1. Introduction
The nautical industry is an important sector worldwide. Some of the countries that are the most influential in the boat building are those ones localized in North America such as the United States of America which is the leader in the sector and on the other hand, the countries localized in the UE such as Germany, Netherlands, Italy, etc.
If we look deeper we can found Italy strong in this sector, in fact was in the top three in the nautical industry before of the 2008-2013 crisis, nowadays is an economy that had decrease so is not as strong as before of the crisis but is again in a trend that grows year by year, as is possible to appreciate from the turnover of the last years.[1].
The nautical sector in Italy is more predominant in building boats of dimensions between the 28-60 meters[2]. Different types of boats such as: motor boats, sailboats, inflatable raft and yachts are known to be the strong points. Many of which are personalized for the client.
The techniques used in boat building in the nautical industry are several; that depends on the boat’s size and also the implementation that is required, i.e., copy a pattern that has already been designed with Glass Reinforced Plastic (GRP) material or created from the scratch using plywood, Steel, Aluminium, etc. Nowadays, most of the procedures to construct boats that exist are manual methods in which few of them in assembly lines are not at all automatized. They shape the individual pieces of the boat, part by part and then manually assemble them.
Then, it’s fair to classify this sector as a handmade production, reliable and custom- mizable. This approach represents a valid building strategy, but on the other hand, it can’t be totally efficient in a growing economy. According to those methods, there are points that can be improved, so that the production of a boat can become smart in terms
of time spent on building a single piece and also in terms of precission as long as human life is linked to it.
Considering the advances in the automated technology and robotic systems, this thesis is proposing another method to build boats of different dimensions and shapes. This approach allows to build a boat model from scratch. Being unnecessary the intervention of an operator in the building process considering that the system is completely automated.
1.1. Short history of the boating
It is possible to hypothesize that the first approach of the boating goes back to the homo sapiens period. Maybe a piece of a tree that falls down in the water make to think about it like a means of transport to go to one side to the other, perhaps it was no to stable, so irrationally was added more pieces of wood and this one was the start of an idea that take place also on the presents days.
The Mediterranean sea from 1500 B.C. it was a scenario of the several nautical boats. If the Egyptians, since the second millennium, favored the fluvial navigation, the Cretans are considered the first true navigators of the eastern area. Around the seventh century B.C., in the Greek civilization, developed a commercial competition, managed through navigation, among some cities like Calcide, Corinto and Eretria. These trade bases became fundamental points for the trade in grain and metals. Then the populations was creating many colonies near this important sea. For this reason, the Mediterranean played a fundamental role establish a link between the motherland and the new maritime bases. Greece dominated the Mediterranean until this became the new medium used by the Roman empire for the political development and unification. In this period, Roman legislation applied the law mare clausum, the periods for navigation were imposed, allowed in the summer, and prohibited in the period from November to March. This law was respected until 1280[3].
Looking as at other important areas outside of the mediterranean civilizations we can see the contribute of the Chinese culture. As the author Massimo Mursio-Sale reports, it appears that the emperor Yang Ti, in the seventh century A.C., possessed over 30,000
pleasure boats that used to run channels. These boats were towed by earth with arms in such a way as to allow him to visit the territory and at the same time show the people their imperial presence[4].
The Viking population also made a fundamental contribution to navigation. With their drakkar even managed to reach the coast of Canada, in America. The drakkar is a type of boat used in the Middle Ages for military purposes and for traveling exploration. It is a boat characterized by a hull about 25 meters long, narrow and slender, with a particularly reduced draft. These peculiarities give the boat speed and the ability to navigate in shallow water allowing to approach the shore and making landings very fast.
A further advantage is given by the symmetry of the form that allows a very fast turnaround. The drakkar presented two different methods of propulsion: oars and sail.
The first one were used near the coast and during the fighting. The sails were square, furled on a single central tree and came used for very long journeys[5]. Regardless of the geographical location of navigation, vessels are developed on a basis at historical times.
1.2. Boat Building Methods
Exist several methods using in the nautical industry to boat building from the standard ones to the customized processes, most of them are develop with wood material because is handy and available in different qualities. There are other materials used like GRP (Glass Reinforced Plastic), Steel, Aluminium and Ferro-cement.
The following are some of the methods used to boat building as a hand-made procedures with wood materials:
1.2.1. Traditional Construction
a) Carvel: Single tapered planks edge to edge and fastened to a framework.
Requires great skills, expensive materials, traditional sealing between planks or glued splines and heavy framework.
Figure 1. Bow of boat being carvel planked. (from Wooden Boat D., 2013) [7]
b) Lapstrake/Clinker: Single tapered planks over lapping edges fastened to transverse timbers. Requires great skills, expensive materials, regular maintenance and is difficult to repair. Can suffer from exposure as the hull gets older.
Figure 2. Bow of boat being Clinker-building. (From Lopez J., 2018) [8]
c) Cold Moulded: Several layers of thin veneers of wood glued to each other over a framework. Fairly high skills and perhaps the production of a jig that becomes redundant. Also uses expensive materials and is difficult to repair.
Figure 3. wooden Romilly being built with cold moulded method. (From Thomas H. , 2018) [9]
1.2.2. Modern Construction
a) Stitch & Tape (Stitch & Glue/Tack & Tape): Pre-shaped panels of plywood stitched edge to edge giving a multi-chine shape with ply frames added. Can use low cost materials, requires few skills and only basic tools. The quickest, cheapest and easiest form of construction. Requires the use of epoxy joins which can be messy. Good for lightweight hulls.
Figure 4. Stitch & Tape kayak boat. (From Danny, 2015) [10]
b) Ply over Frame: Plywood glued/fastened over a rigid framework. Moderate skills required, does not need extensive tools, takes longer than stitch and tape due to the conventional framework. More expensive in smaller boats than stitch and tape but perhaps less so in larger plywood boats. Heavy weight construction.
Figure 5. Plywood framing. (From Marshall, 2012) [11]
c) Strip Plank: Parallel strips of wood glued edge to edge over a temporary building jig and covered in glass/epoxy or wood veneer. Western Red Cedar is usually used which is expensive, moderate skills required but more expensive/time consuming due to the building jig required. Fairly easy to repair and lightweight.
d) Cold Moulded: Similar to conventional cold moulded but sometimes vacuum bagged. Similar to trad cold moulding but often used in conjunction with strip planking to produce a very tough hull. Lightweight construction.
e) Clinker Ply: Similar to trad lapstrake/clinker but with joins between planks glued with epoxy rather than copper clench nailed. Requires expensive materials (ie high quality multi laminate plywood), high skills and extensive tools (ie.
rebate planes etc) and is not easy to repair. Lightweight construction[6].
Figure 6. Build a clinker ply boat. (From Bukas, 2015) [12]
1.2.3. Automatized Construction
In the nautical companies, were also possible to introduce the automatization in the line production. There are different projects that works with a CNC (computer numerical control), machines that are usually compose by sliders and a robot. This system allows to replicate a structure of a boat as many time as is request. The most common CNC machines adapted in the nautical sector creates a boat piece by piece. However, is necessary a post-operational process to link the sections. Is a favorable approach because each boat had several molds, none of them are identical and the halves are not
exact mirror images. The mold makers are talented, but like all hand made products, there are differences between each mold for the same vessel. The end result is a lot of parts that had to be modified, tweaked, or custom made, and this is a time consuming task.
As is shown from Tim Weston picture in the Figure 7 is being build a small boat “Noosa”. He has a router in his workshop and is using it to make his boat with precision. It took him some time while setting all the g-code programs created by a CAM(Computer-Aided Manufacturing) software and also time to set up the machine for cutting plywood, but once everything is set up, the machine cut all the parts of the boat in two hours.
Figure 7. Boat building with a CNC router. (From Weston, 2017) [13]
As this machine is possible to find other similar solutions, therefore is important to highlight the role of the operator, that is still essential in this type of strategies.
Nevertheless, is a possible alternative to increment the boats production and become this sector more efficient.
1.3. Systems
The traditional machines requires a group of information to be transmitted to the movement bodies by the operator acting directly on various commands. When talking
parameters, etc. That creates a demand in the industries to transformed a line of doing that is not fully efficient and safety.
1.3.1. CNC Machines
The first CNC machines were developed in the 1940s and 50s and relied on a common telecommunication data storage technology known as “punched tape” or “perforated paper tape.” Punched tape technology is long obsolete as the data medium quickly transitioned to analog and then digital computer processing in the 1950s and 1960s.
Machining is in general a form to remodel a piece of raw material such as a block of plywood and arrive at a finished product through a controlled material removal process.
Similar to the 3D printing, CNC works with digital instructions from a Computer Aided Manufacturing (CAM) or Computer Aided Design (CAD) file like autoCAD 3D. The CNC machine interprets the design as a g-code instructions for cutting parts. Automated cuts improve the velocity and the accuracy with which the parts can be created.
Often the shaped processes require the use of multiple tools to make the desired cuts.
CNC machines commonly combine tools into common units or cells from which the machine can draw. Basic machines move in one or two axes while advanced machines move laterally in the x, y axis, longitudinally in the z axis, and oftentimes rotationally about one or more axes. Multi axis machines are capable of flipping parts over automatically, allowing to remove material that was previously “underneath.” This eliminates the need for workers to flip the prototype stock material and allows the operator to cut all sides without the need of manual intervention. Fully automated cuts are generally more accurate than what is possible with manual inputs. That said, sometimes finishing work like etching is better accomplished by hand as well as simple cuts that would require extensive design work to program the machine for automation.
The conventional technologies use three strategies drills, lathes and milling. The first one work by spinning a drill bit and moving the bit about and into contact with a stationary block of stock material. The second one is the inverse of drills, spin the block of material against the drill bit. Lathes typically make contact with the material by laterally moving a cutting tool until it progressively touches the spinning material. The
third one and the most common CNC machine in use today, they involve the use of rotary cutting tools to remove material from the stock unit[14].
1.3.2. PLC Controllers & fieldbus
Programmable logic controllers (PLCs) have been an integral part of factory automation and industrial process control for decades. PLCs control a wide array of applications from simple lighting functions to environmental systems to chemical processing plants.
These systems perform many functions, providing a variety of analog and digital input and output interfaces; signal processing; data conversion; and various communication protocols. All of the PLC's components and functions are centered around the controller, which is programmed for a specific task[15].
Figure 8. Simplified PLC block diagram. (From Wright H., 2010) [16]
There are different types of PLC integrated as either single or modular units:
• Compact PLC: Is built by several modules within a single case.
Therefore, the I/O capabilities are decided by the manufacturer, but not by the user. Some of the integrated PLCs allow to connect additional I/Os to make them somewhat modular.
• A modular PLC: Is built with several components that are plugged into a common rack or bus with extendable I/O capabilities. It contains power supply module, CPU and other I/O modules that are plugged together in the same rack, which are from same manufacturers or from other manufacturers. These modular PLCs come in different sizes with
Modular PLCs are further divided into small, medium and large PLCs based on the program memory size and the number of I/O features[17].
The PLC use different communication protocols to transfer information and commands between the PLC and the I/O signals. The protocols are system of rules that allow two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implement by hardware, software or a combination of both[18].
There is a large number of communication protocols used in the automation, the differences arise from the type of laws that govern each system. The most common protocols used in the industrial sector are:
• EtherCAT
• Ethernet Powerlink
• Profinet
• Modbus
• Ethernet/IP
• CAN
• CANopen
1.3.3. Industrial robots
An industrial robot is a robot system used for manufacturing. Industrial robots are automated, programmable and capable of movement on two or more axes. Typical applications of robots include welding, painting, assembly, pick and place for printed circuit boards, packaging and labeling, palletizing, product inspection, and testing; all accomplished with high endurance, speed, and precision. They can assist in material handling[19].
Some of the frameworks of industrial automation systems where the robots were include are:
• Process control
• Numerical control machines (CNC)
• Assembly machines
• Automatic warehouses
• Automatic systems for supervision
• CAD tools
A robot is always used in cooperation with other machinery. These machines together form a workcell.
A workcell must be designed in order to be efficient and to maximize the production. In this line of think is possible to find different configurations:
• Workcells with a central robot, the robot is placed centrally, and its main task is to load/unload the surrounding machines.
• Production line, the robots are placed along a production line. Products are transported by the line and robots execute the programmed tasks (assembly, direct operations, …)
• Workcells with a mobile robot, the robot is placed on a mobile platform; it is moved in different positions of the workcell to execute the programmed activities. The robot can operate with many machineries[20].
