Investigation of ultrasonic-assisted CNC cutting of honeycomb cores

As compared to traditional milling, ultrasonic-assisted cutting of honeycomb core materials has the advantages of small cutting force and superior surface quality. Currently, ultrasonic straight blade V-shaped machining is one of the most efficient roughing processes. The requirement of a processing path to be post-processed based on the processing characteristics of the straight blade cutter is one of the key issues faced while meeting the technological requirements of CNC machine tools for V-shaped machining. A post-processing method of NC code for V-shaped machining of straight blade cutter is proposed in this article. Initially, the V-shaped rough machining process planning is done, followed by the usage of Unigraphics (UG) to output the initial CNC code. Next, the CNC code is executed through the three key technologies of the second arrangement of cutter locations. Later, research is done on information planning of lifting and lowering cutter, along with research on planning of chip breaking toolpath. Eventually, the simulation cutting experiment is carried out through VERICUT. The results demonstrate that the post-processing method can meet the processing requirements.

Simulation of Constant-Volume Removal Rate Machining of Middle-Convex and Varying Ellipse Piston

One kind of constant-volume removal rate machining method of the middle-convex and varying ellipse piston is proposed in this paper. By analyzing the structure and movement relationship of the middle-convex and varying ellipse piston machine, the NC machining model is built. And, the constant-volume removal rate machining model is also built by superposing the variable rotation satisfying the dynamic performance constraints on the uniform rotation of the spindle of the CNC piston lathe. Then, the instantaneous position parameters of each axis of the CNC piston lathe are obtained and turned into NC code. The functional feasibility of the method finally is verified by simulation machining.

Self-optimizing process planning of multi-step polishing processes

Self-optimizing process planning is an essential approach for finding optimum process parameters and reducing ramp-up times in machining processes. For this purpose, polishing is presented as an application example. In conventional polishing processes, the process parameters are selected according to the operator’s expertise in order to achieve a high-quality surface in the final production step. By implementing machine learning (ML) models in process planning, a correlation between process parameter and measured surface quality is generated. The application of this knowledge automates the selection of optimal process parameters in computer-aided manufacturing (CAM) and enables a continuous adaptation of the NC-code to changing process conditions. Applying the presented ML-model, the prediction accuracy of 83% will adapt the process parameters to achieve the target roughness of 0.2 μm. The sample efficiency is shown by the decrease in root mean square error from 0.1–0.28 to 0.02–0.07 μm with additional polishing iterations.

Präzision für Fahrradträume

Der Lohnfertiger Bernd Iwanow folgt stets seinem Bauchgefühl. Ist er von seiner Idee überzeugt, überträgt er sie in einen NC-Code, den seine beiden Hermle-Bearbeitungszentren präzise in die aufgespannten Aluminiumblöcke fräsen. Ergebnis ist das „Fracebike“.

A postprocessing and path optimization based on nonlinear error for multijoint industrial robot-based 3D printing

Multijoint industrial robots can be used for 3D printing to manufacture the complex freeform surfaces. The postprocessing is the basis of the precise printing. Due to the nonlinear motion of the rotational joint, nonlinear error is inevitable in multijoint industrial robots. In this article, the postprocessing and the path optimization based on the nonlinear errors are proposed to improve the accuracy of the multijoint industrial robots-based 3D printing. Firstly, the kinematics of the multijoint industrial robot for 3D printing is analyzed briefly based on product of exponential (POE) theory by considering the structure parameters. All possible groups of joint angles for one tool pose in the joint range are obtained in the inverse kinematics. Secondly, the nonlinear error evaluation based on the interpolation is derived according to the kinematics. The nonlinear error of one numerical control (NC) code or one tool pose is obtained. The principle of minimum nonlinear error of joint angle is proposed to select the appropriate solution of joint angle for the postprocessing. Thirdly, a path smoothing method by inserting new tool poses adaptively is proposed to reduce the nonlinear error of the whole printing path. The smooth level in the smoothing is proposed to avoid the endless insertion near the singular area. Finally, simulation and experiments are carried out to testify the effectiveness of the proposed postprocessing and path optimization method.

Hazards That Can Affect CNC Machine Tools during Operation—An AHP Approach

CNC (computer numerically controlled) machine tools are highly advanced technological systems, used to machine parts by means of metal cutting processes. Their structure and kinematics are very complex, involving accurate coordinated motions on three to five axes. Operating CNC machine tools is a complicated process, which can easily be affected by errors. Nowadays, safety systems and devices are developed in order to make this process safer and more user friendly. Modern CNC controllers are designed to deal with obvious sources of hazards, such as overloads (by means of various sensor systems) and collisions (by checking the NC code syntax and simulating it on the machine). However, despite of these safety systems, various unwanted events still occur during machining operations on CNC machine tools. These means that there are still certain hazards, not so obvious, which can severely affect the operation of CNC machine tools. This work tries to identify and hierarchize the above-mentioned hazards by using an AHP (analytic hierarchy process) approach. The results of the AHP emphasize which hazard has the biggest influence upon the CNC machine tools operation and consequently should be avoided. The results of this work could be used by the machine tools designers to develop new safety features for the existing CNC controllers. Also, the users of the machine tools could focus some of the safety measures during the machining process upon the most significant hazards pointed by the results of the research.

A Framework of Next Generation Adaptive CNC Controller

Modern manufacturing industries have increasingly demanded to bring comprehensive input data described using high-level languages such as STEP-NC, rather than outdated G&M codes into computer numerical control machine tool levels. In current dynamic shop floor environments, predefined numerical control (NC) command generated in early stages is regularly found unusable or unsuitable for the dedicated resources, causing useless efforts used up in the initial process planning and NC code generation. This research aims to propose a new structure of an adaptive CNC controller by taking the advantages of well-known IEC61499 and STEP-NC standards. For realising adaptive CNC controller capability, integration of the native process planning decision-making function into CNC controller will be established. The activities such as cutting tool selection, machining parameter determination and toolpath generation will be issued automatically by the controller itself that subject to available online machine resources. The generic STEP-NC file is employed as data input and arranged accordingly in the IEC 61499 function block software editor. The system is developed in the JAVA environment by using proposed language.