Technology groups and flexible manufacturing
INTRODUCTION:
Technology groups is an approach to manufacturing in which similar parts are identified and grouped to take advantage of their similarities in design and production.
It is also known as group technology and is instrumented using automated manual techniques. When automation is used, the term flexible manufacturing system is generally used.
This work is divided into three sections: Through it we will first describe the characteristics, advantages and disadvantages of technological groups in order to achieve a complete understanding of this approach.
Following this we will enunciate the factors that influence the manufacturing processes, to have an outline that allows us to identify them in what will be our manufacturing design.
We hope that the content of this work is very useful to the reader and that it allows him to reinforce his academic knowledge.
TECHNOLOGICAL GROUPS
Manufacturing practice by which the pieces are grouped into families with similar characteristics (geometric or processing).
CHARACTERIZATION
- A central feature of group technology is the part family.
- A family of parts have similarities in geometric shape and size or in the processing steps used in their manufacture.
In other words:
• Similar parts are identified and grouped to take advantage of their similarities in design and production.
• The similarities between the parts allow to group them as families
The Group Technology concept is well implemented in Cellular Manufacturing.
Group technology is an approach to the production of parts in medium quantities. Parts (and products) in this quantity range are usually made in batches.
Batch production has the following disadvantages:
• Detention time for changes.
• High inventory carrying costs.
Group technology minimizes these disadvantages by recognizing that although the parts are different, they have similarities.
Group technology exploits similarities using similar processes and enabling tools to produce them. The TG is instrumented using automated manual techniques. When automation is used, the term Flexible Manufacturing System is often used.
ADVANTAGE:
Group Technology brings substantial benefits to companies if they have the discipline and perseverance to implement it.
The potential benefits are:
• They promote standardization in the enabling of tools, the installation of supports and dispositions.
• Material handling is reduced because parts move within a machining cell and not within the entire factory.
• Simpler production schedules are possible.
• Production time is reduced.
• Work in process is reduced.
• Process planning is simplified.
• Generally improves worker satisfaction when working in a group technology cell.
• Higher quality work is obtained using this resource.
• Simplify production planning and control.
• Optimally arranges sequence and load, while reducing setup and machining times as well as inventories during the process.
• It makes possible the standardization of the design of the pieces, and minimization of design duplications.
• Manufacturing costs can be estimated more easily, and statistics on materials, processes, number of parts produced, or other factors can be more easily obtained.
DISADVANTAGES:
There are problems in carrying out group technology, among these are:
• An obvious problem is the rearrangement of the machines for production in the plant in the convenient machining cells.
• It takes time to plan and carry out this rearrangement: the machines stop producing during the change.
• The biggest problem with starting group technology is identifying part families: if the plant makes 10,000 different parts, submitting all the part drawings and grouping them into families takes a significant amount of time.
• It is difficult to balance the work and the use of the machine.
• It is difficult to find the right staff for supervision.
FACTORS THAT INFLUENCE MANUFACTURING PROCESSES
• MATERIALS
• MACHINE TOOLS
• COSTS
• PRODUCTION VOLUMES
• MATERIALS.
Most materials in manufacturing can be classified into one of the 3 basic categories:
1. Metals
2. Ceramic products
3. polymers
Both its chemical properties and its physical and mechanical properties are different; These differences affect the manufacturing processes that are used to transform them into final products.
In addition to these three basic categories, there is another:
4. Composite materials
• MACHINE TOOLS.
Machines and tools (as well as work) are used to carry out production operations.
Among all production machines, machine tools are the most versatile, they are not only used to manufacture consumer articles, but also to produce components for other production machines.
All machine tools have a set of parts and activities that distinguish and characterize them. The type of tool depends on the manufacturing process to be carried out.
These machines can be classified into three categories: conventional devastating machines, presses and special machine tools. Conventional devastating machines shape the part by cutting off the unwanted part of the material and producing chips. Presses use various modeling methods, such as shearing, pressing, or stretching. Special machine tools use light, electrical, chemical, or sound energy, high-temperature gases, and high-energy particle beams to shape special materials and alloys used in modern technology.
Turnstile
The lathe, the oldest and most common rotary machine, grips a piece of metal or wood and rotates it while a cutting tool shapes the object. The tool can be moved parallel or perpendicular to the direction of rotation, to obtain parts with cylindrical or conical parts, or to cut grooves. Using special tools, a lathe can also be used to obtain smooth surfaces, such as those produced by a milling machine, or to drill holes in the part.
Roll forming machine
The roll forming machine is used to obtain smooth surfaces. The tool slides on a fixed piece and makes a first journey to cut protrusions, returning to the original position to carry out the same journey after a brief lateral displacement. This machine uses a single-pointed tool and it is slow, because it depends on the routes that are made forwards and backwards.
For this reason it is not usually used on production lines, but it is used in tool and die factories or in workshops that manufacture small series and that require greater flexibility.
Planer
This is the largest reciprocating machine tool. Unlike in profiling machines, where the tool moves on a fixed part, the planer moves the part on a fixed tool. After each swing, the part moves laterally to use another part of the tool. Like the planer, the planer allows vertical, horizontal or diagonal cuts. You can also use several tools at the same time to make several simultaneous cuts.
Milling machine
In milling machines, the part comes into contact with a circular device that has several cutting points. The piece is fastened to a support that controls the advance of the piece against the cutting tool. The bracket can advance in three directions: longitudinal, horizontal and vertical. In some cases it can also rotate. Milling machines are the most versatile machine tools. They allow curved surfaces to be obtained with a high degree of precision and an excellent finish. The different types of cutting tools allow to obtain angles, grooves, gears or notches.
Drilling and boring machines
Drilling and boring machines are used to open holes, to modify or adapt them to a measurement, or to grind or grind a hole to achieve an accurate measurement or a smooth surface.
Drills are available in different sizes and functions, from portable to radial drills, to multi-head drills, automatic machines, or long-length drilling machines. Drilling involves increasing the width of an already drilled hole. This is done with a rotary cutting tool with a single point, placed on a bar and directed against a fixed piece. Drilling machines include caliber drills and horizontal and vertical drill bits.
Grinding machines
Grinding machines are machine tools equipped with precision grinding wheels and adequate systems to hold, position, rotate or move the part in order to be able to fine-tune it to the desired size, shape and finish. The grinding wheel is mounted on a shaft driven by a motor, which makes it rotate at about 30 meters / second. Grinding machines are usually classified according to the shape of the workpiece to be refined, the clamping mode and the structure of the machine. The four types of precision grinding machines are spot grinders, pointless grinders, interior grinders and surface grinders.
Point or exterior grinding machines are used with cylindrical parts drilled through their center at each end, allowing the part to be held between two points and rotated. The pieces ground between the points range from tiny valve sleeves to steel mills with diameters greater than 1.5 m and weights of almost 100 tons.
Pointless grinding machines eliminate the need to drill the ends of the part. In these machines the part is held on a support blade and a regulating wheel, which also controls the rotation of the part. They are used to sharpen objects such as bowling balls, surgical sutures, or tapered roller bearings.
Internal grinding machines are used for finishing internal diameters of gears, bearing guides and similar parts. The grinding wheels are small and rotate at very high speeds, between 15,000 and 200,000 revolutions per minute. The piece rotates slowly while the grinding wheel remains fixed.
Surface grinding machines are used for flat surfaces. The part is placed on a flat bench and held in place by electromagnets or fixing devices. The grinding wheel is lowered onto the workpiece while the bench moves with an alternative movement or rotates slowly.
Polisher
Polishing is the removal of metal with a rotating abrasive disc that works like a cutting mill.
The disc is made up of a large number of grains of conglomerate abrasive material, in which each grain acts as a tiny cutting tool. With this process very smooth and precise surfaces are achieved.
Since only a small part of the material is removed with each pass of the disc, the polishers require very precise regulation. The pressure of the disc on the part is selected with great precision, therefore fragile materials can be treated in this way that cannot be processed with other conventional devices.
Saws
The most widely used chainsaws can be classified into three categories, depending on the type of movement used to make the cut: reciprocating, circular or band. Saws usually have a bench or frame, a screw to hold the piece, a feed mechanism and a cutting blade.
Tools and fluids for cutting
Since the cutting processes involve local stresses and frictions and considerable heat release, the materials used in the cutting tools must be hard, tough and resistant to wear at high temperatures. There are materials that meet these requirements to a greater or lesser degree, such as carbon steels (containing 1 or 1.2% carbon), fast cutting steels (alloys of iron with tungsten, chromium, vanadium or carbon), tungsten carbide and diamonds. Ceramic materials and aluminum oxide also have these properties.
In many cutting operations fluids are used to cool and lubricate. Cooling extends tool life and helps set the size of the finished part. Lubrication reduces friction, limiting the heat generated and the energy required to perform the cut. Cutting fluids are of three types: aqueous solutions, chemically inactive oils and synthetic fluids.
Presses
The presses shape the pieces without removing material, that is, without producing chips. A press consists of a frame that supports a fixed bed, a piston, a power source, and a mechanism that moves the piston parallel or at right angles to the bed. The presses have dies and punches that allow to deform, drill and shear the pieces. These machines can produce parts at high speed because the time required by each process is only the time of displacement of the piston.
Unconventional machine tools
Non-conventional machine tools include plasma arc machines, laser beam machines, electric discharge machines, and electrochemical, ultrasonic, and electron beam machines. These machines were developed to shape high hardness alloys used in heavy industry and aerospace applications. They are also used to shape and engrave very thin materials that are used to make electronic components such as microprocessors.
Plasma arc
Plasma arc machining uses a high-speed, high-temperature jet of gas to melt and remove the material. The plasma arc is used to cut difficult to section materials with other methods, such as stainless steel and aluminum alloys.
To be
Mechanization by laser beam is achieved by directing a laser beam very precisely, to vaporize the material to be removed. This method is very suitable for making holes with great accuracy. You can also drill ceramic and refractory metals and very fine parts without crimping them. Another application is the manufacture of very fine wires.
Electric shock
Electric discharge machining, also known as spark erosion, uses electrical energy to remove material from the part without touching it. A high-frequency current is applied between the tip of the tool and the workpiece, causing sparks to fly that vaporize small points on the workpiece. Since there is no mechanical action, delicate operations can be performed with fragile parts. This method produces shapes that cannot be achieved with conventional machining processes.
Electrochemistry
This type of mechanization also uses electrical energy to remove material. An electrolytic cell is created in an electrolyte, using the tool as a cathode and the part as an anode, and a high intensity but low voltage current is applied to dissolve the metal and remove it. The piece must be of a conductive material. With electrochemical machining many operations such as engraving, marking, drilling and milling are possible.
Ultrasonic
Ultrasonic machining uses high-frequency, low-amplitude vibrations to create holes and other cavities. A relatively soft tool of the desired shape is manufactured and applied against the part with a vibration, using an abrasive material and water. The friction of the abrasive particles gradually cuts the piece. This process enables hardened steels, carbides, rubies, quartz, diamonds and glass to be machined with ease.
Electron beam
This method of mechanization uses electrons accelerated to a speed equivalent to three quarters of the speed of light. The process is carried out in a vacuum chamber to reduce the expansion of the electron beam due to gases in the atmosphere. The electron current strikes a precisely delimited area of the part. The kinetic energy of the electrons is converted into heat when they hit the part, which causes the material to be removed to melt and evaporate, creating holes or cuts. Electron beam equipment is often used in electronics to record microprocessor circuits.
• COSTS
They are the amount disbursed or invested to buy or produce a good.
They can be classified into two broad categories: on the one hand there are fixed costs, such as the rent or rent paid for the facilities and which do not depend on the quantity produced, and on the other hand, the variable costs, which depend on the quantity of raw materials used and wages paid that vary depending on what is produced.
When companies or companies calculate their costs, they usually also evaluate marginal costs and average costs. The marginal is the cost of producing an additional unit. The average cost is the total cost divided by the number of units produced. The price has to be equal to the marginal cost of the last unit produced so that the company does not incur losses when producing this last unit.
Costs provide a basis for determining profit, for planning profit, for control, and for decision making
Throughout history, factors such as inflation, taxation, labor costs, material costs, as well as distribution costs, have driven industries to seek better and cheaper ways of conducting production.
Most products made for the general public only give satisfactory results if they can be mass-produced and marketed at advantageous prices.
Product design affects manufacturing costs (direct and indirect labor, raw materials, and overhead), warranty costs, and field repairs. Many times a simplification in design can improve the cost of a product. By reducing the number of parts manufactured, raw material costs are generally reduced, inventory levels are lowered, the number of suppliers is reduced, and production time may decrease.
• PRODUCTION VOLUMES
The amount of products made by a factory significantly influences how it organizes its personnel, its facilities, and its processes and procedures.
Production volumes can be classified into three categories:
• Low (1-100 units per year)
• Average (101-10,000 units per year)
• High (production of 10, 001 to several million units per year)
Most factory-made products only give satisfactory results if they can be mass-produced and marketed at advantageous prices.
The best product design is as good as its ability to be produced competitively.
The production capacity of a plant directly influences its level of automation, the quantity of materials used in the process and production costs.
A workshop should be designed for maximum flexibility, to deal with the wide variety of products that could be produced.
OUR DESIGN:
BUCKLE - WOOD
Wood, a hard and resistant substance that constitutes the trunk of the trees and has been used for thousands of years as fuel and as a construction material.
CLASSIFICATION
• The woods are classified as hard and soft according to the tree from which they are obtained.
• The wood of deciduous trees is called hardwood, and the wood of conifers is called soft, regardless of its hardness.
• Thus, many softwoods are harder than so-called hardwoods.
WOOD DURATION
Wood is, by nature, a very durable substance.
COSTS:
Wood costs vary according to type. The least expensive woods are those that come from pine.
BUCKLE - STEEL
Iron, due to its abundance and its chemical properties, has become one of the most used metals in today's civilization.
It can be combined with other metals to form new compounds with different properties, called "alloys".
It is a metallic, magnetic, malleable and silver-white element.
It is one of the most abundant metallic elements on the planet. It constitutes approximately 4.5% of the earth's crust.
Iron alloys are those in which the main component is iron, and it is very important as a material for the construction of various equipment.
Its production is very high, due to:
• Abundance of iron in the earth's crust
• Steel manufacturing techniques are economical.
• High versatility.
STEEL:
In general, steel is an alloy of iron and carbon to which other elements are usually added.
It is widely used due to its low cost and properties.
MACHINE TOOLS:
The machine tools that can be used to make our piece in wood are:
• The brush
• The milling machine
• The lathe
This according to the processes that are achieved with each of them.
PRODUCTION VOLUMES:
It is possible to have an average production volume according to the abundance of this material in our environment and seen from an ecological point of view, so that we do not have a negative impact on our habitat.
Modern steel production employs blast furnaces which are perfected models of those formerly used.
* Stainless steels: Resists corrosion (rust) in many environments, especially in the atmosphere. The main component element is chromium (> 11%).
MACHINE TOOLS:
The machine tools that can be used to make our piece in steel are:
• The milling machine
• The bender
• The lathe
• The grinding machine
• Machining center
This according to the processes that are achieved with each of them.
PRODUCTION VOLUMES:
Large production volumes are possible according to the abundance of this material in the Earth's crust.
SUMMARY
• Technological groups is the manufacturing practice by which parts are grouped into families with similar characteristics (geometric or processing). Exploit the similarities using processes and enabling similar tools to produce them.
• One of its main advantages is that: material handling is reduced because the parts move within a machining cell and not within the entire factory, and manufacturing costs can be estimated more easily, and can be obtained more easily statistics on materials, processes, number of parts produced or other factors
• The biggest downside to this approach is that part families need to be identified to start group technology: if the plant makes 10,000 different parts, submitting all part drawings and grouping them into families consumes a significant amount of time and the machines stop working during the change which translates into losses for the plant.
• The factors that directly influence manufacturing processes are materials, costs, machine tools and production volumes, that is, the behavior of the processes will depend on them.
• Our design was a buckle and was based fundamentally on the comparison of the characteristics and properties of wood and steel and to see advantages and disadvantages of both, so that a decision was also made based on costs, machine tools necessary to carry it out and the possible production volumes.
Bibliographic references:
1. FUNDAMENTALS OF MODERN MANUFACTURE: Materials, Processes and systems. Mikell P. Groover. Ed. Prentice May. Chap 1 and 38
2. PRODUCTIVITY AND OPTIMIZATION: Manufacturing Eng. Daniel t. Koening. Marcombo Publications. (advantages of Technology Groups)
3. MANUAL OF INDUSTRIAL ENGINEERING VOL. I. Gabriel Salvendy. Editorial Limusa. (Technology Groups)
4. MATERIALS AND MANUFACTURING PROCESSES FOR ENGINEERS. Lawrence E. Doyle / Leach / Schrader / Singer. Editorial Prentice Hall
5. MANUFACTURE: ENGINEERING AND TECHNOLOGY. Kalpakjan –Schmid. Editorial Prentice Hall
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