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Keys for Redesign Industrial Facilities in a Current Productive Environment
Pablo Carrizosa I. Eng1, a *, Oliver Rubio M. M.Sc1,b, Julián Mora O. Eng1,c
and Álvaro Guarín G. PhD 1,d
1Universidad EAFIT - carrera 49 N° 7 Sur – 50 Medellín - Colombia - Suramérica [email protected], [email protected], [email protected], [email protected]
Keywords: Redesign methodologies, Dynamic value stream map, Discrete event simulation, Lean manufacturing, Manufacturing systems, Product lifecycle management
Abstract. Today companies don’t have time and resources availability to stop their production to
evaluate new layout and strategies, unless the results are guaranteed. Developing or redesigning
products, gathering them in a product family and creating product platforms can be expensive tasks
that represent a meaningful outlay for companies if they don’t have the adequate tools in order to
facilitate the work. Thus, it is important to define the most appropriate manufacturing system as
well as the performance of the chain value and the equipment layout in order to achieve an optimal
production with the best quality and the shortest times and production costs. Therefore,
computational tools, validated by working strategies and philosophies as Lean Manufacturing (LM)
and Product Lifecycle Management (PLM) become necessary. After the evaluation of products, the
value chain and the layout, these tools allow the construction of models and simulations as dynamic
Value Stream Map (dynamic VSM), to analyze the actual process functioning or future process
plans and PLM software, to estimate production flows, equipment and human labor requirements
without stopping the normal production activities and providing competitive advantages to the
company.
Introduction
The decision of establishing, modifying, moving or removing work stations in order to improve
the facility’s productivity is quite risky. Thus, they must be strongly supported. For this reason, a
series of steps are proposed, based on existing tools validated in industrial environments, which can
help companies to take decisions in order to achieve the plant’s redesign successfully. First, by
applying LM methods as VSM, the current state of the plant is analyzed in order to propose waste
reduction and upgrades in the facilities. Then, performing the simulation of production flows
through a software of discrete event simulation (DES) designed for PLM systems, allows to
intervene in the redesign of the plant to be able to make modifications to the current model and
evaluate the required improvements within what is known as a dynamic VSM, permitting the
development of a greater amount of analysis, process variations and generating possible scenarios
comparable to each other enabling a more accurate decision making.
The benefits offered by strategies such as Flexible Manufacturing Systems (FMS) and
Reconfigurable Manufacturing Systems (RMS), product families and platforms generation,
modularization processes as well as tools such as Integrated Computer Manufacturing (ICM) allow
to evaluate the best solutions for redesigning the plant whether or not the creation of Manufacturing
Cells (MC), different production lines or other strategies to form layout. A valid table model in
terms of cost and time reduction with an increase in the quality of both products and process is
looked for.
Approach
In order to redesign a facility layout, it is required to start by evaluating and inspecting the
products as well as defining product platforms and families that would provide an optimal
Applied Mechanics and Materials Vols. 752-753 (2015) pp 1312-1319 Submitted: 07.10.2014© (2015) Trans Tech Publications, Switzerland Revised: 04.12.2014doi:10.4028/www.scientific.net/AMM.752-753.1312 Accepted: 29.12.2014
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 181.133.161.17-14/02/15,23:00:14)
fabrication process. Manufacturing systems must be considered the starting point in order to
propose a production strategy and implement all the appropriated tools. The aim is to achieve an
adequate layout and resources use. For this, there are simulations technologies and validated tools
as VSM and other applicable LM methods. At the end, it is possible to define a layout by employing
computational tools that allow identifying not only the best work point's position, but also internal
transportation equipment, workers quantity, materials distribution, and much other information that
could be obtained doing an accurate analysis.
Products Evaluation
Redesigning industrial facilities not only must involve the production process. For optimal and
reliable results, products and product groups must be evaluated as well. Some methodological tools
allow the identification of efficiency in the fabrication process and facilitate the redesign decision.
An important example of this are: Design For X (DFX) and Design For Manufacturing and
Assembly (DFMA), where software like Boothroyd and Dewhurst[1] let to evaluate, according to
the projected product quantities, optimal processes and materials for the fabrication. These tools
also allow making a comparative analysis between different design alternatives.
Another important tool, called Design for Variety (DFV), evaluates product platforms families
and identifies which components are more important, reducing the impact of variety in product life
cycle costs [2]. In order to evaluate product families there can be applied the product line
commonality index (PCI). This index shows the possibility that products of the same family could
share parts effectively (modularity) reducing total parts number (multifunctionality) [3]. In DFX
there is a large variety of tools to explore depending on the product and process requirements.
The Production Technologies Research group in EAFIT University performed an academic
exercise where it was proposed to design and fabricate a chess board with all its pieces, which had
to be modular. Thus, all of them were made by several parts and some of these parts were common
for several pieces, Fig 1. For this exercise it was employed the methodology proposed in this
document in order to obtain a product, layout and production in an efficient and successful way.
Design, manufacturing and engineering computer assisted tools (CAD/CAM/CAE) were applied as
they are crucial in both academic and industrial environments nowadays. These tools not only allow
defining the product formally, but also help identifying the type of materials needed and the proper
quantities to produce each piece, as well as calculating resistance and physical characteristics of
each component and fabrication times.
Fig. 1 Modular chess conformation
Applied Mechanics and Materials Vols. 752-753 1313
Adaptable Manufacturing Systems
In the past, manufacturing systems were configured once, for a stable environment. Nowadays
turbulent environments demand facilities a permanent adaptability of their manufacturing systems.
Companies must leave behind old procedures and re-configure their organizations continuously.
Some of the most effective manufacturing systems used in the present are:
Cellular Manufacturing Systems (CMS). A cell is a group of work points, machines and
equipment dedicated to a process, a sub component or a whole product that is progressively
organized for a continuous flow between work stations without time loss. The most important
problem in CMS is the cell establishment according to family parts and machines group. Once this
problem is solved it enables any part to be processed within a cell with minimum interaction with
other cells [4].
Flexible Manufacturing Systems (FMS). The concept of Flexible Manufacture was introduced as
a response of a mass personalization necessity and a greater sensitivity to changes in products,
production technologies and market. The main objective in FMS is to show the cost-effectiveness
relation in manufacturing parts that can change over time, with shorter replacement lapses, in order
to achieve productivity and flexibility simultaneously [5]. The main FMS components are:
computer numerical control (CNC) machines, robots and material handling systems (MHS).
Reconfigurable Manufacturing Systems (RMS). These systems are designed to make fast
changes in the structure, hardware and software components in order to adjust production capacity
and functionality within a product family in a quickly way to respond to an unpredictable market
changes [5]. There are a number of technologies available today to achieve physical and logical
reconfiguration in manufacturing systems, but the implementation of RMS still requires additional
development of specific key technologies [6].
Fig. 2 Machine functional reconfiguration [7]
In the chess exercise, for pieces manufacture, prototyping CNC lathes and mills were used. It
required a CMS with a fluid transit of the parts between workstations and a flexible and
reconfigurable capacity to allow the fabrication of the different kinds of pieces in the same
equipment. Equipment layout, conveyor utilization and storage systems help increasing productivity
and reducing times. Thus, generating a 3D model of the manufacturing cells allow the visualization
of the different work spaces, helping to improve the plant distribution and becoming a base to
further simulations.
Fig. 3 is a render of the didactic production micro plant for chess modular pieces. There are two
main manufacturing cells, each one with a materials rack, the proper CNC machines and
transportation conveyors there is also an assembly line and a side area with computers to simulate
and evaluate the process.
1314 Advanced Engineering and Technology
Fig. 3 Didactic production micro plant for chess modular pieces
Value Stream Map Visualization.
In order to make improvements to the plant, the first thing to do is a process map to identify the
most important issues involved with the manufacture and that are related with time, quantity and
quality when implemented. Lean manufacturing has shown that production processes can be
optimized through highly applicable and simple tools that add value to the process. According to
Ohno [8], "LM is widely considered the major step in the development of products beyond the mass
production of Ford." The theory behind the lean philosophy consists in creating more value with
less. During the last decade, competition among organizations has become a matter of not only
productivity, but also the overall performance of the supply chain [9].
One of those tools are valued maps (VSM) that allow visualization of the current and future
production flows, tracing the waste generated in the processes and drawing the route to identify
opportunities for improvement. A value chain is defined as the group of activities (value and non-
value added) that is employed to produce a product or service, or a combination of both for a client
[10]. These actions consider the flow of information and materials within the global supply chain
[11]. In order to identify the source of the waste, non-value added activities and improvement
opportunities, the value chain must be mapped using tools and systematic techniques such as VSM
[10].
Fig. 4 Value stream map scheme [10]
Applied Mechanics and Materials Vols. 752-753 1315
Process Simulation
Discrete event simulation (DES). If the VSM is the picture of the process, the simulation is the
video. DES programs simulate production flow in a system, tracking state changes in model
components when they occur. Unlike the continuous simulation, where time runs in a continuous
state, in the DES time jumps from one event to the next scheduled event, considering only the
necessary processing times. This stochastic technique is selected due to its capability of dealing
with the uncertainty resulted by customer demand patterns, the variability in operation times and
resources availability in addition to high variance in handling systems [12].
Production flow simulation has several uses as: Creating a realistic virtual model of the process
operation; determining and optimizing processing times; evaluating the influence of errors in the
process; identifying bottlenecks and shutdowns in the production flow; determining labor
requirements; evaluating different layout alternatives; optimizing the sequences at production
orders; improving operation control strategies; comparing different scenarios depending on the
production requirements; validating the process design in the planning process; reducing work in
process (WIP); assessing the impact of capital investment; improving production flow (throughput),
resources utilization and the use of facilities; determining storage buffers capacity, number of
required forklifts and conveyors, schedules and production sequences [13].
According to the Association of German Engineers (VDI) Policy 3633, it is estimated that 20%
of the investment costs are influenced by the results obtained by simulating. A reduction around 2%
and 4% of the investment costs is obtained, and only around 0.5% and 1% of the investment costs
correspond to simulation costs [10].
Simulation Phases. The VDI describes three phases that guide simulation users through production
and logistics.
Fig. 5 Phases for a simulation study according to the Association of German Engineers VDI [13]
Selecting the DES Software. At the time of deciding which simulation software to use, it is
necessary to take into account different factors. There are several options of discrete event
simulation software in the market, some of them are more powerful than others like simul8 and
promodel, both have a quick learning curve and allow running simulations with a very good degree
of complexity. There is also DES software like Dassault Sistems or Siemens, each one of these are
part of a suite pack to work on the Product Lifecycle Management (PLM). PLM represents the
missing link between CAD, digital manufacturing and simulation. It also represents the virtual
1316 Advanced Engineering and Technology
world and the interfaces with the enterprise resource planning system (ERP) supporting the physical
side of modern manufacturing throughout the supply chain [14]. Therefore, a simulation program
associated with a PLM platform enables interaction and information transfer with other programs,
involving all those that are related with the process.
VSM and Simulation. The combination of Value Stream Maps and simulation is a powerful
strategy that is called dynamic VSM. The structure and symbology of the VSM are used in a
simulation program making this analysis more truthful and realistic; in consequence the future
model can be more accurate and really predictable. Within the range of DES software it is possible
to obtain libraries to do dynamic VSM. This software has the necessary LM tools, like kanban or
fifo, to formulate the VSM. In Figure 6 it can be seen a typical structure of VSM in a Siemens plant
simulation.
Performing a dynamic VSM instead of classic VSM, represents benefits like: The ability to
examine various product groups and process variations; a reliable dimensioning of the capacity
requirements of the system; real parameters are determined such as delivery reliability, aggregate
value, delivery times and inventory; dynamic effects such as fluctuations in demand,
malfunctioning machines, shift changes and maintenance of equipment are considered; the
calculation of kanban levels and sizes of containers are based on the dynamic fluctuations;
quantifiable results to compare current and future states.
Fig. 6 Dynamic VSM in plant simulation [15]
Layout Analysis
Once the product structure, manufacturing systems applicable to the process, production flows
and value chain behavior are known, it is necessary to organize the physical space of the plant to
operate in the most optimal way. Arranging the layout of a factory depends on many factors that
must be analyzed. The order of processes to be performed initially determines the layout of the
equipment, manufacturing cells and production lines. There should also be considered the storage,
access routes, employees, carriers, etc. Making changes to the distribution requires strong
arguments due to its impact in terms of time and money. For a successful layout diagnosis, PLM
offers simulation analysis based on the facility plans, even in 3D. It is important to give the program
as much data as possible; the exact trajectory of each piece, the transformation that it suffers,
process and transportation times, location of storage places and shipping area, the devices and
Applied Mechanics and Materials Vols. 752-753 1317
routes to move the parts, etc. All this information allows the software to calculate and produce
reports that facilitate in an enormous way decision making.
In the layout analysis, the typical elements to consider are: Determining manufacturing cells to
manage more effectively the flows, share machinery and perform multiple operations in different
components, generating a cluster matrix; generating a quick view of the flows in general, product
flow diagrams, equipment utilization reports, material flow and handling; timing analysis in
material handling activities; creating routes and schedules for the everyday forklift deliveries
minimizing delivery times; organizing and classifying products in the storage area; packing and
organizing products into containers for shipment, generating a detailed operation report [15].
Fig. 7 Layout simulation in Tecnomatix Factory Flow [15]
Conclusion
The steps, tools and considerations presented in this paper, are the main elements of the path that
nowadays companies should follow in order to redesign or improve the production process. The
facility examination, starting from the product evaluation, considering production strategies,
distribution and use of equipment, and the storage and dispatch; combined with the use of validated
philosophies as successful as Lean Manufacturing, all within the digital environment, offers
amazing possibilities to be assertive in decisions making, enabling to use design and simulation
tools that make work easier and allow significantly reducing time and production costs.
1318 Advanced Engineering and Technology
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