In this thesis developing a manufacturing system is conducted as a project for a customer of Incessant Ltd. Incessant Ltd. is a company founded in 2008 that provides development services to its customers. In this case the customer is a small-sized manufacturing com- pany producing metal products for industrial uses. In the most manufacturing cases of the company, the completed products are assembled from separate metal pieces with brazing. The manufacturing system functions completely manually and the goal of the development project is to improve it to a semi-automated level, consequently increasing the efficiency of the whole system. Due to confidentiality reasons detailed information about the company or its products are not provided in this thesis and the focus is on the manufacturing system itself.
5.1 Previous manufacturing system
In the manufacturing process of the company small-sized metal pieces are being brazed, cooled and later assembled to the final product. One of the products consists of three pieces of brazed assemblies and this thesis focuses on this brazing phase of the manu- facturing system. The products are sold for industrial purposes but more specific infor- mation is not provided in this thesis.
The materials being assembled are stainless steel and tungsten carbide. The pieces are rather small and the size of the joint area is 4 times 9 millimetres. A suitable filler metal for the materials is being used and it consists of copper, zinc and nickel. The filler metal has good qualities in strength since a high tensile force, approximately 500N/mm2, is applied to each product when in use. An appropriate flux is being used and it is a type designed for this specific filler metal. The heat for brazing is applied with a manual torch and the gas is a mixture of acetylene and oxygen. The melting point of the filler metal is 990° Celsius and is therefore the operating temperature being used.
Before developing the manufacturing system, the brazing process functioned completely manually. In the first step a production employee prepares the brazing process by placing the assembled metals on a support and then adds the filler metal. The pieces are then being shifted to the next employee who brazes the assembly by using a manual torch.
Next, the pieces and supports are moved on a table to cool and the first employee re- moves the assemblies from the supports. Lastly, the same employee cleans the supports with water and angle grinder and returns them to the beginning of the system. Mean- while, the second employee only focuses on performing the brazing operation since its duration is as long as the other operations combined.
The manufacturing system is used for producing similar products in two different sizes.
Assemblies are piled on the supports in batches. 5 pieces of small assemblies and 3 large assemblies fit on one support and the supports are always fully loaded. This thesis focuses on the larger assembly when examining the previous system, since it is pro- duced in larger quantities and more frequently than the smaller one. The whole system occupies space for approximately 20 square meters. Cleaning the supports reserves the largest area since the operation requires a water container and a table. The actual braz- ing occupies the smallest area and is placed in the corner of the system due to the heat it produces.
The process is designed to be carried out by two employees, one of which places the pieces on the supports and the other one performs brazing. However, since the orders have become larger and more frequent, one extra employee has lately been required.
This employee also participates in placing the parts on the supports and helps with shift- ing and cleaning. When performed normally by two employees, the capacity of the man- ufacturing system is 57 assemblies per hour and 228 per day. That is because the em- ployee responsible for brazing has several other tasks and the time reserved for the brazing process is four hours a day. Three assemblies being required for the final prod- uct, approximately 76 finished products are produced each day. Consequently, the value of one employee’s work is 38 products a day and the productivity of the system is 57 per hour when the system is running.
5.1.1 Challenges
The current manufacturing system of the customer faces various challenges, the most notable of which is the low volume of the production. The system produces products in small batches, since 3 assemblies of larger pieces are placed on one support. The pro- cessing time of one batch is 360 seconds. Both operations, placing and brazing, take 180 seconds each, shifting and cleaning the supports being included in the placing op-
speed of the production system is still determined by the brazing operation. As a result, a constant bottleneck is caused by the brazing operation if more than one employee places the parts. Incomplete assemblies pile up and the waiting time of the assembly increases. If more employees would be recruited to perform the brazing operation, the bottleneck would probably decrease but this solution would require investments for the equipment and maintain high manufacturing costs.
Due to a rather time-consuming manufacturing, the company is not able to fulfil all the orders of its customers and its delivery times are long. The orders and deliveries are not in a balance since the demand of the product is higher than the output volume. Predict- ability of manufacturing is also rather difficult since the production relies on the employee responsible for brazing. In addition, when examining the costs of the final product, the share of the manufacturing costs is high compared to the raw materials, storing or trans- portation costs. The raw materials itself are rather inexpensive but the manufacturing increases the price not adding comparably enough value to the finished product. Since the manufacturing is slow and requires manual performing by several employees the costs are difficult to decrease by other actions.
When considering quality, manually performed system experiences some challenges.
Even though the strength of the created joint is good, its tolerances are comparably high.
Small metal pieces are difficult to place accurately by hand and therefore vary notably by place when being assembled. Minor alteration in the place of the brazed piece does not result in a reduced quality of the final product. However, predicting quality is rather difficult, as well as estimating the ultimate average strength of the product when the tol- erance is high.
Lastly, safety issues are one of the challenges of the current system since manually performed tasks tend to expose employees to higher risks. The heat produced in manual torch brazing creates dangerous situations for the employees since the flame is easily accessible for external factors. When performed manually the torch may be easily con- trolled to point in the required direction but it can accidentally turn to a wrong one when controlled by human. Working with heat and direct flame always exposes employees to risks and they should be minimized as effectively as possible.
5.1.2 Requirements and expectations for development
Due to efficiency, manufacturing speed and safety issues the company decided to invest in a development service, aiming to improve its manufacturing system. The target is to create a system which would not possess bottle necks nor rely on a performance of a single employee. The decision was to improve the system by replacing some manually performed operations with machines. This solution would release the bottle neck, stabi- lize the production speed and make the manufacturing more efficient and predictable.
The upcoming system is going to be conducted as a project and it is executed by Inces- sant Ltd. as a development service. The customer has given the requirements for the project, such as a budget, schedule and the extent of space available. The exact budget is only known by the development team and it includes all the purchases and equipment, such as machines, materials and supports. The available area for the new system is a rectangle of its shape and its size is six times three meters. All the equipment, tables and paths for shifting and moving must fit inside this area.
The target for finishing the project is in April 2018. The performance of the new system is then evaluated by using a measurement chart designed for the project. The measure- ment chart can be found in the attachments of this thesis. Different parameters, such as lead time, productivity and duration of the process, are examined in the chart before starting the project. Targets for each parameter are calculated and filled in the chart and are used for guidance when developing different aspects. When the project is finished, the results are filled in the chart and compared to the previous results and targets.
The aim of improving the manufacturing system is to increase the productivity of the system and enable faster and more predictable production speed than before. It is cal- culated that if the brazing operation took 90 seconds, a steady manufacturing speed would be achieved. That is because other tasks of the process take 180 seconds when performed by one employee and it halves with two. If the brazing speed can be devel- oped faster than 90 seconds, it provides more flexibility and is therefore desirable but not necessary. In this case, more employees could be added in the placing operation and it would consequently increase the output.
If the brazing operation reached the speed of the placing, the capacity of the system would be 114 assemblies in an hour. This would be a remarkable improvement since it
long-lasting operation would be placing the pieces and its flexibility is convenient for the system. More placing stations are easily inserted if the orders increase remarkably. The stations do not require many special equipment and are therefore low investments. Due to this kind of system the customer would be able to fulfil its orders when the output is in a balance with orders.
In addition to increased efficiency and productivity the new system is desired to function more hours per day than the previous one. The previous system functioned for approxi- mately four full hours per day due to other mandatory tasks of the brazing employee. If this employee was replaced by a machine the production system would not be de- manded to stop during the working time, which is eight hours a day. Consequently, the output per day is estimated to increase remarkably due to increased operation times and productivity. Releasing employees for other tasks would also improve the performance of the company since more time is reserved for other tasks, such as designing and de- veloping products and systems.
5.2 System development and management
When it comes to manufacturing strategy, the company follows one including features from make-to-order and assemble-to-order strategies. When a customer places an or- der, manufacturing is activated and the products are assembled from parts according to the order. However, since the demand is rather steady, some products are occasionally produced to the stock. Fortunately, the physical size of the product is small, so storing them is not comparably expensive or challenging. The parts used by the company gen- erally suit for many of their products which is typical for an assemble-to-order strategy.
The manufacturing system is aimed to be developed by following some guidelines of lean. The inventories are targeted to be kept low, especially work-in-process inventories.
As many pieces as possible are chosen to be standard parts or suitable for multiple products to enable flexible usage and ordering. The system is targeted to maintain righto- mation and utilize its resources effectively. These aspects are kept in mind when man- aging the development and making decisions concerning the new manufacturing system.
5.2.1 Finding the right level of automation
Before beginning to redesign the manufacturing system a careful examination of the old system had to be made. Finding the right level of automation individually for this manu- facturing company was essential to achieve the full utilization of its machines and avail- able resources. Previously presented Figure 4. Level of technology, can be applied to serve as a guideline for this case. When examining the production volume and the vari- ation of the products, the result seen from the chart is a little lower than a medium level.
According to this result, it might not be beneficial to automate most of the system, but rather choose one or few operations for the target of investments.
To comprehend the system more clearly, process charts of two different situations were sketched. The first situation occurs when the number of products determined by the or- ders can be assembled by two employees, one of which performs brazing and the other one placing, cleaning and shifting. This situation is illustrated in the Figure 7 below.
Figure 7. Process chart, two employees.
The operations with a grey background, placing and cleaning, are performed by the first employee and are both included in the 180 seconds designated in the figure. This time also contains shifting between processes, which is not further specified in the chart due to its short durability and occasional alteration. Since cleaning does not occur in the end of every cycle but is performed in batches when several supports have piled up in the cooling station, a separated cleaning time is not specified in the figure either. Brazing is the only task of the second employee and is marked with yellow in the figure. Cooling occurs between the brazing and cleaning times and does not require performance from the employees.
When only examining Figure 7, the manufacturing system seems rather constant and reliable. However, when the situation two takes place and two employees are performing the placing operation, the chart appears totally different. This is illustrated in the Figure 8.
Figure 8. Process chart, three employees.
In this process chart, the same designations apply as in the previous figure. As per- ceived, the brazing operation forms a bottle neck in a situation where more than one employee participates in placing. Below brazing operation, the boxes illustrate supports carrying products that are waiting to be processed. Idle time refers to this waiting time in seconds and is calculated in the figure for the first six supports. Idle time seems to in- crease by 180 seconds after every second support. After a while, the idle time of a sup- port will escalate to several minutes.
Having considered the operations and possibilities for automation with the help of the process charts, it was confirmed that at least brazing operation would have to be auto- mated. Automating brazing is rather simple and inexpensive and would fit in the budget of the customer. When considering automating the placing operation as well, the small size and required precision of the pieces would require an advanced industrial robot to perform the task. The budget of the customer would not cover the costs of a robot so automating placing operation was discarded. In addition, when comparing the costs of a robot to the increased efficiency it provided, the investment would not be profitable for a small-sized manufacturing company.
Cleaning and shifting being insignificantly small operations when comparing them to the lead time of the product, automating them would not be profitable in this state. For that reason, the only operation considered beneficial for automating was brazing, and was therefore agreed to be confirmed in the development plan. With this plan rightomation is targeted to be achieved, as well as the full utilization of the machines and resources.
5.2.2 Designing the layout
Having decided the operation to be automated, a new layout had to be planned. The best option turned out to be designing a product layout where placing is conducted man- ually and the brazing operation functions with a low level of assistance, which in this case is supervising the process. In this layout, placing operation is located in the beginning of the system and is performed on wheeled tables. Employees place the pieces on special supports and add the filler metal ready for brazing. The tables are then rolled to the beginning of a conveyor, which is designed to move the parts through the brazing oper- ation.
Supports are shifted manually on the conveyor and the tables are rolled back to the placing station. The conveyor moves with a steady speed and an accurate position of a support is ensured with the help of two guidance blocks on the conveyor. Two torches meant for semi-automated brazing are placed next to the conveyor and they melt the filler metal when the parts are shifted past. In the end of the conveyor the supports slide on a slope to a table where they cool for an appropriate amount of time. Lastly, an em- ployee removes the assemblies from the supports, cleanses them and returns them to the placing stations. A sketch of the layout is visualized in the Figure 9 below.
Figure 9. Designed layout.
The system requires careful designing and the supports, conveyor and torch need to be precisely chosen. A good support is simple and easy to use when the parts are being placed on it. It provides accuracy and has a low chance for mistakes. Support must be precisely located on the conveyor with a 45-degree angle to achieve accurate and repet- itive quality. To enable the easy guidance of a support, its edges must be smooth and even. The supports used in the old manufacturing system are therefore not prospective options anymore and new ones must be designed.
The conveyor must be durable for high temperatures since it is exposed to a direct flame.
Its length depends on the efficiency of the torch and the more powerful the torch is, the faster the brazing operation is. This would result in a short conveyor, which saves space and probably financial resources. A good torch is consequently powerful and reaches the temperature of 990° Celsius fast. The temperature of the flame must be steady and adjustable since smaller pieces require less heating than larger ones.
The wheeled tables do not have to be durable for a direct flame but must be suitable to be used next to high temperatures. A table must be able to carry at least 100kg over a square meter, which is the weight of the maximum load. The table has to have a good movability and an ergonomic height, preferably adjustable for the employees. The slope and the table in the end of the conveyor must endure high temperatures since they hold the heated supports.
5.2.3 Managing the project
Since the development project had many requirements, high goals and a targeted finish- ing time, a precise project management was essential for managing the project. The management was started by listing the required qualities for the project and the new system and the limitations the customer had determined. The next step was to create a schedule for the project which it was first sketched by using Microsoft Excel. A detailed schedule was created on Microsoft Project Plan, including the beginning and end dates of the tasks and a demonstrating Gantt chart. The schedule consisted of bigger steps, such as ordering and assembling, and smaller steps, like preparing, designing and shar- ing information.
Since the project included various components and delivery times, comprehending the