in achieving efficient and high-precision machining. By analyzing the symmetrical properties of complex surfaces and the corresponding vector fields, this paper discusses the current status, difficulties, and core problems of relevant methods, pointing out the direction of breakthroughs and the future development trend. The findings provide a reference and basis for the realization of efficient and high-precision CNC machining of complex surfaces.

D2 steel is an industrial tool steel. It is widely used in the tool and die industry for making cutting tool inserts, bending inserts, restriking inserts, etc. which can be taken out after their tool life. D2 steel is a very tough steel and difficult to machine also. High generations tool bits like Tungsten carbides and Titanium carbides are required to machine them. The heat treatment follows the machining process. Their machinability is very low. CNC machines are often used to finish them. Often they are machined using programs on UG-NX Uni Graphics(CAM) and DELCAM. And they have to be machined in three steps. Roughing operations, followed by Semi-Finish machining and the last step is finish machining.CNC machining centers are versatile in their applications in metal removal processes. Often they are so modernized that just like many manufacturing operations, metal removal can be automated too. The need for CNC machining arises due to extensive finishing requirements in the aerospace, automotive industries. However, the CNC or Computer and Numerically controlled machining process usage is not limited to these industries only. Tool and Die industry also is heavily dependent on CNC material removal and machining processes as now replaceable inserts are widely used in this industry.

Machining processes remain an unavoidable technique in the production of high-precision parts. Tool behavior is of the utmost importance in machining productivity and costs. Tool performance can be assessed by the roughness left on the machined surfaces, as well as of the forces developed during the process. There are various techniques to determine these cutting forces, such as cutting force prediction or measurement, using dynamometers and other sensor systems. This technique has often been used by numerous researchers in this area. This paper aims to give a review of the different techniques and devices for measuring the forces developed for machining processes, allowing a quick perception of the advantages and limitations of each technique, through the literature research carried out, using recently published works.

There are various electrical discharge machining techniques and experimental researches could be necessary in order to establish the operating conditions for an optimal machining process. Some theoretical considerations concerning the process of generating the surface asperities as a consequence of the electrical discharge machining process were elaborated. Experimental method was applied in order to evaluate influence exerted by some input factors (pulse on time, pulse off time, average intensity of electric current) on certain surface roughness parameters (Ra, Rz, Ry and Rq). One developed an experimental research by using a copper tool electrode and a workpiece made of high speed steel, in accordance with the requirements specific to a complete factorial experiment with three independent variables at three levels. A ram electrical discharge machine was used as machining equipment. One measured the surface roughness parameters specific to the machined surfaces. Empirical mathematical models of type power functions were established by using the method of least squares.

For the purpose of ultra-precision grinding large scale and complex off-axis aspheric optics effectively and automatically, computer-aided NC programming system was developed in this article. First the mathematical model of aspheric parallel grinding was analyzed, and the manufacture process of aspheric grinding is designed. Then the system architecture was established, which included initial grinding module, on-machine measuring module and error compensation grinding module. After inputting process and aspheric parameters, the system could calculate the grinding wheel X/Z/Y coordinates precisely and simulate the grinding pathway automatically, and then create grinding CNC program, which could control the grinding wheel to move along the aspheric surface. And the on-machine measurement CNC program was created to acquire the form error by displacement sensor. By combining the form error with the aspheric surface coordinates, the grinding wheel coordinates could be calculated and compensation machining CNC program was created. Using this system to manufacturing one large scale and off-axis aspheric optics, the PV of final form error was below 3.0μm, and the RMS was below 0.5μm.

Electron beam melting (EBM) is one example of a 3D printing technology that has shown great promise and advantages in the fabrication of medical devices such as dental and orthopedic implants. However, these products require high surface quality control to meet the specifications; thus, post-processing, such as with machining processes, is required to improve surface quality. This paper investigates the influence of two-part orientations of Ti6Al4V EBM parts on the CNC machining (turning) process. The two possible EBM part orientations used in this work are across EBM layers (AL) and parallel to the EBM layer (PL). The effect of the EBM Ti6Al4V part orientations is examined on surface roughness, power consumption, chip morphology, tool flank wear, and surface morphology during the dry turning, while using uncoated carbide tools at different feed rates and cutting speeds. The results showed that the AL orientation had better surface quality control and integrity after machining than PL orientation. Using the same turning parameters, the difference between the roughness (Ra) value for AL (0.36 μm) and PL (0.79 μm) orientations is about 54%. Similarly, the power consumption in AL orientation differs by 19% from the power consumption in PL orientation. The chip thickness ratio has a difference of 23% between AL and PL orientations, and the flank wear shows a 40% difference between AL and PL orientations. It is found that, when EBM components are manufactured along across-layer (AL) orientations, the impact of part orientation during turning is minimized and machined surface integrity is improved.

Aiming at the data acquisition and monitoring of energy consumption in intelligent CNC machine tools and machining processes, a design and application scheme of a multifunctional integrated energy consumption data acquisition system based on current, voltage, power and energy consumption sensors and MTConnect protocol is proposed. The software and hardware module of acquisition and transmission is designed. The “plug and play” signal acquisition and transmission devices used for real-time data acquisition in the CNC machining process are developed and implemented, and a multiple CNC device networking scheme based on MTConnect protocol is given. The test result shows that the multi-functional integrated energy consumption data acquisition system developed can effectively obtain real-time data such as current, voltage, power, and energy consumption during the operation of NC device. It is used to monitor the process and the state of the machine tool, and can be used conveniently by MTConnect.

This study proposes a method based on on-machine measurement to control the machining error in the blade CNC machining process. Firstly, the mechanism of machining error formation of the near-net-shaped jet engine blade are analyzed, and the composition of the machining error source and its impact are qualitatively analyzed. Secondly, the adaptive CNC machining process are introduced. Thirdly, the influence of adaptive CNC machining process on the final machining errors is analyzed. The results show that the adaptive CNC machining process is of the excellent ability of machining errors control, and this method is effective in machining error control.

Optimization is rightly claimed to be the most significant factor distinguishing the modern approach to machining processes from the orthodox one. Practical results can be obtained from the application of mathematical modelling and optimization techniques. The paper presents a procedure for solution of machining process optimization problems, with the use of theory of graphs and Bellman's optimum principle. The finite graph G=(N, A) (where -N denoted a set of nodes and A the set of arcs) here presents the set of feasible solutions. Each are represents a corresponding machining operation and each path the feasible machining process. A number can be associated with each are : the increment of criterion for optimality. Using the optimum principle we can find the shortest possible path in the graph, thus solving given problems of choice for the optimal machining process. There is a variety of ways in which the performance criterion can be formulated. In this paper only those performance measures having sufficient economical justification are considered. We may minimize the costs of machining processes, or optimize economical effectiveness of capital engaged. The method presented can be applied with every additive criterion, as well as with some non-additive ones. A practical example illustrates the field of possible application of this method.

Tool compensation determines the machining precision and quality . There are tool length compensation,tool radius compensation and corner radius compensation in CNC system .The parameters of these compensation are all static.The purpose of this study was that the machining precision and quality were improved by changing the parameters of tool compensation,based upon changing the static parameters into the dynamic parameters of tool compensation.The three tool compensations were introduced and discussed about these being used in machining process and the function in processing.The concept of dynamic tool compensation was proposed in this paper. The method was used that the dynamic parameter substituted the static parameter in the processing by calculating . The process machining crafts information was included in tool compensation in every process step. The computer program was finished about how to calculate the dynamic parameter. The results indicate that high-precision machining is within the range of the maximum probability and the large machining error is within the range of the minimum probability by useing this method. Further more, the end qualified product is more than before.Process indicators and tool compensation merged is a breakthrough research by probability calculating for impoving the machining precision.We confirmed that the proposed method could be l used widely.