2013

Ahmad Syihan IsmailAhmad Syihan IsmailAhmad Syihan IsmailAhmad Syihan Ismail

IE 5617-Lean Concept and Applications

Industrial Engineering

Northeastern University

RECONFIGURABLE

Ahmad Syihan IsmailAhmad Syihan IsmailAhmad Syihan IsmailAhmad Syihan Ismail

Lean Concept and Applications

Industrial Engineering

Northeastern University

LEAN PRINCIPLE ON

RECONFIGURABLE MANUFACTURING SYSTEM

LEAN PRINCIPLE ON

MANUFACTURING SYSTEMS (RMS)

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TABLE OF CONTENT

TABLE OF CONTENT .................................................................................................................. 1

I. BASIC LEAN PRINCIPLE .................................................................................................... 2

II. MANUFACTURING SYSTEMS ........................................................................................... 3

III. CONCEPT OF RECONFIGURABLE MANUFACTURING SYSTEMS (RMS) ................ 5

IV. LEAN TOOLS IN RMS .......................................................................................................... 6

V. CONCLUSION ....................................................................................................................... 9

REFERENCES ............................................................................................................................. 10

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I. BASIC LEAN PRINCIPLE

Lean principle recently becomes prominent tools since the competition being tighter in

global market. The basic idea was developed by Toyota with Toyota Production System

(TPS) in late 1980s which focuses on eliminating waste, reducing inventory, improving

throughput, and encouraging employees to bring attention to problems and suggest

improvements to fix them [1]. Figure 1 show how the TPS works in Toyota which has been

successfully used and provide continuous growth in term of net profit, sales performance,

and process effectiveness.

Figure 1 Toyota Production System

Just In Time (JIT) is one of famous tools that control the inventory order as much as they

need at a moment. The other tool is Kanban or CONWIP (Control Work In Progress) that

manage the flow of material in manufacturing step. Andon cord also a good tool that able to

prevent the flow of defect on product and fixed immediately.

Womack redefined TPS or “The Toyota Ways” as another term that was introduced by

Jeffrey Liker in his book, into lean principle which is aiming to deliver value in product that

meets the customer needs. The main focus is how to discover the waste in entire process and

eliminate it. To do that, he introduced five lean thinking to accomplish lean target which are

Value, Value Stream, Flow, Pull, and Perfection [2].

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By exploring what customer need on the product, each company able to define what kind

of value that would be delivered to the customer and precisely estimate demand. Next step,

stream of value should be able to found in the manufacturing or process from upstream to

downstream. By looking at the current state of value stream though Value Stream Map

(VSM), some waste or bad process have to be noticed and easily introduce a refinement

process which provide shorter cycle time, higher productivity, and possibly lower production

cost. The improvement process doesn’t work unless Pull System implemented which is based

on the demand. To preserve the improved system, pursuing perfection is obligation to

guaranty the system work continuously and long lasting.

II. MANUFACTURING SYSTEMS

As the global competition being tighter, global market provides serious effect to the

demand that easy to change. By the variety of customer need, every company should be able

to provide the variety of product with different requirements, specifications, and abilities. In

the other hand, some companies struggle with resources issue which has huge manufacturing

facility and has higher operational cost but run in low utilization.

The fluctuation of demand gives significant impact to manufacturing processes and

strategies. Most manufacturing companies use two previous prominent systems which called

Dedicated Manufacturing System (DML) and Flexible Manufacturing System (FMS). DML

is the simple system that can be adjusted the productivity level but not designed to handle

multiple products in a short time. In the other hand, even those are not part family, FMS has

ability to run production process of multiple products that consist of general-purpose

Computer Numerically Controlled (CNC) machines and other programmable form. However,

its productivity could not be scaled up at the moment.

To overcome it, new manufacturing system should be considered which called

Reconfigurable Manufacturing Systems (RMS). This system recently developed and invented

by several experts in Industrial field. Here is the graph that shows how the RMS works in

capacity, cost, and functionality parameter and able to respond the market change, compared

to DML and FMS. This performance truly matched with the lean principle that able to catch

the different customer need but able to keep high production rate.

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Figure 2 The comparison of three systems, RMS, DML, and FML in term of capacity, functionality, and system cost

The detail comparison was shown in table below with some additional parameters such as

system structure, system focus, machine structure, and production cost of each part.

Table 1 Comparison of Manufacturing Systems

Parameter DML FMS RMS

System Structure Fixed Adjustable Adjustable

System Focus Part Machine Part Family

Machine Structure Fixed Fixed Adjustable

Scalability No Yes Yes

Flexibility No General Customized

Productivity Very High Low High

Machine Tools DMT CNC RMT

Cost per part Low (single part, fully utilized)

Medium (Several parts )

Medium (Parts at variable demand)

By several advantages of RMS that easily found from the table above such as

changeability of the system structure and machine structure, easiness on scalability, and

possibility on simultaneously operating tools, definitely RMS is a solution of future

manufacturing system to catch global competition that require responsiveness of

manufacturing strategies. The only disadvantages that probably happen are the productivity

that not as high as DML system and cost part that relatively high. In addition, because of the

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volatility market which provide difficulties on predict future demand, it is hard to define a

suitable time to apply this system.

III. CONCEPT OF RECONFIGURABLE MANUFACTURING SYSTEMS (RMS)

The summary of core characteristics of RMS as a global view of integrated system is

explained below [3]:

1. Customization, the flexibility to produce several part in specific range (family part),

2. Convertibility, the ability to transform the function of system and machine,

3. Scalability, the ability to adjust the productivity and able use crossover configuration,

4. Modularity, the ability to change the control and module to different requirement or

specification,

5. Integrability, the ability to flow the product, information, and control interface,

6. Diagnosability, the ability to inspect the quality of product.

To fill the gap of customization, RMS require another unique tools which called

Reconfigurable Machine Tool (RMT) that hardly to found neither in Dedicated Machine

Tools (DMT) or Computer Numerically Controlled (CNC). Another tool that covers

diagnosability and quickly responds the defect in the product is RIM (Reconfigurable

Inspection Machine). The complete system will be shown by the picture below.

Figure 3 a whole system RMS featured by RMT and RIM

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Some practical mathematical methods and common equations are used to find the best

configuration. Here is the equation that used to calculate minimum number of machine (N)

that needs daily demand (Q), total machining time for the part (t), and machining reliability

(R).

� = ��������� ��� (1)

The basic equation for calculating the number of possible RMS (K) also provided below,

by consider possibility of the number of stages (m) that can be selected. Noted that Eq. (2)

applied to calculate N machine which arranged in m stages (up to m=N) and Eq. (3) applied

to calculate the number of RMS configuration which m equal to N. By both Eq. (2) and (3),

we can defined the number of symmetric configuration and eliminate asymmetric

configuration as well.

� = ∑ �� − 1� − 1�

���� = 2��� (2)

� = � �����!�����!�����!� (3)

Next, we should limited the number based on the ability to meet the cycle time that based

on the customer demand and total production time, or in lean terminology is known as Takt

Time by the equation below.

�� !!"�# = ������ �$�%$ (4)

IV.LEAN TOOLS IN RMS

The detail of lean concept that implemented in RMS will be shown in small part of

system which called Cell. It much easier to identify tools that used in the system and basic

value of lean that each tools support. Pull system play a big role in the system that shows

how the lean principle works. It would give several inputs such as demand, product

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specifications, and production timing and endorse the system to responds the changes as

quick as possible. The detail of tools will be described below.

U-Shaped Cell is a preferred shape of cell design that eliminates one of 8 types of waste

in lean thinking, unnecessary movement. When one step is done, the workers just simply turn

around to another step at the place [4]. Thus, the added value process moves around without

any additional movement of worker at that cell.

Figure 4 a single cell machine with U-Shaped arrangement

Another feature is Information Board that provides the detail information of work

process, standard work at specific cell, and repair procedures. In addition, it should be easy to

read by worker and attached neatly in cell. Indeed, all procedure that mention earlier should

support the 5S or mostly people know as Japanese Kitting Tools.

RMT (Reconfigurable Machine Tool) is one of important tools that bring the character of

RMS, customization. The context of customization is this machine able to do several

machining jobs, but in specific range of dimension. For example, one machine with three-

axis able to finish the milling process on two type of cylinder engine head with different

angle with respect to horizontal: 300 and 450. In case, using six-axis machine (CNC), surely

those axis are barely used yet when produce the engine which mostly waste the axis of

motion and has lower utilization of all axis. RMTs surely help enterprise to reduce waste of

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functionality and resources [5]. It also enforces the engineer to a design a common part that

used into diverse product. The picture below shows the prototype of RMT that utilized by

three-axis motion.

(a) (b)

Figure 5 (a) Two types of engines, and (b) Prototype of three-axis RMT

In term of scalability performance, each machine has to be attached by four-small wheels

in every edge. This feature will help worker to adjust the position of machine from the

current to different configuration. Sometime machine should be added to reduce cycle time

when the demand is high. In another occasion, a configuration required small number

specific RMT to reduce space floor. Perhaps, in same facility another manufacturing

configuration would be placed in different space floor.

To improve the quality of product, every cell should be featured RIM (Reconfigurable

Inspection Machine) that able to diagnose any defect that appears immediately during the

normal production and easy move to different position. This feature meets the improvement

concept that endeavor the quality of every product. Similar to Andon Cord, this machine will

detect the defect and deliver the signal to worker give a treatment on it.

Beside several tools that have been mentions above as a basic tool which characterize the

system, the other additional tools such as Kanban and single-piece-flow also able to adapt

into system. Kanban tools are seeking the inventory level in each cell managed the number of

material that allowed to go to next cell. One-piece-flow also helps the worker to control and

monitor the material flow in specific amount and tackle the overproduction issue.

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V. CONCLUSION

Reconfigurable Manufacturing System (RMS) has not applied widely in modern

manufacturing. Moreover, it need time to prove that the system is able to tackle global

change and find the mature design so the cost of production would be reduce significantly.

However, by bringing up the Kaizen (continuous improvement) into development process, it

would be the answer of several obstacles that faced by most manufacturing enterprises

nowadays.

In term of lean practice, RMS plays huge role as a lean agent in manufacturing system

which keeps pursuing the perfection. Each component of RMS has unique characteristic and

represented the soul of lean principle. In addition, the other lean tools also easy to be adopted

to RMS which should consider the need and the significant improvement that company earn.

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REFERENCES

1. Stump, Brandon, Fazleena Badurdeen. “Integrated Lean and Other Strategies for Mass

Customization Manufacturing: A Case Study.” Journal of Intelligent Manufacturing

(2012) 23: 109-124.

2. James P. Womack and Daniel T. Jones, (2003). “Lean Thinking: Banish Waste and

Create Wealth in Your Corporation”, New York: Free Press.

3. Koren, Yorah and Moshe Shpitalni. “Design of Reconfigurable Manufacturing Systems.”

Journal of Manufacturing Systems. Volume 29, Issue 4, 2013: 130-141.

4. Lean Manufacturing: Principles, Tools, and Methods. 2009. Version 2.5. Bosch Rexroth

Group.

5. Landers, R. G., B. K. Min, Y. Koren. “Reconfigurable Machine Tools.” CIRP Annals –

Manufacturing Technology. Volume 50, Issue 1, 2001, Pages 269-274

6. Chahal, Virender. “An Advance Lean Production System in Industry to Improve

Flexibility and Quality in Manufacturing by Implementation of FMS and Green

Manufacturing.” IJETAE. Volume 2, Issue 12, December 2012

7. Wang, Wencai, Yorah Koren. “Scalability Planning for Reconfigurable Manufacturing

Systems”. Journal of Manufacturing Systems 31 (2012): 83-91