International Journal of Scientific & Engineering Research, Volume 4, Issue 12, December-2013 305
ISSN 2229-5518
Improvement of Manufacturing Processes Utilizing Value Stream Mapping Technique: Cement Sacks Factory as an Industrial Case Study
Mahmoud A. El-Sharief
Abstract— Lean manufacturing is a production system, which was first developed by Toyota Production Systems (TPSs) to reduce wastes while improving the operational and environmental performance of manufacturing and industrial businesses. While the global industrial market suffers from gnarled competition, lean manufacturing philosophy is providing an effective methodology to reduce cost and maximize profit. In addition, the market no longer accepts waste caused by out of control production or inefficient processes. A commitment to quality and lean operations will result in quality improvement, waste elimination and reduction in time and costs.
Value stream mappings (VSMs), a lean manufacturing tool, which originated from the Toyota Production Systems (TPSs), is known as “material and information flow mapping.” This mapping tool uses the techniques of lean manufacturing to analyze and evaluate certain work processes in a manufacturing operation. This tool is used primarily to identify, demonstrate and decrease waste, as well as create flow in the manufacturing process. VSM can be created merely using paper and pencil; however, more advanced maps are created using Microsoft Visio as well as Microsoft Excel.
This paper describes practical implementation strategies for using lean manufacturing and an industrial case study (Cement Sacks
Factory) is included. After lean manufacturing methodology has been applied to the case, results are produced as Cement Sacks Factory
process efficiency is raisedIby 4.31J% and the TAKST time is reduced abEout 56%. R
Index Terms— Lean Manufacturing; Value Stream Mapping; Waste elimination; Facility layout; inventory; transportation; Case study.
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HE critical starting point for lean thinking is value. As stated Womack et al. [1] value can only be defined by the ultimate customer. Moreover, it is only meaningful when expressed in terms of a specific product (a good or a service, and often both at once) which meets the customer's needs at a specific price at a specific time. Value is created by the pro- ducer. From the customer's standpoint, this is why producers
exist.
With going on years , world has achieved great steps in in-
dustrial life to people, thus made countries to compete with
them in grossing their industrial fleet. Therefore, industrial as-
sociations expanded to include many sectors in the same associ- ation. With competition between power centers in world and war between them, industrial association has begun to find sys- tems to manage its big factories. Hence, many systems ap-
peared, such as “lean”, “six sigma " and " lean six sigma “.
Lean Manufacturing is the systematic elimination of waste from all aspects of an organization’s operations, where waste is viewed as any use or loss of resources that does not lead direct- ly to creating the product or service a customer wants when they want it. In many industrial processes, such non-value add- ed activity could comprise more than 90 percent of a factory’s total activity [1].
Lean manufacturing is the processes, techniques, strategies and initiatives being implemented by companies around the world
that aim to reduce unnecessary and unproductive tasks, activi- ties and behaviors in the work environment. In other word, lean manufacturing is implemented in order to reduce waste and improve the organization production and morale.
There are many tools and techniques in lean manufacturing that can be implemented but the selection of effective lean tool, and technique in lean manufacturing is hard to choose. Wrong decision will affect the waste and time. Lean thinking is a highly involved method of managing an organization to improve the productivity, efficiency, and quality of products and services.
T. MELTON [2] stated the benefits of lean manufacturing are:
• Help to produce business outputs as fast as possible.
• Convert a business enquiry to a finished output; then it
can hold less row material and finished stock inventory.
• Hold lower inventory levels means need less cash to
run the business.
• Able to produce work faster.
• Can do more with the same resources (machinery, peo-
ple).
• Can complete work faster than competitors.
• Reduce the cash required for your business attractive.
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A few of the more common practices of the lean manufac- turing are:
• Just In Time: Producing only what is need, when it is need, and in only the needed quantities; reducing work-in-process inventory.
• Kanban: A card that signals production of a set quantity of goods once that number of goods has been used by a customer process.
• Production leveling (or heijunka): Spreading procuction evenly over time; reducing batch sizes to one.
• Setup time reduction: Reducing the time to changeover between producing different products; required level- ing production.
• Standardized work: Documented, detailed work proce- dures religiously followed by everyone doing the job such that the work is performed the same way every time.
• Multi-skilled workers: Workers trained in multiple job tasks so work can be assigned flexibly to balance the line dynamically.
The philosophy of identification and elimination of the waste is:
• The central theme of a lean manufacturing production system.
ping (VSM) is a collection of all actions value added as well as non-value added that are required to bring a product or a group of products that use the same resources through the main flows, from raw material to the customers. These actions are those in the overall supply chain including both information and opera- tion flow which are the core of any successful lean operation. Value stream mapping is a special type of flow chart that uses numbers and symbols known as “the language of lean” to im- prove the flow of material and information.
Ulf K. Teichgraeber et al [4] stated that there is a need to un- derstand the entire manufacturing system in order to create VSM and gain maximum benefits, which are:
• In order to visually display where waste occurs in the process and to distinction between values add and non- value add activities (waste), a value stream map (VSM) is drawn because the main principle of lean manufac- turing is to reduce waste in an operation, such as long lead times, defects and material waste.
• Shows the linkage between material and information flow of a product
• Identifies all types of waste in the value stream and take steps to try eliminating them.
• Once the current state VSM is created, it becomes the baseline for improvement and for the creation of a fu- ture state value stream mapping FSVSM. The FSVSM
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• A dynamic and constantly improving process depend-
ent upon understanding and involvement by all em-
ployees.
• Successful implementation that requires all employees
must be trained to identify and eliminate waste from
their work.
• Waste exists in all work and at all levels in the organi-
zation.
There are seven types of wastes [1]:
• Over-production, producing more than needed, and/or
producing faster than needed.
• Wait time, idle time that is produced when two de-
pendent variables are not fully synchronized.
• Transportation, any material movement that does not
directly support a Lean Manufacturing System.
• Processing, effort that adds no value to a product or
service.
• Inventory, any supply in excess of process require-
ments necessary to produce goods or services Just in
Time.
• Motion, any movement of people that does not contrib-
ute added value to the product or service.
• Reworks or Corrections, repair of a product or service
to fulfill customer requirements
Jim Womack et al. [3] presented that a Value Stream Map-
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• Mahmoud A. El-Sharief is currently Assistant professor in mechanical
Engineering Department, Faculty of Engineering, Assiut University,
71516 Assiut, EGYPT. E-mail: msharif@assiut.edu.eg)
can then be used as a world class manufacturing im-
plementation road map.
The procedure of the VSM creation is:
1. The Current State Value Stream Map
• Select the product family that will be mapped
• Decide what the goal for improvement will be
• Form a team to collect data and map the select- ed value stream
• Walk the flow and collect data on the value stream
• Value Stream Map terminology
• Value stream map standard symbols
• Draw a map of the value stream
2. Analysis the Current conditions
• Identify value added and waste
• Choosing appropriate waste reduction meth- ods and reconfigure process to eliminate waste and maximize value
3. Take actions and create the Future State Value Stream
Map.
Value stream maps are created for a single product, or a fami- ly of products. A family isa group of products with similar
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routings, similar process times, and customers with similar needs and demand rates. ‘Similar’ means that while there may be some variation, it is recognizable that all members of the group have the same set of core operations. Products may vary by color, size, or one or two steps in the production pro- cess. H.J. Warneckeet al. [5] presented the reason for concen- trating on a family of products is that lean improvements such as cells and kanban systems only work well if all products in the stream are similar in process times and routings.
There are different opinions about what the goal should be. First opinion for Advocates of the TPS style of lean manufac- turing will claim that production at takt time is the only ac- ceptable goal of the improvement process. Second opinion is that takt time is an outcome, not a design parameter. Whether the goal is to reduce cost by eliminating waste, or to produce in time with customer demand, value stream mapping is an essential tool, and it is independent of anyoneproduction phi- losophy.
Value stream mapping is the best done by a team in a work- shop format. This is because few people really understand the entire value stream, or have the knowledge to anticipate the
impacts of specific changes to it. A team with a variety of
• Time line: After the completion of the map, a timeline is drawn below the process boxes to indicate the production lead-time and value added time.
• Production lead-time: The time that a particular product spends on the shop floor from its arrival until its completion.
• Value added time: This time represents the sum of the pro- cessing times for each process.
• Process cycle efficiency = Value added time/ total cycle time
• Value Stream Map and Selected Standard Icons: VSM
symbols is not standardized and there are many variations.
Value stream map uses special symbols to represent where there is waste in manufacturing processes and to help find ways to eliminate that waste.
The current state map is simply a set of connected operations and queues starting with a supplier and ending with a customer. After the data collection is complete, all of the data can be collected in a single spreadsheet or transferred directly to the value stream map from each team member’s notes as follows:
• Draw customer, supplier and production control icons.
• Enter customer requirement.
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members is therefore required.
The team members should have a form for gathering data on each step (including work centers, queues, raw materials arri- val, shipping to the customer, and operators).
• Value-added activities: An activity that transforms or shapes material or information, the customer wants it and it is done right the first time.
• Non value added – needed activities: Activities which caus- ing no value to be created but which cannot be eliminated based on current state of technology or thinking required (regulatory, customer mandate, legal).
• Non value-added activities: Activities that consumes re- sources but create no value in the eyes of the customer.
• Cycle time:Cycle time is the time required to execute activi- ties in a process (including value-added and non-value added time)
• Takt time:Measure of customer demand - how much is re- quired in the time available
Takt Time = available time / time customer demand rate for available time
• The information flow: Indicates how each process will know what to make. The information flow is drawn on the upper portion of the map. The information flow is drawn from right to left on the map and is connected to the material flow pre- viously drawn.
• Calculate takt time.
• Draw outbound shipping icon and truck with delivery fre- quency.
• Draw in bound shipping icon and truck with delivery fre- quency.
• Add process box, in sequence, left to right.
• Add collected data box below.
• Add communication and information flow arrows.
• Obtain process attributes. Add to data box.
• Add operator symbols.
• Add inventory locations and level in days of demand and graph at bottom.
• Add push and pull icons.
• Add other information.
• Add working hours.
• Add value and non-values add time.
• Calculate total value and non-value add times.
Value stream mapping is a process designed to reduce lead-time to make product flow and to eliminate waste (non-value added opera- tions or activities). All for purpose of meeting customer demand at the lowest cost and with the highest quality [6]. Lean thinking relies on recognizing the “seven wastes” over-production, over-processing, inventory, motion, scrap, waiting and transportation. With simula- tion, it is easy to avoid the traditional problem of eliminating waste
at an operation where there is no net gain [7]. That is because the
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revised system’s performance can be compared to the current state to
see the impact of the proposed change.
Matthias Holweg et al. [8] stated that there are many waste elimina- tion methods that can be applied in a given situation, but selecting the appropriate method is not easy. Consideration must be made of cost disruption to other product families and parts of the production system, operator skills, maintenance, reliability, space and so forth.
The future state map is nothing more than an implementation plan that highlights what kind of lean tools are needed to eliminate the waste, and where they are needed in the product value stream. Creat- ing a future state map is done through answering a set of questions concerning issues related to building of the future state map and technical implementation related to the use of lean tools. Based on the answers to these questions one should mark the future state ideas
directly on the future state map. After creating the future state map,
• Encourage proper maintenance activities
• Provide a visual control of operations or activities
• Provide flexibility to adapt to changing conditions
A lean plant/shop floor layout have significant impact on the organi- zation's performance. Material and information flow is organized and streamlined. A lean plant layout is an effective way to improve prof- itability and throughput while increasing safety [9]. The elimination of wasted movement and implementing line balancing can signifi- cantly reduce costs and reduce cycle time to provide speed of deliv- ery and improved throughput.
Figure 1 shows an example for process flow analysis, which allows visualization of the movement of people or materials. This can quickly lead to an understanding of where inefficiencies exist and how to eliminate them. It is critical to layout work in the order it will occur to the greatest extent possible, in order to eliminate the waste of movement.
Fig. 1. Processes flow
the last step is to carry it out by trying to implement the different
Receiving, Inspection and
Row Material
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ideas generated by the future state map on the actual value stream.
Layout is an integral part of a Lean manufacturing strategy. Mean- ingful restructuring requires corresponding physical changes in the layout. Flow is one of the main five concepts of lean manufacturing, but in order to achieve smooth flow important decisions must be taken and that is to plan and design a layout that is integrated to other concepts of lean along with the flow.
Facility layout decision is based on criteria aimed at creating an ef- fective and efficient workflow and high standard production. Con- versely, a layout re-design can be the catalyst for re-structuring. A layout project properly done can demonstrate the need for change to an organization reluctant to tear itself apart and rebuild. Therefore, requirements for effective layout are:
• Minimize material handling costs
• Utilize space efficiently
• Utilize labor efficiently
• Eliminate bottlenecks
• Facilitate communication and interaction between workers, between workers and their supervisors, or between workers and customers.
• Reduce manufacturing cycle time and customer service time
• Eliminate wasted or redundant movement
• Facilitate the entry, exit, and placement of material, products, and people
• Incorporate safety and security measures; Promote product and service quality
Shipping
Heat
Treatment
• Name: Cement sacks factory
• Area: 6250 m2
• No of products: 2X (for itself & other factories)
• Layout: Figure 3 represents the cement sacks factory layout
Figures 2 to 11 show the sequence of production processes in the
Cement Sacks factory case study.
Fig. 2. Transport the craft paper roller with the forklift
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Fig. 3. Set the craft paper roller in the beginning of the production line
Fig. 4. Get ink from ink tank (printing)
Fig. 8. Guides to improve the overlapping process and movements
Fig. 9. Sacks stick (tubing)
Fig. 5. SelecIt the suJitable Crile
Fig. 6. Installation of the Crile
SEFig. 10. RPreparing for the final sacks (separation)
Fig. 11. Final product ready to store
Fig. 7. First steps in sacks forming (overlapping)
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Table 1. Processes requirements
Step | Process Description | No. of Worker | Distance (m) | Task time (min) | Wait time (min) |
1 | Remove cover | 1 | 12.5 | 2:00 | 0 |
2 | Printing | 1 same worker | 12.5 | 00:05 | 02:00 |
3 | Overlapping | 1 same worker | 12.5 | 00:05 | 0 |
4 | Guides | 1 same worker | 12.5 | 00:05 | 0 |
5 | Glutinous | 1 same worker | 12.5 | 00:05 | 0 |
6 | Tubing | 1 same worker | 12.5 | 00:05 | 0 |
7 | Separation | 1 same worker | 12.5 | 00:05 | 0 |
As reported before, VSM is the tool of lean manufacturing, "Simple Follow product's production path from customer to supplier and carefully draw a visual representation of every process in the materi- al and information flow". VSM is all the actions (both value added
and non-value added currently required to bring a product through
the main flows essential to every product. Figure 12 presents the
current layout of the Cement Sacks factory.
Figure 13 presents the current VSM of the Cement Sacks factory.
VSM Data Set:
• Product flow unit of 10,000-cement packs.
• Handling using two forklifts with speed = 47 m/min each.
• Coding time for one 5,000 sacks pallet = 1 min.
Product:
Cement packs consist of:
• Craft paper
• Glue
• Ink
Customer Requirements:
• Pallet=5000 packs.
Working Time:
• Shift time = 6.75 hr.
• Break time = 1.25 hr.
Manufacturing Process:
Manufacturing processes for a sample consists of 10000 packs are shown in table 2
Transport the f inal product to the f inal inventory wi th fork lift
24 m 45 m 15.909 m
100 m
72 m
Transformer
Electrical
Panel
Bot 1 Tuber 1
Compressor
Bot 2
Gate 1
12.5 m
Fork l ef t path depends o n working production li ne
Final product inventory capacity
(5 million bag)
Elevator
Glue stati on
cafeteria
Elevator
U p Up
Bot 3
Bot 4
Bot 5
Bot 6
Line 2
Line 3
Tuber 2 Gate 2
Tuber 3 Gate 3
Gate
Fork l ef t path depends o n working production li ne
Fork l ef t path depends o n working production li ne
Fork l ef t path depends o n working production li ne
Change clothes room
Toilets
Transp ort the bag s with fork lift Bags Temporary storage ar ea
from the acti ve line to th e
tempo rary storag e area
Waste material
112.36 m^2
Raw material inventory
(craft paper) – Inventory capacity 4000 ton
SCALE: 1:500
Fig. 12. Current Layout of the Cement Sacks Factory
Fig. 13. Current VSM of the Cement Sacks Factory
Column
Table 2. Value and non-value added times of the manufacturing processes for the cement sacks factory case study
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From raw material inventory
- Handling of raw material
- First stage of production:
- Manufacturing primary product (size = 2 ballet)
- Handling primary prod- uct to the final production steps
to the production line by using forklift.
It includes the following processes:
• Printing
• Cutting
• Glowing
• Tubing
• Separation
• Collecting
By using two forklifts to handle the two ballets in the same time.
This activity time includes:
• The time for set the last
220 packs on the pallet.
• Forklift down time.
• Forklifts time to handle pallets between the two production stages.
It includes the following processes:
• Feeding
Non value added time =
48 sec
Value added time =
2727.27 sec
Non value added time =
36 sec
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- Second stage of produc-
- Final manufacturing steps
- Handling final product to the temporary inventory
• Opening
• Valve installation
• Gluing
• Closing
• Collection
The time for this process includes:
• The time for set the last
220 packs on the pallet.
• Forklifts caring and down time.
• Forklifts time to trans- fer the pallets.
• Coding time.
Value added time =
2727.27 sec
Non value added time =
147.809 sec
- Temporary inventory This step is taken for sacks to drying glue
Value added time =
9613.33 sec
- Handling pallets to the final product inventory
This uses two forklifts to handle the two pallets
Non value added time =
180 sec
- Final product inventory Final sacks storage Out of process descrip- tion
• Break down and repairing time for one cycle = 8 /45
= 0.178 min.
• Total value add time =15067.87 sec.
• Total non-value added time = non-value add time +
break down time + losses time.
- = 411.809 + 480 + 300.
- = 1191.809 sec.
• Process time = 15067.87 +1191.809 = 16259.679 sec.
• Process efficiency = 15067.87/16259.679 = 92.67%.
These value stream maps show the effect of applying lean think-
ing on the efficiency of the production lines for the Cement Sacks Factory as shown in table 3. Figures 14 and 15 show the modified layout and VSM respectively of the Cement Sacks Factory.
Table 3. Impact of the lean thinking on the Cement Sacks Factory
Modification Reasons Result
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• The net profit for one bag = 0.2 L.E
• The daily bag production 90000 bags
• The daily net profit = 90000*0.2= 18000 L.E
After reviewing budget and income statement, the total cost =
205600L.E and capital recovery rate= 205600/18000 = 12 days
The non-value added time will be reduced to =315.409 sec in- stead of 1191.809 sec. Therefore the efficiency of the production line cycle will be increased to = 94.98 % instead of 92.67 %.
Value stream mapping has proven to be an effective way to ana- lyze a company’s current production state and point out problem areas. The visual nature of value stream mapping, by combining information and material flow on one map, depicts how the two relate to the lead-time. By applying lean thinking and VSM tech- nique in the Cement Sacks Factory case study, there are many benefits can be obtained as:
• Reduction in the handling cost which add to the pro- duction cost.
• Reduction in the forklift way from the temporary in- ventory to the final product inventory.
• Reaching the maximum benefit of the forklift.
• Reduction in the time required for handling between temporary and final product inventory to 100.85 sec instead of 180 sec. This means that the reduction per- centage is 56.
• Conveyor length = 12 meter
• Conveyor width = 4 meter
• Conveyor velocity under zero load = 120 m/min
• Conveyor velocity under max. load = 40 m/min
• Conveyor max load = 15 ton
Table 4 shows budget statement (this budget will show the cost of three motorized conveyors)
Table 4. Cost review for roller conveyor
There are many factors contributing to the lead-time, that is, order
handling, planning, procurement, delivery, inspection, manufac- turing, handling, picking, packing and delivery. This paper focus- es on analysis of manufacturing data for reducing lead-time and addresses within Make and Plan. Future work can be carried out on design, order handling, delivery or reassembly since those are also important factors affecting production and lead-time in the company’s operations.
Components | Number | Cost per three units |
Roller conveyor | 3 | 15000 L.E |
Chain belt | 3 | 600 L.E |
15 hp. Driver motor | 3 | 190000 L.E |
Total cost= 205600 L.E |
• After applying this modification, the handling time between tubers and bottomers, will be reduced by
17.25 sec.
• The production time for one cement bag = 0.655 sec.
• This will show that in the 17.2 sec. will produce 27 bag
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24 m 45 m 15.909 m 100 m
72 m
Tra nsforme r
Elect rica l
Bot 1
Tu ber 1
Ga te 1
Fork left path depends on working production line
Pane l Bot 2 12.5 m
Fin al p rod uct inv en tory
c apa ci ty
(5 mill ion ba g)
E leva tor
Gl ue
st a tio n
c afet eria
E leva tor
Up Up
Bot 3
Bot 4
Bot 5
Bot 6
Line 2
L ine 3
Tu ber 2
Tu ber 3
Ga te 2
Ga te 3
Ga te 4
Fork left path depends on working production line
Fork left path depends on working production line
T ra nsp ort the bag s with fork lift from the the temporary s to ra ge area to t he fina l produc t invent ory
Cha nge c lothes room
T oilet s
Transport the bags with forklif t from the active line to the temporary storage area
Bags Temporary storage area
Compressor
Wa ste ma teri al
112.36 m^2
R aw mat erial invent ory
(c ra ft pap er) –
I nvent ory ca pa cit y 4000 t on
SCALE: 1:500
First modification: Column
Handling between tuber and
Seconde modification
bottomers using roller conveyor to transport tow ballet s fillin g with 10000 packs
Ramp
Third modif ication :
Fill tow ballet s with 10000 Inventory
packs ready t o us e in next work
Change factory door position
Change final product inventory door pos ition
Conveyor specification:
Conv eyor v elocity with zero load = 120 m/min
Conv eyor v elocity with max. load = 40 m/min
Max. load = 15 ton
day
Fork lift
toilet
truck
Power = 15 hors power
Rolle r conveyor
Fig. 14. Modified Layout of the Cement Sacks Factory
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Fig. 15. Future VSM of the Cement Sacks Factory
[8] Matthias Holweg, “The genealogy of lean production”, Journal of
Operations Management, Vol. 25, 2007, pp. 420–437.
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