THE SPECIFICITY OF PUNCH PRESSES PROGRAMMING

Journal for Technology of Plasticity, Vol. 36 (2011), Number 2 DOI: 10.2478/v10211-011-0012-1

THE SPECIFICITY OF PUNCH PRESSES PROGRAMMING Vladimir Blanuša, Milan Zeljković, Dragiša Vilotić, Slobodan Tabaković Faculty of Technical Sciences, Trg D. Obradovića 6, Novi Sad, Serbia ABSTRACT Starting from the general model of the programming process, this paper presents the manual programming procedure for punch presses. The programming process workflow is presented and control programs are defined to make the maximum number of workpieces arranged on the same metal plate using two different punch presses: Amada Vela II and Trumpf Rotation 2000. Because the control systems of these machines belong to different generations, the obtained results should be understood by taking this fact in consideration. The control programs analysis included: the length and complexity of the programs, the complexity of the programming process, the number of used tools, roughness achieved by this method of processing, etc. The technological capabilities of the above machines for particular workpiece were analyzed. The mutual dependency of cutting step and radius are shown for two values of roughness: h = 0.3 mm (mean deviation of free size) and h = 0.03 mm by (IT6 - the highest quality achieved by using the fine cutting technology) for both outer and inner cutting. The advantages and disadvantages of the programming procedure were comparatively analyzed for both machines. Keywords: sheet metal manufacturing, punch presses, programming.

1. INTRODUCTION Punch presses (presses for partial separation – cutting or perforation) are machines used for making workpieces from metal sheets by numerically controlled process of cutting and perforation. Compared to the original definition of machining centers as it is defined in machining technology, these machines can also be named as processing centers for cutting and perforation. These machine tools perform a large number of strokes per time unit while the desk with a metal sheet moves in the planar coordinate system, which allows cutting straight-line and curvilinear contours. The metal sheet shaping machines can be, depending on the driving mechanism, divided into mechanically (crank presses), hydraulically and electrically driven machines [10]. They are used in applications in small series and individual production for metal sheet processing to obtain

122 workpieces of different geometric shapes, as well as machines for unconventional processing (machines for LASER based metal sheet processing and water-jet processing machines). There exists also the possibility to integrate systems for manipulation of workpieces with the machine and obtaining in this way flexible technological modules for the processing of metal sheets. One of disadvantages of these machines is the requirement for high values of breaking force for processing thicker and materials of greater strength. Recently, this problem is solved by integrating these systems with LASER based systems, so that the LASER is used to warm-up the metal sheet in the processing area thus reducing the processing power for penetration [2]. By integrating these processing types the concept of hybrid and hybrid processing machines are introduced, which is one of the contemporary trends in the development of machining tools, both for deformation based processing and classical machining based processing. As disadvantage of these machines the curvilinear surface roughness is considered and, consequently, one of possible directions to solve this problem is application of combined laser-punch machines [6]. Programming of the machines mentioned above plays an important role in their implementation and use. Similarly to standard machining tools, machines for unconventional processing of metal sheets and punching and cutting machines can be programmed manually and automatically [7,11]. This paper shows an analysis of the manual programming process of control programs for two machines that were available to authors: Amada Vela II and Trumpf Rotation 2000 [1,9].

2. THE MANUAL PROGRAMMING PROCEDURE The term "manual punch presses programming" is used to describe a series of activities to be performed to define a control program for the machine to solve a specific task. From the perspective of automation, the manual programming is the lowest level of programming which is used if technological adjustment for workpieces with simple geometry is needed or if the user has no programming system for automated programming available. The general model of the programming process of NC punch presses, as well as NC machines for unconventional processing is very similar to the usual NC machine tool programming process. The general punch presses programming process model is shown in Figure 1. According to this model the programming process has three characteristic phases: • Design of the basic processing sequence - defining the technological process; • Elaboration of certain phases of processing; • Preparation (development) of the control program. Design of the basic processing sequence for manual programming is done by technologist. Basic input in this phase is the fabrication drawing of the workpiece, basic technological task (which defines the amount of workpieces, special requests, etc.). In this phase technologist uses his/her knowledge, experience, intuition, etc. This phase of designing the basic processing sequence, in principle, is practically the preparation for the next phase of the programming process. Within this phase, as well as in next phase, very important activity is the analysis of workpiece (fabrication) drawing(s). Although this is a preparatory stage in the process of punching and cutting machines programming, failures that occur in this phase are difficult to correct and can cause price increase of the production process and, also, occurrence of erroneous products. Elaboration of individual phases of processing is the second phase in the process of technology definition. Within this phase it is possible identify certain sub-phases which correspond to the normal process of technological design, in which specific output is generated in from of relevant documents. The results of some sub-phases are represented by following documents:

Journal for Technology of Plasticity, Vol. 36 (2011), Number 2

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Clamping plan; Manufacturing plan; Tool plan.

It should be noted that certain sub-phases are iteratively repeated in order to obtain the best solutions for specific requirements in a given facility.

Fig.1 - General model of the programming process The Clamping plan defines the choice of preform, layout of workpieces on the metal sheet, coordinate system and positioning and clamping of the metal sheet. Activities related to the clenching plan definition are shown in Figure 2.

Fig.2 - Activities related to the clamping plan definition In addition to manual clenching plan definition, it can be generated by some software system for automated programming, if they have the ability to quickly and efficiently perform scheduling of workpieces on the metal sheet, by taking into account the utilization of material (e.g. the ProENGINEER product provides a module for programming punching and cutting machines, which allows deployment of workpieces on the metal sheet). This is especially important for mass production, where optimal utilization of the metal sheet provides significant savings in material.


124 Although punch presses are not intended to be used in mass production and usually they represent a solution for flexible low-volume production, it is also important to assure utilization of materials. Additionally, the technologist must take care to leave enough distance from the edge of the metal plate for workpieces deployment (due to shrinkage and processing) and the distance between the workpieces (depending on the selected cutting tool). A clamping plan for specific workpieces processing from a metal sheet is shown in Figure 3.

Fig.3 - The clamping plan The manufacturing plan is a document which contains necessary information for the realization of the processing according to defined technological sequence and contains also all information necessary to perform all individual processing steps.

Fig.4 - Activities related to the manufacturing plan definition


125 Detailed processing plan defines all operation steps with technological parameters (overlaps, bridges, etc.). Figure 4 shows the activity sequence during the processing plan definition, which is shown in Figure 5.

Fig.5 - The manufacturing plan The tool plan is a document which defines punches and related matrices, as well as the positions of the tools in the tool carrier. In other words, the tool plan is a document that defines the selected tools to perform specific processing operations. Figure 6 shows the sequence of activities in the definition of the tool plan, where there is necessary to define the total number of tools, the position of the tool in the tool carrier, correction for tools, geometry and dimensions.

Fig.6 - Activities related to the tool plan definition The tool plan for the manufacturing plan shown in Figure 5 is shown in Figure 7.


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Fig.7 - The tool plan (for the manufacturing plan given in Figure 5) Particular attention should be paid to the layout of tools in the tool carrier, especially taking in consideration the tool replacement time and uniform tool weight distribution. Setting of tools to one side only leads to the asymmetry of loads of tools carrier, which cause some problems. If tools are spread uniformly, the time to replace the tool may be longer, but uniformity of load is achieved. Number of tools in the carrier varies from manufacturer to manufacturer and machine type (number of tools in the tool carrier can vary from ten to hundred tools). Making the control program. Definition phase of the control program preparation (the programming) - as well as previous phases – is done by technologist - programmer. During the process programmer uses previously defined clenching and processing plans, as well as selected tools and rules specific for the machine for which the control program is prepared. The process of defining the control program is essentially a process of transformation of defined plans into numerical program (code) recognizable by the machine, i.e. the implementation of clenching, processing and tool plans, as they were defined in previous phases.


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3. DEFINITION OF TECHNOLOGICAL PARAMETERS AND CREATION OF THE PROGRAM Defining a specific workpiece processing technology, with manual programming, largely depends on the knowledge and experience of technologist-programmer. Below are listed some of the questions that need to be answered during the programming process. The main criteria to be taken into consideration by technologist are related to maximal utilization of the metal sheet, minimization of the processing time and required accuracy of the processing. For example, the distance between the workpieces should be large enough to ensure that the workpieces can be processed with appropriate tools and that the bridges between them remain of the required size. These bridges must exist to ensure that the workpieces remain connected to the metal sheet until the last processing stroke so bridges of 0.5 mm width at a distance of 120 to 150 mm should be provided, regardless of the thickness of the sheet. Bridges are usually left on the edges of the outer contour of the workpiece. In case of internal cuts – nibbling, it is not possible to leave the bridge at edges so they are set in the middle. After processing is finished, the separation of pieces from metal sheet is done by engaging the soft rubber hammer in the zone of bridges. Based on the technology of these machines on the one hand and requirements related to the accuracy of the workpiece on the other hand, the programming must take into account the moving of tools from the roughness point of view. Roughness of the inner and outer contours (based on geometric conditions shown in Figures 8 and 9), can be calculated by the following expressions:

Fig.8 - Roughness for inner contour processing

h = R − (R −

h = (R +

Fig9 - Roughness for outer contour processing

D 2 d 2 D d ) − ( ) − ( ) 2 − ( ) 2 - Roughness for inner contour processing 2 2 2 2

D 2 d 2 D d ) − ( ) − R − ( ) 2 − ( ) 2 - Roughness for outer contour processing 2 2 2 2


128 Having in mind that the measure of tolerance and surface roughness class is defined on drawing, a fundamental question during programming is with which tool and with which processing step the same result can be achieved. For this reason, below are shown the expressions to determine the step in cutting the workpiece of known radius and diameter of the selected tool. Expressions are obtained using the programming system Wolfram Mathematica: 1. d=

2. d=

Inner cutting D 2 h 2 − h 4 − 2 D 2 hR − 2 Dh 2 R + 4h3 R + 4 DhR 2 − 4h 2 R 2 h 2 − 2hR + R 2

Outer cutting D 2 h 2 − h 4 + 2 D 2 hR + 2 Dh 2 R − 4h 3 R + 4 DhR 2 − 4h 2 R 2 h 2 + 2hR + R 2

In order to facilitate the application of these terms in productive environment, the following text contains graphs to determine the maximal tool strokes for two values for roughness, five tool diameters and a range of radius of inner and outer contours of the workpiece. The Figures 10 and 11 contain graphical representation of the dependency of cutting stroke d and the contour radius R for roughness h = 0.3 and h = 0.03 mm and tool diameter D = 10 – 50mm for case of inner cut. Figures 12 and 13 display the dependency of cutting stroke d and the contour radius R for roughness h = 0.3 and h = 0.03 mm and tool diameter D = 10 – 50mm for case of outer cut. For example, by using these graphics for the required inner contour surface roughness less than or equal to 0.3 mm, for radius for workpiece contour of 50 mm and the tool diameter of 10 mm, the maximal stroke obtained is d = 3 mm.

Fig.10 - Dependency of the stroke d from radius R for roughness 0,3mm for inner cutting


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Fig.11 - Dependency of the stroke d from radius R for roughness 0,03mm for inner cutting

Fig.12 - Dependency of the stroke d from radius R for roughness 0,3mm for outer cutting

Fig.13 - Dependency of the stroke d from radius R for roughness 0,03mm for outer cutting


130 The following text shows the specificities for programming of the Trumpf Rotation 2000 and Amada Vela II punch presses for processing of the crossbeam support, which is shown in Fig.14.

Fig.14 - The crossbeam support To create this workpiece on the Trumpf 2000 Rotation punch press three tools are needed (tools carrier has 12 places for the reception of tools): two tools of rectangular cross-section 40x5mm and 25x5mm and one circular cross-sectional tool with diameter of 10mm. The fast pace of this machine is 65m/min while the processing speed during the punching and cutting is much lower and is ranged from 8 - 15m/min - depending on the type and thickness of the material. When defining the processing steps it is necessary to define the overlap size in the process of punching, depending on the length of the contour and dimension of the tool, either in straight or curved punching. Besides the configuration of the workpiece and the dimension of the tool, in defining the size of the overlap one should take in consideration the requirements of productivity, ie. the processing time. In this case, programming is done using subroutines, where the subroutine is defined for each step; this subroutine was executed for each workpiece, allowing one tool to be used to do all steps for all workpieces – the criteria was to minimize the tool change, because the tool change takes about 10s. For straight contours cuts the same tool was used as for longitudinal and transverse cutting but function to turn the tool holder was used. As shown in Figure 4, first step was to make all holes on all workpieces by using the circular cross-section tool; after this tsep, the nibbling (cutting) of curves was done by calling the other two subroutines, using the same tool. After that, the rectangular cross-section tool was used to cut inner contours oh rectangular shape, where the appropriate subroutines and the function to turn the tool holder were used. The same tool was used for steps 7 and 8 on all workpieces. The third tool was used to cut the remaining outer edge, by calling the appropriate subroutines and using the function to turn the tool holder. Part of the main processing program and some of the subroutines are shown in Figure 15.


131 MAIN PROGRAM: % (DFS, P12345) N10 (*MSG, MAIN PROGRAM NO 12345) N20 (MSG, TKICKNESS AND DIMENSION OF THE SHEETMETAL 3 mm X1000 Y600) N30 G92 X640 Y200 N40 G71 (DIMENSION SYSTEM METRIC PROGRAMING) N50G06 X7.3 Y3.9 M20 (ACCELERATION PROGRAMMING) N60 F10 N70 S3 N80 (MSG, WZG RUND 10) N85 T01 N90 G90 G00 X210 Y55 F65 M20 N100 Q12 N110 M20 N120 G90 G00X690 Y55 F65 M20 N130 Q12 N140 M20 N150 G90 G00 X210 Y220 F65 M20 N160 Q12 N170 M20 N180 G90 G00 X690 Y220 F65 M20 N190 Q12 N200 M20 N210 G90 G00 X210 Y385 F65 M20 N220 Q12 N230 M20 N240 G90 G00 X690 Y385 F65 M20 N250 Q12 N260 M20 N270 G90 G00 X215 Y165 F65 M20 N280 Q12 N290 M20 N300 G90 G00 X695 Y165 F65 M20 N310 Q12 N320M20 N330 G90 G00 X215 Y330 F65M20 N340 Q12 N350M20

SUBPROGRAMS: % (DFS, P12) (cutting of circular holes) N5 (MSG, SUBROUTINE NO.12) N10 G71 N15 G91 N20 G01 X0 Y0 F12 M25 N30 X60 Y0 H3 N40 M20 N50 M00 N60 G90 M02

% (DFS, P13) (inner cutting by radius 1) N5 (MSG, SUBROUTINE NO.13) N10 G71 N15 G91 N20 G02 X200 Y55 N30 X155 Y100 I0 J45 E3 F12 M22 N40 M20 N50 M00 N60 G90 M02

% (DFS, P14) (inner cutting by radius 2) N5 (MSG, SUBROUTINE NO.14) N10 G71 N15 G91 N20 G02 X-155 Y50 N30 X-200 Y95 I-45 J0 E3 F12 M22 N40 M20 N50 M00 N60 G90 M02

Fig.15 - Segment of the control program for Trumpf Rotation 2000 punch press Punch Press Amada Vela II has a control system of older generation, so programming, in accordance with its capabilities, was performed without the use of subroutines. Maximum speed of fast pace for these machines is 70 m/min while the processing speed during the punching and


132 cutting is about the same as on the previous machine. This machine has been programmed without turning tool holders, which required to be put into the multi-position tool carrier double tools of the same geometric shape and dimensions that were rotated for an angle of 90°. The tool carrier accepts 58 different sizes of tools and one must take in consideration also in which carrier position is the tool mounted (from the standpoint of tools dimension and weight distribution). By using the control system of this machine, in case of straight cut cycle, the cycle is defined in such way that the overlap size is determined depending on the length of cutting and dimension of the tool (the designer should not take this into consideration). In the specific case, the G98 function is used for programming to repeat the procedure without the use of subroutines and, at the same time, to ensure the production of multiple workpieces from the same metal sheet. Processing of these workpieces can be done in two ways. One way is to first process the workpieces which are set in position A (the first sub-operation) (Figure4) and then the processing stops and the metal sheet is rotated for 180 °; then the workpieces are processed in position B (the second sub-operation). By this processing solution the same program is used, but it is necessary to stop the machine and rotate workpieces, position and tighten them again. In the second case a new reference point should be defined, from which follows the multiplication of workpieces is done, but for this redefined position of workpieces appropriate new macros should be written. Figure 16 shows a segment of the control program for the punch press machine Amada Vela II. % N10 ( MAIN PROGRAM O 555) N20 ( 3 X1000 Y600) N30 G92 G21 X12700 Y12700 N40 G71 (DIMENSION SYSTEM METRIC PROGRAMING) N50 G98 X1000 Y3000 I48000 J16500 P1 K2 N60 U1 N65 M12 N70 G90 G72 X20000Y2500 N80 G28 I2000 J0 K4 T306 N90 G90 G72 X20000 Y10000 N100G68 I5000 J18000 K9000 P-1000 Q300 T306 N105 M13 N110 V1 N120 G75W1Q1 N130 U2 N135 M12 N140 G90 G72 X2500 Y2500 N150 G66 I10000 J0 P2500 Q500 T317 N155 M13 N157 M12 N160 G90 G72 X2500 Y1200 N170 G66 I10000 J0 P2500 Q500 T317 N175 M13 N180 V2 N190 G75 W2 Q1 N200 U3

N260 G75 W3 Q1 N270 U4 N275 M12 N280 G90 G72 X30500 Y0 N290 G66 I4950 J9000 P2500 Q5000 T203 N295 M13 N297 M12 N300 G90 G72 X15500 Y10000 N310 I4950 J9000 P2500 Q5000 T203 N310 M13 N320 V4 N330 G75 W4 Q1 N340 U5 N345 M12 N350G90 G72 X20000 Y5000 N360 G66 I9950 J0 P4000 Q500 T219 N520 G98 X4500 Y9000 I48000 J16500 P1 K2 N530 U7 N545 M12 N540 G90 G72 X20000 Y2500 N550 G28 I2000 J0 K4 T306 N555 M13 N557 M12 N560 G90 G72 X20000 Y10000 N570G68 I5000J18000K9000 P-10000 Q300 T306 N575 M13 N580 V7 N590 G75 W7 Q1


133 N205 M12 N210 G90 G72 X3000 Y2500 N220 G66 I10000 J9000 P2500 Q500 T203 N225 M13 N227M12 N230 G90 G72 X12500 Y2500 N240 G66 I10000J9000 P2500 Q500 T203 N245 M13 N250 V3

N600 U8 N605 M12 N610 G90 G72 X2500 Y2500 N620 G66 I10000 J0 P2500 Q500 T317 N625 M13 N627 M12 N630 G90 G72 X2500 Y12000

Fig.16 - Segment of the control program for Amada Vela II punch press

4. CONCLUSION The topic of programming the high-productive machines for metal sheet processing is for many years a significant area of research in production engineering. With the aim of creating a unified methodology for programming numerically controlled machine tools, this paper describes all stages in a preparation process of the control programs for punch presses, with detailed insight into the activities that are specific and which are significantly different from the machine tools for cutting processing. This is especially true for clenchin plan definition and tool plan preparation, which is determined by the shape and dimensions of the metal sheet and by the geometry and characteristics of the tools used on these machines. In addition to the programming process of punch presses, a typical error is shown which occurs due to the shape and the specifics related to the movement of the tool and it is manifested in the form of surface roughness. Considering the importance of this phenomenon in processing, the paper presents a method of determining the tool step depending on surface roughness, as well as the graphical display of dependencies of tool step tools and dimension of the curvilinear cut that can be processed with a given roughness. Finally, the paper describes the programming procedures which are applicable to the punch presses, for two most common manufacturers of machines that are often used in an industrial plant in Serbia. By comparing these procedures, it was concluded that the methodology for programming machines made by Amada manufacturer allows creation of shorter and simpler control programs when processing one type of workpieces on the same metal plate. On the other hand, the methodology used on the machines manufactured by Trumpf is an universal solution that is suitable for processing of two or more kinds of workpieces on the same metal sheet. Based on analyses shown in this paper, one can conclude that the programming of NC punch presses (i.e. numerically controlled machines for metal sheet processing) may, with certain modifications, be treated and implemented as the programming of numerically controlled machine tools for machining.

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134 [3] Kief, H., Roschiwal, H.: NC/CNC Handbuch 2007/2008, Hanser, ISBN:978-3446409439, 2008. [4] MATE, www.mate.com., Pristupljeno 20.07.2011 u 13.00h. [5] Plančak, M.: Dictionary of metal forming, Faculty of technical sciences, Novi Sad, ISBN:978-86-7892-063-9, 2007. [6] Raggenbass, A., Reissner, J.: Stamping – laser combination in sheet processing, CIRP annals-Manufacturing tehnology, ISSN:0007-8506, Volume 38, Issue 1, Pages 291-294, 1989. [7] Tabaković, S., Zeljković, M.: NC technique and technology, manual for programming of Amada Vela II punch presses, Faculty of technical sciences, (Authorized lectures in Serbial language), Novi Sad, 2005. [8] Tilley, S.: Integration of CAD/CAM and Production Control for Sheet metal Components Manufacturing, CIRP annals-Manufacturing tehnology, Volume 41, Issue 1, Pages 177-180, 1992. [9] Trumpf, Programing manual TC 2000 R, Edition 07, 1999. [10] Vilotić, D., Plančak, M.: Metal forming machine tools umformmaschinen - CRANK PRESSES (in serbian) , Faculty of technical sciences, Novi Sad, ISBN:978-86-7892-275-6, 2010. [11] Zeljković, M., Borojev, Lj., Tabaković, S., Antić, A., Živković, A.: Programming of NC machine tools (in serbian), Faculty of technical sciences, Novi Sad, ISBN:978-86-7892-3296, 2010.


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SPECIFIČNOST PROGRAMIRANJA PUNCH PRESE Vladimir Blanuša1, Milan Zeljković1, Dragiša Vilotić1, Slobodan Tabaković1 Faculty of Technical Sciences, Trg D. Obradovića 6, Novi Sad, Serbia

REZIME Polazeći od opšteg modela procesa programiranja u radu je prikazan postupak ručnog programiranja punch presa. Prikazan je tok programiranja i definisani upravljački programi za izradu maksimalnog broja istih obradaka raspoređenih po tabli lima na dve punch perse i to Amada Vela II i Trumpf Rotation 2000. Upravljački sistemi navedenih mašina pripadaju različitim generacijama pa rezultate navedene analize treba posmatrati i u tom svetlu. Izvršena analiza upravljačkih programa je obuhvatila dužinu istih, složenosti postupka programiranja, broj korištenih alata, hrapavosti koja se ostvaruje ovim postupkom obrade itd.. Analizirane su tehnološke mogućnosti prethodno navedenih mašina na konkretnom izradku. Prikazane su zavisnosti koraka i radijusa prosecanja za dve vrednosti hrapavosti i to h=0,3 mm (srednje odstupanje slobodnih mera) i h=0,03 mm (IT6- kod tehnologije finog prosecanja) kod spoljašnjeg i unutrašnjeg prosecanja. Razmatrane su prednosti i nedostatci postupka programiranja jedne u odnosu na drugu mašinu. Ključne reči: obrada delova od lima, punch prese, programiranje.
