外文資料翻譯--量化控制機(jī)床精確度、性能、可用性的一個(gè)全面方法（英文）

1、8–3 A Holistic Approach to Quantifying and Controlling the Accuracy, Performance and Availability of Machine Tools Peter Willoughby1,* , Mayank Verma1, Andrew Peter Longstaff2, Simon Fletcher2 1 Mac

2、hine Tool Technologies Ltd., 307 Ecroyd Suite, Turner Rd, Lomeshaye Business Village, Nelson, BB9 7DR, UK 2 Centre for Precision Technologies, University of Huddersfield, West Yorkshire, UK Abstrac

3、t With today’s ever increasing demand for improved accuracy and faster material removal rates, CNC machine tool manufacturers and users are under pressure to supply and maintain machinery with a high de

4、gree of accuracy and performance. Although some machine tool users have their machines “checked”, there is no formal method of establishing the capability of a machine tool as an overall measure of it

5、s performance, accuracy and availability. This paper identifies the key performance indicators for modern CNC machines and highlights the technical difficulties in understanding machine tool capabilit

6、y. To solve the problem, a novel method of measuring, analysing and controlling the overall capability is presented. The philosophy and process of machine performance evaluation, optimisation and

7、 monitoring (MPEOM) is explained. The paper also illustrates how conventional “Lean” techniques can be utilised to simplify the complex area of machine tool metrology allowing for the integration of t

8、he process into modern manufacturing systems. Keywords: Lean manufacturing, Metrology and measurement, Sustainable manufacturing, Precision machining, Condition monitoring. 1. Introduction Many high precision ma

9、nufacturers are aware of the problematic areas within their processes and the impact they have on the cost and ability to remain competitive. Although quality, performance and availability levels

10、 might be measured in some form, the data only represents the symptoms of underlying problems within the manufacturing process. As a result, manufacturers usually engage in process improvement where

11、‘Lean’ strategies such as Kanban, Kaizen, TPM and Six Sigma are implemented to improve organisational efficiency and overall equipment effectiveness (OEE), Gibbons [1]. Unfortunately this process improvement w

12、ill often stop at the machine tool level due to the complexity of machine tool systems and a skills shortage throughout the industry. ISO DIS 263003- 1(E) Machine Tools – Reliability, availability and

13、 capability provides an indirect measurement of capability by evaluating the machining process. This methodology was developed in the automotive industry and is particularly suited to large batch manufactu

14、ring due to its use of statistical process control (SPC). The short term capability of a specific process can be evaluated, however should the process be changed or a different area of the m

15、achine be required then capability of the asset is no longer known. 1.1 Machine tool complexity CNC machine tools are continuously increasing in flexibility and functionality, but the added complexity

16、leaves many end- users struggling to keep up with the technology. When the capability of the machine tool is in question, not only is it often unknown, but methods of establishing it are also

17、 unclear. This leads to a situation where assumptions, based on non- factual or untraceable information, are made and proliferate among all relevant departments. As a result, the equipment is iso

18、lated from organisational quality systems. Figure 1 illustrates a typical manufacturing system where all other processes are managed by some kind of auditable or “Lean” system. The interface of the m

19、achine tool into this system is often disregarded. Fig. 1. Managing the manufacturing process A Holistic Approach to Quantifying and Controlling the Accuracy, Performance and Availability of Machi

20、ne Tools 315 implementation of such a system via a machine tool service and calibration based organisation. It has been seen from industrial experience of others that the separate implementation of ‘

21、classic’ lean approaches regularly fail due to large financial, human and technical requirements which end- users are unlikely to be able to justify or provide. A strategy has consequently been developed

22、 that requires a simple yet effective system to facilitate an approach to any manufacturing cell irrespective of size, location and complexity. This system, called MPEOM, has been applied to a full spectrum

23、of machine tools ranging from small manual lathes to very large multi- axis gantry machines and is presented in the following section. 2. The MPEOM? Framework MPEOM? (Machine Performance Evaluation Optim

24、ise Monitor) is a six stage continuous improvement process with can be used to evaluate, optimise and monitor the condition of machine tool systems. It is a ‘lean’ tool that can be used to p

25、ull the machine into a quality system and creates the structure of TPM. The cycle can be seen as shown in Figure 3. Fig. 3. The MPEOM cycle The system picks up on a lean strategy often us

26、ed in TPM and Sig Sigma. It is an evolution of a Plan, Do, Check, Act cycle and can also be compared to the five stage DMAIC process. Each stage of the MPEOM? process will be explained in

27、 the following section of this paper. 2.1 Pre- assessment review The pre- assessment review brings together manufacturing engineers, production, maintenance and machine tool specialists. During this revie

28、w the part or range of parts produced on a selected machine and the machining process key performance variables (KPVs) are analysed and formalised. The results of the meeting include: ? classificatio

29、n of the machine as reliability or accuracy biased ? a clarification of machine performance requirements ? identification where part/process specific auditing/measurement actions are required ? a metrol

30、ogy index based on machine configuration ? measurement equipment requirements 2.2 Machine condition evaluation Once objectives have been set for the machine, it is then audited. During this audit crit

31、ical mechanical, electrical/electronic and metrological characteristics of the machine are investigated. This includes assessment of: ? all main mechanical components ? all main electrical and electron

32、ic components ? the machines axial geometry to ISO 230 – 1 and OEM specifications ? the machines structural geometry to ISO 230- 1 and OEM specifications ? the machine’s measuring systems in ac

33、cordance to ISO 230 -2 ? the machine’s dynamic capability in accordance to ISO – 4 ? artefact accuracy During this evaluation non- intrusive tasks can be carried out also, which can include cleaning o

34、f the machine, adjustments and optimisations to any minor machine faults and its geometry and measuring systems. 2.3 Post- assessment review The data collected on the machine is presented to the r

35、epresentatives from the maintenance and production departments through comprehensive reporting and charting. All machine issues or out of tolerance metrology items that could not be rectified during the evalua

36、tion stage are flagged. Concessions are negotiated, based on budget and time available for optimisation and the level of performance that is required from the machine. Once an agreement has been reac

37、hed by the team, plans are formulated for any rectification and optimisation work on the machine. 2.4 Machine condition optimisation The optimisation of the machine is a sub- cycle within the MPEOM pro

38、cess, consisting of four levels. Level 1 involves optimisation which can be carried out non-intrusively such as adjusting machine geometry using conventional mechanical alignment techniques, adjustme

39、nt of CNC controller setting and general servicing actions. Should it be agreed that this would be insufficient a Level 2 optimisation is subsequently used. This would consist of a partial rebuild

40、 of the machine using the machine and process requirements as the specification guideline. Such corrective action could include removal of critical machine components for repair and/or re- engineering. A Level 3 opt