Design and application an integrated element selection model for press automation line

Materials & Design Materials and Design 28 (2007) 217–229 www.elsevier.com/locate/matdes

Design and application an integrated element selection model for press automation line Kerim Cetinkaya

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Division of Machine Design and Construction Education, Faculty of Technical Education, University of Zonguldak Karaelmas, Karabuk, 78050, Turkiye Received 16 November 2004; accepted 6 April 2005 Available online 16 June 2005

Abstract There are many things that make useful automatic line systems for metalworking machinery. Press automation systems have been widely used in the industry for sheet metal processing. This paper presents a new approach towards elements selection of an automatic line for sheet metal forming. Automation line element selection is a complex, tedious task, and there are few tools other than checklists to assist engineers in the selection of appropriate, cost-effective elements. It has been described as an integrated press automation line elements selection system called press automation elements selection advisor (PAESA) model in this study. The PAESA has incorporated 10 stages of integrated factors such as property profile of possible elements, defining of developed elements, firm research, company contact and costumer service, specification of requirements, driver mechanisms, environmental selection and cost, system accuracy, product strategy and fine selection. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Automation; Press; Sheet metal Strip; Dies; Decoiler; Straightener; Feeder

1. Introduction A typical automatic line for sheet metal forming processes consists of six elements which are: 1. decoiler, 2. straightener, 3. feeder, 4. the press, 5. die and 6. sheet metal strip, as shown in Fig. 1. For thin metal strips, the distance between the straightener and the feeder is selected by experimentation, which later serves the industrial practitioners sufficiently well. Generally, different feeders such as a roll feeder, a clamp feeder, a hydraulic/pneumatic feeder and an electronic (servo control) feeder are used practically in the industry. There are many things that make element successful in the workshop. Many different methods for materials selection and design have been presented over the last couple of decades. A method was reported by Edwards

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Tel.: +90 370 433 82 00; fax: +90 370 433 82 04. E-mail address: [email protected].

0261-3069/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2005.04.007

that brings an approach to a materials selection model that is an integral part, in an integrated product development model, in which both physical and metaphysical properties are analysed for different types of products [1]. The minimisation problem for the weight of the entire bottom structure under static load conditions, including stiffness, strength and buckling constraints, is formulated and solved for each material application, mass and materialsÕ price used for selection of elements, the assessment of an environmental impact of materialscandidates during the entire life cycle of the structure is considered [2]. The introduction of new, or modified or alternative materials and processes for a given application is dependent on satisfying a lot of different factors [3]. Design aspects and examples of methods to fulfil demands for manufacturing, assembly, disassembly, service, recycling, etc., are also presented as well as environmental friendly solutions for product development [4]. Achieving the match with design requirements

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2. Automation line and its elements 2.1. Automation

Fig. 1. A typical automatic line elements for sheet metal forming (EAE machinery) 1 – decoiler, 2 – straightener, 3 – feeder, 4 – press, 5 – die, 6 – sheet metal strip.

involves the following steps: translating design requirements, a procedure for screening out, a scheme for ranking the surviving materials and process, a way of searching for supporting information about the topranked candidates, giving as much background information about their strengths, weaknesses, history of use and future potential as possible [5]. In the design of dies casting as cheaply and rapidly as possible, suitable die size, locations of gating system, and selection of an appropriate die casting machine, shortened lead-time in designing a new die for new product, cooling time, cooling channel locations, and flow rates relations are estimated and presented [6]. Process selection involves three steps which are the ÔmenuÕ of all available processes, lowest cost and safety with environmental issues [7]. The materials profiles information is structured on the basis of: what they are, design notes, typical uses, competing materials, environmental aspects and technical notes, and the materials processes [8]. A procedure for the selection of cutting tools is capable of cutting conditions and estimates component cost, based on the properties of the work piece material and features attributes, which include surface finish and tolerances, as well as using a number of production criteria such as material removal rate, tool life, machining time, and cost [9]. Such a methodology was developed defining the requirements of the design and identifying the attributes of the relevant subset of processes, an evaluation of a design considering both technical viability (including the product quality during processing and in the finished part), and economic viability [10]. A case study involving design limitations and performance requirements in cost estimation is presented to illustrate the use of the integrated approach [11]. Comparative information on the performance and properties of the engineering materials under consideration; the influence of total cost on the selection of the optimum material is discussed [12]. The purpose of this article is to provide a straightforward selection procedure. It will become apparent that a much wider choice of feeder than drive is available: the underlying reason appears to be that power matching is required for an efficient feeder. The classes of elements studied here are detailed for the press automation system.

The term automation has many definitions. Apparently, it was first used in the early 1950s to mean automatic handling of materials, particularly equipment used to unload and load stamping equipment [13]. It has now become a general term referring to services performed, products manufactured and inspected, information handling, materials handling, and assembly, all done automatically (i.e., as an automatic operation). Amber and AmberÕs yardstick for automation was presented in 1962 [13]. A portion of chart that they developed has been updated and is included here as Table 1. Abbreviated form is that each level of automation, in which no human attribute that is begin replaced (mechanised or automated) by the machine. Automation as we know it today begins with the A (3) level in Table 1. Self-adjusting and measuring machines are of the A (4) level, replacing human adjustment and allowing these machines to be self corrected. At the A (5) level, the system would detect the increase in deflection due to increased forces (due to the toolÕs dulling) and reduce the feed to reduce the force. The A (6) level reflects the beginning of artificial intelligence, in which the control software is infected with elements (subroutines) that permit some thinking on the pan of the software. In a metal working machinery, multiple die sets are mounted side by side along the slide. After the completion of each stroke, a continuous coil or individual work pieces are automatically and progressively advanced to the next station by a mechanism. 2.2. Presses Many types of presses have been developed to perform the various cold-working operations. When selecting a press for a given application, consideration should be given to the capacity required, the type of power (manual, mechanical, or hydraulic), the number of slides or drives, the type of drive, the stroke length for each drive, and the type of frame or construction. Table 2 lists some of the major types of presses, in general, mechanical drives provide faster motion and more positive control of displacement. The available force usually varies with position, so mechanical presses are preferred for operations that require the maximum pressure near the bottom of the stroke, such as cutting, shallow forming and drawing and progressive and transfer die operations. In contrast, hydraulic presses produce motion as a result of piston movement, and longer or variable-length strokes can be programmed within the limitations of the cylinder. Hydraulic presses are preferred for operations requiring a steady pressure throughout a substantial stroke (such as deep drawing), operations requiring wide

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Table 1 A portion of yardstick for automation Order of automation

Human attribute replaced and mechanized

Discussion and examples

A(3) Automatic repeat cycle or Open loop control

Diligence: no feedback but repeats cycle automatically, Carries out routine instructions without aid of man Open end or nonfeedback

A(4) self-measuring and adjusting feedback or closed loop system

Judgment: positional feedback, measures and compares (output) to desire size or position (input) and adjusts to minimize any error

A(5) Adaptive or computer control: automatic cognition

Evaluation: adaptive control; deductive analysis; feedback from the process, Evaluates multiple factors on process performance, evaluates and reconciles them, Use mathematical algorithms

A(6) Expert systems or limited self-programming

Learning: by experience

All automatic machines, Loads, processes, unloads, repeats – System assumed to be doing okay. Probability of malfunctions negligible Obeys fixed internal commands or external program, Repeats cycle; open-loop numerical control or automatic screw; transfer lines, Record player with changer, Automatic screw mach, Bottling machines, Clock works, Donut maker, Spot welder, Engine production lines, Casting lines, Newspaper printing machines, Transfer machines Closed loop; numerical control; self- measuring and adjusting devices, feedback from product position, size, velocity, etc. Multiple loops are possible (input, proses, output, feedback), product control, can filling, N/C machine tool with position control, self adjusting grinders, windmills, thermostats, waterclock, fly ball governor on steam engine Computer control; model of process required for analysis and optimization, Process performance must be expressed as equation, N/C machine with A/C capability, Maintaining pH level, Turbine fuel control Limited self-programming; some artificial intelligence (AI); expert systems, Subroutines are a form of limited self-programming, Trial and error sequencing, Develops history of usage, Phone circuits, Elevator dispatching

variation and high or widely variable forces in stroke length [13,14]. 2.3. Description of dies and their function The word ‘‘die’’ it itself means the complete press tool in its entirety, with all the punches, die buttons, ejectors, strippers, pads, and blocks, simply with all its components assembled together. A die set is the fundamental portion of every die. It consists of a lower shoe (or a die shoe) and an upper shoe, both machined to be parallel within a few thousandths of an inch. There are considerable differences in the way dies are built to function. In some, the metal strip is fed through the die, which produces the desired part in stages. Another die makes a complete part with each stroke of the press. All the various types of dies fit loosely into five categories, where they are grouped according to the type of work they produce. These are; cutting dies, bending and forming dies, drawing dies, compressive dies and miscellaneous dies [14]. 2.4. Sheet metal strip Sheet metal of every form, such as a strip or a sheet, displays a definite grain line. It is the direction along which the material was produced in the mill-rolling process. In strips, the grain line usually runs lengthwise

along its longest edge. The grain direction in sheets may vary, and designers must always make themselves familiar with it prior to planning a production. Sometimes the cost of the strip or sheet, the shape of the product, the location of its bends, and other criteria do not allow for the proper lengthwise positioning of the grain. The overall production requirements are the main factors in considering the size of a die and the number of finished products per stroke of a press. The output for a press should be increased by producing more than one part at a single stroke. Every strip design should begin with an assessment of the location of pilot holes. These openings must be pierced at the first station, serving afterwards as a guide and a locating arrangement for the strip on its way through the die [14,15]. Table 2 Classification of the various drive mechanisms of commercial presses Manual

Mechanical

Hydraulic

Kick presses

Crank Single Double Eccentric Cam Knuckle joint Toggle Screw Rack and pinion

Single-slide Multiple-slide

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2.5. Decoilers Easy and concentric holding of coil on the mandrel and the breaking system are developed characteristics of decoilers design and production in the industry, coil weight is up to 10,000 kg and strip width is up to 1600 mm. Decoilers may be motorised, non-motorised, mechanical mandrel expansion and hydraulic mandrel expansion or may have only retarding break system. Generally, motorisation is advisable when the feeding length of the press die is long, hydraulic mandrel expansion is advisable when the sheet metal strip coil is heavy. If there is a motorised straightener on the automation line, only a breaking system or non-motorised decoiler is sufficient. Mechanical mandrel expansion is sufficient when feeder and die upper plate is assembled together. Upper pressure arm is necessary for thick sheet metal strip but is also useful to prevent loosening of the coil. Sometimes using double decoilers helps to eliminate the coil loading time and are preferred by manufacturers for evaluating their working time very efficiently. Operation types are possible as start–stop at a fixed speed of 12 rpm or variable speed operation from 0 to 15 rpm [16–19]. Some decoiler types and sizes produced by Firm A [16] are shown in Table 3. 2.6. Straighteners High precision coil straighteners are built using high quality hardened and ground steel straightening rollers. Generally, versions of the mechanism is built with 11 rollers. Two or four of them are feeding rollers and nine or seven of them are straightening rollers. For gap adjustments, top non-driven straightening rollers are separately adjusted using a worm screw-down mechanism. Bottom rollers are driven by synchronised gears,

Table 3 Decoiler types and sizes of Firm A

which are powered by a direct-coupled gear motor to the main feeding roller. Pneumatic opening of feeding rollers, motorised gap adjustment, entry and exit squaring quiding, strip and take-up unit are used on different types of straighteners in the industry. Loop sag control system requirements are arm limit switch, proximity detector and ultrasonic sensor. For straighteners max. sheet metal strip thickness is up to 7 mm and max. sheet metal strip width is up to 1600 mm [16–19]. Some straigtener types and sizes produced by Firm B [17] are shown in Table 4. 2.7. Feeder One of oldest and most familiar methods of press feeding is the roll feeder. Some feeder types and sizes produced by Firm A [16], Firm E [20] and Firm F [21] are shown in Tables 5–7. An adjustable eccentric is mounted onto the end of crankshaft providing a fixed 180° feed angle. Two opposed feed rolls clamp the sheet metal strip while a one-way clutch, connected to the eccentric, feeds the sheet metal strip during the upper half of the press cycle. The low inertia feed rolls and shaft are precision ground to assure concentricity. Hard, chrome plated upper and lower rolls are mounted in sealed anti-friction bearings driven by precision anti-backlash gearing to maintain full tooth engagement for any material thickness. These feeders are designed for maintenance free operation and repeatability of ±0.05 mm without the use of plot pin is obtainable [16–21]. 3. Design and application of an integrated element selection model for press automation line Press automation line elements selection advisor (PAESA) is given in Table 8. Design and application

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Table 4 Straightener types and sizes of Firm B

of an integrated element selection model is represented here as a simple step schedule or framework for the designer to follow. PAESA starts with the property profile of possible elements and is carried out from step 1 to 10. Then let the idea be influenced by each step and, if it still seems to be of interest and worthy of selection, continue to the next step, subjecting the idea to careful and appropriate analysis. In a modern, integrated product development process, the materials selection was integrated into the development model [1]. It must be remembered that the workplace for an element using (essentially mechanical) is the material itself. Here, the method for selecting an element is the design and application of an integrated element selection model for press automation line. The PAESA model typically starts with step 1, with an idea of a new press automation line, possible elements or profile property. The ideas can be quite different, as illustrated by the following examples: a new

Table 5 Feeder types and sizes of Firm A

element to replace an existing die set, a new automation line or sub-assembly to improve an already existing automation line or a new automation line for a specific product. Definition of developed elements is done in step 2. Through steps 3 and 4, firm research, company contact and customer service must then be carried out before the specification of requirements, step 5, can be evaluated; driver mechanisms, environmental influences and system cost are represented in steps 6 and 7; system accuracy and firms are argued in step 8; next product strategy after existing product in automation line and final selection after online similation of press automation elements are discussed in steps 9 and 10. The steps of PAESA model are explained in details as follows. 3.1. Property profile of possible elements Property profile of possible materials: select some possible materials and check if they fulfil the require-

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Table 6 Feeder types and sizes of Firm E

Table 7 Feeder types and sizes of Firm F

ments. If no material is found, try to change the requirements (e.g., design, expected lifespan, etc.) [1]. A typical automatic line for sheet metal forming comprises a decoiler, a straightener, a feeder, a press, a die and sheet metal strip, as shown in Fig. 1. Few types of decoilers have been developed to perform the various cold-working operations listed here. When selecting a decoiler for a given application, consideration should be given to the capacity required, the type of position (vertical or horizontal), with regard to its multifunction (internal or external squeeze) [16], the number of coil loading, the expansion type of power (mechanical, hydraulic or pneumatic) [17,18], the type of drive (motor-

ised or non-motorised) [16–19] and the type of frame or construction, electronic servo control system [19]. Straighteners can be evaluated with regard to their construction as: Cradle straighteners: this machine is recommendable especially for sheet metal strip thicker than 1.3 mm and not having very delicate surfaces [18]. Decoilers are placed on the same body together with the straightener [16]. Separated straighteners: high precision roll straighteners are built with nine rollers [17–19]. Two of them are feeding rollers and the rest are straightening rollers. Straighteners placed on decoilerÕs body: this type of straighteners is assembled on the same body together with the decoilers.

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Table 8 Design and application an entegreted element selection model

Feeders. According to their energy supply, there are several categories of feeders, their main difference being in the automation line they use. Here is recognised: Mechanical feeders: where the sheet metal strip transferring is supplied by some mechanical means, such as roll and clamp [16,20]. Hydraulic feeders: utilizing the pressure of water or other fluid media [17–19]. Pneumatic feeders: sheet metal strip operating is performed with the aid of pressurised air [17,21]. Electronic feeders: where the sheet metal strip is moved by the application of electronic force [17–20].

3.2. Definition of developed elements The definition of existing elements must be clarified from the beginning of the selection of a certain element. As mentioned earlier, trying to avoid automation line selection that does not fit into the business concept of the company can be detrimental to the success of that element. Different companies or trademarks are more or less directly connected to a certain selection of elements. Three important market groups are pointed out as P – prestigious products, M – moderately products

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and F – functional products. Some companies span two groups, but rarely span all three groups [1]. For a press automation line, some products are pointed out at each group individually as follows. Group P: with ultimate quality prestigious products are servo controlled in the press feeding automation system consisting of three main machines – decoiler, straightener and feeder. Group M; moderately priced products may choose tandem type pneumatic feeders for high speed presses, hydraulic feeders for heavy and thick sheet metal strip, double decoilers for evaluating their working time very efficiently, and for high precision separated straighteners. Group F: functional products for the low-price market, the functionality is more important here. Vertical or horizontal and internal or external squeeze decoilers, cradle straighteners, mechanical feeders may be included in this group. 3.3. Firm research Costumers and firms meet face to face somewhere, for example; local or national or international trade fairs, exhibitions, conferences, world wide web, such Profiilikeskus Roll forming Know how as company that is perform everything for sheet metal handling from Northern Finland seem on Web pages of European Business Directory. CustomersÕ choice between firms is based on the full price they incur, which is defined as the service charge (homogeneous across customers and servers) plus the expected waiting cost (homogeneous among service providers but heterogeneous among customers) [22,23]. Firms are driven out of the market in two circumstances, when firmsÕ unit profit margin becomes zero or when their market share becomes zero. The important assumption on a Ôde-strategisedÕ firm behaviour, based on the idea that firms persistently differ in their organisational routines, can be articulated assuming the existence of different technological regimes which affect learning processes within industries and consequently the evolution of industrial structures [24,25]. The efficiency of the decision making involves goals and policy, planning, monitoring/data recording and evaluation. Physical output (price, quantity) is used as the dependent variable in many studies, leading to an estimate of technical efficiency [26]. The ‘‘experimental’’ portfolio comprises firms with significant amounts of intangible assets that have been relatively stable over the past 3 years [27]. 3.4. Company contact and customer service More and more companies now rely on the benefits of e-mail communication as a means of ensuring customer service. To date, very few publications have explored the role of this medium in the establishment of an interper-

sonal relationship between customer and company. Old producers differ from new producers with regard to the invitation to stay in contact with the company [28]. More recently, it has been argued that marketing is more complex than a simple dichotomy. As summarised, a series of dimensions are used to distinguish between four types of market practice: transaction, database, interaction, and network marketing. Relationships may be with customers, distributors, suppliers, competitors, and so on [29]. 3.5. Specification of requirements A detailed instruction about how something should be designed or made, detailed description of what a job involves, a clear statement of what is needed or wanted are some of the specifications. Harmonious arrangement or relation of parts or elements within a whole as in a design is called ‘‘Balance’’. There is in bodies a principle of unity and activity which corresponds to what the Scholastics call Ôsubstantial formÕ as the metaphysical concept of force. Metaphysical principles (such as the Aristotelian–Scholastic substantial forms) must not be used in the physical explanation of particular phenomena, it is also true, on the otherhand, that even in scientific notions there are implicit concepts which cannot be reduced to extension and motion [30]. The first requirements which are determined often relate to the desired performance of the product, such as will it be useful enough? Another important consideration is the processability of the part, such as will it be functional enough? The first set of design decisions, therefore, are often concerned with assessing the technical aspects of the design, in order to determine whether the engineering requirements can be met. In this step, the definitive design selection, from among all those presented by the working group and in agreement with company specifications, is carried out. The following was indicated: physical requirements (weight, dimensions, driver mechanism, etc). Weight is the most important for decoilers which care on coil. In Table 9, some types of decoiler and their weight capacity are given. The functional requirements move the selection from the narrow to the large part of the automation line. The specific functional requirement to broaden the candidate set in several steps is the definition of the high-level functionality. It is very likely that the broker will find no candidates. Strip thickness and width are important for straightener selection. In Table 10, some types of straightener and their sizes are given. Compatibility ensures that components short-listed as good candidates can actually cooperate to build a system. Compatibility is a further criterion on selection. The layers of a port may implement the link and be closer to the physical aspects – function and method invocations, parameter passing, networking – or may contribute to define the

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Table 9 Pysical requirements for decoilers Pysical attributes

Firm A

Firm B

Firm C

Firm D

Max. coil weight capacity (kg) Target group (P, M, F) Max. strip width (mm) Expansion type (B: breaking, M: motorised, E: servo)

1500 F 300 B/M

10,000 F/M 1600 M

10,000 F/M 1500 M

10,000 M/P M/E

Table 10 Pysical requirements for straighteners Pysical attributes

Firm A

Firm B

Firm C

Firm D

Max. strip width (mm) Target group (P, M, F) Max. strip thickness (mm) Driven type (M: motorised, E: servo)

300 F 2 M

1600 F/M 5.0 M/E

1500 F/M 7.0 M/E

1600 M/P 10 E

semantics of the messages that are transmitted. The compatibility check requires some extra effort to componentsÕ suppliers during the classification process but it provides a powerful mechanism to retrieve only useful components from a huge set [31]. Different driver mechanisms are used in feeders and strip sizes are important for selection, as given in Table 11. The choice of the actual component to adopt is referred until the other components are chosen and the alternative components can be evaluated in the context of the overall selection as shown in Table 12. two or more elements are integrated in a compact system. Metaphysical explanation of the requirements of a product, nature must always be explained mathematically and mechanically, provided it is remembered that the very principles or laws of mechanics or of force do not depend on mathematical extension alone, but on certain metaphysical reasons. Consideration will only be given to the engineering aspects of the design without involv-

ing the non-functional (e.g., aesthetic, user-friendliness) design elements specifically [32]. 3.6. Driver mechanisms Here, three different elements and their drive system in press automation line are discussed. Sheet metal strips are automatically transferred from decoiler to metal working machines. Decoilers: where the work force is supplied by some mechanical means, such as a retarding breaking system, if there is a motorised straightener in the automation line, only a breaking system is sufficient, for example Firm A and Firm C. Motorisation is advisable when the feeding length of the press die is long or the coil is thick or heavy, Firm C. Motorised, nonmotorised, mechanical and hydraulic mandrel expansion decoilers presented, Firm B. Both electric motor and servo system drive are used with very sensitive dies Firm D.

Table 11 Pysical requirements for feeder Pysical attributes

Firm A

Firm B

Firm C

Firm D

Firm E

Firm F

Max. strip width (mm) Target group (F, M, P) Max. strip thickness (mm) Accuracy (mm) Max. stroke (mm) Mechanical feeder (C/R) Hydrolic pneumatic feeder (H/P) Electronic feeder (E)

300 F 3

1600 F/M 5 0.05

1500 M/P 7 0.05

1600 P 10 0.05

300 F 3.5 0.05 200 R

150 F 2.2

225 C H/P E

E

250 P

E

E

Table 12 Integrated systems Compact system elements

Firm A

Decoiler–straightener Straightener–feeder Decoiler–straightener–feeder

X

Firm B

Firm C

X

X X

Firm D X X

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Straighteners: two types of operations are possible. There are start–stop operation at a fixed speed or variable speed operation using a AC motor. For gap adjustments, top non driven straightening rollers are separately adjusted using a worm screw-down nechanism. Bottom rollers are driven by synchronised gears which are powered by a direct coupled gear motor to the main feeding rollers, Firm B and Firm C. Servo system drive is used with very sensitive dies, Firm D. Decoiler is placed on the same body together with the straightener (called cradle straightener) and an electric motor is used for drive, Firm A and Firm B. Feeders: one of oldest and most familiar element of press automation line is the roll feeder, Firm E and another one is clamp feeder, Firm A. In both of them, the work force is supplied as mechanical by cam Firm A or roll Firm E. Tandem type pneumatic feeder is proposed for high speed presses and hydraulic feeders for heavy and thick bands, Firm C. The straightener with servo motor provides straightening and feeding in one machine. Especially, for the straightening and feeding of the thick bands it provides a unique solution, Firm B and Firm C. Over the years, significant improvements have been made in the area of press feeding system, Firm C and Firm D. The compact system is controlled by servo motor and Plc system. In compact system, there are together three elements: decoiler, straightener and roll feeder. Finally, only pneumatic feeder element is produced by Firm F that can choose light weight coil and thin sheet metal strip for high speed press. 3.7. Environment and cost estimating The selection of a sample starts from an analysis of the environment, i.e., the identification of a necessity that has not been satisfactorily fulfilled (product), and that allows the elaboration of a real problem. It can also start from an attempt of finding an appreciative characteristic using the structural, functional and formal analogy for further application in a project [33]. Environmental considerations in the selection of the materials used in components, meeting functional and performance requirements while minimising the environmental impact associated with the productÕs entire life-cycle [34]. Bovea and Vidal [35] have established a criterion for selecting materials with low environmental impact during the wood based furniture design. Some of the considerations and difficulties in selection of materials to minimise environmental impacts are discussed [36]. In this study, hydraulic infiltrates and pressing air seem as environmental effects, these are complex and large systems and need to widely spaces. Select materials that minimize pollution during extraction, processing, deployment, recycling and disposal, consequence of design and manufacture decisions, especially production processes, that impose minimal damage to the environ-

ment, while simultaneously enhancing the quality of human life [37,38]. Cost models for a manufactured component or system can have several purposes. Function-costing and/ or parametric methods interpolate the cost of a component or system that is a variant of an existing family for which historic cost data already exist [39]. The cost of a sheet metal part with features made by shearing, drawing and folding can be estimated by analysing correlations between the costs of previously made parts with these features against their size, shape and complexity, and then locating the new part in this field of costs. Activity and resource-based costing methods seek to calculate and sum the cost of each unit operation involved in the manufacture of a component or system; retrieval of materials, set up time, time to perform step, die mounting time, time to pass to next step, resources of materials, energy, capital, time and information associated with the manufacture of the component [40]. 3.8. System accuracy and firm experience A prerequisite for the automatic control of the metalforming system (process, tool, press) is extreme accuracy during each single stroke cycle of the press and during the whole batch time [41]. The actual start of recording a stroke cycle of the press is initiated by a pick-up of the crank angle of the press. The data processing is done in such a way that force diagrams can be plotted as a function of time, the crank angle or the slide travel. Quite often, inspection devices are placed in the machines or in devices between the machines, so the inspection is performed automatically. Inspection by a machine instead of a person is faster, easier, and more repeatable. In the press automation line, typically, two or four powered feed rolls are used depending on sheet thickness [13,15]. The feeding accuracy of the roll feeders is 0.05 mm for 1 m, thanks to servo technology such as Firm B and Firm E. An alternative to the roll feed is a servo hydraulic grip (clamp) feed system. Because the grippers move between physical stops, the system produces a repeatable length tolerance of 0.1 mm. Every strip design should begin with an assessment of the location of pilot holes. In the die, pilots provide for a guidance of strip by sliding into at least two pierced openings, located at the extreme edges of the sheet metal strip, and positioning, or fine adjusting the surrounding material around their bodies. Mounting of pilots utilises the same procedure as that described for mounting of punches [14,15]. Firm A should be a functional company, but it does not provide any information on the accuracy of tolerance and feeders as given in Table 3. Pilots provide for a guidance of strip, positioning and accuracy. Firm C has 30 years experience in the field of production of linear and radial transfer line for press automation sys-

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tems, feeding length adjustment with 0.05 mm accuracy of different feeding length, back and forward setting in the program. Standard feeders, being relatively cheap, can be mounted directly on the dies, thus reducing installation time of Firm C and Firm F, such feeders have pilot opening device as standard. Firm E has made servo roll feed systems, these are designed for maintenance free operation and repeatability of 0.05 mm without the use of pilot pin is obtainable. 3.9. Product strategy The lean production approach to manufacturing demands that small lots be run. This is impossible to do if machine setups take hours to accomplish. Both setup time and automation line element capacity are important elements of press automation line for buyers. Each of them is selected firstly according to press type and capacity than depending upon what widely and thinly sheet metal strip component is produced in the company. Setup time reduction occurs in four stages. The first two stages involve determining what is currently being done in the setup operation. The setup operation is usually videotaped and everyone concerned gets together and reviews the tape to determine the elemental steps in the setup. The next two stages involve separating all setup activities into two categories, internal and external. Internal elements can be done while the machine is running. This elemental division will usually shorten the lead time considerably. If, at the end of a batch, for the production of another type of component, the dies have to be changed, than, the values of the forming process characteristics and the press adjustment devices are set up, for instance, stroke adjustment, blank-holder adjustment, pressure in the hydraulic overload system, number of strokes per minuite, etc. When, after some time, the same tool is used for the production of the next batch, the same values of the influencing parameters are reestablished on the press/tool system. For the protection of the press and tool set-up, an upper and lower limit of the force and the force-travel diagram of a reference-forming process can be programmed. 3.10. Final selection At this stage, the options remaining after the initial screening are reduced to a smaller set of possible processes, by assessing whether they can achieve the basic production criteria when the primary technical requirements are considered. Computer aided process planning uses computer software to determine how a part is made and how system elements are performing their function and how system elements are set up in press automation system. The objectives of process control and analysis and the gained improvements in the process are the following: visualisation, monitoring, and analysis of the

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forming process [41,42]. Suitable automation line solutions and alternatives are found as an effective match between material physical requirements and the different features of various element types. The constructed target prototype of automation line is successfully validated through as visual by computer or any screen [43]. Designer should know to input product or strip size, the weights or important values for these attributes [44]. The working medium can be pressurised air, or pressurised liquid. When selecting a press for a given application, consideration should be given to the capacity required, the type of power (manual, mechanical, or hydraulic). Programmed into the computer are models (mathematical equations) that describe how this process or system behaves, how this behaviour is bounded, and what aspect of the process or system is to be optimised [45,46].

4. Examples Many companies set up automation line for transferring sheet metal strip. For example, ORS was established in Turkey as the first specialised manufacturer of High Precision Ball Bearings [47]. Cages and shields are produced from deep drawn steel strip in multiplestation, fully automatic presses. Eregli Iron and Steel Factories (ERDEMIR), which is the largest iron and steel company in Turkey [48]. This company has used servo compact system, flexible producing lines, cut to length line, slitting line, control can be executed manually or automatically, feeding speed can be adjusted via the screen. As the documents and on-line systems shown in this company have used elements of group P; with ultimate quality prestigious products are servo controlled in the press feeding automation system consisting of three main machines which are decoiler, straightener and feeder or servo compact system. Another example is Yilmazoglu metal forming company [49] in OSTIM organised industrial area in Turkey. There are three presses (one hydraulic and two mechanical), one lathe, one milling machine, and some mechanical devices in workplace. Only pneumatic feeders and manual or break system opening decoilers are used in this firm. Standard feeders, being relatively cheap, are mounted directly on the dies, thus reducing installation time of Firm C and Firm F. These elements of Group F: functional products for the low-price market, the functionality is more important here. Initially, PAESA collects the information on element attributes from step 1 to step 10 by performing requirements of the designer, following the search path constructed in the knowledge base. It then matches its knowledge to the specific values of the attributes and informs the element type being selected. The following questions are presented to the system during a typical integrated consultation as shown in Table 13.

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Table 13 A typical integrated consultation 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

What does the company prefer? (prestigious, moderation, functionality) Which type of material is transfered? (roll strip or flat strip) Which type of press is used in workplace? (hydraulic or mechanic) What is the stroke length of strip? Is servo control unit required in the automation line process? (required, not required) Which type of driver system is used for feeder? (clamp, roll, hydraulic, pneumatic, electronic) Is combined feeder needed for strip transfer? (straightener–feeder together) Is combined straightener preferred? (decoiler–straightener together) Which type of decoiler is preferred? (manual, motorised, position, double load) What is wishing product accuracy? (0.1 or 0.05 mm per 1000 mm)

5. Discussion The PAESA model is a modern method for selection element of successful and useful product production in press automation line. The model, accessible as a straightforward manual, is in a format that is simple and lucid and can be used for almost all types of physical products and elements, ranging from simple singlecomponents, devices and mechanisms such as a die shoe, hydraulic actuator, to more complex products, such as a motorcar comprising thousands of components. However, for a complex system it is necessary to use the PAESA model for both the individual elements and the whole systems. The modelling process can therefore become quite unwidely in manual form if complex products are analysed in fine detail as in [1]. This PAESA method is developed to select the most appropriate element for a particular application. The selection of an appropriate element is based on matching the accuracy tolerances of product to the requirements of an application.

6. Conclusion A large number of elements of press automation line have been evaluated to allow the performance of some elements like strip stroke length, driver system, mechanism, weight capacity, accuracy, workplace, cost, strategy; each specialised for a particular set of requirements – individual, two element combined and compact. Both element type and performance create the need for methods to enable comparison and selection, allowing the choice of a feeder to meet a mount of press requirements. A way of achieving these goals is described in this paper, which presents integrated method to guide the selection process with 10 steps, an example and using system studies that display the utility of the method. Consequently, the end step of the selection phases in this work is presented which are visual graphic representation techniques, such as simulation and animation in three dimensions by using computer for selection elements of a press automation line. From

this, customers can obtain on screen visual model of systems before actual systems set up in work place.

Acknowledgements The present research work has been supported by Zonguldak Karaelmas University Research center. The author gratefully acknowledges the support of Zonguldak Karaelmas University.

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