Oriental Metal Industries (OMI) Sdn. Bhd. is a company that produced steel wheel and assisting in wheel assembling for customer.
In steel wheel production process, six type of line are served to complete the process. That are, rim line, shearing line, press line, assembly line, electrodeposition (ED) painting line, that create black based colour on the wheel and lastly the top coat low point (TCLP) line before it transferred to wrapping process and then delivered to the customer.
This project will focus on TCLP line. This line received all models of steel wheel because of the process it run in the plant. Majority of the model produced by this company run through this line before it be wrapped up. This line consists of two processes. Firstly, the top coating process, which provides spraying process to create coloured coating on the wheel. The second process is the low point marking process. An auto low point marking machine assign to make a tiny white marking on the wheel lowest point. The Function of the low point is to help the assembly module team to assemble the wheel and tire together.
Wheel model produced by this company that went through the TCLP line are OMI4JVB, OMI4QFB, OMI6HSB, OMI5PCS, OMI6.5S8B, OMI6.5YFB, OMI5BLB and OMI5.5A8B. All wheel model mentioned above went through different process in TCLP line. Flow chart below shows how the flow of the wheel in TCLP line according to the model. The flow of the TCLP line are shown in Figure. 1
Figure 1. wheel model flow through TCLP line process
1.1 Problem Statement
Recently, model for OMI4JVB and OMI4QFB need to change its colour from black to yellow for safety reason. Time study need to be done to test the cycle time for the model. The time study also done to OMI4PCS and OMI6.5S8B model.
The trial are run in October. The takt time for all TCLP line process for that month is 13.83 second. Result of the bottleneck from time study done are as shown below:
Model Cycle time/Bottleneck (sec.) Process
OMI4PCS 23.1 Spraying
OMI4JVB 28 Spraying
OMI4QFB 29.7 Spraying
OMI6.5S8B 16.05 PDI
Table 1. Result of cycle time for all wheel model that went through TCLP line process
Table 1. shows the result of bottleneck in certain process. Focused are on OMI4JVB and OMI4QFB that produce a big gap between the cycle time and takt time. The problem like this need to be overcome. The time availability and line capability are the item that need to be given attention.
a) To identify bottleneck process using time study
b) To analyse spray process using 4M method
c) To suggest improvement on spray process
1.3 Importance/Significance of Project
a. Increase productivity in TCLP line, so there will be no problem in catching time required to produce product requested.
b. Increase productivity for company
1.4 Scope of project
c. Time study and improvement are focusing on TCLP process line.
d. Focusing on spraying method or technique in top coating process.
e. Involving model that went through top coat process that are OMI4QFB and OMI4JVB.
A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period. A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant. (The Writing Centre, 2010)
2.2 Steel Wheel Manufacturing
Steel wheel manufacturing is one of big field of manufacturing in manufacturing engineering (HAYES, 2002) . It came as an important character in the automotive industry. The process of making the steel wheel between various of maker around the world is quiet same as the part of the steel wheel usually does not come with big differences. The main part of the wheel are disc and rim.
Wheel disk and wheel rim are produced in separate production processes and subsequently welded together in an assembly line. The wheel disk is produced from coil stock in a deep drawing process using a progressive press (shaping and punching). The associated wheel rim is produced in the wheel rim line. Same goes in Lemmerz factory, the basic product is a sheet metal coil.
The coil is unwound and cut to length, and subsequently pre-bent (round bending) and welded into a circular blank. This circular blank is then profiled via roll stands and is shaped into the typical wheel rim profile. In the assembly line the disk is pressed into the wheel rim, welded, checked and subsequently dip-primed. A new wheel is ready every 6 seconds. What may sound relatively easy here in reality involves the integration of a variety of process technologies and their interlinking into an approximately 200 m long production line.
The step of making the steel wheel run in the plant can be review as below:
2.6.1 The welding process
The complex control process starts with welding of the circular blank in the wheel rim line. This procedure is technologically very demanding and consists of the following steps:
1. The two ends of the round-bent sheet are brought together via a hydraulic axis until they are in contact.
2. Once they are in contact, they are heated by applying a controlled current. The round-bent pieces are then welded together, with the material being upset during the welding process. During this process, in addition to the current and the pressure, the position of the hydraulic axes involved is also monitored.
Therefore, several processes correlate with each other, i.e. the pressure and the position control for upsetting the sheet metal and the control of the welding current. Until now, the welding process used a proprietary control and a PC-based system for generating, managing and downloading the welding programs and for generating the set values. The wheel rim line manufacturer, Fontijne, combines both processes via a Beckhoff TwinCAT control system, thus demonstrating its performance and flexibility, particularly for the realization of technological control processes.
2.6.2 Profiling of the wheel rim blank
The next production step is the profiling of the wheel rim blank
in three successive roll stands. Figure 2 show This process is also more demanding than it may appear at first glance. The blank is transported step-wise into the roll stands. The upper and lower rolls close in a controlled way to generate the profile. At the start of each manufacturing stage, the peripheral speed of the two rolls is adjusted to the mean radius of the wheel rim blank.
Once a frictional connection between the two rolls has been established via the wheel rim material, the process control is changed to moment control. Here too, high computing capacity and deterministic machining at short cycles is required. Due to its nearly inexhaustible reserve capacity, a TwinCAT PC control is able to meet these two requirements extremely well. .
Figure 2. Profiling of the Wheel Rim (Source: HAYES)
2.6.3 Final assembly of wheel disk and wheel rim
The last operation, i.e. final assembly of wheel disk and wheel rim, is just as complex. A robot positions the wheel disk in front of a camera system, which detects the rotational position. The wheel disk is then placed into a wheel rim positioned on two walking beams. A gripper for clamping the wheel is positioned on each side of the walking beam. Once the gripper engages, a frictional connection is established between the two beams via the fixed wheel. During transport, the beams are synchronized with high precision in order to avoid mechanical damage. The beams are synchronized electronically via TwinCAT through linear master- slave coupling.
The wheel disk is pressed in via a press, creating a firm connection. The height of the burner heads in the subsequent welding stations is adjusted depending on the height of the wheel disk patch. Four weld seams are simultaneously produced. For this purpose, 4 burner heads are symmetrically arranged at each station. Each burner can be individually fine-tuned, i.e. one axis for vertical and radial positioning, one for lifting or for positioning of the wheel under the burner heads, and one rotational axis for rotating the wheel during the welding process are available. Measurement and quality control of the finished wheel are carried out with a specially developed camera and image processing system.
The assembly plant consists of 57 servo axes, of which 42 are synchronized, highly dynamic axes for the production (machine cycle: 6 s), the rest are purely asynchronous feed axes. The servo axes and a further 1500 digital and analog I/Os of this machine are controlled via a single TwinCAT controller. The position controllers cycle time for all 57 servo axes is 3 ms and ensures a real time load of the control system of only 50%.The control system manages a total I/O address space of several thousand bytes. The performance capability of a TwinCAT control system could scarcely be documented more impressively.
Figure 3. Wheel rim and wheel Disc assembled and welded together (Source: HAYES)
2.3 Automotive Coating
Following to the coating process that introduced by Henry Ford who founded Ford Motor Company. In 1900 till 1920â€™s, they implemented coating process that used conventional brush and paint it on the car body. Just like the way we usually used to make a coating on a wood. Henry Ford (1900) mentioned that the car that wanted to be paint ca be in any colour the customer like, as long as it is â€œblackâ€. Furthermore, this process take 40 days to complete.
During the early 30â€™s the auto industry \"stoving enamels\" based on alkyd resins had been introduced. Initially the product was applied much like the \"varnish\" used earlier based on Croll, S. 2009. These enamels were originally selected because of a higher gloss yield than varnish. They were also thicker and applied a little faster. Then, spray gun had been introduced by a dentist to replace the brush method somewhere between 1930 and 1940. Using spray gun, the work can be done faster than the method using brush. It can minimized sanding between coatings and applied the product evenly. Now, the works that have to take over a month could be done in a third of the time. This product and process was the system of choice for most vehicle manufacturers until the 1950â€™s (J. Mohd Fakrul Razi 2015).
Another significant enhancement in paint technology was the development of â€œalkydâ€ enamel paints that were introduced on some car models in the early 1930s (Standeven, H. 2006). These enamels formed a very durable film because of molecular bonding reactions that occurred after the paint was sprayed onto the vehicles and then cured or baked in an oven. However, alkyd enamel paints were degraded by oxidization in sunlight, which caused colors to fade slowly or dull (Nelson K. Akafuah 2016).
The improvement of spray method did not stop just there, by 1960â€™s there are introduction of acrylic stoving enamels that can improve durability of enamel finishes (Learner, T. 2000). The application of this idea are manually using spray gun and then bake the product in the oven resulting glossy finish. However the manual style of spraying causing uneven coating thickness.
In the late 1970s, The topcoat painting process was introduced, the process was split into a pigmented enamel basecoat, followed by a clear enamel finish.
Today, automobile painting processes are more standardized than they have ever been because of the benefits of inorganic pre treatments, cathodic electrodeposition, liquid or powder primer surfacers, liquid base coats, and one or two component solvent-borne clear coats (Nelson, 2016).
Automotive coatings continue to evolve as they either satisfy or are anticipated to meet customer expectations and environmental regulations while also lowering manufacturing and ownership costs (Nelson, 2016).
The three common stages that are now practically done in many spray coating process are, top coat, base coat and clear coat. Compared to this project, the spray done in top coat low point are the combination of base coating element plus clear coating element that using thinner as the medium for clear purposed.
The paint spray cycle of an automobile can be visualized to start from the paint guns that spray toward a car surface. After the applicator atomizes the paint, only a portion of the paint droplets coat a vehicle surface. Broad and significant issues with automotive painting include: paint transfer efficiency (TE); coating deposition; energy consumption; energy efficiency; inspection of finished surface qualities; and environmental and workplace safety. Issues related to finish quality can be analyzed regarding the atomizer designs, paint formulation and composition, and surface modification .
The performance of an automotive coating can be assessed from different views, e.g., the durability of the exterior and interior paint finishes or the aesthetic features . However, limitations exist on the paint properties, process capabilities, and, most importantly, the amount of money that can be spent to improve the finish . Consequently, each automotive company defines its colour and appearance standards, which are to meet or exceed the levels reached by competitors and customer expectations. Particularly important is the uniformityâ€”or harmonyâ€”among all components.
2.4 Spraying technique
In finishing any component the most efficient combination of spray gun movements must be carefully planned in order to produce the best results (Steve, 1995). At the same time the parameters within which the gun operates best must also be considered. The spraying technique should also need to be aware. If the gun is held too close to the work surface, more paint will be deposited and the gun will need to be moved faster to prevent runs and sags and possible solvent entrapment.
Likewise, if the gun is held too far from the work, the atomised droplets may dry completely before coming into contact with the work surface, causing excessive spray dust and dry spray, (as shown in Figure 4).
Figure 4. Spray dust atomisation comparison between two different gap (Source:Spray Gun Technique;DevilBiss)
The relation between the gun distance and the stroke speed is easier to see when actually spraying. The sprayer will soon become experienced in moving the gun target distance closer or further away to permit a comfortable speed, while depositing a full wet coating of material. Remember at all times that the Conventional Air Atomising gun is designed to spray at 6 - 8â€ inches and deviation from this distance by altering fluid flows and air pressures is not good practice. It could lead to other paint defect problems.
A flat round disc is sprayed like any other plane surface, spraying the edge as shown in Figure 5, and then spraying the centre.
Figure 5. Vertical strokes sprayed at the ends of a panel help reduce overspray from horizontal strokes (Source:Spray Gun Technique;Ds)
Mounting certain types of work on a turntable which can be revolved easily can allow an object to be sprayed with one or two simple motions without shutting o99ff the spray gun more than once or twice.
Figure 6. Finishing a wheel hub cap in one continuous stroke using a rotating work holder (Source:Spray Gun Technique;DevilBiss)
Such continuous, or nearly continuous, operation of the gun will assure maximum coverage per unit of time and so will produce a maximum output from the spraying operation.
Bottleneck is a value that gathered from cycle time study on certain process. It can caused major impact on production system because it create congestion in a production system. It occurs when workloads arrive too quickly for the production process to handle. The inefficiencies brought about by the bottleneck often create delays and higher production costs (Investopedia). The term \"bottleneck\" refers to the shape of a bottle, and the fact that the bottle\'s neck is the narrowest point, which is most likely place for congestion to occur, slowing down the flow of liquid from the bottle.
2.6 Ishikawa Diagram â€“ 5â€™Mâ€™ method
In finding problem and gathering information for improvement purpose there are a method that usually called 4â€™Mâ€™,5â€˜Mâ€™, 6â€™Mâ€™ used to make the improvement come to real. This â€˜Mâ€™ method is a simple method used to analyse causes and consequences. 5â€™Mâ€™ method for example is based on five causes (Management Mania;5M Method).
It is a version of the Ishikawa/Fish bone/cause-and-effect diagram. It is a very versatile method that is used to identify causes of risks, inefficiency, poor quality or other problems in business processes or is used for finding problems. To illustrate the causes the fish-bone diagram is used.
1. Manpower - causes are in humans, people
2. Machines - causes are in equipment, such as machinery, computers, tools, instruments, technology
3. Materials - causes are in defect or material properties
4. Methods - causes are in the rules, regulations, laws or standards
5. Management - causes are in improper management
2.6.1 Advantages of fishbone diagram
Because of it characteristics that can assist in overcoming the problem occur in an organisation, it should help us in making our company progress smooth. It should make impact in certain process if the process have a problem (Gupta, 2007). Some of its advantages are:
1. Fishbone diagrams permit a thoughtful analysis that avoids overlooking any possible root causes for a need.
2. The fishbone technique is easy to implement and creates an easyâ€toâ€understand visual representation of the causes, categories of causes, and the need.
3. By using a fishbone diagram, you are able to focus the group on the Êºbig pictureÊº as to possible causes or factors influencing the problem/need.
4. Even after the need has been addressed, the fishbone diagram shows areas of weakness that â€ once exposed â€ can be rectified before causing more sustained difficulties.
2.7 Recognizing and Managing Bottlenecks In Process Plants
In parts manufacturing and assembly process, company commonly used the combination of power from human and machine to complete those product in time required. There are no problem for machine to complete its job and follow whatever task assign on it. Routine maintenance on it is enough to make sure the machine in a good condition. The problem of bottleneck usually come from human error, misconduct, inconsistency and many other false method in completing the job (Peter, 2011).
Managing bottleneck will be focusing on people. It will focus on certain aspect, such as:
1. Appropriate staffing for the task
2. Task levelling
3. Judicious of overtime
Random events, such as demand fluctuation, order arrival time, material shortage, priority variation etcetera can also caused bottleneck shiftiness in the production (Chen & Shen, 2010). But, if there are a problem there will be a solution. Especially in make-to-order production processes, bottleneck shiftiness can be caused by large variability in technological procedures. It means that production resources are not equally utilized and in different periods, another of them can be a bottleneck.
Some of the suggestion for solution that stated by Chen & Shen (2010) to overcome bottleneck are:
1. Setting buffers ahead of the bottleneck machines in case of a low demand fluctuation.
2. Paying more attention to control of material release and production scheduling in case of a great demand fluctuation in order to lower the probabilities of shifting bottleneck through the whole production.
3. Using Drum-Buffer-Rope technology with three kinds of buffer areas (bottleneck buffer, assembly buffer and consignment buffer) in case of facility exception.
Figure 7. Circle chart of the theory of constraint (Goldratt, 1990)
2.8 Plan Do Check Act (Pdca) Improving Quality Through Agile
PDCA (planâ€“doâ€“checkâ€“act) is an iterative four-step quality improvement and management agile process typically used for the better of the business strategy. PDCA is a successive cycle which starts off small to test potential effects on processes, but then gradually leads to larger and more targeted change (K.A.Chandrakanth).
The four step of PDCA explained by K.A Chandrakanth as below:
Establish the objectives and processes necessary to deliver results in accordance with the expected output (the target or goals). By making the expected output the focus, it differs from other techniques in that the completeness and accuracy of the specification is also part of the improvement.
Implement the new processes, often on a small scale if possible, to test possible effects. It is important to collect data for charting and analysis for the following \"CHECK\" step.
Measure the new processes and compare the results (collected in \"DO\" above) against the expected results (targets or goals from the \"PLAN\") to ascertain any differences. Charting data can make this much easier to see trends in order to convert the collected data into information. Information is what you need for the next step \"ACT\".
Analyse the differences to determine their cause. Each will be part of either one or more of the PD-C-A steps. Determine where to apply changes that will include improvement. When a pass through these four steps does not result in the need to improve, refine the scope to which PDCA is applied until there is a plan that involves improvement. The PDCA value must be implemented not only for a company, but for individual improvement. It is a needs to adopt PDCA at an individual level to continuously improve oneâ€™s effectiveness and ability to achieve and deliver the daily goals set.
The PDCA method also be done in an IT company to create a high level quality product. The implementation of the method done stage by stage from individual, program that run in the company, production line and also in the organisation level. The step to adopt this PDCA is just to make sure the Tektornix company achieve wholistic improvement from the base to the top (K.A. Chandrakanth). So to this project that will try to implement the PDCA step in order to make sure the quality of improvement for the project can be success.
The methodology describes the broad philosophical underpinning to your chosen research methods, including whether you are using qualitative or quantitative methods, or a mixture of both, and why.
You should be clear about the academic basis for all the choices of research methods that you have made. \'I was interested\' or \'I thought...\' is not enough; there must be good academic reasons for your choice. What to Include in your Methodology
If you are submitting your dissertation in sections, with the methodology submitted before you actually undertake the research, you should use this section to set out exactly what you plan to do.
The methodology should be linked back to the literature to explain why you are using certain methods, and the academic basis of your choice.
If you are submitting as a single thesis, then the Methodology should explain what you did, with any refinements that you made as your work progressed. Again, it should have a clear academic justification of all the choices that you made and be linked back to the literature.
3.2 Lean Six Sigma
Lean Six Sigma is simply an effective methodology used to fix a problem. Simply put, Lean Six Sigma helps you identify the cause of a problem and implement a fix based on facts, rather than assumptions. This produces improved results and success that you and your team, managers and organization can be proud of. It is based on common sense practices and is completed in five phases (Go Lean Six Sigma, 2016). Refer to Figure.9 below:
Figure 9. Lean Six Sigma steps flowchart
3.2.1 Analysis Current Condition
To evaluate whether the line is capable to meet customer requirement of producing a product, time study are first done in the top coat low point line. Here the method of time study are done using stop watch timing technique.
To perform a time study process, certain tools need to be used. The tools are such as:
1. Digital stopwatch
A watch (Figure. 10) that can be started and stopped very quickly and that is used for measuring the amount of time that is taken to do something (such as to run a race). Have a lap function that can help us in counting repetitive job. It also have memory function to save time taken, acting as reference after enough cycle time gathered from certain activity.
Figure 10. Digital stopwatch. (Source: watches88.com)
2. Time study sheet
The Process Study Sheet (Figure. 4) is used to define and record the time for work elements in a process. Before timing, opbserve and list the work elements required to produce one element. Then observe and define the actual time required for each individual work element.
Table 2. Time study sheet example. (Source:sawyoo.com/post employee study template)
Time study or stop watch timing technique is the basic technique for determining accurate time standards. They are economical for repetitive type of work. Figure.10 shows the time study process:
1. Select the work to be studied.
2. Obtain and record all the information available about the job, the operator and the working conditions likely to affect the time study work.
3. Breakdown the operation into elements. An element is a instinct part of a specified activity composed of one or more fundamental motions selected for convenience of observation and timing.
4. Measure the time by means of a stop watch taken by the operator to perform each element of the operation. Either continuous method or snap back method of timing could be used.
5. At the same time, assess the operators effective speed of work relative to the observerâ€™s concept of â€˜normalâ€™ speed. This is called performance rating.
6. Adjust the observed time by rating factor to obtain normal time for each element.
Normal = Observed time Ã— Rating
7. Add the suitable allowances to compensate for fatigue, personal needs, contingencies. etc. to give standard time for each element.
8. Compute allowed time for the entire job by adding elemental standard times considering frequency of occurrence of each element.
9. Make a detailed job description describing the method for which the standard time is established.
10. Test and review standards wherever necessary.
After process of time study done, all the data gathered from four models selected earlier are key-in the computer. This is because, the data needs to be re-concurrence with the amount of volume steel wheel to be processed. Here in OMI, after the numbers of time study gathered. The numbers will be used in six types of data collection file that are:
1. Time study table
2. Yamazumi chart
3. Standardized work combination chart
4. Standard working chart
5. Process capacity sheet
6. Job instruction sheet
After the result of the data have been taken and collected into its destination. The result for top coat low point model especially for OMI4QFB and OMI4JVB model are zoomed in to see its impact in catching the time required in completing the volume requested.
3.2.2 Define Target, Strategy and Tactics
Following to Figure. 9, the next step in lean six sigma is to define target for the project. Since the result of the time study are not in a good condition, solutions need to be implement in the project to overcome those problem. Before making any action, firstly the objective of this project need to be clear. It will lead the project to it destination. The objective listed will then show the project what the target it will achieved.
Strategy and tactics often associated to a teamwork counter measuring method for any problem that happened to a certain team. So do for this project. The objective and target aimed in the earlier stage are then shared to the management and line workers. This is to make sure all the person involved in the line know what really happened at their workspace. All the idea shared through this planning process will be review and verify to make sure the strategy planned achievable reflected to the company ability. Also, it need to be reasonable to be done depend on the company capability to invest some fund, if the strategy planned need to use the money to complete 4M need in this project.
3.2.3 Do the Kaizen
When the discussion process done from top to bottom workers in the company, especially for those who work in the top coat low point line. It is time to â€˜walk the talkâ€™ the Kaizen. All the idea and strategies that have been picked during the discussion phase will be implement at the plant. â€˜Plan-do-check-actionâ€™ and â€˜Trial and Errorâ€™ method will be used during the process of testing the proposed solution. It will done one by one, depending on it priority and availability of the tools to objectify the idea presented earlier.
As the â€˜kaizenâ€™ being tested it effectiveness on the spraying process, evaluation process also need to be done concurrently or done if any problem happened that need some attention on it. The time study will be used again to find whether the idea that try to be implemented on the spray process give impact on it. Video recording method will also be use to find anything unforeseen, dangerous or uncommon during the trial process.
3.2.4 Evaluate result
Evaluation on the â€˜kaizenâ€™ trial process will be done after the process finished. All the data gathered from the process such as cycle time, bottleneck, uncommon error and anything that can be noticed during the trial process will be taken to discussion to decide either the idea is reasonable to be achieved or not. If not, there are two option will be done next. Either move on to the next solution or improve the existing solution and try it again on spray process.
The lean six sigma method is some kind like PDCA method. Just, the evaluation method in â€˜lean six sigmaâ€™ for this project will be try and if it does not success, strategy and tactics step will take action repeatedly as the project also expected to make trial and error method for the improvement trial.
This project aim to make the cycle time of the spraying process faster than the current condition by using line balancing method that separate the work element been done in the spray process. Thus, making the top coat low point line smooth. Finally will make the company productivity increase by time.
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