Commercial CAM System Research Articles

Study of tool paths calculated by different commercial CAM systems and influences on the real machining time and surface roughness for milling free-form geometries

Today, there are many commercial CAM systems available capable of generating NC codes for milling free-form geometries up to 5-axis. However, the quality of these NC codes has not yet been well discussed so far. Apparently, on the computer screen and the geometrical simulation provided by CAM, tool paths calculated by different CAM systems seem to be the same. However, as observed in this work, NC codes differ expressively according to the CAM software applied, and it affects the productivity and quality of the machined surface. Thus, a study was carried out to investigate this issue. A representative workpiece with free-form geometries was designed; a data acquisition system from an open architecture CNC was developed and NC codes were generated by five worldwide commercial CAM systems. The finishing milling operation was evaluated. The results presented difference of up to 30% on the real machining time, differences in the feed rate oscillation and up to 2 times the surface roughness value. This work reveals an essential limitation on the CAM algorithm and arises a new point for benchmarking CAM systems, which brings an opportunity to improve the calculation of tool paths for milling free-form geometries.

Adaptive method of 5-axis milling of sculptured surfaces elements with a curved line contour

In this paper, an attempt to develop a new adaptive method of controlling the axis orientation of a toroidal milling cutter (leading angle α) depending on the radius of curvature (radius ρ1 in the feed direction, i.e. on a curved contour) of the treated surface profile in a 5-axis milling process was made. An application of this method required the development, based on the results of simulation and experimental tests (own tests), of a special procedure for selection of the lead angle α of the milling cutter depending on the continuously changing radius of curvature ρ1 in the direction of the milling cutter. This procedure was implemented in a commercial CAM system, thus modifying the classical strategy of controlling the movement of the tool into an adaptive strategy. The proposed method after entering the criterion of the permissible value of the deviation of shape Δk and limiting the permissible parameter Ra of the surface roughness, allows adapting the lead angle α of the toroidal axis to the current value of the radius of curvature ρ1 of the processed composite surface profile. By conducting experimental research on the example of the blade machining of the turbine blade, it was shown that the concept of a new method of controlling the axis of the toroidal milling axis allows the parameters of the lead angle and radius of curvature (α, ρ1) to increase the accuracy of the 5-axis surface treatment of complex elements with contours curvilinear by about 25 %.

Funkcjonalność rozpoznawania cech technologicznych w komercyjnych systemach CAM

Funkcjonalność rozpoznawania cech technologicznych w komercyjnych systemach CAM

A new approach to contour error control in high speed machining

High speed machining technology attempts to maximize productivity through the use of high spindle speeds and axis traverse rates. The technology is dependent upon the development of suitable mechanical hardware, electrical drives and associated control software to ensure that all components are used to maximum advantage. The role of the control software is particularly demanding since one needs to maximize traverse rates while providing the necessary accuracy, and indeed providing a margin of safety to deal with unexpected changes in process, or system parameters. There have been relatively few improvements in commercial CAD or CAM systems that would help machine tool users to take maximum advantage of high speed machining; rather the majority of the approaches have been undertaken at the machine tool controller level. This paper uses circular interpolation and corner tracking to compare several such control techniques, (Cross Coupled Control (CCC), Zero Phase Error Tracking Control (ZPETC), and Realtime Frequency Modulated Interpolation (FMI)), each of which have been proposed in the literature order to improve machining accuracy. None of these approaches are found to be universally successful when used alone and the authors, in this paper, examine the use of these systems in combination. Particular attention is focused upon an extension of a simplified version of cross coupled control together with Frequency Modulated Interpolation. It is shown that the combined system performs extremely well, and is easily actuated at high frequencies with conventional hardware. A custom built high speed x-y table is used to confirm system performance with multiple constraints present.

Five-axis tool path generation in CNC machining of [formula omitted]-spline surfaces

Because of its flexible topology and robust data structure, the T-spline surface has become the trend of free-form surfaces representation in the realm of CAD design, animation and CAE. Yet its application in manufacturing has not been fully explored. In this work, the possibility of direct tool path generation on the T-spline surface has been discussed. An improved space-filling curve (ISFC) tool path planning algorithm has been proposed to exploit the advantage of T-spline as a mathematical representation of free-form surfaces in CAM process, as well as to overcome its disadvantages such as irregular boundaries and holes in the pre-image. The turning problem in traditional SFC has been tackled using Hermite compensation curves. Finally, a prototype system has been developed to implement the proposed algorithm and actual machining has been conducted. The result shows the feasibility as well as the efficiency of the proposed method for T-spline surfaces tool path generation compared to commercial CAM system.

An accurate surface error optimization for five-axis machining of freeform surfaces

This paper presents an accurate surface error interpolation algorithm for five-axis machining of freeform surfaces. One of the most important steps in the interpolation process is to calculate the next cutter contact (CC) point according to the present one. In this paper, the next CC point is calculated by an accurate chord evaluation method. This method is developed based on the cutting simulation process, which can be vividly described as firstly planting dense grasses on the tool path curve and then cutting them when the tool moves by. The left lengths of the grasses either positive or negative are considered to be the machining error. The method is accurate also because the tool geometry and the tool orientation changes during five-axis machining are taken into consideration. With this method, the chord errors between CC points are controlled uniform along the tool path. The proposed interpolation algorithm is compared with the commercial CAM systems like PowerMILL and UG. The results show that the proposed algorithm can significantly reduce the number of cutter locations meanwhile confine the chord error. A real cutting experiment is implemented, and the result indicates its promising value in industrial applications.

Fast Cutter Workpiece Engagement Estimation Method for Prediction of Instantaneous Cutting Force in Continuous Multi-Axis Controlled Machining

In order to realize high productivity in rough machining processes, a fast simulation system is needed for multi axis controlled machining to predict instantaneous cutting force. The new efficient algorithm to estimate an engagement between the end mill cutter and the machined workpiece in continuous multi axis controlled machining processes is proposed. In order to shorten calculation time for the engagement area, and to improve the real-time prediction of instantaneous cutting force, a new concept is introduced for adapting ultra-parallel processing technology. The proposed method assumes the engagement as a large number of divisions located on the locus of cutting edges. The inclusion estimation process between an estimation point in each division and the machined workpiece volume is resolved into two kinds of simple inclusion estimation – and between the estimation point and tool swept volume and the other between the estimation point and initial workpiece shape. In this paper, a new prototype system based on parallel processing technology known as the general purposed graphic processing unit (GPGPU) is developed and the proposed algorithm is verified with the prototype system. The system shows good performance for complicated NC programs generated by commercial CAM system and realizes real-time simulation of instantaneous cutting force.

CAD/CAM Strategies for a Parallel Kinematics SPIF Machine

Single point incremental forming has attracted the interest of researchers in the last decade for the production of prototypes and small batch production of sheet-based parts [1, 2]. This technique allows the manufacture of parts without using expensive die sets. The SPIF (Single point incremental forming) process can be performed on different equipments such as adapted CNC milling machines, serial robots and built proposed machines [3]. Every solution has advantages and disadvantages. This work presents the CAD/CAM strategies for a parallel kinematics SPIF machine, designed and built at the University of Aveiro [3]. This machine brings a new approach to the SPIF industry. The machinery used to perform SPIF operations has limitations in their work volume with limited movements and in the magnitude of applicable forces. With that in mind, this machine was projected to overcome that obstacle, and was provided with a system with 6 degrees of freedom, while maintaining the ability to apply high loads. The disadvantage is the increase in volume occupied by the kinematic system. The manufacture of new parts could be reached out with more flexibility on the chosen tool path. The first step is the product design in the commercial CAD system. Next step is generating the tool path of the forming tool. This step is very important to achieve the desired part shape. It is used a commercial CAM system (EdgeCAM 2012®), which has resources from three up to five axis strategies. The last step is to send the information to the machine’s control system, based on real-time software. This paper will describe each step with more details.

Evaluation of Dynamic Behavior of Machine Tools for Sculptured Surface Manufacturing

The production sector of molds and dies is under a continuous pressure for process optimization due the high lead time required for the production of complex tools. In recent years, to improve this sector, numerous studies have been aimed at optimization of the CAD/CAM/CNC chain. However, despite recent technological innovations such as development of cutting tools, machine tools, and process simulation systems, the machining step still represents a major bottleneck in this process. The current generation of Numerical Control (NC) programs that represents the tool path do not consider the dynamic characteristics of the machine tool in the decision-making process to choose the most appropriate cutting strategies, resulting in NC programs that do not reach levels of excellence. The main objective of this paper is to present the development of a reference index based on the dynamic characteristics of the Machine Tool to support the NC programming with a commercial CAM system. This index considers the Machine Response Time (MRT) of NC controller, the acceleration and deceleration on the axes of the machine tool and the tool path segment (size and inclination). The index makes possible an experimental evaluation of relationships between the programmed feed rate for the tool path and dynamic performance due to movements of the machine axes, thus becoming an important decision-making factor in choosing the best machining strategy and consequently a better plan of the production process in die and mold industries.

Integration of Additive Manufacturing and Virtual Verification Strategies within a Commercial CAM System

Computer-Aided Design and Applications is an international journal on the applications of CAD and CAM. It publishes papers in the general domain of CAD plus in emerging fields like bio-CAD, nano-CAD, soft-CAD, garment-CAD, PLM, PDM, CAD data mining, CAD and the internet, CAD education, genetic algorithms and CAD engines. The journal is aimed at all developers and users of CAD technology to ptovide CAD solutions for various stages of design and manufacturing. The journal publishes all about Computer-Aided Design and Computer-Aided technologies.

Predictive model of tool wear in milling with coated tools integrated into a CAM system

The coated tool wear evolution in milling at constant cutting conditions can be described analytically based among other factors on the cutting edge entry impact duration. A tool wear predictive mathematical model for milling parts of complicated geometry was created employing this methodology and a commercial CAM system. Parameters of the developed model were determined based on experimental results. In this way, the expected tool wear growth during numerically controlled milling can be estimated, considering the cutting penetrations along the tool paths, the process up or down kinematic and other factors. The application of the introduced model is demonstrated through appropriate examples.

Computation of optimal tool length for 5-axis ball-ended milling of molding die

The research presents an efficient computation of optimal tool-length for 5-axis mold and die machining. The proposed procedure analyzes input NC data generated by a commercial CAM system and computes the minimum feasible tool-length via slight modification of tool orientation at the selected NC blocks where tool-length reduction is required. The test result shows that the research is especially useful in five-axis machining steep wall features of deep cavities in an injection molding die. The developed system is used at a domestic molding die manufacturing company.

Estimation System of Accurate Cutting Time Based on Actual Feedrate Identification

The estimation of accurate cutting time before cutting is important for improving productivity. Estimation of cutting time calculated by length of tool path / command feedrate can easily be obtained in commercial CAM systems because NC programs contain machining information, such as tool positions, feedrate, etc. However, the actual cutting time is longer than cutting time calculated by length of tool path / command feedrate due to acceleration and deceleration which occurs along the tool path. In this study, an estimation system of accurate cutting time based on the control system of the machine tool is proposed. Experiments were conducted to cut complex shapes using the NC machine tool to compare the actual cutting time, estimated cutting time of commercial CAM systems and those of the proposed system. The estimation error of the proposed system was only 2 %, while the estimation error of a commercial CAM system was 51 %.

Cutter Location Generation Method for Improving Feedrate and Machining Accuracy Based on Control Characteristics of Machine Tool

All types of NC machine tool interpolation are fundamentally based on linear interpolation, using the minimum interpolation unit of the drive. However, linear interpolation causes issues when machining curved surfaces, such as the feedrate not reaching the command feedrate and fluctuations occurring unexpectedly. These are mainly due to the NC interpolation process, and feedrate limiters. In addition, linear interpolation also decreases machining accuracy through inner cornering errors which are caused by acceleration and deceleration. Finally, it also lowers surface quality, by causing tatami patterns during zigzag cutting, due to differences in the locations of acceleration and deceleration in the forward and backward paths. Thus, in order to solve such problems, a method of generating cutter location data with consideration to the machine tool control characteristics, which are the NC sampling time, the feedrate limiters, and acceleration and deceleration, is proposed. The effectiveness of the proposed method is confirmed by simulations and experiments. Compared with a commercial CAM system, the proposed method increases the feedrate, smoothes acceleration and deceleration, and reduces the cutting time by approximately 50%. The proposed method also improves the surface quality and eliminates tatami patterns.

Fast Cutter Workpiece Engagement Estimation Method for Prediction Of Instantaneous Cutting Force in Continuous Multi-Axis Controlled Machining

This study proposes a new efficient methodology to estimate an engagement between cutter of endmill and machined workpiece surface in continuous multi axis controlled machining process. In order to shorten calculation time for the engagement domain and realize real-time prediction of instantaneous cutting force, a new concept adapting ultra-parallel processing technology is proposed. In the proposed concept, the engagement domain is divided into a large number of estimation point. Then, inclusion estimation process between the estimation point and the machined workpiece volume is decomposed into simple estimation processes about tool swept volume. The developed prototype system shows good performance for complicate NC programs generated by commercial CAM system.

A new sheet metal forming system based on incremental punching, part 2: machine building and experiment results

The paper is the second of the two papers on a new sheet metal forming system of incremental punching. In the first paper, the mechanics model is introduced, and the computer simulations are carried out. This paper consists of two parts: the design and building of an incremental punching machine and experiment results. The machine is a three-axis computer numerical controlled (CNC) machine with a high-speed hydraulic punching head. Given a part, the punch path can be generated using commercial CAM systems with some modifications. Then, the machine takes over forming the part punch by punch. The formability of this system is also investigated giving the maximum forming angle. Following the first paper, two examples are studied in details. The experiment results indicate that the new system is effective for sheet metal rapid prototyping. Finally, some future research topics are discussed.

Integrated rough machining methodology for centrifugal impeller manufacturing

In mechanical engineering, most products or components, especially those for aerospace applications, are designed to fit the requirements of free-form surface features. The impeller often required by 5-axis machine operations is a key component of the aerospace industry. When 3-axis CNC machining center is used to manufacture the impeller, great difficulties, i.e., collisions between the cutting tool and impeller, need to be overcome. Presently most commercial CAM systems for 5-axis control lack generality, and functions for the rough tool-path generation are far from sufficient. Although the rough machining is the most important procedure influencing the machining efficiency and the condition for the following finishing process, many difficulties arise in performing 5-axis rough machining. The main objective of the present study is to overcome this problem by integrating the state-of-art machining technology, and consequently effective rough tool-paths are to be generated. This study aims to implement the algorithm of the constant scallop height method to improve tool-path planning of rough machining. As a result CL data based on the geometry model of blade and hub are generated. The CL data are confirmed by comparing them with original CAD model through software simulations and later by machining experiments. The verification results show that the machining methodology and procedure adopted turn out to be a successful case.

Process planning and NC-code generation in manufacturing of press dies for production of car bodies

This paper presents a process planning system that generates process plans and NC codes for machining of press dies, which are used in manufacturing the body panels of cars. This system consists of three modules: a macro-process planning system that generates process plans for major parts of press dies; an operation planning system that generates operation plans and NC codes for free-form surfaces; and an NC-code post-processor that analyses and modifies NC codes. Fifteen major part-families (PFs), along with their standard process plans, are defined for macro-process planning. A process is a set of unit operations, which can be completed without changing the set-ups. Details, such as cutting tools, cutting conditions, and tool paths are decided upon during the operation planning stage. After generating cutter location (CL) files, using commercial CAM systems, the operation planning system selects cutting tools and their lengths to generate NC codes. At the final stage of process planning, the NC code post-processor adjusts feed rates along the tool path to reduce machining time while maintaining the quality. In order to adjust the feed rate, the machining load per each tool-path segment is estimated using virtual machining.

CAD-CAM integration using machining features

Commercial mechanical CAD/CAM packages provide a rather low level of automation of process planning tasks and a weak connection between their CAD and CAM/NC part programming modules. Features have primarily been used as geometry construction 'macros' without fully realizing their potential in supporting downstream applications, such as process planning. This paper demonstrates the use of features in automating certain process planning tasks and integrating CAD and CAM modules in commercial CAD/CAM software. Automated process planning involves two important tasks; machining feature extraction and feature-based process planning. The CAD model of the part and the stock is exported via STEP from the commercial CAD system to an external machining feature recognition system. The recognized features are used in conjunction with knowledge-based methods to prepare a process plan for the part. Set-up Planning, Operation Sequencing and Tool Selection are performed automatically based on criteria such as feature shapes, feature locations, tool access directions and feasibility of workpiece locating and clamping. Features and manufacturing attributes are exported to a commercial CAM system for toolpath generation and verification. A prototype system was implemented in conjunction with a commercial CAD/CAM package, SDRC/I-DEAS.

Optimizing tool selection

Selecting optimal cutting tools that can answer to the performance criteria of manufacturing economics (quality, productivity, cost, etc) is an important step in planning the manufacture of components. Achieving this, however, is difficult because of the many constraints involved in the tool selection process. This paper describes a method for determining a theoretical optimal combination of cutting tools given a set of 3D volumes or 2D profiles. Optimal tools are selected by considering residual material that is inaccessible to oversized cutters and the relative clearance rates of cutters that can access these regions of the selected machining features. The current implementation described does not give exact results because several machining parameters have been ignored during the selection process, such as tool path length, plunge rates, etc. However, the experimental studies carried out to verify the theoretical results suggest that while these factors may influence the absolute values calculated, in general, their influence on the relative ranking of the tools is insignificant. The results presented here suggest that the 'correct' combination of tools could significantly reduce machining times. Consequently, the paper concludes with a discussion of how modifications to typical tool path generation routines in commercial CAM systems could improve productivity.