Development of a Bar Changer for a Punching Machine

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Development of a Bar Changer for a Punching Machine

Zamen Shafai

Mechanical Engineering, master's level 2020

Luleå University of Technology

Department of Engineering Sciences and Mathematics

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Abstract

This master thesis was performed at the Mechanical department at Outotec AB, Skellefte˚a. Outotec AB is a technology company as well as a project company, selling complex mining technology and plant projects. Outotec’s technologies are used for applications such as producing base metals, processing iron ore etc. Outotec is running a program called ‘Fully automated smelter’ where manual hazardous work must be avoided. A machine which automatically replaces punching bars on the punching machine is needed.

This thesis project aimed to investigate if the punching bar changer will be a proprietary purpose-build machine or an industrial robot. The five-step concept generation method was used for concept development during this thesis project.

For gathering knowledge and information about the project area, experts have been interviewed to obtain information for the start of the project. The gathered information and knowledge from interviews and literature studies have been used as a base when the concepts were generated. Seven concepts were generated and evaluated using a screening matrix. The concept that best satisfied the set requirements were further developed, designed and simulated. The two scenarios have been in- vestigated and a design concept of the proprietary purpose-built machine has been presented. The result from concept evaluation and simulation indicated that both alternatives are applicable in this area. But to make a decision a more in-depth calculation of the associated cost and investigation of the design is necessary.

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Acknowledgements

This master thesis is the final part of the Master of Science program in Mechani- cal Engineering at the Lule˚a University of Technology, Department of Engineering Sciences and Mathematics. This thesis is also a part of the course E7011T, De- gree project in Mechanical Engineering, specialisation Machine Design, Master of Science in Engineering. This thesis project has been performed at Outotec AB located in Skellefte˚a.

I like to express my gratitude towards Outotec AB for the opportunity to perform this thesis. I would also like to thank all of who have helped me make this master thesis. Thanks to all engineers at Outotec AB both in Skellefte˚a and Kil for their contribution to this thesis project. It has been educational and, I have been developed a lot by collaborating with those engineers at Outotec AB

A special thanks to my supervisors at Outotec AB, Niklas J¨arnel¨ov and Jens Hard- ell at LTU for the wise advice and guidance during the project.

Zamen Shafai

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1 Introduction

1.1 Background

A punching machine is used to clean the air injection orifices (named tuyeres) in Pierce-Smith converters for secondary copper converting. It is accomplished by driving steel rods (punching bars) though the tuyere and thereby knocking off the accretions that tend to form at the tuyere to smelt interface. The punching bars are changed manually, when they are damaged, worn or when another type of bar needs to be used. The manual bar changing is potentially hazardous and, as it is usually done by the same operator that is operating the punching machine from the control room, creates an unwanted down-time in cleaning the air injection orifices during the manual handling.

1.2 Converting of Copper

Copper has been used for thousands of years- originally in jewellery and small ob- jects, nowadays it is used in many different areas. Copper is of great importance to today’s society especially in electricity and electrical applications because of its excellent conductivity. About 60 percent of the produced copper is used to conduct electricity and heat [1].

The converting of copper matte that is the second half of the smelting/converting sequence by which most Cu-Fe sulfur concentrates are made into metallic copper.

The process oxidises the iron (Fe) and sulfur(S) from the molten furnace matte with air or oxygen-enriched air to produce molten copper. It is most often done by using a cylindrical Peirce–Smith converter (PS-converter), which blows the blast into molten matte through submerged tuyeresv[2]. The PS-converter is shown in Figure 1.

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1.3 Peirce-Smitt Converter

The Peirce-Smith converter furnace was developed by William H. Peirce and Elias A.C. Smith in the early 1900s as a development of the Manh´es-David process, [4].

For many decades the PS-converter has been the most important process for copper converting. More than 80 percent of the produced copper worldwide comes from this type of converter [5]. PS-converter is a horizontal cylinder lined with basic bricks that can be rotated about its long axis. A modern industrial PS-converter is typically about 4500 mm diameter by 12000 mm long. It consists of a 50 mm steel shell lined with approximately 500 mm of magnesite (chrome refractory brick) [2].

Blast air is blown through a horizontal row of tuyeres, as it is shown in Figure 2.

The tuyere blockage and severe refractory erosion are the most challenging problems. In practice, to maintain the flow of air or gas, the punching of tuyeres with a special punching machine is necessary to remove accretions that block the gas flow [6].

Figure 2: Schematic view of Peirce-Smith converter tuyere with details [2].

1.4 Punching machine

A punching machine is an important component in modern copper smelters. The primary job of the punching machine is to clean the holes in a Pierce-Smith converter and ensure that the air can freely flow into the converter and oxidises with sulfur and other substances. Previously, the cleaning process was done manually but now it can be done automatically by using, for example, one of Outotec’s punching machines. However, the bar used to clean the holes wears out and dam-

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today.

The punching machine has been developed since the first mechanical punching machine was produced in the late 1940s. The punching bars were integrated into the tuyeres and that was a problem because the flow of air was effected negatively.

A new type of punching machine was needed to solve the problem.

At the end of the 1960s, a new type of the punching machine was invented by among others of Albert Pelletier. The punching bars were driven by a hydraulic actuator which was separated from the tuyeres and, this resulted in less compressed air losses [7]. By reducing the losses in terms of compressed air, the copper production efficiency increased.

Figure 3: Outotec’s punching machine.

Nowadays, the punching machine can be remotely controlled, and, the punching bars can be driven either by hydraulic or pneumatic actuators to achieve the re-

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1.5 Aim and Objectives

This thesis project aims to automatize the punching bar changing procedure and thereby the appropriate aspects to study are:

• To investigate if the punching bar changer will be an industrial robot or a proprietary purpose-built machine.

• Designing of the punching bar changer.

• To design a bar attachment that can be handled by the punching bar changer.

• To design a bar store for different type of bars.

• A 3D CAD model of the punching bar changer.

1.6 Scope and Limitations

This thesis will be carried out over a period of 20 weeks, which is the major limitation of this project. Because of the limited time, the primary focus of this thesis project is to investigate if the punching bar changer will be an industrial robot or a proprietary purpose-built machine.

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2 Theory

2.1 Concept Generation

A product concept is an approximate description of the technology, working prin- ciples and form of the product. The illustration of a concept can be either a sketch or a rough 3D-model and it is usually accompanied by a short textual description [8].

Five-Step Concept Generation Method

Concept generation is an integral and relatively inexpensive part of the concept development phase. It can be done, relatively quickly compared to other parts of the development process but it can be costly if the faults are discovered late in the process. The team will be more successful if there is a structured approach for concept generation [8].

The five-step method is an organized and structured approach to generate concepts.

By using this method the likelihood of costly problems will be reduced [8]. The method is illustrated in Figure 4 and it includes the following steps:

1. Clarify the Problem.

2. Search externally.

3. Search internally.

4. Explore systematically.

5. Reflect on the solutions and the process.

Clarify the Problem

The clarification of the problem is done by having a general understanding of the first step. Some design challenges are too complicated and therefore a decomposition of the problem is necessary. The problem decomposition happens when the problem is broken down into smaller subproblems [8]. Once the problem com- position is done by using functional decomposition, it is easier to understand and manage the problem in a better manner. Also, the team can easily focus on critical subproblems.

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Figure 4: Illustration of the five-step concept generation method.

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Search Externally

The intention of external search is to find the existing solutions to the overall problem but also to the subproblems identified during the problem clarification step.

External search for solutions is basically an information-gathering process and an ongoing procedure that appears continuously throughout the whole development process [8]. This step is usually done by gathering related knowledge about the present solutions, both by studying the competitive products in the market and technologies related to the subproblems.

There are many ways to gather information from external sources and some of them are as follows: interviews with lead users and consults experts, literature and patent searches and benchmarking with related products.

Search Internally

In this step, the internal search is done by using the personal and existing team knowledge to generate creatively new solution concepts. This process is doable both individually and by a group of people working together. There are five valuable leading lines for improving individual as well as group internal search or brainstorming:

1. Suspend judgement 2. Generate a lot of ideas.

3. Welcome ideas that may seem infeasible.

4. Make plenty of sketches.

5. Build sketch models.

In order to generate more and better concepts it is preferred that people should generate concepts individually. The brainstorming can be done by a group of people but the concepts are generated by individuals will have greater quality and quantity in compression to the group [8]. Both individual and group sessions are useful but the group sessions are crucial when it comes to building consensus, communicating information and refining concepts. The classification tree is aimed to divide the entire space of possible solutions into several specific classes that will facilitate comparison and pruning.

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Explore Systematically

By doing the external and internal search activities, the team will have collected many concept fragments-solutions to the subproblems. The purpose of the sys- tematic exploration is to navigate if it is possible to organize and synthesize these solution fragments. It can be done by using a classification tree or concept combination table [8].

Reflect on the solutions and the process

In this step, the team members are able to reflect and discuss whether they had concentrated too much on one or another area. The team has also, the possibility to identify opportunities for improvement in subsequent iterations or future projects.

2.2 Literature Study

Theory studies were necessary at the beginning of the project to be able to understand the copper converting process. To understand how the copper converter and punch machine works was essential to be able to move forward in problem-solving.

Literature studies led to an increased understanding of the process and thus a better understanding of the problem. The gathered information and knowledge in literature studies together with knowledge obtained from interviews were used as a basis when generating concepts.

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3 Methodology

This chapter describes the methods used during the project.

3.1 Approach

In order to create a structured approach, a plan was created in the beginning of the project. The concept development phases follow the five-step concept generation method, used by Ulrich & Eppinger in Product design and development [8].

3.2 Planning

In order to have a general overview and a common foundation of the project, meetings with the supervisor and experts were set up at the very beginning. A project plan was made as guidance for the project.Limitations for the project were defined together with the supervisor and others who were involved in the project in order to guarantee that the limitations are reasonable. From the project description, the aim and objectives of the project were clarified and verified with the experts and supervisor. In order to fulfil the aim of the project, an approach was formulated as a guideline. The approach covered several questions to turn to during the ongoing project. The plan was updated continuously to ensure that the aim is fulfilled within the time frame of the project.

3.3 Identification of Customer Needs

In order to get a clear picture of the project goal and reasonable limitations, experts and supervisor were invited to meetings. What was unclear from the project description was discussed so the needs that the system would have to meet were clarified. These were summarised into eight subjective needs. The needs were then organized and weighted relative to each other with help of pairwise prioritization matrix. This method forms a large matrix where the rows and columns are num- bered from 1 - 8 which represent the needs that have been identified. In the matrix, column x meets row y so needs x and y are weighed against each other and are awarded 0, 1 or 2 points depending on how important they are relative to each other. The sum between the two needs should always be 2. When all needs were weighted relative to each other, their final scores which represented the weight of the need were summarized. The reason why this method was used, was to get an overview of the importance of the different needs relative to each other.

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3.4 Specification of Requirements

By translating the developed needs into quantifiable metrics, a more objective, description of the developed needs is obtained. Ideal and permitted values were linked to this metric which the solution either should or was desired to fulfil. The metrics were developed together with the supervisor and other experts in the field, based on the discussion regarding suitable values and metrics that the solution must meet.

3.5 Concept Development

To have a structured approach for concept development, the five-step concept generation was used [8]. Clarify the problem was the first step and a good understanding of the problem was necessary for the next step, problem decomposition and focusing on crucial sub-problems. The second step was to search for externally by interviewing experts and other people who were working in the problem area and studying literature. The third step was to search internally, where the concepts were generated individually. The fourth step was to explore systematically the concepts. The fifth and the last step was to reflect on the solution and the process.

3.5.1 Clarify the problem

To fully comprehend the problem, the design study regarding copper converter and especially the punching machine was done. This involved studying literatures, different documentations, interviewing experts and visiting the Copper Smelter, R¨onnsk¨ar in Skelleftehamn. Information and knowledge regarding problem area was gathered at this stage.

3.5.2 Search externally

After the problem was clarified, it was time for the external search. The design study was done in order to search externally for solutions related to the problem and subproblems. For identifying the existing solutions to this problem, experts at SEW-Eurodrive and Outotec both in Skellefte˚a and Kil were interviewed several times. Since it does not exist solutions of this type, looking at other machines that were quite similar to this problem helped get inspiration, especially lifting cranes, loaders, carousels and sawmill machines.

3.5.3 Search internally

Criteria regarding the design of punching bar changer, bar machine and subproblems was created in different categories during the design study. For generating concepts, these subproblems were used as a baseline. The concepts were generated separately within each area by using brainstorming.

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3.5.4 Explore systematically

In this part, the generated concepts were structured and organized to study the potential of further development by combining two or more concepts or develop each concept separately or remove the concept if the potential was low for further development.

3.6 Concept Generation

To start the concept generation, some knowledge was required in the field. A literature study was conducted to see which solutions are used in the problem area.

Experts were also interviewed to gain increased knowledge and understanding of the problem. The obtained information and knowledge from the literature studies and interviews were used as a baseline for concept generations of the proprietary purpose-built machine. In general, the project was unique because previous work did not exist on it. Because of this, studying other similar solutions or machines like loaders and industrial robots was necessary and it was done to get inspiration before concept generation was started.

The concepts were generated individually by using the brainstorming method. The concepts were sketched and visualised by using pen and paper. Then another session of brainstorming was implemented and the different solutions were compiled into a morphological matrix to obtain a better overview of what different opportunities there were to combine concepts.

3.7 Concept Evaluation and Selection

In order to make a rough screening of the concepts, an elimination matrix was made with criteria that were considered central to the project. To select the most promising concepts and to reduce the number of concepts, a concept screening was performed. Finally, the concepts could be weighted by using scoring to indicate which concept(s) that were suitable to proceed with.

3.8 Final Design

The selected concept which was described in words and sketched in two dimensions (2D) was converted to 3D-models and further developed using the 3D CAD software SolidWorks.

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3.9 FEM Simulation

A FEM analysis was then performed on the main parts of the design to verify that all components were able to withstand the applied loads. For FEM analysing, simulation in SolidWorks was used. The element type used for simulation was 3D elements with the element size of the 20 mm. The shafts were fixed in each of the simulation parts. The type of fixture used for simulation were both fixed geometry to fix the keyways and bearing fixture to fix the bearing locations. The load was applied to the location of the punching bar to simulate the upper jaw and the outer arm. To simulate the inner arm, the load was applied on the bearing surfaces, there the shaft will be located. The material used for simulation is S355JR.

3.10 Industrial Robot

To gather information and knowledge about industrial robots, experts and engineers have been interviewed, at Outotec Kil AB. The interviews have been held digitally either via telephone or via Microsoft Teams. In addition to interviews, industrial robots have been studied on the internet, specifically on Kuka’s website.

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4 Results

This section presents the results from the work with the methods in the previous chapter.

4.1 Customer Needs Identification

The requirements that were identified and developed together with experts at Out- otec for the project are presented in Table 1. The needs were then organized and weighted relative to each other by pairwise prioritization according to appendix ??.

This method helped to get an overview of the importance of the different needs relative to each other. When the needs were weighted against each other, their final scores were summarized, which shows the importance of each requirement. It turned out that the availability, durability, simplicity and lifting capacity were the most critical needs, see Table 4.

Table 1: The identified customer needs

The product must be as simple as possible and therefore it is important that it meets these requirements. For the product to have better availability, it needs to have a relatively long lifespan and long service interval, the longer the service interval the better. It needs to be simple to maintain the product. The physical size of the product should be reasonable as the installation space can vary and in some places, it may be limited. It should be uncomplicated to install and the implementation cost should not be expensive. The product must be reliable and

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4.2 Specification of Requirements

The requirements specification was created based on the needs given in Table 1 is reported in Table 2, where the metrics are linked to the need number. The metric values were determined based on the conditions of the environment, the weight of the needs and the discussions with involved engineers and supervisor at Outotec.

Almost all metrics are demands, which means that they must be met, but there are also some metrics that are desired to be met, for instance, metric number ten the machine weight.

Table 2: List of product specifications. The relative importance of each metric and the units for the metric are also shown.

The life expectancy of the product is 15 years, or more, depending on the operating conditions and care of service. The product is expected to have high availability and the marginal value of the availability is 90 percent. But the ideal value is more than 95 percent. The elevation at the site will vary depending on which country it will be used and therefore the expected range for the work elevation is from -100 to 3500 meters. The product must have a minimum lifting capacity of 20 kg. The expected operating temperature interval is from 10 to 40 ^◦C.

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4.3 Concept Presentation

In this section, the results from concept generation are presented. The concepts were developed based on the requirements specification.

4.3.1 Concept Generation

The brainstorming session resulted in 7 different concepts which are shown in Ta- ble 3. To sift quickly through the unreasonable concepts, they were evaluated and compared to each other. Thereby the concepts were reduced to five concepts, the Chain-band and Lifting with linear motion were eliminated. The Chain-band was a complex concept with more joints compared to other concepts and the implementation of the concept would not be simple. Lifting with linear motion was quite similar to the Hanging Lift concept but more complex and consequently, it was eliminated.

Table 3: The generated concepts from brainstorming.

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4.3.2 Lifting Roller

The Lifting Roller concept works by lifting the punching bar from the punching machine to a certain height. Then the chain-band starts to move and picks up the punching bar and transports it to the punching bar storage, see Figure 5. The punching bar storage moves vertically to position the punching bars to the correct position. This concept is inspired by conveyors. There are both advantages and disadvantages to this concept. One advantage is that the chain-band is durable, and, as a consequence, the service interval period will be longer. An example of the disadvantage is that the concept consists of several parts that make it complicated.

Another challenge with this concept is that there will be some changes to the punching machine that is not desirable. For instance, some jacks must be mounted on the punching machine to be able to lift up the punching bar to a certain hight.

Figure 5: Illustration of lifting roller concept.

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4.3.3 Mini-Robot

The Mini-Robot consists of three arms. Each arm is actuated by using an electrical linear actuator, as shown in Figure 6. The movement is in the x- and y plane except for the outermost joint - the gripper joint. There are some difficulties with this concept. One is the number of joints, the fewer joints, the better from an application point of view because more joints make it more complex. Another challenge with this concept is to get the right angle of rotation. There are also benefits to this concept. To mention some, it is simpler and cheaper to manufacture in comparison to lifting roller and that because, firstly, it is driven by linear actuators, and, secondly, it has a simple design. The linear actuator is not expensive to buy.

This concept is inspired by loader and cranes.

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4.3.4 Rotational Robot

The rotational robot is similar to the Mini-Robot but with some differences. One thing that differentiates them is that the rotational robot rotates at the bottom around the y-axis, see Figure 7. This concept is also inspired by loader and cranes.

The advantages of this concept are that it is simple, compact compared to lifting roller. Since there are several joints and actuators, it will have reduced durability compared to simple bar changer. As a consequence, the service interval will be shorter. The durability and service interval will have a direct effect on availability.

Figure 7: Illustration of rotational robot concept.

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4.3.5 Hanging Lift

The Hanging Lift concept is shown in Figure 8. It is supposed to hang over the punching machine and, it moves linearly to pick up the punching bar from different positions. This concept is inspired by overhead cranes. The benefits of the hanging lift are that it is not taking mush space on the floor and, the bar storage will be simple. From the application point of view, it is challenging to make it work. One of the main problems with this concept is stability. It will be challenging to make it stiff enough since it will be hanging on construction over the punching machine.

Figure 8: Illustration of hanging lift concept.

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4.3.6 Simple Bar Changer

The Simple Bar Changer consists of two arms and three joints, see Figure 9. To be able to move the arms, servomotors will be used. The concept idea came from industrial robots. It is simple compared to the previously presented concepts. Some advantages of this concept are that it has fewer joints in comparison to mini-robot and taking less space because of its size. It is more likely that availability and durability increase because of its simplicity. Due to the use of servomotors, the desired angle of rotation can be achieved even though there are only two arms.

The angle of rotation is the angle that the punching bar changer will rotate to be able to pick up the punching bar from the punching machine and leave it in the bar storage and vice versa. In case of a power failure, the simple changer will not fall on the floor because the servomotors have a self-locking feature.

Figure 9: Illustration of simple bar changer concept.

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4.4 Concept Generation of Bar Storage

Regardless of which punching bar changer concept that will be chosen bar storage is required. The type of bar storage concept that will be chosen depends on which punching bar changer concept that will be the final concept.

The concept generation of bar storage resulted in four different concepts and they are presented in this section.

4.4.1 Rack and Carousel

The rack is stationary and it has five shelves for the input punching bars and two for the output, according to Figure 10a. The shelf number of the final design can vary depending on the needs. The idea with this type of concept was that it could move vertically, up and down. By moving vertically, it is possible to position the different shelves at the correct height. The movement in the vertical direction is enabled by using linear actuators. The input shelves will be filled up with new bars when they are empty by an operator. The old and used bars will be removed from the output shelves. The benefit of this concept is that the operator can safely fill and clear the shelves, from the rear. From the ergonomically perspective, it is also beneficial for the operator to have an adjustable working height.

The Carousel is another concept with a few shelves which presented in Figure 10b.

In contrast to the previous concept- the rack, carousel will have a rotary motion about the z-axis to position the shelves. The rotation is enabled by using a servo- motor. The operator can safely fill and clear the shelves from the rear. There are also ergonomic advantages with this concept and that the operator can adjust the working height. Since the working height is adjustable, operators with different lengths can work without any issue.

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(a) View of Rack (b) View Carousel

Figure 10: Basic sketch of bar machine concepts, rack and carousel.

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4.4.2 Revolver and Flat Concept

The Revolver concept will rotate about the z-axis and, thereby, the punching bar can be positioned in the correct place, see Figure 11a. This concept can not be useful in combination with other punching bar changer concepts except for the mini-robot. To be able to use this concept, it is necessary to have a rotational motion at the top of the bar changer and, this property only can be found in the mini-robot.

The flat concept is stationary with a flew punching bar holders, as shown in Fig- ure 11b. This concept is suitable to combine with all concepts except for the lifting roller. In particular, the flat concept intended to be used in combination with the hanging lift due to its linear motion. To mention one of the beneficial properties of the flat concept is its simplicity. But on the other hand, it is necessary to fill it up frequently to have enough bars in place and, that is not an ideal property, especially in terms of time.

(a) Revolver concept (b) Flat concept

Figure 11: Principal sketch of Revolver and Flat concepts.

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4.5 Concept Evaluation and Selection

As previously mentioned in the method section, a pairwise prioritization matrix was created and was used to weigh the needs against each other, see Table 4.

This method was used to get an overview of the importance of the different needs relative to each other. The result turned out that the availability, durability, simplicity and lifting capacity were the most critical needs. According to the pairwise prioritization matrix, the product should be simple with good availability, durability and lifting capacity. It means that the product must be robust and not have many moving parts. It should also be simple to service and replace the parts on the product.

Table 4: Pairwise prioritization matrix.

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These concepts were evaluated, in a screening according to Table 5. The criteria in Table 4 are the most important need specifications that are described in Table 1 but reformulated. Because there were not many concepts, no iterations needed either in the screening step or the scoring step. During the evaluation and selection process, the availability and durability have been in focus because they are important.

Table 5: Screening of concepts.

The screening part resulted in that two concepts were eliminated and three concepts went further to the next step which is scoring. The result from the scoring was that the simple changer concept becoming the final concept, see Table 6. The weight numbers in the second column come from the needs rating, see appendix ??. The numbers are obtained by dividing the sum the rows by the sum of the last column (the sum of the Total column) and then rounded up or down to whole numbers.

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Table 6: Scoring

When the punching bar changer concept was selected, it was time to choose one of the bar storage concepts. The natural choice of bar storage was the rack concept because it is the most suitable concept. The reason for this choice is that firstly, this concept has a large storage capacity which is necessary and secondly, it is simple and stationary. It means that no extra movement is needed. When the rack concept was selected, it was intended that it would be combined with the simple bar changer.

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4.6 Detailed Design and FEM Simulation

This section presents the further development made from the concept selections, development of simple bar changer and the rack.

4.6.1 The Gripper

The gripper consist of two main parts, the upper jaw and the lower jaw see Fig- ure 12a and Figure 12b. There is also a shaft and an attachment that is used to connect a linear actuator to drive the upper jaw, as shown in Figure 12c. Only the upper jaw moves when it is in operation.

(a) Lower jaw (b) Upper jaw

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4.6.2 Outer Arm

The outer arm consists of an arm, mounted together with a shaft and a plate, according to Figure 13a. The plate will be mounted, to the lower jaw of the gripper by using screws and nuts. To drive the gripper a linear actuator will be mounted, on the arm and the upper jaw of the gripper, see Figure 13b.

(a) View of outer arm. (b) Assembly of gripper and outer arm.

Figure 13: View of the outer arm and assembly of gripper and outer arm.

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4.6.3 Inner Arm

The inner arm consists of two identical rectangular steel profiles connected by a transverse profile which is of the same type. The arm will be driven by the shaft mounted on it, see Figure 14a. The inner arm will be mounted, on the flange by using 4-Bolt Flange Bearings. The flange is mounted on the base attachment as shown in Figure 14b.

(a) View of inner arm. (b) Flange and base attachment.

Figure 14: View of the inner arm and base attachment.

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4.6.4 Assembly of Simple Bar Changer

Figure 15 is showing when all parts are assembled together. To drive the inner- and outer joint, geared servomotors and chain will be used. An illustration of simple bar changer is shown in appendix A, when it is on the place and picking up a punching bar from the punching machine.

Figure 15: Illustration of mounted simple changer.

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4.6.5 Final Design of Rack

The final design of the rack has five input- and three output shelves as it is shown in Figure 16. An illustration of the rack is shown in appendix B, when it is put in place and the simple bar changer picking up a punching bar from the rack. When the front punching bar is picked, the other punching bars will roll down and will be positioned for the next picking. This process will continue as long as there are punching bars on the shelves. The empty shelves will be filled up by operator from the rear. The used punching bars, which picks up from the punching machine, will be placed on the bottom three shelves.

Figure 16: View of final design of rack.

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4.6.6 FEM Simulation Upper jaw

The FEM analysis results of the upper jaw are presented in Figure 17a and Fig- ure 17b. The force applied on the upper jaw was 500N which is the maximum load that the upper jaw can be loaded with. As the result shows, the maximum displacement is 0,05 mm and the maximum stress is 16 MPa. The displacement is very small and the stress is significantly lower compared to the yield stress of the material. The material used in simulation models is S355JR with the yield strength of 355 MPa.

(a) Deformation of upper jaw. (b) Stress.

Figure 17: FEM results of the upper jaw.

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Outer arm

A load with the magnitude of 500N was applied on the lower jaw where the bar will be placed which is mounted on the outer arm and the FEM results are shown in Figure 18a and Figure 18b. The load applied on the outer arm is the maximum load that it can be loaded with. The displacement is under 2 mm which is very low for this application. The maximum stress is 134 MPa and that is below the yield stress of the material. The material used in simulation models is S355JR with the yield strength of 355 MPa.

(a) Deformation of outer arm. (b) Stress.

Figure 18: FEM result of the outer arm.

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Inner arm

Simulation results of the inner arm show that the deformation is around 2 mm and the stress is 137 MPa, according to Figure 19a and Figure 19b. Both the displacements and stresses are low. The material used in simulation models is S355JR with the yield strength of 355 MPa.

(a) Deformation of inner arm. (b) Stress.

Figure 19: FEM result of the inner arm.

4.7 Industrial Robot

An industrial robot is a robot system used for manufacturing. Industrial robots are automated, programmable and capable of movement around three or more axes. Typical applications of industrial robots include welding, painting, assembly, lifting and packing heavy parts, packaging and operating machines. All these operations accomplished with high endurance, speed, and precision. Industrial robots are manufactured for instance by ABB and KUKA, among others.

An industrial robot called foundry robot has been used since 2010 in Chile, according to engineers at Outotec Kil AB. The work environment where foundry robots have been used is similar to the work environment of copper converting. Therefore, it is fully possible to use a foundry robot in this application.

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4.8 Cost Calculation

In this section, the estimated costs of both options will be discussed and compared.

4.8.1 Cost of Simple Bar Changer

An estimated cost calculation of the simple bar changer was made according to appendix C to see approximately what the price will be. But also to be able to compare it with the price of the foundry robot. The cost calculations are based on different sources. For instance, the programming cost is based on a calculation from engineers at Outotec Kil AB, the manufacturing cost is based on a calculation from Stilmek AB and the cost of motors and steering is based on a calculation from engineers at Outotec Skellefte˚a AB. The total cost of the simple bar changer is estimated to 2030 kSEK. The prototype cost is not included in this sum.

4.8.2 Prototype Cost

To be able to validate the concept, building a prototype is necessary. Building a prototype will cost approximately 370 kSEK. To manufacture the simple bar changer and the bar storage will cost about 180 kSEK including tender and material costs. Purchasing of motors, linear actuator, bearings and control system cost will be about 210 kSEK, according to engineers at Outotec AB.

If the prototype is usable and can be sold, no extra cost will be added to the total cost. Basically, the prototype cost is the same cost as manufacturing the first simple bar changer and bar storage. If it is not possible to use the prototype, it will result in an extra cost of 370 SEK which will be added to the total cost.

In case the prototype cost is added to the total cost, then the final sum will be approximately 2400 kSEK.

4.8.3 Industrial Robot Cost

A foundry robot with a lifting capacity of 120 kg will cost approximately 300 kSEK.

This is a fixed cost and will not be possible to avoid or change it significantly. A total cost of the foundry robot estimated to 1070 kSEK, according to appendix D. The cost of designing and manufacturing of the bar storage is the only common cost which is the same for both simple bar changer and the industrial robot.

When it comes to the industrial robot, some of the costs will be reduced to 50 percent of what it will cost for the simple bar changer. For instance, the product documentation and manual cost.

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4.9 Comparison between industrial robot and simple bar changer

An industrial robot is an established and well-developed product with a range of different application areas. Thus, industrial robots are durable and accessible, which means minimal maintenance and minimizing disruptions in production. Us- ing an industrial robot in this application is a bit advanced but on the other hand, it is not limited in this application. It is possible to use the industrial robot in other applications. Outotec will have some financial benefits by using industrial robots because the companies that sell robots have a certain warranty period on their products.

The industrial robot has its benefits since it is a ready product but, it will also bring some challenges which are not beneficial for Outotec. The disadvantages of using the industrial robot will be, for example, that several subcontractors are involved. Since Outotec needs to buy robots from other suppliers, Outotec will be dependent on them, especially when it comes to service and maintenance.

The advantages of using the proprietary purpose-built machine (simple bar changer) are, for example, that Outotec will be not dependent on other suppliers in the same way as using robots. In the beginning, the proprietary purpose-built machine will cost more than the industrial robot because it requires quite much work regarding design, production, validation and administration. But during the time the costs will decrease specifically after the first machine has been built and validated. For instance, the design cost will be significantly reduced. In the long term run, Out- otec will have financial benefits by making the proprietary purpose-built machine.

Outotec will save both time and money by using the proprietary purpose-built machine because it will be simpler and cheaper when it comes to maintenance and service compared to the robot. Outotec will also be able to have income by selling spare parts, training and service to its costumers in combination with the proprietary purpose-built machine.

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5 Discussion

The design of the proprietary purpose-built machine is complicated considering that it will compete with an industrial robot. The industrial robot is made by thousands of engineers which have put thousands of hours on it. Another challenge with this project is that it is the first step toward automation in this specific area and previous experience does not exist. Based on these challenges, the project was demanding especially at the start.

As result of the limited project time frame, the main focus has been on the proprietary purpose-built machine. The time spent on the industrial robot is not proportional to the time spent on the proprietary purpose-build machine.

The five-step concept generation has been used during this project and this method does not indicate the amount of time that might be put into each step. The amount of time spent on this thesis project is different in each step, some step took more time and some less. For example, the time spent on the last two steps was less compared to the others. However, the information and knowledge obtained from step two and three was very valuable when it comes to concept generation.

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6 Conclusions

The aim of this thesis project was to investigate if a punching bar changer will be a proprietary purpose-build machine or an industrial robot. An investigation of both cases has been performed and a 3D model of the proprietary purpose-built machine has been presented. An estimated cost calculation for both proprietary purpose-built machine and industrial robot was prepared.

An industrial robot called foundry robot is already used in a similar application so it is definitely possible to use foundry robot for changing punching bars. Using a foundry robot can be a bit advanced for this application, but at the same time the foundry robot can be used for other operations.

It is possible to build a proprietary purpose-built machine with standard components. From the FEM simulation, it was shown that stress and deformations are small. The proprietary purpose-built machine will cost more compare to the foundry robot at the start but a lot of the costs will either disappear or will be reduced after the first machine is built. For example, the testing cost will be disap- peared and the design cost will be significantly reduced. When it comes to service and maintenance there will be benefits because it will be simpler and cheaper.

The simple bar changer will have better availability because of its simplicity but also because of that Outotec will not be dependent on other suppliers for instance, regarding service and maintenance. In addition, it will also be able to sell spare parts, training and service to the costumers. In the long term run, it would be beneficial to build a proprietary purpose-built machine for this application.

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7 Future Work

The future work is to calculate the costs in detail for proprietary purpose-build machine but also for the industrial robot. A detailed price calculation makes it easier to make the right decision regarding the choice of those two alternatives.

It is also necessary to investigate whether the customers want to invest in these solutions and what is more attractive and interesting from their perspective. Based on this investigation, a deeper analysis is desirable for the choice of direction.

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8 References References

[1] ”Scandinavian Copper Development Association”, [Online]. Available:

https://copperalliance.se/koppar-och-kopparlegeringar/koppars-anvandning/el- och-energi/ [Accessed 14-02-2020]

[2] Mark E. Schlesinger, Matthew J. King, Kathryn C. Sole and Willian G. Dav- enport, Extractive Metallurgy of Copper (5th edition), pp.127, 2011.

[3] Wikipadia, [Online]. Available: https://en.wikipedia.org/wiki/

Converting_(metallurgy). [Accessed 18-02-2020]

[4] J. Kapusta and t. Warner International Peirce-SmithConverting Centennial, San Francisco: TMS, pp. 16-20, 2009.

[5] A. Lossin, Ullman’s Encyclopedia of Industrial Chemistry, vol. 10, Weinheim:

Wiley-VCH, 2012.

[6] A. Vaarno, Applied Mathematical Modelling, vol 22, issue 11., pp. 907-920, 1998.

[7] Vaikuntam, I. Lakshmanan, Innovative Process Development in Metallurgical Industry: Concept to Commission, pp.70, 2016.

[8] K. T. Ulrich and S. D. Eppinger, Product Design and Developement, New York:

McGraw- Hill Education, 2016.

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Appendices

A Simple bar changer in place and picking up a

punching bar from the punching machine

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B The rack in place and the simple bar changer

picking up a punching bar from it

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C Estimated cost calculation of simple bar changer

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Development of a Bar Changer for a Punching Machine