Parag Vichare

Surface roughness prediction model for CNC machining of polypropylene

Cutting strategy research has traditionally been focused on hard materials that are intrinsically difficult to machine. An increase in the desire for personalized products has led to the requirement of the direct machining of polymers for personalized products. Little research is evident in the literature on the analysis of optimal machining parameters for machining materials such as polypropylene. One of the vital factors that affects the quality of polypropylene products and the respective machining strategy is surface roughness. This research is aimed at extracting information on the machining of polypropylene materials. A surface roughness predictive model based on neural networks has been developed. The design of experiments approach is used to obtain an adequate predictive model for the process planning which is further utilized as an input to the predictive model. The model mainly hinges on three independent variables namely spindle speed, feed rate, and depth of cut. Extensive experimental work on different network topologies and training algorithms has been performed to predict the behaviour of the surface roughness for machined polypropylene products. The results illustrate the benefits of being able to determine surface roughness values. This allows for the determination of optimal cutting strategies and tooling for the required surface roughness. The performance predictive model has been found to be satisfactory over the dataset for polypropylene machining. Hypothesis testing has also been carried out to identify the confidence of the predictive model.

A unified manufacturing resource model for representation of computerized numerically controlled machine tools

Abstract The capability of any manufacturing system primarily depends on its available machine tools. Thus machine tool representation is a vital part of modelling any manufacturing system. With the rapid advances in computerized numerically controlled (CNC) machines, machine tool representation has become a more challenging task than ever before. Todays CNC machine tools are more than just automated manufacturing machines, as they can be considered multi-purpose, multi-tasking, and hybrid machining centres. This paper presents a versatile methodology for representing such state-of-the-art CNC machining system resources. A machine tool model is a conceptual representation of the real machine tool and provides a logical framework for representing its functionality in the manufacturing system. There are several commercial modelling tools available in the market for modelling machine tools. However, there is no common methodology among them to represent the wide diversity of machine tool configurations. These modelling tools are either machine vendor specific or limited in their scope to represent machine tool capability. In addition, the current information models of STEP-NC, namely ISO 14649, can only describe machining operations, technologies, cutting tools, and product geometries. However, they do not support the representation of machine tools. The proposed unified manufacturing resource model (UMRM) has a data model which can fill this gap by providing machine specific data in the form of an EXPRESS schema and act as a complementary part to the STEP-NC standard to represent various machine tools in a standardized form. UMRM is flexible enough to represent any type of CNC machining centre. This machine tool representation can be utilized to represent machine tool functionality and consequential process capabilities for allocating resources for process planning and machining.

A STEP-NC Compliant Methodology for Modelling Manufacturing Resources

Manufacturing enterprises of all sizes, from small subcontractors and job shops to transnational aerospace and automotive giants, rely on a vast array of resources to generate added value and accomplish their business goals. These resources are comprised of human resource, knowledge resources and technological resources. Achieving business goals requires relevant, timely and well-calculated decision-making. A decision making process requires a model of the decision domain to be constructed with the necessary fidelity to achieve acceptable results and to determine the best course of action in the problem context. A reliable representation of manufacturing resources is therefore necessary for making correct decisions along the manufacturing chain. In this chapter a STEP-NC compliant methodology for representing technological manufacturing resources is presented. This modelling approach is based on mechanical elements that constitute machine tools and other manufacturing hardware together with their kinematic links and is developed with a focus on supporting process planning decisions. Models for various types of machines are presented at the end of the chapter to highlight the flexibility of this approach in modelling manufacturing resources.

An information model for process control on machine tools

Recent advances in technologies involved in CNC manufacturing systems have provided industry with the capability to machine complex products. However, there is still no guarantee for these advanced systems to manufacture products to their required specification the first time. This results in large scrap rates of manufactured components and requires skilful resources (human/bespoke solutions) to adjust the involved processes. The solution to this problem is the development of a machine tool process control system which would be able to provide the corrective measures in-process. At the core of this system, is a kernel to map the information in the manufacturing CAx chain. Using the existing high level information on component design, machining processes, manufacturing resources and measurement, process control can be maintained. This leads to seamless information flow in the manufacturing process chain. This paper presents and describes a machine tool process information model. A computational platform for developing a machine tool process control system has then been discussed. This computational prototype has been further realised and demonstrated using a prismatic case study component.

Unified representation of fixtures: clamping, locating and supporting elements in CNC manufacture

A CNC machining operation is the outcome of the application of the integrated capabilities of various resources within the CNC machining centre. Part fixtures, clamping and other location mechanisms are essential subsets of CNC machining resources. Today, various fixturing techniques and attachments available in the market allow manufacturers to enhance their production capability without buying expensive machine tools. This technology-rich fixturing domain is detached while representing and exchanging machine tool resource information for making manufacturing decisions. The research work in this article utilises the STEP-NC compliant unified manufacturing resource model (UMRM) for representing fixtures in conjunction with the parent CNC machining centre. Thus, UMRM is enhanced in this context to represent various fixtures such as universal vises, chucks, pallets and auxiliary rotary tables among others. The major contribution of this article is the application of the extension of the UMRM approach for representing fixturing domain, which allows generic modelling of fixtures and loading devices in addition to machine workpiece and process modelling. This would enable the stage of automated process planning and manufacturing. The universal approach in representing resource information allows the data to be utilised for making a wide variety of manufacturing decisions.

Computer numerical control machine tool information reusability within virtual machining systems

Virtual machining allows simulation of the machining process by realistically representing kinematic, static and dynamic behaviour of the intended machine tools. Using this method, manufacturing-related issues can be brought to light and corrected before the product is physically manufactured. Machining systems utilised in the manufacturing processes are represented in the virtual machining environment, and there is a plethora of commercial virtual machining software used in the industry. Each software system has a different focus and approach towards virtual machining; more than one system may be needed to complete machining verification. Thus, the significant increase in the use of virtual machining systems in the industry has increased the need for information reusability. Substantial time and money has been put into the research of virtual machining systems. However, very little of this research has been deployed within industrial best practice, and its acceptance by the end user remains unclear. This article reviews current research trends in the domain of virtual machining and also discusses how much of this research has been taken on board by software vendors in order to facilitate machine tool information reusability. The authors present use cases which utilise the novel concept of machining capability profile and the emerging STEP-NC compliant process planning framework for resource allocation. The use cases clearly demonstrate the benefits of using a neutral file format for representing machining capability profiles, as opposed to remodelling and/or reconfiguring of this information multiple times for different scenarios. This article has shown through the use cases that machining capability profiles are critical for representing recourse information from a kinematic, static and dynamic perspective that commercial software vendors can subsequently use. The impact of this on mainstream manufacturing industry is potentially significant as it will enable a true realisation of interoperability.

Design and implementation of machine tool static error feedback model

CNC manufacturing has continuously strived to meet the increasing customer demand of quality control parts with minimum lead time. This essentially means developing CNC machine tool solutions which will result in less variation in the dimensions of manufactured products. It has been established in the recent past that static errors on a machine tool area major contributors in the overall errors for manufactured parts. The authors have proposed a feedback model to compensate the machine tool static error and provide compensated part feature positions. This model has been developed to map the static errors (as an effect of the movement in the kinematic joints of the machine tool) with the deviations in the locations of the part features. It has been then tested in a real time manufacturing environment using an industrially inspired test piece. The significant improvement in measurement results (for drilling positions) of manufactured parts shows the efficacy of the model.

A Novel Information Modelling Approach for Representing Parallel Kinematic Machine Tools

Abstract Today Parallel Kinematic Machines (PKM) are re-attracting attention in the manufacturing practice due to their advantages over traditional serial kinematic structures. Still very few PKMs are on the market due to limited CNC controller support. In addition, most commercial postprocessor development tools lack the capability to represent all aspects of parallel kinematic structures. A novel universal approach is proposed in this paper for representing PKM structures as well as serial kinematic machine tools. This universal approach can be adopted as a basis for developing a generic postprocessor to support serial and parallel kinematic machine tools.