- Email: [email protected]
Forming of Non-axisymmetric Products
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Available Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Procedia Manufacturing 00 (2018) 000–000 Procedia Manufacturing 00 (2018) 000–000
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www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Manufacturing 27 (2019) 7–12 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
ICAFT/SFU/AutoMetForm ICAFT/SFU/AutoMetForm 2018 2018
Forming Forming of of Non-axisymmetric Non-axisymmetric Products Products
Manufacturing Engineering Society International Conference 2017, MESIC 2017, 28-30 June a b* a, M. Rozmysłowiczb* M. Pieszak 2017, Vigo (Pontevedra), Spain M. Pieszak , M. Rozmysłowicz a a b b
Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland
Costing models for capacity optimization in Industry 4.0: Trade-off between used capacity and operational efficiency Abstract Abstract
A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb
The subject of this paper is to show the developed synchronous spinning machine for asymmetric products and the nonThe subject of this paper is to show athe developed synchronous spinning machine for asymmetric products and the nonUniversity of Minho, 4800-058 axisymmetric trial products manufactured by the developed method.Guimarães, SpinningPortugal is one of the metal forming processes used to axisymmetric trial products manufactured bby the developed method. Spinning is one of the metal forming processes used to Unochapecó, 89809-000 Chapecó, SC, Brazil produce hollow products from metal sheets and it is favorable for small- and medium-low production because the tools required produce hollow products from metal sheets and it is favorable for small- and medium-low production because the tools required are inexpensive. Spinning technology has been traditionally used to produce axisymmetric parts and it has been developed in are inexpensive. Spinning technology has been traditionally used to produce axisymmetric parts and it has been developed in recent years. Asymmetric spinning is a metal spinning method that can produce non-axisymmetric products. Trial spinning recent years. Asymmetric spinning is a metal spinning method that can produce non-axisymmetric products. Trial spinning experiments of asymmetric sheet metal forming were successfully carried out by using the machine that was developed for this Abstract experiments of asymmetric sheet metal forming were successfully carried out by using the machine that was developed for this purpose. The developed machine can synchronize the radial and axial position of the roll with the spindle (mandrel). purpose. The developed machine can synchronize the radial and axial position of the roll with the spindle (mandrel).
Under the concept Published of "Industry 4.0", B.V. production processes will be pushed to be increasingly interconnected, © 2018 The Authors. by Elsevier 2019 The B.V. © 2018 Authors. Published by Elsevier B.V. necessarily, much more efficient. In this context, capacity optimization information based on a real time basis and, This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) (https://creativecommons.org/licenses/by-nc-nd/4.0/) This is an openthe access article under CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) goes beyond traditional aimresponsibility ofthecapacity maximization, contributing also for organization’s profitability and value. under of the scientific committee of ICAFT/SFU/AutoMetForm 2018. Selection and peer-review Selection lean and peer-review underand responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018. Indeed, management continuous improvement approaches suggest capacity optimization instead of Keywords: Metal spinning; Asymmetric shape; optimization Sheet metal; Tool trajectory maximization. The study of capacity and costing models is an important research topic that deserves Keywords: Metal spinning; Asymmetric shape; Sheet metal; Tool trajectory contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical model for capacity management based on different costing models (ABC and TDABC). A generic model has been 1. Introduction developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization’s 1. Introduction value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity Rotary forming technologies constantly intensively developed and applied in manufacturing processes. optimization might hide operationalare Rotary forming technologies areinefficiency. constantly intensively developed and applied in manufacturing processes. Products made withPublished the use of the spinning are widely used as components for manufacturing such items © 2017 The Authors. by Elsevier B.V.technology Products made with the use of the spinning technology are widely used as components for manufacturing such items as lamp shades, rocket engineof parts or ventilation system spinning methodsConference applied in Peer-review under responsibility the scientific committee of the components. ManufacturingCurrently, Engineeringthe Society International as lamp shades, rocket engine parts or ventilation system components. Currently, the spinning methods applied in 2017. industrial practice are limited to the production of axially symmetrical products. A trend noticeable in worldwide industrial practice are limited to the production of axially symmetrical products. A trend noticeable in worldwide research on forming sheet metal products is special spinning, e.g. non-axisymmetric spinning. The issue of nonresearch on forming sheet metalCapacity products is special e.g. non-axisymmetric spinning. The issue of nonKeywords: Cost Models; ABC; TDABC; Management; Idlespinning, Capacity; Efficiency axisymmetric product forming by spinning is still little known, Operational even though research on this topic began in the midaxisymmetric product forming by spinning is still little known, even though research on this topic began in the mid1. Introduction * Corresponding author. Tel.: +48 61 657 0555; fax: +48 61 657 0721 * The Corresponding author. Tel.: +48 657 0555; fax: +48 61 657 0721for companies and their management of extreme importance cost of idle capacity is 61 a fundamental information E-mail address: [email protected] E-mail address: [email protected]
in modern production systems. In general, it is defined as unused capacity or production potential and can be measured 2351-9789 2018 The Authors. Published by Elsevier B.V.hours of manufacturing, etc. The management of the idle capacity in several©ways: tons of production, available 2351-9789 © 2018 The Authors. Published by Elsevier B.V. This is anAfonso. open access under the761; CC fax: BY-NC-ND (https://creativecommons.org/licenses/by-nc-nd/4.0/) * Paulo Tel.:article +351 253 510 +351 253license 604 741 This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection peer-review under responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018. E-mailand address: [email protected] Selection and peer-review under responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018.
2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under of the scientificbycommittee the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2019responsibility The Authors. Published Elsevier of B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018. 10.1016/j.promfg.2018.12.036
8 2
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
1980s. This results from difficulties in synchronizing the working movement of tools in the spinning of nonaxisymmetric products, as well as from the need to have a specialized, custom test bench. Asymmetrical products should be spun without the use of cams or springs on a machine, which has the capability to precisely control the position of the tools. In contrast to traditional spinning process, an additional radial component of movement is required, which results from axial asymmetry of the spinning block and different distances of points on its surface from the axis of rotation. This creates a risk of collision and makes it difficult to describe the forming movements, creating a high risk of tool collisions in the event of mismatches of tool movements. It is necessary that the movements of the spinning roll keep up with the radial changes in the shape of the product being manufactured. There are various designs of spinning machines for non-axisymmetric products. In article [1], the authors carried out research using a machine in which the spinning roll is controlled with the use of springs. A spinning machine with spring-controlled roll movement allowed obtaining non-axisymmetric products with approx. 24% thinning of the material. In paper [2] the authors also present the results of work on asymmetric spinning. The authors built a spinning machine in which the movement of the mandrel and the feed of the roll were synchronized by pulse control. Attempts to obtain an asymmetrical product were made on 1 mm thick aluminum disks. The movement path of the roll was controlled by software taking into account the errors resulting from the gradual pulse control. Asymmetric shaping was successfully carried out using the developed synchronous method. The authors managed to obtain an elliptical cross-section product. In article [3] the authors investigated the spinning of a symmetrical cylindrical and a non-axisymmetric workpiece with a square cross-section. The article describes the theoretical foundations for developing the movement path of the spinning roll. Researchers managed to obtain a nonaxisymmetric product with a square cross-section. Increased material thickness was observed in the corners of the drawpiece. The technology of spinning non-axisymmetric products is complicated not only because of the complexity of the spinning roll movement and the difficulty in describing it, but also because of the number of parameters which affect the process. In article [4], research was undertaken on the spinning of a non-axisymmetric product with a triangular cross-section. The authors investigated the influence of certain process parameters on the drawpiece geometry. This paper presents a machine specially designed and built to conduct asymmetric spinning tests. The creation of a dedicated test bench made it possible to perform preliminary research on the production of prismatic products with an elliptical and square cross-section. Further in the paper the case of preliminary research on forming of square products (with rounded edges in corners) and some observations on the approach to the design method of the path of tool movements is described. 2. Test bench For the purposes of research on the development of the asymmetric spinning technology, a spinning machine was designed and built, which is shown in Fig.1a. This machine has been designed for high transverse accelerations of the spinning roll and enables precise synchronization of tool movements. It consists of the following modules: a headstock, a carriage, a frame, a main drive mounting and three motors. The spindle drive is implemented as a servomotor and a synchronous toothed belt with zero tooth clearance. In turn, the spinning rolls are driven by servomotors with a reduced moment of inertia and ball screws with a pitch of 20 mm. The torques, relatively high considering the size of the machine, achieved by the motors driving the ball screws, provide the spinning roll with a possibility for precisely following the mandrel. The small dimensions of the unit allow for easy tool changes and transport. Asymmetrical spinning requires precise positioning of the mandrel in relation to the forming tools, which creates problems with repeatability of clamping when standard tool fixing methods. In the adopted design solutions, the precise axial alignment of the spinning block is ensured by the interaction of two conical surfaces, and its angular alignment by the actual measurement of the indications of the dial indicator and the recording of the optimal initial position of the tool in the machine control system. The machine is equipped with a professional Mitsubishi control system M70 (Fig.1b). Such a solution ensures repeatability of the angular positioning of the machine spindle and allows obtaining high tool accelerations without losing the precision of movement. Machine movements are described by means of G-codes, which are commonly used in industrial practice.
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000 a)
9 3
b)
Fig. 1. (a) The designed and built special spinning machine; (b) Machine control system
Assuming some simplifications, the control code is generated by: Defining the start and end points of intermediate movements. Determination of the asymmetrical shape at the start and end points and the distance between tools for the different angular positions of the spindle at these points. Calculation and linear interpolation of intermediate points. Calculation of numerical values for G-codes describing intermediate movements. Generation of the final G-code and transfer of data to the control system. The adopted G-code generation solutions can be applied to different product shapes with the restriction that forming movements must follow straight lines. 3. Results of research on spinning asymmetrical products Preliminary tests carried out for square products (with rounded edges in corners) showed that due to non-axisymmetry of the initial material, the product and the forming movements applied, significant wall thickness differences are observed in various zones. The greatest differences in wall thickness occur primarily between the product area closest to the axis of rotation and the area furthest from it. Moreover, there are significant differences in thickness depending on the distance from the bottom of the drawpiece. This shows that in the case of asymmetrical workpiece there is higher variety in stress and strain than in the case of traditional non-axisymmetric product. In the case of products with a square cross-section, the described differences in wall thickness and the distance of points on side walls of the product are significant, which results from the complicated cross-section shape and the adopted path of spinning roll movements. The development of the optimal preform shape as in the case of stamping rectangular products in this case acquires special importance and determines the characteristics of the final product such as wall thickness in individual zones or the correctness of representing the assumed shape. In the case of traditional spinning methods, most often forming movements in the direction of decreasing values of the Z axis and return movements at increasing values of the Z axis are used (Fig. 2a). Due to the difficult description of the spinning movements, the first step was to test the spinning of square asymmetrical products by using the spinning movements only in the first direction (Fig. 2b). The material high
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
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plasticity DC04 was used and the thickness of 1.5 mm. In the first strategy of spinning movements, the movements applied were along straight lines at inclination angles of 75°, 60°, 45°, 22.5° and 0° to the horizontal at the initial angular position of the mandrel (for one-way shaping). As a result of the tests carried out, in the first variant of movements it was not possible to obtain the product with the assumed depth, using different shapes of the initial material and different combinations of spinning movements. It was observed that no material was drawn in at the square cross-section radii, the result of which was excessive thinning and tearing of the material in this area each time. It was planned to obtain a product with a depth of 30 mm and the smallest possible flange at the end of the spinning process. An example of a product with a broken side wall is shown in Fig. 3. a)
b)
Fig. 2. a) The case of forming also in the return movement; b) Successive spinning movements in the first direction
The tests were carried out with the use of a tool with a square cross-section of the working part with dimensions 80 x 80mm, rounded radii of 20 mm (in the cross-section) and 5 mm (in the longitudinal cross-section) and the depth of 60 mm. Another tool was the spinning roll with a diameter of 50 mm and the rounding radius of 5 mm. Due to the failure of obtaining a correct workpiece with the use of the first strategy of spinning movements, a decision was made to modify the path of movements by adding return movement forming with the use of the same shapes of the initial material.
Fig. 3. Product with a broken side walls
Due to the lack of a proper spinning process for one-way spinning segments and problems with wrinkling, another spinning strategy was started using the "curved" movements in both directions. This method of roll movement enables the roll to shape in the reverse movement, increases the inclination of the flange and reduces undesirable drawing of the material. Because of the method used to describe the movement of the forming tools, some simplification of this method of shaping was adopted. The curves were converted into a set of segments and after applying many linear interpolations a simplified description of the movement in the form of G-codes was obtained. The designed path consists of segments where the end of one is the beginning of another and each of them describes the movement of the whole roll in relation to the system of coordinates of the machine. In the control programs used, each code line
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
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corresponds to a spindle rotation of 1°. Due to the experience gained so far, when describing the tool movement, a description of the movement of the theoretical point of contact of the spinning roll with the material, reduced to a common system of coordinates for each intermediate movement. An example of how to change curves into a set of segments is shown in Fig. 4. The method of converting curves into segments is based on experience and is a certain approximation of the original state. Developed and modified method of movements’ description can be also applied to other geometries like elliptical or triangular. Also, in this case, DC04 material with a thickness of 1.5 mm and the same shape was used. As a result of spinning using the second strategy of spinning movements, the drawpiece shown in Fig. 5 was obtained. In order to obtain correct workpiece, different shapes of initial material were applied. Some modifications of trajectory were also being carried out.
Fig.4. Conversion of the curve into segments for the purpose of developing the path of spinning movements
Fig. 5. Obtained asymmetric product
Wall thickness [mm]
The obtained product was tested on the Coordinate Measuring Machine by continuous scanning. The thickness of the material of the workpiece side wall was determined in zones A and B (Fig. 5) at various distances from the front surface. The results are presented in the form of a graph in Fig. 6. 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0
zone A zone B 3
6
9
12
15
18
21
24
27
Distances from the front surface [mm] Fig. 6. Wall thickness distribution
30
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
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It should be noted that the product has the highest wall thinning in zone B. The material in this zone is evenly stretched to about half of the product height. Then the thickness of the material is stable and no further thinning is observed. In zone A, on the other hand, the wall thickness is higher, although at half of the drawpiece height the greatest thinning occurred. These differences may result primarily from different resistance of the material in the roll radius zone for different angular positions of the mandrel, which is a result of different shapes of the initial material, the assumed path of spinning movements and the shape of the product itself. In both cases, the differentiation of material thinning reduces the stiffness of the drawpiece. The workpiece is then more susceptible to the occurrence of elastic deflection of the walls instead of full forming, which, as noted during the tests, in the case of asymmetrical products, may have a significant impact on achieving the final effects. In this case it may be helpful to keep a small stiffening flange of an appropriate shape in the intermediate stages of the forming process. The shape of this flange and of the initial material itself must take account of the different drawing resistances in the various zones, as is the case, for example, with square products. During the preliminary tests of asymmetrical spinning the significant variety of wall thickness with the use of different initial material shapes was being observed. The same observation was occurring even for slight modification of trajectory. With the increase of products’ depth, thickness of the side walls for second strategy of movement was higher than for the first one. Observed effects had a repetitive character. Additional factors that may influence the effects achieved should be further investigated and are beyond the scope of this paper. An important observation is the fact that the quality of obtained products has been significantly improved by the use of spinning movements based on a curve discretized into segments and the use of return movements for forming. This significantly reduces the observed wall thinning and unfavorable wrinkling. The application of shaping in the return movements with the use of developed method of converting curves into segments seems to be favorable as well for other geometries. The development of the technology of spinning non-axisymmetric products, especially of the shape of truncated pyramids (press forming requires several operations then), in the future may be an important alternative to the press forming technology and even expanding or hydroforming. 4. Summary In order to improve the process and eliminate material wrinkling, further improvement of the spinning movement path is planned. Some observations have been made from preliminary tests of asymmetrical spinning: 1. 2. 3.
4.
Due to the varied nature of the deformation in individual zones of the product, the paths of movements should be fine-tuned to take into account geometric variability of the product as a function of the spindle rotation angle. The use of the optimal shape of the blank for the paths of movements being developed should facilitate even material drawing into the radius zone of the spinning roll. The shaping movements on the return side help reduce the angle of inclination of the side wall material of the product. The smaller angle of inclination makes it easier to move the material within the radius zone of the spinning roll. One of the results is less stretching of the workpiece wall. The occurring compression and upsetting of the material in the return movement compensate the thinning of the workpiece side walls, which increases the uniformity of the distribution of the drawpiece wall thickness. When designing the process of forming products, it is preferable to keep a minimal stiffening flange. This supports the spinning process by improving the product rigidity during the intermediate forming stages and enables the material to be upset in the reverse direction, resulting in an additional reduction in wall thinning.
5. References [1] B. Awiszus, F. Meyer, Metal spinning of non-circular hollow parts, Proceedings of the Eighth International Conference on Technology of Plasticity, 2005, s. 353-355 [2] Ichiro Shimizu: Asymmetric forming of aluminum sheets by synchronous spinning, Journal of Materials Processing Technology, 2010, No. 210, p. 585-592. [3] Y. Sugita, H. Arai, Formability in synchronous multipass spinning using simple pass set, Journal of Materials Processing Technology 217, 2015, s. 336-344 [4] Q.X. Xia, Z.Y. Lai, J.X. Qu, X.Q. Cheng, Inuence of processing parameters on forming quality of non-circular spinning, Proceedings of the 11th International Conference on Manufacturing Research (ICMR2013), 2013, s. 275
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Available Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Procedia Manufacturing 00 (2018) 000–000 Procedia Manufacturing 00 (2018) 000–000
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www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Manufacturing 27 (2019) 7–12 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
ICAFT/SFU/AutoMetForm ICAFT/SFU/AutoMetForm 2018 2018
Forming Forming of of Non-axisymmetric Non-axisymmetric Products Products
Manufacturing Engineering Society International Conference 2017, MESIC 2017, 28-30 June a b* a, M. Rozmysłowiczb* M. Pieszak 2017, Vigo (Pontevedra), Spain M. Pieszak , M. Rozmysłowicz a a b b
Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland Metal Forming Institute, Jana Pawła II 14, Poznań 61-139, Poland
Costing models for capacity optimization in Industry 4.0: Trade-off between used capacity and operational efficiency Abstract Abstract
A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb
The subject of this paper is to show the developed synchronous spinning machine for asymmetric products and the nonThe subject of this paper is to show athe developed synchronous spinning machine for asymmetric products and the nonUniversity of Minho, 4800-058 axisymmetric trial products manufactured by the developed method.Guimarães, SpinningPortugal is one of the metal forming processes used to axisymmetric trial products manufactured bby the developed method. Spinning is one of the metal forming processes used to Unochapecó, 89809-000 Chapecó, SC, Brazil produce hollow products from metal sheets and it is favorable for small- and medium-low production because the tools required produce hollow products from metal sheets and it is favorable for small- and medium-low production because the tools required are inexpensive. Spinning technology has been traditionally used to produce axisymmetric parts and it has been developed in are inexpensive. Spinning technology has been traditionally used to produce axisymmetric parts and it has been developed in recent years. Asymmetric spinning is a metal spinning method that can produce non-axisymmetric products. Trial spinning recent years. Asymmetric spinning is a metal spinning method that can produce non-axisymmetric products. Trial spinning experiments of asymmetric sheet metal forming were successfully carried out by using the machine that was developed for this Abstract experiments of asymmetric sheet metal forming were successfully carried out by using the machine that was developed for this purpose. The developed machine can synchronize the radial and axial position of the roll with the spindle (mandrel). purpose. The developed machine can synchronize the radial and axial position of the roll with the spindle (mandrel).
Under the concept Published of "Industry 4.0", B.V. production processes will be pushed to be increasingly interconnected, © 2018 The Authors. by Elsevier 2019 The B.V. © 2018 Authors. Published by Elsevier B.V. necessarily, much more efficient. In this context, capacity optimization information based on a real time basis and, This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) (https://creativecommons.org/licenses/by-nc-nd/4.0/) This is an openthe access article under CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) goes beyond traditional aimresponsibility ofthecapacity maximization, contributing also for organization’s profitability and value. under of the scientific committee of ICAFT/SFU/AutoMetForm 2018. Selection and peer-review Selection lean and peer-review underand responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018. Indeed, management continuous improvement approaches suggest capacity optimization instead of Keywords: Metal spinning; Asymmetric shape; optimization Sheet metal; Tool trajectory maximization. The study of capacity and costing models is an important research topic that deserves Keywords: Metal spinning; Asymmetric shape; Sheet metal; Tool trajectory contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical model for capacity management based on different costing models (ABC and TDABC). A generic model has been 1. Introduction developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization’s 1. Introduction value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity Rotary forming technologies constantly intensively developed and applied in manufacturing processes. optimization might hide operationalare Rotary forming technologies areinefficiency. constantly intensively developed and applied in manufacturing processes. Products made withPublished the use of the spinning are widely used as components for manufacturing such items © 2017 The Authors. by Elsevier B.V.technology Products made with the use of the spinning technology are widely used as components for manufacturing such items as lamp shades, rocket engineof parts or ventilation system spinning methodsConference applied in Peer-review under responsibility the scientific committee of the components. ManufacturingCurrently, Engineeringthe Society International as lamp shades, rocket engine parts or ventilation system components. Currently, the spinning methods applied in 2017. industrial practice are limited to the production of axially symmetrical products. A trend noticeable in worldwide industrial practice are limited to the production of axially symmetrical products. A trend noticeable in worldwide research on forming sheet metal products is special spinning, e.g. non-axisymmetric spinning. The issue of nonresearch on forming sheet metalCapacity products is special e.g. non-axisymmetric spinning. The issue of nonKeywords: Cost Models; ABC; TDABC; Management; Idlespinning, Capacity; Efficiency axisymmetric product forming by spinning is still little known, Operational even though research on this topic began in the midaxisymmetric product forming by spinning is still little known, even though research on this topic began in the mid1. Introduction * Corresponding author. Tel.: +48 61 657 0555; fax: +48 61 657 0721 * The Corresponding author. Tel.: +48 657 0555; fax: +48 61 657 0721for companies and their management of extreme importance cost of idle capacity is 61 a fundamental information E-mail address: [email protected] E-mail address: [email protected]
in modern production systems. In general, it is defined as unused capacity or production potential and can be measured 2351-9789 2018 The Authors. Published by Elsevier B.V.hours of manufacturing, etc. The management of the idle capacity in several©ways: tons of production, available 2351-9789 © 2018 The Authors. Published by Elsevier B.V. This is anAfonso. open access under the761; CC fax: BY-NC-ND (https://creativecommons.org/licenses/by-nc-nd/4.0/) * Paulo Tel.:article +351 253 510 +351 253license 604 741 This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection peer-review under responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018. E-mailand address: [email protected] Selection and peer-review under responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018.
2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under of the scientificbycommittee the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2019responsibility The Authors. Published Elsevier of B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of ICAFT/SFU/AutoMetForm 2018. 10.1016/j.promfg.2018.12.036
8 2
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
1980s. This results from difficulties in synchronizing the working movement of tools in the spinning of nonaxisymmetric products, as well as from the need to have a specialized, custom test bench. Asymmetrical products should be spun without the use of cams or springs on a machine, which has the capability to precisely control the position of the tools. In contrast to traditional spinning process, an additional radial component of movement is required, which results from axial asymmetry of the spinning block and different distances of points on its surface from the axis of rotation. This creates a risk of collision and makes it difficult to describe the forming movements, creating a high risk of tool collisions in the event of mismatches of tool movements. It is necessary that the movements of the spinning roll keep up with the radial changes in the shape of the product being manufactured. There are various designs of spinning machines for non-axisymmetric products. In article [1], the authors carried out research using a machine in which the spinning roll is controlled with the use of springs. A spinning machine with spring-controlled roll movement allowed obtaining non-axisymmetric products with approx. 24% thinning of the material. In paper [2] the authors also present the results of work on asymmetric spinning. The authors built a spinning machine in which the movement of the mandrel and the feed of the roll were synchronized by pulse control. Attempts to obtain an asymmetrical product were made on 1 mm thick aluminum disks. The movement path of the roll was controlled by software taking into account the errors resulting from the gradual pulse control. Asymmetric shaping was successfully carried out using the developed synchronous method. The authors managed to obtain an elliptical cross-section product. In article [3] the authors investigated the spinning of a symmetrical cylindrical and a non-axisymmetric workpiece with a square cross-section. The article describes the theoretical foundations for developing the movement path of the spinning roll. Researchers managed to obtain a nonaxisymmetric product with a square cross-section. Increased material thickness was observed in the corners of the drawpiece. The technology of spinning non-axisymmetric products is complicated not only because of the complexity of the spinning roll movement and the difficulty in describing it, but also because of the number of parameters which affect the process. In article [4], research was undertaken on the spinning of a non-axisymmetric product with a triangular cross-section. The authors investigated the influence of certain process parameters on the drawpiece geometry. This paper presents a machine specially designed and built to conduct asymmetric spinning tests. The creation of a dedicated test bench made it possible to perform preliminary research on the production of prismatic products with an elliptical and square cross-section. Further in the paper the case of preliminary research on forming of square products (with rounded edges in corners) and some observations on the approach to the design method of the path of tool movements is described. 2. Test bench For the purposes of research on the development of the asymmetric spinning technology, a spinning machine was designed and built, which is shown in Fig.1a. This machine has been designed for high transverse accelerations of the spinning roll and enables precise synchronization of tool movements. It consists of the following modules: a headstock, a carriage, a frame, a main drive mounting and three motors. The spindle drive is implemented as a servomotor and a synchronous toothed belt with zero tooth clearance. In turn, the spinning rolls are driven by servomotors with a reduced moment of inertia and ball screws with a pitch of 20 mm. The torques, relatively high considering the size of the machine, achieved by the motors driving the ball screws, provide the spinning roll with a possibility for precisely following the mandrel. The small dimensions of the unit allow for easy tool changes and transport. Asymmetrical spinning requires precise positioning of the mandrel in relation to the forming tools, which creates problems with repeatability of clamping when standard tool fixing methods. In the adopted design solutions, the precise axial alignment of the spinning block is ensured by the interaction of two conical surfaces, and its angular alignment by the actual measurement of the indications of the dial indicator and the recording of the optimal initial position of the tool in the machine control system. The machine is equipped with a professional Mitsubishi control system M70 (Fig.1b). Such a solution ensures repeatability of the angular positioning of the machine spindle and allows obtaining high tool accelerations without losing the precision of movement. Machine movements are described by means of G-codes, which are commonly used in industrial practice.
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000 a)
9 3
b)
Fig. 1. (a) The designed and built special spinning machine; (b) Machine control system
Assuming some simplifications, the control code is generated by: Defining the start and end points of intermediate movements. Determination of the asymmetrical shape at the start and end points and the distance between tools for the different angular positions of the spindle at these points. Calculation and linear interpolation of intermediate points. Calculation of numerical values for G-codes describing intermediate movements. Generation of the final G-code and transfer of data to the control system. The adopted G-code generation solutions can be applied to different product shapes with the restriction that forming movements must follow straight lines. 3. Results of research on spinning asymmetrical products Preliminary tests carried out for square products (with rounded edges in corners) showed that due to non-axisymmetry of the initial material, the product and the forming movements applied, significant wall thickness differences are observed in various zones. The greatest differences in wall thickness occur primarily between the product area closest to the axis of rotation and the area furthest from it. Moreover, there are significant differences in thickness depending on the distance from the bottom of the drawpiece. This shows that in the case of asymmetrical workpiece there is higher variety in stress and strain than in the case of traditional non-axisymmetric product. In the case of products with a square cross-section, the described differences in wall thickness and the distance of points on side walls of the product are significant, which results from the complicated cross-section shape and the adopted path of spinning roll movements. The development of the optimal preform shape as in the case of stamping rectangular products in this case acquires special importance and determines the characteristics of the final product such as wall thickness in individual zones or the correctness of representing the assumed shape. In the case of traditional spinning methods, most often forming movements in the direction of decreasing values of the Z axis and return movements at increasing values of the Z axis are used (Fig. 2a). Due to the difficult description of the spinning movements, the first step was to test the spinning of square asymmetrical products by using the spinning movements only in the first direction (Fig. 2b). The material high
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
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plasticity DC04 was used and the thickness of 1.5 mm. In the first strategy of spinning movements, the movements applied were along straight lines at inclination angles of 75°, 60°, 45°, 22.5° and 0° to the horizontal at the initial angular position of the mandrel (for one-way shaping). As a result of the tests carried out, in the first variant of movements it was not possible to obtain the product with the assumed depth, using different shapes of the initial material and different combinations of spinning movements. It was observed that no material was drawn in at the square cross-section radii, the result of which was excessive thinning and tearing of the material in this area each time. It was planned to obtain a product with a depth of 30 mm and the smallest possible flange at the end of the spinning process. An example of a product with a broken side wall is shown in Fig. 3. a)
b)
Fig. 2. a) The case of forming also in the return movement; b) Successive spinning movements in the first direction
The tests were carried out with the use of a tool with a square cross-section of the working part with dimensions 80 x 80mm, rounded radii of 20 mm (in the cross-section) and 5 mm (in the longitudinal cross-section) and the depth of 60 mm. Another tool was the spinning roll with a diameter of 50 mm and the rounding radius of 5 mm. Due to the failure of obtaining a correct workpiece with the use of the first strategy of spinning movements, a decision was made to modify the path of movements by adding return movement forming with the use of the same shapes of the initial material.
Fig. 3. Product with a broken side walls
Due to the lack of a proper spinning process for one-way spinning segments and problems with wrinkling, another spinning strategy was started using the "curved" movements in both directions. This method of roll movement enables the roll to shape in the reverse movement, increases the inclination of the flange and reduces undesirable drawing of the material. Because of the method used to describe the movement of the forming tools, some simplification of this method of shaping was adopted. The curves were converted into a set of segments and after applying many linear interpolations a simplified description of the movement in the form of G-codes was obtained. The designed path consists of segments where the end of one is the beginning of another and each of them describes the movement of the whole roll in relation to the system of coordinates of the machine. In the control programs used, each code line
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
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corresponds to a spindle rotation of 1°. Due to the experience gained so far, when describing the tool movement, a description of the movement of the theoretical point of contact of the spinning roll with the material, reduced to a common system of coordinates for each intermediate movement. An example of how to change curves into a set of segments is shown in Fig. 4. The method of converting curves into segments is based on experience and is a certain approximation of the original state. Developed and modified method of movements’ description can be also applied to other geometries like elliptical or triangular. Also, in this case, DC04 material with a thickness of 1.5 mm and the same shape was used. As a result of spinning using the second strategy of spinning movements, the drawpiece shown in Fig. 5 was obtained. In order to obtain correct workpiece, different shapes of initial material were applied. Some modifications of trajectory were also being carried out.
Fig.4. Conversion of the curve into segments for the purpose of developing the path of spinning movements
Fig. 5. Obtained asymmetric product
Wall thickness [mm]
The obtained product was tested on the Coordinate Measuring Machine by continuous scanning. The thickness of the material of the workpiece side wall was determined in zones A and B (Fig. 5) at various distances from the front surface. The results are presented in the form of a graph in Fig. 6. 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0
zone A zone B 3
6
9
12
15
18
21
24
27
Distances from the front surface [mm] Fig. 6. Wall thickness distribution
30
M. Pieszak et al. / Procedia Manufacturing 27 (2019) 7–12 Author name / Procedia Manufacturing 00 (2018) 000–000
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It should be noted that the product has the highest wall thinning in zone B. The material in this zone is evenly stretched to about half of the product height. Then the thickness of the material is stable and no further thinning is observed. In zone A, on the other hand, the wall thickness is higher, although at half of the drawpiece height the greatest thinning occurred. These differences may result primarily from different resistance of the material in the roll radius zone for different angular positions of the mandrel, which is a result of different shapes of the initial material, the assumed path of spinning movements and the shape of the product itself. In both cases, the differentiation of material thinning reduces the stiffness of the drawpiece. The workpiece is then more susceptible to the occurrence of elastic deflection of the walls instead of full forming, which, as noted during the tests, in the case of asymmetrical products, may have a significant impact on achieving the final effects. In this case it may be helpful to keep a small stiffening flange of an appropriate shape in the intermediate stages of the forming process. The shape of this flange and of the initial material itself must take account of the different drawing resistances in the various zones, as is the case, for example, with square products. During the preliminary tests of asymmetrical spinning the significant variety of wall thickness with the use of different initial material shapes was being observed. The same observation was occurring even for slight modification of trajectory. With the increase of products’ depth, thickness of the side walls for second strategy of movement was higher than for the first one. Observed effects had a repetitive character. Additional factors that may influence the effects achieved should be further investigated and are beyond the scope of this paper. An important observation is the fact that the quality of obtained products has been significantly improved by the use of spinning movements based on a curve discretized into segments and the use of return movements for forming. This significantly reduces the observed wall thinning and unfavorable wrinkling. The application of shaping in the return movements with the use of developed method of converting curves into segments seems to be favorable as well for other geometries. The development of the technology of spinning non-axisymmetric products, especially of the shape of truncated pyramids (press forming requires several operations then), in the future may be an important alternative to the press forming technology and even expanding or hydroforming. 4. Summary In order to improve the process and eliminate material wrinkling, further improvement of the spinning movement path is planned. Some observations have been made from preliminary tests of asymmetrical spinning: 1. 2. 3.
4.
Due to the varied nature of the deformation in individual zones of the product, the paths of movements should be fine-tuned to take into account geometric variability of the product as a function of the spindle rotation angle. The use of the optimal shape of the blank for the paths of movements being developed should facilitate even material drawing into the radius zone of the spinning roll. The shaping movements on the return side help reduce the angle of inclination of the side wall material of the product. The smaller angle of inclination makes it easier to move the material within the radius zone of the spinning roll. One of the results is less stretching of the workpiece wall. The occurring compression and upsetting of the material in the return movement compensate the thinning of the workpiece side walls, which increases the uniformity of the distribution of the drawpiece wall thickness. When designing the process of forming products, it is preferable to keep a minimal stiffening flange. This supports the spinning process by improving the product rigidity during the intermediate forming stages and enables the material to be upset in the reverse direction, resulting in an additional reduction in wall thinning.
5. References [1] B. Awiszus, F. Meyer, Metal spinning of non-circular hollow parts, Proceedings of the Eighth International Conference on Technology of Plasticity, 2005, s. 353-355 [2] Ichiro Shimizu: Asymmetric forming of aluminum sheets by synchronous spinning, Journal of Materials Processing Technology, 2010, No. 210, p. 585-592. [3] Y. Sugita, H. Arai, Formability in synchronous multipass spinning using simple pass set, Journal of Materials Processing Technology 217, 2015, s. 336-344 [4] Q.X. Xia, Z.Y. Lai, J.X. Qu, X.Q. Cheng, Inuence of processing parameters on forming quality of non-circular spinning, Proceedings of the 11th International Conference on Manufacturing Research (ICMR2013), 2013, s. 275