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Task description
Title of Master Thesis:
Entwicklung und Auswahl von Handlungsstrategien zur Planung
von Betriebsmittelrekonfigurationen
Inv.- Nr.: 00/00
Author: Ada Poraqi Supervisor: Jonas Koch
Start: 01.10.13 End: 07.04.14
Situation:
In the last years, changeability for manufacturing resources became one of the main paradigms in manufacturing planning. To improve changeability, modularization of machines, devices and equipment has been identified as an important enabler. In order to identify e.g. the appropriate approach, depth and degree for modularization, specific information of e.g. the manufacturing resource, process and product requirements are required.
Objective:
Main objective of this thesis is the review, categorization and evaluation of existing types of manufacturing resources and modularization approaches for these resources. Also, sources of information about potential influences causing / requiring modularity of manufacturing resources should be identified and allocated to manufacturing resource modules. Based on these results, a concept is to be developed to structure, categorize and allocate manufacturing resources, their modules and relevant information about influences.
Approach:
Review of enablers for changeability and especially the enabler “modularization” of manufacturing resources
Analysis and evaluation of modeling approaches, methods and tools for modularization (e.g. approach, depth, degree of modularization, modularization structures)
Review, analysis and evaluation of information required for planning of modularization / causing / requiring modularity of manufacturing resources
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Development of a concept to cluster and allocate relevant information about influences with manufacturing resources and their modules
Agreement:
By the academic supervising of Mrs. Ada Poraqi by Mr. Dipl.-Ing. Jonas Koch intellectual property of the iwb became part of this thesis. Publication or dissemination of this thesis to third parties requires authorization by the head of iwb. I agree, that this thesis is archived as pdf file in the digital thesis database of the iwb and in stock in the iwb-owned library, which is only accessible for iwb-employees.
Garching, 07.04.2014
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Table of Contents
Table of Contents……….. III List of Figures……… VI List of Tables………...VIII
1 Motivation ………..………..……… 1
1.1 Evolution of paradigms ………...………. 1
1.2 The product and production life cycle ………...……… 2
2 Basic Information ………..……….……...………... 3
2.1 Changeability ………..………. 4
2.1.1 Change drivers……….………..………. 6
2.2 Enablers ………..….………. 6
2.3 Modularity ……….………. 7
2.3.1 The theory of modularity………. 7
2.3.2 Module………..…….8
2.3.3 Benefits of Modular Construction……….….………… 9
2.3.4 Modularity of Manufacturing System……….…….. 9
3 State-of-the-art ………..……11 3.1 Tools……….………. 11 3.1.1 Hand tools………..…….11 3.1.2 Power tools………. 12 3.2 Handling devices………..………….. 13 3.3 Transport system……….………... 14 3.3.1 Hand trucks……….…………... 14 3.3.2. Conveyors………...….……. 14
3.3.3 Automated guided vehicle - AVG……….……..…… 14
3.4 Traditional Machine Tools ………..…….. 16
3.5 Automated machines………...…….. 17
3.6 CNC Machine ………..…….. 20
3.7 Industrial Robots……….... 22
3.7.1 Definition of robots………..………. 22
3.7.2 Cylindric geometry robot………. 24
IV
3.7.4 Articulated geometry robot……….. 25
3.7.5 Cartesian geometry robot……… 25
3.7.6 Gantry robot……….……….. 26
3.7.7 SCARA robot (Selective Compliant Assembly Robotic Arm)...…. 26
3.7.8 Other structures……….... 26
3.7.9 Manipulators pick-and-place………..……. 27
3.7.10 System to increase the volume of work……….. 27
3.7.11 End Effector…..………..……. 28
3.8 Flexible Manufacturing System - FMS…..……….. 28
3.8.1 Focused Flexibility Manufacturing Systems - FFMSs………. 29
3.9 Reconfigurable Manufacturing System - RMS ………... 30
3.10 Reconfigurable Multi-technology Machine Tools - RMM……… 30
3.11 Categorization of Manufacturing Resources……….31
3.11.1 Degree of Flexibility - DF………31
3.11.2 Degree of Changeability -DC……… 33
3.11.3 degree of Modularity - DM………. 35
3.11.4 Summary Table………... 36
4 Modularization of Manufacturing Resources……… 40
4.1 Modular design of manufacturing resources………. ….41
4.1.1 Definition of modular design………... 42
4.2 Four principle of modularization……… 43
4.2.1 Principle of separation………...43
4.2.2 Principle of unification………...44
4.2.3 Principle of connection……….. ……….. 44
4.2.4 Principle of adaptation………. ……… 45
4.3 Modularity for (Re)configurability……….. ………. 45
4.4 Modularization of Machine tools………47
4.4.1 Modules of CNC machine……… 47
4.5 Modularization of industrial robot……….. 50
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5 Information for planning of modularity……….. 55
5.1 Analysis of market needs………... 56
5.2 External factors of influence……….. 56
5.3 Analysis of change drivers………. 56
5.4 Analysis of processes………. 58
5.5 Enterprise constraints………. 59
5.6 Part features………. 59
5.7 Technical characteristics of manufacturing resources………... 60
6 Concept for information base modularity planning………….…………... 61
6.1 Manufacturing resources for different system……….. 61
6.2 Method for analysis of processes ……….. 62
6.2.1 Decomposition of processes………. 62
6.2.2 Allocation of resources to activities………. 63
6.2.3 Activity sequencing and P.E.R.T………. 63
6.2.4 Clustering of activities……… 65
6.2.5 Comparison among processes………. 65
6.2.6 Allocation of activities to machine……… 66
6.2.7 Analysis activity – machine……… 66
6.3 Information for modularization of manufacturing resources…………...67
7 Summary and Outlook……….68
7.1 Summary……….. 73
7.2 Critical analysis of the results……… 74
7.3 Outlook……….. 75
List of Literatures………. 76
VI
Table of Figures
Figure 1: The paradigm shift in the time………... 2
Figure 2: Evolution of Product, Process and Manufacturing life cycle…………. 2
Figure 3: Modularization of manufacturing system………. 7
Figure 4: KUKA KR 180……….. 7
Figure 5: Standard 4-cup vacuum handling device………...15
Figure 6: Handling device for final assembly………. 15
Figure 7: Pneumatic balances………..15
Figure 8: Automatic lathe……….. 20
Figure 9: Multi-spindle lathe………. 20
Figure 10: Milling multiple carousel………. 20
Figure 11: Capacity of adaption – costs of manufacturing resources………… 40
Figure 12: Machine tool modular construction kit and examples of workspace configurations………..41
Figure 13: Principle of separation and trade-offs……….. 44
Figure 14: Modularity for (re)configurability……….. .... 46
Figure 15: Modules of Working center……… 48
Figure 16: Degrees of freedom of CNC machine ……… 48
Figure 17: Overview of CNC machines……….. 48
Figure 18: Reconfigurable modular robot system………. 51
Figure 19: Modules of articulated robot.………. 53
Figure 20: joints articulated robot and degrees of freedom………. 53
Figure 21: Pyramidal classification of planning resources information……... 55
Figure 22: Modularization compared to production systems……….. 58
Figure 23: Phases of processes analysis………...62
Figure 24: Decomposition of processes………. 63
Figure 25: Allocation of resources to activities……….. 63
VII
Figure 27: Clustering of activities………65
Figure 28: Comparison of products processes………..66
Figure 29: Allocation of activities to machine……… 66
Figure 30: Scale for evaluation of information……….. 67
VIII
List of Tables
Table 1: Classification of industrial robots……… 23
Table 2: Variant of Likert scale……….. 24
Table 3:
Degree of Flexibility of manufacturing resources……… 25Table 4: Degree of Changeability of manufacturing resources……….. 30
Table 5: Degree of Modularity of manufacturing resources………34
Table 6: Summary table……… 40
Table 7: Technical characteristics of CNC Working center………. 50
Table 8: Technical characteristic of Comau Smart S1………. 54
Table 9: Breadth and depth of the product portfolio of the company…………. 57
Table 10: Classification of manufacturing resources………. 61
Table 11: Analysis activity – machine………. 67
Table 12: Information for modularization of manufacturing resources……….. 68
Table 13: Future outlook of “information based planning of reconfiguration
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1 Motivation
Today’s manufacturing environment changes rapidly. Product life cycles are
shortening, companies face high international pressure, customer
requirements increase and technological innovations accelerate
[BIEDERMANN et al. 2010, ELMARAGHY et al 2009, BIEDERMANN et al. 2011, BRIEKE et al. 2007].
These factors strongly influence the enterprise in its interior, particularly the system of production and manufacturing resources. They must be able to respond quickly to external changes and, therefore, manufacturing resources must be flexible and, especially, have a high degree of (re)configurability. To achieve these, academics and economists have tried to find solutions to the latest challenges through methodologies that includes: identification of change drivers (internal and external) of enterprise and application of the enablers [ELMARAGHY et al 2009, p. 8], the application of which leads to a sustainable business resilience [BAUERNHANSL et al. 2012].
Particularly, in this thesis we deal with the enabler of modularity, the application to manufacturing resources, their degree of modularity and approach to the application of the right degree of this enabler. This topic will be discussed in later chapters.
In the 1.1 (1.1 Evolution of the paradigms) and 1.2 (1.2 the product and production life cycle) points we analyse better the causes that led to these new challenges.
1.1 Evolution of the paradigms
Manufacturing systems have evolved over the years in response to many external drivers including the introduction of new manufacturing technologies and materials, the constant evolution of new products and the increased emphasis on quality as well as the escalating global competition and pressing need for responsiveness agility and adaptability [ELMARAGHY et al. 2009, p. 3].
All these changes have influenced deeply the enterprises who have operated in a stable market and now in a constantly changing market. As we can imagine, the factories can’t concentrate all their efforts internally and based on the paradigm of efficiency but have to continually confront with the external word to verify the ability to respond to market requirements.
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Several manufacturing systems paradigms have appeared as an result of volatility in market demands, changing customer’s preferences, need for more products differentiation and customization [ELMARAGHY et al. 2009, p. 4]. So the fast changes in the actual environment have introduced new manufacturing system paradigms, such as flexible and reconfigurable manufacturing. In the Figure 1 we can see the differences between the enterprises of the past, then work in a stable market and the actual situation that requires more commitment to have success in a really turbulent and unpredictable environment and globalized market which increase the competition.
Figure 1: The paradigms shift in the time.
As we can see in the Figure 1, in the past businesses concentrated all their efforts inside for increase productivity and reduction waste but, now in a really changing and uncertain word the companies need to continually check the requirements of the market and therefore they must take a look always to the surrounding environment.
1.2 The product and production life cycle
It is increasingly evident that the era of mass production is being replaced by the era of market niches. The key to creating products that can meet the demands of a diversified customer is a short development cycle yielding low cost. High quality goods in sufficient quantity to meet demand. [BRIEKE et al. 2007, p. 783]
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One result of the dynamics of markets is the mutation of the product life cycle characteristic and the increasing divergence of the life cycles of the associated processes and equipment, Figure 2.
Figure 2: Evolution of Product, Process and Manufacturing life cycle [according to BRIEKE et al. 2007 and ELMARAGHY et al. 2008, p. 5]
In the past, the enterprises put on the manufacturing system and the process for one or a few products and they have a life cycle as the products. This was the mass customization period but now, the product life cycle is shorter and the companies have to be able to make innovation and create new product that meet the customer’s preferences.
In the current market, so uncertain and unpredictable, a “rigid” system for each product can’t work and brought them to fail because it require much set up time and large investments in fixed assets. So the factories have to put on manufacturing system and process that can be flexible and able to change quickly. There are fundamental paradigms for survive. However, the application is not simple. Requires studies of the market, future predictions and internal analysis. Many researchers and economists have tried in recent years to find solutions, methods to reduce complexity and make companies lean and changeable.
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2 Basic Information
After the analysis of the paradigms and the change in the life cycle of products, we explore the significance of these principles that characterize the needs of companies that operate in today’s markets.
In the section 2.1 (2.1 Changeability) we analyse the paradigm of changeability: now essential characteristic for companies who operating in turbulent environment.
Over the years approaches and methods have been developed to help companies to be flexible and changeable through individuation and application of change drivers (2.1.1 Change drivers) and enablers (2.2 Enablers) [according to ALMARAGHY et al. 2009] focusing on modularity enabler (2.3 Modularity).
2.1 Changeability
Due to this rapid evolution, as previously explained, the paradigm of Changeability is now the foundation of today's businesses. The prerequisites for successful participation in dynamic and global production networks require that the production processes, resources, plants structures, manufacturing systems layouts as well as their logistical and organizational concepts be adaptable quickly and with low effort. This ability is necessary for production companies to withstand the continuous changes and the turbulent manufacturing environment facing them, and can be described as ‘changeability’ [ELMARAGHY et al 2009, p. 6].
Changeability marks the acquirement of a complete factory to adapt itself to changing requirements in a reactive or proactive way. In contrast to flexibility, changeability is perceived as a potential to perform necessary changes outside predefined corridors. Compared to flexibility, the range of capability will not be provided but pre-thought for possible changes [KREGGENFELD et al. 2013, p. 492]. In fact, academics and economists have studied the methods that help industrial companies to anticipate external changes (market, technology etc. ..). These methods basically consist in identifying drivers of change in the specific company and especially in the application of enablers: key to make the company changeable.
One chance to react to changing requirements is to apply the principle of modularization. In literature, modularity is referred to as one of the five change
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enablers (2.2 Enablers) and thus has a wide influence on the changeability of production systems [KREGGENFELD et al. 2013, p. 492].
2.1.1 Change drivers
One main aspect is to define the objects that have to be changeable and their appropriate degree of changeability. The impulse for a change is triggered by change drivers, whose categories are:
o Volatility measured by volume fluctuation over time.
o Variety is the scope of the products’ variants, both in basic models as
well as in variants within the models with respect to size, material and additional features.
o A major change driver is a new company strategy, e.g. a decision to enter a new market, to sell or buy a product line, or to start a strategic turn around program, etc [ALMARAGHY et al. 2009, p. 8].
2.2 Enablers
A factory that is designed to be changeable must have certain inherent features or characteristics that will be called changeability enablers. Changes can most often be anticipated but some go beyond the design range. This requires providing innovative change enablers and adaptation mechanisms to achieve modularity, scalability and compatibility. While changes may not always be anticipated, the behaviour of their enablers should be pre-planned for all scenarios to ensure cost effective adaptability.
There are two types of change enablers: hard or physical enablers and soft or logical enablers. The “physical/hard” change enablers include the physical attributes that facilitate change. These characteristics are not only limited to the machinery but they also apply to the factories infrastructures, physical plant and buildings. Hardware changes also require major changes at the “logical/soft” enablers level, such as the software systems used to control individual machines, complete cells, and systems as well as to process plan individual operations and to plan and control the whole production. The logical enabling technologies extend beyond the factory walls to the strategic planning levels, logistics and supply chains. In addition, manufacturing changes are not limited to the technical systems; they include the business organization and
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employees that should also be planned and managed effectively [ELMARAGHY et al. 2009, p. 8].
They enable the physical and logical objects of a factory to change their capability towards a predefined objective in a predefined time and are not to be confused with the flexibility types or objectives. An enabler contributes to the fulfilment of a transformation process. Furthermore, the enablers characterize the potential of the ability to transform and become active only when needed. The characteristics of an enabler positively or negatively influence a factory’s ability to adapt.
The enablers have to be apply in every level of manufacturing system. The main enablers are:
o Universality represents the characteristic of factory objects to be dimensioned and designed to meet the diverse tasks, demands, purposes and functions. This enabler stipulates an over-dimensioning of objects to guarantee independence of function and use.
o Scalability provides technical, spatial and personnel incrementally. In particular, this enabler also provides for spatial degrees of freedom, regarding expansion, growth and shrinkage of the factory layout.
o Modularity follows the idea of standardized, pre-tested units and elements with standardized interfaces. It also concerns the technical facilities of the factory (e.g. buildings, production facilities and information systems) as well as the organizational structures (e.g. segments or function units). Modules are autonomous working units or elements designed to ensure high inter-changeability with little cost or effort, which are commonly known as ‘Plug and Produce Modules’.
o Mobility ensures the un-impeded movement of objects in a factory. It covers all production and auxiliary facilities, including buildings and building elements, which can be placed, as required, in different locations with the least effort.
o Compatibility allows various interactions within and outside the factory. It especially concerns all kinds of supply systems for production facilities, materials and media. It also facilitates diverse potential relationships regarding materials, information and employees. Besides the ability to detach and to integrate facilitates, this enabler allows incorporating or eliminating products, product groups and work pieces, components, manufacturing processes or production facilities in existing production structures and processes with little effort, by using uniform interfaces [ALMARAGHY et al. 2009, p. 18].
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A practical approach to measure changeability is to compare the desired changeability with the existing change potential and start the necessary actions to reduce the gap according to the strategy, urgency and importance to survive.
Between the enablers discussed above, we decided to develop the modularity enabler. This approach is typically used in products: putting together different modules we get new products. If this could be achieved with low set-up times, the company could keep up with the market time. This would lead immense advantages regarding the flexibility and (re)configurability and would make the company more changeable. For this reason we have decided to explore this concept to see how to get what is explained above: going to analyse the productive resources, their characteristics, their degree of modularization and the strategies to be used for a correct choice of the manufacturing resources that suit the different types of manufacturing systems.
2.3 Modularity
In this section, modularity is introduced. In 2.3.1 (2.3.1 The theory of modularity) we find a description of the application of this theory to different objects. In 2.3.2 (2.3.2 Module) there is different definitions of module concept. In 2.3.3 (benefits of modular construction) are listed the benefits but, also, the issues arising from incorrect application of this principle. Finally, in 2.3.4 (Modularity in Manufacturing system) it’s described the application of the theory inside the manufacturing system; this is the scope of thesis work.
2.3.1 The theory of modularity
The theory of Modularity is an implementation common in technology fields; e.g. software, modular code, internet constructs [GENTILE 2013, p. 203]. Literally with this theory is defined as the decomposition of a complex factor in the simplest factors. This is a practice used since the times of the Egyptians; the pyramids were built in a modular way.
In the technical community, modularization is a solution exploited at all levels of the systems architecture including: operational structure, product structure, mechanical hardware, electronics packaging, micro-electronics, and software,
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that achieve desirable and usually predictable system benefits [GENTILE 2013, p. 203].
Manufacturing industrial products are developed, both structurally and functionally, in a highly modular fashion to simplify design, accelerate construction, and minimize repair and maintenance with the objective of yielding cost savings in product evolution and sustainment.
2.3.2 Module
A formal definition of a “Module” in the technical context of this paper is: “an independent unit that can be combined with others and early rearranged, replaced, or interchanged to form different structures or systems”. The exploitation of formal definitions used herein follows:
A module: is an entity which owns a function (or service) at a defined
performance and can share that function through the employment of an integral interface;
A modular Architecture: is a entity composed of multiple modules,
requiring:
o Behaviour and boundary conditions to be compatible and consistent for module types to join;
o Contains least 2 modular functions and 2 interfaces;
o Of any size and complexity (module boundaries are scalable);
o Will merge or join through interoperable interfaces (uniquely, selectively or universally);
o Can transfer and/or share functional content (functionally is additive);
o The propensity to form modular entities exists prior to the formation of modules [GENTILE 2013, p. 204].
2.3.3 Benefits of Modular Construction
Modular designs can provide systems design benefits that are attractive to cost and effective in enhancing product support and reliability. Correctly applied, the following modularity benefits are expected:
Quick integration due to well Understood Interfaces;
Fast and Easy Reconfiguration/Integration for Rapid Diverse
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Ease of Maintenance, Fast Repair at all levels of maintenance, Low
LCC;
Spares Optimization: Less Maintenance Resources, Replacement parts;
Intuitive Assembly, Staging, Testing and Operation;
Multiplicity of modules will exhibit emergent capabilities.
The caution is, if incorrectly applied modularity can add overhead that can impact top level performance objectives. Key questions arise “when is there enough modularity in a design?” and “are there guidance and performance assessment tools for modular solutions?” The answers of these questions are the goal of the work thesis [GENTILE 2013, p.205]
2.3.4 Modularity in Manufacturing System
Modularization is one of the most important change enablers that can help the enterprises become changeable to the frequent mutations in products, production technologies and manufacturing systems due to globalization, unpredictable markets, increased products customization and the quest for competitive advantages. By the term modularity means the decomposition of complexity by creating smaller units. This principle, that is used a lot in products, can be applied to manufacturing systems towards the decomposition of the process activities in simple activity.
The theory of modularity is also frequently used within the production system at every level as a deconstruction of complex activities into smaller tasks and simple. We can see that in the picture below:
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How we can see in Fig.1 to every activity is assigned machines, devices, equipment and it contains organization and staff. So the activity that you can correlate with others and create a new entity that have a new function take the name of Modularity. But this isn’t easy to put on in the reality; this method requires a deep analysis of the company products and manufacturing systems to identify the requirements; but the external and the internal influences change this. To face the resulting challenges, every enterprise has to define technically and organizationally realizable as well as cost-effective actions in an appropriate time. One chance to react to changing requirements is to apply the principles of modularization [KREGGENFELD et al. 2013, p. 491].
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3 State-of-the-art
In this chapter, we create an overview of key manufacturing resources and evolution endured by them, over the years. Let's start with the first tools (3.1 Tools) used by operators to perform simple tasks and arrive to the CNC machines (3.6 CNC Machine) and robots where we have machine with computerized control, flexibility and changeability thanks to systems more modular. In addition to manufacturing resources we also consider: Focused Flexibility Manufacturing Systems - FFMSs (3.8.1 Focused Flexibility
Manufacturing Systems – FFMSs) and Reconfigurable Multi-technology
Machine Tools - RMM (3.10 Reconfigurable Multi-technology Machine Tools - RMM) that are principles and theories for development of specific machines that best adapt to their specific needs. At least, we summarize (3.11.4 Summary Table) the various resources according to degree of flexibility (3.11.1 Degree of Flexibility - DF), degree of changeability (3.11.2 Degree of Changeability - DC) and degree of modularity (3.11.3 Degree of Modularity - DM).
3.1 Tools
The analysis of manufacturing resources begins with hand tools (3.1.1 Hand tools) and power tools (3.1.2 Power tools): simple tools, portable, cheap that we can find in each production unit but with a very low productivity, as we can imagine. For this reason, over the years we have seen an improvement of these tools through motorization and computerization of these.
3.1.1 Hand tools
The first tools used in production systems were tools that worked with the simple human labor. These tools have undergone an evolution over time: the engines were added and slowly, the human labor has been eliminated, except for control and maintenance. But these tools are used, however, given the low price although they have very low productivity. In the list below, there are the typical tools that we can find in every workshop:
Reamers: correcting a little the diameter or the alignment of the holes
already made, to finish them. They are used successfully on both circular and square hole section;
Burins: thin chisels with steel toes used for special engravings;
Screwdrivers: screwing and unscrewing with slotted or phillips head;
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Thread cuttings: threading and create cylindrical rods threaded rods,
bolts and screws. They generate external male threads;
Scissors and shears;
Filing tools: used for smoothing and chamfering of wood and metal
objects;
Hammers: depending on the material to beat and the purpose, we can
use iron, rubber, wood or copper hammers.
Clamps: clamping the workpiece and keeps it locked during the
processing, usually for working or adjusting threads or mounting other elements.
Pliers: used to hold small items during processing. There are also
adjustable pliers able to hold objects of different diameters;
Hacksaw: designed to cut wood, metal or other materials, in order to
divide a piece into smaller pieces according to the measurements you want.
Hand drill.
Those are some of the simple tools that we can find in the worshops. In general these tools can be classified into three categories:
Measuring tools (calipers, mocrometer, comparator): necessary to verify
that the measures comply with the tolerances of machined parts;
Cutting tools (hacksaw, scissors, reamers, etc..);
Moving tools: using for moving the piece inside the workpiece. They are
trucks that help the operator in the transport operations.
3.1.2 Power tools
The power tools have developed as a result of the need to increase processing time. The types of power tools are approximately the same of hand tools but they are actuated by an additional power source (lathe, drill, etc.) They are always tools used by the operator and another thing interesting about these instruments is the portability. Portable power tools have obvious advantages in mobility. In contrast, there are the stationary tools (granding machine, milling machine, planer, etc.) that we call machine tool and we consider in the following pages.
13 3.2 Handling devices
The handling devices are devices that help the operator in the proper movement, orientation and positioning of the pieces without this involving physical effort for him. in the market we can find numerous variations designed for specific cases including the assembly that represents the area of greatest use. The advantages of these devices are:
Safety: most of them are equipped with safety interlock system that
doesn’t allow the operator to accidentally disengage the part during transfer;
Ergonomics: handling devices can be designed with manual or powered
tilt and rotation packages, wich allow the operator to orient the part to the proper position with minimal effort;
Flexibility: they allow to rotate and move along axes in different
directions and follow different paths through the use of the joy-sticks held by the operator.
These devices change according to the characteristics of the pieces that have to be moved and positioned. The factors that influence the choice of different handling devices are mainly dimensions and weight; obviously the gripper (the end-effector) will vary according to these. Another factor that we have to consider is that these devices required the continuous presence of the operator during all the work process. Below we can show some examples (Figure 5-6-7).
Figure 5: Standard 4-cup vacuum handling device; Figure 6: Handling device for final assembly; Figure 7: Pneumatic balancers; [INGERSOLLRAND]
14 3.3 Transport systems
The transport systems include: Hand trucks, Conveyors, Vehicles. They include all the system that deal with transport of the pieces between the different workshops during the working process.
3.3.1 Hand trucks
Transport systems manual are undoubtedly the easiest way to handle objects into industrial environment. They are driven by human operator and are characterize by a low load capacity and a low rate production (deliveries/hour). There are different type of hand truck according to dimensions of the product (a two wheels truck, a four-wheels truck called dolly, a hand forklift)[DINI 2013, p. 7.3].
3.3.2 Conveyors
With the term “conveyor” is meant a system capable of moving object continuously or intermittently on a given path along which develops the same conveyor. There are various types that differ depending on the device used to move objects:
belt conveyors: the objects are placed directly on translating belt;
roller conveyors: objects move by relying on rotating rollers;
chain conveyors: a translational motion objects attached to a chain in
motion;
rail conveyor: this system can be used where it is necessary to keep an
object fixed to a platform with the locking devices.
Conveyor unlike the hand trucks are systems with high production rate but high rigidity as the pieces can only follow the paths defined by them[DINI 2013, p. 7.5].
3.3.3 Automated guided vehicle (AGV)
Among the various types of transport systems currently available for industrial uses, undoubtedly the AGV systems represent the ideal answer to the needs of automation, flexibility and modularity. AGVs are automated guided vehicles capable of moving directly on the floor of the factory, allowing you to move
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objects without being bound by chains or pathways identified by the rails. The constituent elements of an AGV are:
- Frame: is the supporting structure of the vehicle and contains inside, in addition to the devices described below, also the power supply batteries and devices which ensure the arrest of the vehicle (bumper) in the case of accidental impact against an obstacle. These are usually made of elastic elements that deforms as a result of impact, commanding the stopping of the vehicle;
- Locomotion system: it is constituted by the wheels which allow the movement of the vehicle and its steering. You can have different provisions of the wheels. The most common fall into three categories:
4-wheels, automotive style: usually have two front steering wheels and
two rear wheels powered. This arrangement ensures a remarkable stability of the vehicle in the curve, but its mobility is limited by the high radius of curvature of the steering device;
3-wheel: composed of two non-steering rear wheels and one front wheel
steering and motorized. The radius of curvature is smaller than the previous case (the vehicle is able to rotate around the middle point of the rear axle), but the stability during cornering is penalized by the presence of only three points of support;
4 wheels, with provision to rumble: this configuration involves the use of
two drive wheels central, non-steered, each driven by an independent motor. The other two free wheels to steer are placed one in the front and one in the rear area of the vehicle, so as to form, together with the two drive wheels, the vertices of a rhombus. Control of the direction in this case does not provide for a controlled steering of the wheels, but rather a differential control of the speed of the two drive wheels. In this way, the gear in the rectilinear direction is obtained by moving the wheels at the same speed and with the same sense of rotation, while cornering the outside wheel is achieved by impressing a speed greater than the inside. It is evident that if the drive wheels are moved at the same speed but with opposite direction of rotation, one obtains a steering angle of the vehicle around its centre point, thus allowing to change direction in especially tight spaces, such as those that may occur in a typical industrial environment (for example in the corridors bounded by production lines or from the shelves of a warehouse).
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- Loading platform: has the purpose of housing the objects that are to be transported by the vehicle. The type of the platform obviously depends on the type of load to be transported and the way in which this must be handled during the step of loading or unloading.
- Navigation system: this control system allows the vehicle to perform a particular trajectory through the use of appropriate sensors and actuators. - System programming: it allows programming of the trajectories that the vehicle has to perform. This function is carried out through a special user interface through which you can store the paths to follow, and the operations that the vehicle must be made during the operations of loading and unloading. - Communication system: this system ensures the wireless communication between the vehicle and the control device and traffic management land site. The transmission and reception of data can be performed using various technologies, infra-red devices, radio frequency system, up to the latest Bluetooth devices [DINI 2013, p.7.13].
3.4 Traditional Machine Tools
A machine tool is a machine designed to transform the shape and size of objects of any material, by selective removal of supramaterial in various forms, using tools.
The machine tools have their primary field of application in manufacturing industry and mechanical engineering, especially in metalworking.
The components of a machine tool are various, the principles:
o The bench is the structure of the machine tool and requires a high weight to provide stability and rigidity to the same, as well as good resistance to various types of stress (especially flexion) and absorption capacity of the vibrations that are generated during the machining of the workpiece . For these reasons, the material often used is cast iron, but in most modern machines is also widespread welded steel structure. o Eletric motors convert electrical energy into mechanical energy, and
may be in direct or alternating current. The electric motors, which can be in a variable number (typically one or two), provide the energy for all the motions of the machine and have different power, depending on the motion that must feed. The engine with the heaviest load is the one that powers the movement of labor, the total power is estimated in the order of magnitude of kW.
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o Driving head contain commands and mechanical transmission organs adapted to convert the motion of the electric motors, increasing or decreasing the number of turns and consequently the torque. The driving head balances and the rotation of the spindle, while the special levers vary the number of turns which are expressed in (r / min).
o The trees are the elements conveying the motion, turning to a certain number of revolutions, on them can be keyed of transmission organs. Generally the trees are divided into motor shaft (driven directly by the rotor of the electric motor) and driven shafts (connected to the crankshaft driven shafts or other means of transmission). The last drive shaft, which provides the motion of work, is defined spindle and on it are grafted organs of clamping the workpiece or the tool.
o The spindles most common are those of self-centering type, with three radial clamps placed at 120 ° of inclination between them, which flow through a rack system to take up the piece in the vice. This system allows the assembly and disassembly of the piece with extreme speed, even in a fully automatic way.
The main manual machine tools are:
o Lathe: a machine tool used for the machining of a workpiece placed in rotation. The processing is done by machining and is said turning;
o Milling machine: engine, usually quite powerful, which is attached by means of a spindle, a tool with sharp edges that rotate on the axis of the tip itself. It designed to perform the cutting action on the side of the tool rather than at the tip, thus eroding the material rather than by puncturing;
o Drill: machine tool, used to make holes or processes that require the use of circular tools;
o Grinding machine: machine tool used for the finishing of metal pieces are able to obtain a considerable dimensional and geometrical precision and to work even on very hard materials such as hardened steels.
o Planer: portal machine, large, with two uprights, a cross member fixed and one mobile, provided with one or more tools single lip acts to smooth continuous surfaces or shaping of pieces having large size with very narrow tolerances (0.02 mm).
18 3.5 Automated machines
Automate a process means: eliminate the manual operations, reduce human intervention for the control of machines and make, if possible, operations and processes contemporaneous. The first machines were designed to execute automatically always the same cycle. These types of machines, also known as “dedicated”, specially designed to achieve a given product are based on an automation predominantly obtained with electro-mechanical devices designed to perform very precise movements to the organs of the machine itself. it is therefore easy to understand how small changes of the production cycle, due to updates or changes in the product, involve long and expensive interventions on the production system that can lead to its complete renovation. The benefits of automation are, as we know, mainly:
o reduction of production time; o improving productivity;
o reducing the costs of labor (higher level of job for the worker and increasing safety);
o improving the quality of the product.
However, compared to non-automated machines have: o High cost of planning and preparation;
o High initial cost of the machine;
o Problems of reliability and high maintenance costs.
The first machines were designed to execute automatically always the same cycle. These types of machines, also known as “dedicated”, specially designed to achieve a given product are based on an automation predominantly obtained with electro-mechanical devices designed to perform very precise movements to the organs of the machine itself. It is therefore easy to understand how small changes of the production cycle, due to updates or changes in the product, involve long and expensive interventions on the production system that can lead to its complete renovation[DINI 2013]. Below you find first examples (Figure 8-9-10) of automation:
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Figure 8: Automatic lathe; Figure 9: Multi-spindle lathe; Figure 10: Milling multiple carousel [DINI 2013, p. 1.5-1.6]
Following the evolution of the market recorded in the second half of the twentieth century, it was the occurrence assiastito two opposite trends:
o the transformation of the large series in a series of smaller size, under the thrust of technological evolution, competition between the producers, which leads to a rapid obsolescence of products, and the request of customers to a greater diversification;
o the transformation of the small series in larger series, to reduce production costs through greater standardization of artifacts.
The result was then a gradual shift down to the average series, accompanied by the need to frequently change and reconfigure the production system. From this need arises then the concept of flexible automation, implementable through machines able to work different types of products and reconfigurable quickly and relatively inexpensive. This form of automation, definitely more costly than the previous one, is then used in the production very variable, consisting of batches of small and medium size. These machines having the capability of (re)configurability, it is not necessary to replace them completely when a model out of production, contrary to what happens with rigid systems such as transfer lines. the investment costs can be broken down on a greater number of elements produced, belonging to different models[DINI 2013, p. 1.4-1.8].
In the next section, we find the CNC machines that are a perfect example of flexible automation.
20 3.6 CNC Machine
With the progress of production systems, in the second half of the twentieth century has seen a gradual shift of traditional machine tools (mainly a manual but also automated with electromechanical systems), the so-called machine tools (Numerical Control) and then CNC (Computerized Numerical Control). These machines are called so because the information given to them (positioning of tables, moving the same speed of the tool, tool type, etc.) are derived from the design and manufacturing cycle of the piece and stored in numerical form, suitably encoded, into the control computer.
Such storage is done through the programming operation of the machine, namely the operation of writing and placing in memory of the sequence of information, encoded in a special language, necessary to make the machine perform the same processing cycle required.
A machining program of a mechanical component on a given machine tool (also known with the term of the part program) thus contains all the necessary information in order to perform the various operations, the unity of government of the machine reads and interprets the information in so as to control the organs of movement and the other devices according to the sequence set by the succession of the information.
The CNC Machine is control system that allows you to control and coordinate the movements and functions of a machine, with the aim to follow the tool trajectories and pre-planned operations, using numerical information. The advantages of CNC machines are:
Reduction in labor costs;
increase in production;
improvement of quality;
high flexibility;
versatility;
Lower space;
However, issues of numerical control are:
High cost of purchase;
Cost of technical assistance;
Cost of programming.
A normal CNC machine is made in a similar way to its corresponding manual, but some components more mounts :
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encoders, which inform the on-board computer on the movement and
position of the axis on which they are mounted. There are both linear encoders (encoders) that rotary, some encoders are absolute, ie relate an exact measurement of position, while others are relative, that is to say just how many steps you are moving the axis in motion and in which direction it is going.
special electric motors to control the movement of the axes;
special units that power and control the movement of the motors
mentioned above. Depending on the type of motors (three-phase or direct current, with resolver or encoder) and depending on the type of feedback , the drive will be more or less complex.
the computer, called "control", which captures data from the encoders
and the instructions from the operator and from the program, establishing the position of the tool and governs the movements during the execution of the work program. Very often in modern machines the control is divided in two parts: a board machine in the electrical and in the operator's console, separate and external to the machine, which takes care of the video to show directions and menus, to receive via the keypad orders and NC programs and to manage the dialogue with any external computer. If you can steer the car from an external computer via a communication line ( serial , Ethernet, etc.).
CNC Machine Tools can be classified as follows:
Single-purpose machines (lathes, milling machines, etc.): machines
able to perform only one type of processing;
Turning Centers: a CNC lathe is a machine tool used to perform turning
operations or operations which have the purpose of obtaining external and internal surfaces of revolution variously shaped. Motions characteristics of the process are essentially: the cutting motion, rotary and continuous, possessed by the workpiece mounted on the spindle; the advancement motion, rectilinear or curvilinear, lying on a plane passing through the axis of the spindle, and always owned by the tool;
Machining Centers: a CNC machining center is a multipurpose tool, that
is able to perform various types of processing (milling, drilling, etc..) thanks to a large number of tools available in the warehouse. The tool is positioned on the spindle and therefore possessed the continuous rotary cutting motion. The advancement motion during the machining is generally owned by the tool and the workpiece, positioned on the table [DINI 2013, p. 4.3].
22 3.7 Industrial Robots
In this section we deal with industrial robots, among the most innovative resources: capable of performing a wide range of key activities. We start from the description of the components of a robot: we look at the types of joints and links that characterize them (3.7.1 Definition of robots). The we make an overview of the main robots. In the end, we look at the opportunities that these resources harm to the increase the volume of work thanks to the modular structure that they possess (3.7.10 System to increase the volume of work).
3.7.1 Definition of robots
To define a robot in a way that is generally acceptable to every manufacturer and user is difficult. A definition that distinguishes industrial robots from the many different automated machines currently used in manufacturing is necessary, however. Many single-purpose machines, often called hard automation, have some features that make them look like robots. Without some definition, it would be difficult to sort industrial robots out from the millions of automated machines so that they can be studied. The International Standard Organization (ISO) defines an industrial robot in standard ISO/TR/8373-2-3 as followed:
A robot is an automatically controlled, reprogrammable multipurpose, manipulative machine with several reprogrammable axes, which may be either fixed in place or mobile for use in industrial automation applications.
The key words are reprogrammable and multifunctional, because most single-purpose machines do not meet these two requirements. Reprogrammable
implies two points: (1) the robot’s motion is controlled by a written program,
and (2) the program can be modified to change significantly the motion of the robot arm. Multifunctional emphasizes the fact that a robot must be able to perform many different functions, depending on the program and tooling currently in use. For example, a robot could be tooling currently in use. For example, a robot could be tooled and programmed in one company to do welding, and in a second company the same type of robot could be used to stack boxes on a palletizer [REHG 1992, p. 5].
Thus, the fundamental characteristic of an industrial robot is to be able to perform mechanical work, such as smudge or other technological processed such as welding or painting, mounting a suitable tool on its appendix
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operational. Some of the most common operations that the robots are able to carry out are:
Subservience to machine tools (loading of the workpieces that have to
be processing and unloading of the worpieces that were been processed);
Loading and unloading;
Assembly of elements (for example, the assembly of components on
electronic boards, etc..);
cutting by laser or water jet;
painting;
small machining, such as drilling, milling, contouring, etc. ..
applications of glues or sealants;
Welding (electric arc, laser, etc..);
Palletizing and de-palletizing (loading and unloading of items on pallets);
Operations of dimensional measurement and control via probes.
The robots are composed by:
Joint (Ji): kinematic joints. Every joint gives one degree of freedom;
Link (Li): rigid instruments.
The joints can be:
Prismatic (P): allow linear motion;
Rotoidal (R) allow the rotary motion;
The Rotoidal joints can be:
Torsional type (RT);
Flexional type (RF).
The different types of robots can be summarized in the table below, according to the first three joints from the base:
Robot type J1 J2 J3 function
Cylindrical geometry robot RT P P Serving machine tool,
palletizing, assembly, etc.
Spherical geometry robot RT RF P Serving machine tools
(replaced by articulated robot)
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Articulated geometry robot RT RF RF In the case of
extended volumes, or in the case of work stations located on the
same rectilinear line
Cartesian geometry robot P P P Assembly, machine
tool tending, welding and painting
Gantry robot P P P Suitable for working in
large spaces especially for shift operations materials
and palletizing operations and depalletization
SCARA robot RF RF P Designed for
automatic assembly (high speed positioning and high
repeatability) Table 1: Classification of industrial robots
The additional degrees of freedom are placed on the wrist, consist of three parts:
Pecking;
Roll;
Hand.
The robots usually, have between 3 and 6 degrees of freedom.
3.7.2 Cylindrical Geometry Robot
A cylindrical geometry robot can move its gripper within a volume that is described by a cylinder. The cylindrical geometry arm is positioned in the work area by two linear movements in the X and Y direction, usually using ball-screw drives, and one angular rotation about the Z axis. I
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The axes on cylindrical geometry robots are driven pneumatically, hydraulically, or electrically.
Some of the advantages of the cylindrical geometry are as follows:
horizontal reach into production machines is possible;
the vertical structure of the machine conserves floor space;
a very rigid structure is possible for large payloads and good
repeatability.
The particular arrangement of the movements of the individual axes such that these structures are particularly suitable for operations characterized by the manipulation of objects in the radial direction or vertical such as, for example, servo machines, palletizing, assembly, etc.[DINI 2013, p. 6.5]
3.7.3 Spherical Geometry Robot
The Spherical geometry arm, sometimes called polar, requires coordinated motion in every positioning axes for movement in the X, Y, or Z directions. Spherical arm geometry positions the wrist through two rotations and one linear actuation. In theory the rotation about the axis Z could be 180 degree or greater, and the waist rotation about axis 1 could be 360 degrees [DINI 2013, p.6.8].
3.7.4 Articulated Geometry Robot
The Articulated robot has the structure most versatile and widely used in the manufacturing industry. Its configuration is composed of several links connected by revolute pairs. The number of Kinematic pairs, and then degrees of freedom can vary from a minimum of 4 to a maximum of 6-8. When it has a number of degrees of freedom greater than or equal to 5, it is also called anthropomorphic, reflecting the fact that its structure and its movements resemble those of a human arm. Although it generally presents no particularly large volumes of work, has the considerable advantage of being able to reach the various point from various directions and orientations of the hand. For this reason, they are very good for assembly operations, welding and painting. Anyway, the particular kinematic constituted throughout by revolute joints requires a control system more complex than, for example, to a Cartesian robot [DINI 2013, p.6.10].
26 3.7.5 Cartesian geometry robot
The Cartesian robot has three main movements achieved through many prismatic pairs. Every point reached by the robot is defined by a set of three Cartesian reference, allowing programming of movements easier. Typically have structures quite cumbersome, especially because the rail applied to the basement which allows the displacement along one of three axes. They are used in case it’s necessary to work on more stations located on a same straight line[DINI 2013, p. 6.8].
3.7.6 Gantry robot
Cinematically they are similar to Cartesian robots, though they are also made up of three prismatic couples that cover a useful volume of work in the form of parallelepiped. The portal supports the movement of the arm and can be as large size allowing you to cover large areas of work. The same structure also allows to have the terminal in a vertical to access the work area with movement from above, thus avoiding blockage of the said area with the presence of the robot itself. This characteristic makes this type of robot particularly suitable for use in large spaces especially for operations for moving materials and operations of palletising and (de)palletising [DINI 2013, p.6.9].
3.7.7 SCARA robot (Selective Compliant Assembly Robotic Arm)
This robot was developed by Japanese professor Makino expressly to perform assembly operations automatically. The structure provides a very quick positioning and high repeatability. Cinematically consists of three rotations around three axes parallel (one of which is possessed by the wrist) and a linear movement along a vertical axis. The term selective compliance is to indicate a particular characteristic of the structure designed specifically to facilitate the operations of assembly: the particular arrangement of the first two couples revolute fact allow a selective pliability of the structure, or a softness that can only take on a plane perpendicular to the direction mounting. This feature can be particularly useful in precise operations (insertion of a pin in a hole) that require small adjustments of the position taken by the robot to successfully complete the operation [DINI 2013, p.6.12].
27 3.7.8 Other structures
They have been designed and built structures with geometries robot capable of satisfying specific requirements dictated by particular industrial operations. In this regard, we can distinguish the following two categories:
Hybrid structures: structures formed by the combination of multiple facilities previously listed. For example, there are hybrid systems obtained by the combination of a SCARA robot and an articulated robot, for a total of 6 degrees of freedom;
Parallel kinematic structures: structures are newly designed, completely different from those reported in previous paragraphs. This configuration is specifically designed to quickly unloading and loading of presses, in which case the structure, similar to a articulated parallelogram, enables rapid movement of the objects horizontally, while providing a smaller footprint in the vertical direction and easy insertion in space, usually narrower, between the open melds of a press [DINI 2013, p. 6.15].
3.7.9 Pick-and-place manipulator
A manipulator pick-and-place is not really a robot, but a unit of manipulation unit usually used for simple operations of gripping and positioning of objects in production processes in which it is required cyclically always the same type of movement. They are generally pneumatically operated, with two or three degrees of freedom and axes of translation and/or rotation. The run along each axis is fixed in advance by the positioning of mechanical limit switches, so although it’s widely used in automation systems, this manipulator lacks a
fundamental characteristic to be considered a real robot: the
(re)programmability.
It’s important to note that there are many possibilities to realize customized these types of manipulators, by assembling modular components. By combining these manipulators is therefore possible to obtain the pick-and-place structure in Cartesian, cylindrical, etc [DINI 2013, p. 6.16].
3.7.10 System to increase the volume of work
As it was stated in the preceding paragraphs, very often the basic configurations of the robot are added accessories that enhance their performance. It this way the robot can not only translate the end effector within
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the useful volume of work, but it may also orient in order to correctly perform the required task. In some applications, it may be required that the robot is able to cover large areas of work, even higher that those permitted by their configuration based.:
In the case the increase of the races of the individual axes is sufficiently
limited (up to a few tens meters) to the main structure may be added additional axes;
In the case the increase required is much more substantial (several tens
meters and more) is used in real mobile robots, robot or vehicle mounted mobile on rails or directly on the floor of the production department [DINI 2013, p. 6.16].
3.7.11 End effector
The end effector of a robot can be represented by one of the following:
Gripper
Tool
The grippers are devices that allow you to grab objects and then manipulate (moving, installing, replacing, etc..). Utensils vice versa can be of various types, depending on the kind of work involved: tools for welding, milling, painting, tools for the application of glues, laser heads or water-jet cutting. The grippers can be broadly divided into the following categories, according to the principle used for grasping and holding the piece positioned:
Mechanical gripper;
Depression gripper;
Expansion gripper;
Magnetic gripper;
Contactless gripper;
Gripper for special application.
The characteristics of each gripper must have are:
High precision grip: understood essentially as a positioning repeatability
of the grasped object and then with respect to the gripper axis of the robot wrist. This parameter affects the repeatability;
High execution speed of grasping and releasing the object: this
parameter directly affects the time required to perform the operations of manipulation;
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Low weight: lower is the gripper weight major is the weight of the object
transported;
Small footprint: it allow you to access more easily in narrow areas[DINI
2013, p. 6.28].
3.8 Flexibility Manufacturing System – FMS
As it was mentioned in section 3.5 (3.5 Automated machines) over the years we have seen the development of flexible automation that has shifted the enterprise from rigid automated manufacturing system to flexible manufacturing system.
Now, companies producing mechanical components to be assembled into final products produced in high volumes, in order to remain competitive, must deal with critical factors such as: tight tolerances on the parts, short lead times, frequent market changes and pressure on costs. Obtaining optimality in each of these areas can be difficult and companies often define production objectives as trade-offs among these critical factors [ALMARAGHY et al. 2009, p. 47].
The flexibility degree of manufacturing system represents a critical issue within the system degree phase. On the one hand, it is considered a fundamental requirement for firms competing in a reactive or proactive way. On the other hand, flexibility is not always a desirable characteristic of a system.
This point needs to be clarified since in many cases flexibility can jeopardize the profitability of the firm. It is rather frequent to find in the literature descriptions of industrial situations where flexible manufacturing systems have unsatisfactory performance, cases where the available flexibility remains unused, or cases where the management perceives flexibility more as an undesirable complication than a potential advantage for the firm.
To reach this goal all activities ranging from the detailed definition of the manufacturing strategy to the configuration and reconfiguration of production systems must be redesigned and strictly integrated [ALMARAGHY et al. 2009, p. 48].
3.8.1 Focused Flexibility Manufacturing Systems – FFMSs
The simultaneous need of flexibility and productivity is not well addressed by available production systems, which tend to propose pre-selected types of
