3.2 - Technical Concepts

From Wikibooks, open books for an open world
Jump to: navigation, search

The following technical concepts are drawn from various fields of engineering, the sciences, good design practice, computer networking, and a desire for sustainability. They are particularly relevant to the design and operation of self-expanding production. This is not to negate the importance of the whole of the various engineering fields, many of which are necessary to design any factory, whether seed type or conventional.

Conservation of Flows[edit]

In the sciences and engineering, Conserved Properties are ones which do not change as a closed system evolves. Under ordinary conditions, matter and energy are conserved properties. Another way of putting this is they do not appear or disappear from nothing. Since the value does not change over time, we can write equations where the total at one time is equal to the total at another time, although the components that make up the total may have changed. Open systems allow inputs and outputs to enter and leave, respectively. We can also write equations for open systems, where the total now is equal to the total at a previous time, plus or minus any quantity that has entered or left the system in the interim. These equations can then be used to solve problems or answer questions about the design and operation of the system.

We can apply these kinds of conservation rules beyond just matter and energy, to all types of resources, including such items as data or human labor. So when designing a factory, any change in the amount of a resource within the system must come from a flow into or out of the system, or by conversion of the resource into some other form. The rule applies to individual parts of the factory as well. As a consequence, process flows cannot have detached endpoints within the system, since that would imply appearance or disappearance of the resources in the flow. Flows must connect between parts of the system, or lead outside it. If a process consumes more raw materials or energy than is embodied in the products, the conservation rule tells us there must also be some waste material or energy outputs. An efficient design will identify these waste flows, and try to make use of or minimize them rather than ignoring them.

Systems Approach[edit]

Figure 3.2-1. Open system diagram with boundary.

From the point of view of Physics, an open system is conceptually a simple box which has flows into and out of it, and some amount of resources and objects inside. We make that idea more useful for engineering design by expanding on it and applying it recursively at multiple levels. A System is defined as a functionally, physically, and/or behaviorally related group of regularly interacting or interdependent elements. It is distinguished from its surroundings by a System Boundary (Figure 3.2-1). The boundary is a mental construct drawn around a collection of elements for the purpose of design and analysis. It is not a physical boundary like a fence. A system may have parts that are physically separated, such as a satellite TV network where the broadcast center, satellite, and home equipment are very far apart. These parts, however, are functionally related and interact, so their design is usefully done as a whole, rather than as unrelated items. A system also has a time dimension during its existence, and will evolve over that time. The Systems Approach tries to optimize the design, not just at a single point in time, but across the whole time it exists. So it considers everything from the design stage to final disposal when the system is obsolete. Flows across the system boundary therefore are distributed in time as well as location.

From our conservation of flows rule, any flow of matter, energy, data, or any other kind, which crosses the system boundary, results in an equal change in the quantity inside the system. Flows going in increase the amount, and flows going out reduce the amount. An example of a very simple system is a personal checking account. Deposits increase your balance, and payments reduce them. While flows do not appear from nothing or vanish into nothing, parts of a system known as a Functional Elements can transform inputs into different outputs. For example, a machine tool can convert metal bar stock + electricity into a finished part + metal chips. Each part of a system, when considered individually, also must obey the conservation rules, and can be considered as a smaller system, or Subsystem. By breaking a system down into smaller and simpler functional elements and applying the conservation rules to each you can trace and account for everything moving in and out of a system, and all of the flows and operations that happen inside.

Modular Design[edit]

In general, we won't know ahead of time all the needs for factory growth and the types of products to make. Traditional factories, with large fixed pieces of equipment like a blast furnace, can produce a lot of output, but are not flexible, and therefore typically have unused capacity. For example, if the blast furnace is used to 80% of capacity, 20% is unused. If demand grows to 120% of capacity, an entire second furnace is needed, again leaving unused capacity. For US industry as a whole, capacity utilization has averaged 80% from 1972 to 2015, with a low of 66.7% in 2009 and a high of 85.3% in 1988-89. Therefore we would prefer a design which can change in smaller increments, rather than a monolithic fixed design that is hard to change. One way to provide flexibility and better capacity use is through Modular Design.

Modular design is the setting of envelopes and interfaces so that different elements can work together without special changes. This concept is in common use in a number of fields. For example, building construction in the US uses standard increments of two feet for lumber, so that pieces will fit together with less cutting and waste. Personal computers use standard sockets for processors, memory, and add-in cards, so that a wide variety of parts can be added as desired, without changing the case or motherboard. For an evolving factory, we can extend this idea to the building layout, with standard modular locations for equipment and their utilities. We can also apply the modular concept to vehicle and robot design. A vehicle would have standard chassis sizes, and standard locations to mount engine, wheels, construction implements, or robot arms. In both cases, this makes it easy to expand or modify things as needed.

If the volume of production or the mix of outputs changes, having the equipment in smaller modules allows you to better match the output to the demand. Alternately you can replace a given size machine with a larger one that occupies a larger space on the factory floor. In addition to making the equipment more flexible and efficient, modular design is easier. Rather than needing to design every possible equipment or building layout, you only have to design the individual modules, and then put them together as needed.

  • Module Sizes

Figure 3.2-2. Dimensions of standard Lego bricks.

A defining characteristic of modules is using specific sizes and spacing so that items will fit together easily. A popular example of this is the Lego building toy (Figure 3.2-2). Lego uses an 8 mm module, which is suitable for toy construction. Real products need a wider range of sizes, from smaller to much larger. Industrial design often uses Preferred Numbers which are nearly equal multiples in a geometric series. Our approach is to use a base scale that starts with 1, 2, 5, and 10 times a power of 10 times a metric unit. This gives a range of module scales that are 2 or 2.5 times larger than the last. The actual module sizes are then 1-6 times the base scale. This gives overlapping size ranges, since 6 times a given scale is more than the 1 times the next larger one. So with a 5 cm base scale, 5, 10, 15, 20, 25, and 30 cm would be module sizes in one dimension. A hardware component would then be any number of integer modules in size of the appropriate scale.

This approach can handle a wide range of sizes while still fitting within standardized modules. Spacing of mounting holes then follows the same system, with the holes a multiple of a module size apart. As an example, building a vehicle from a chassis, motor, and wheels would not require special parts if they all use the same size modules and hole spacing. A factory can be laid out with column spacing and equipment layout based on a particular module size. Different sized equipment is more likely to fill the space, because they are all even multiples or fractions of a module. This minimizes wasted space and allows placing of standard utility connections.

  • Standard Interfaces and Protocols

As paradoxical as it may sound, a standard interface can make things more flexible. Electrical outlets are standardized, but they allow plugging in almost any device at any location. There are already standards for connecting automated equipment, such as the Common Industrial Protocol, and for exchanging design data, such as STEP (ISO 10303 ), so such standards do not have to be developed from scratch. A full set of standards for a factory would include physical as well as data items. Physical standards include placement and types of utility connectors (power, data, water, etc.) so each machine can be "plugged in" without custom design. It would also include standard floor loads and other building features. The PCI standards for desktop computer expansion slots are an example this sort of modular system. The physical, power, and data connectors are standardized so any expansion card can fit any slot of matching type.

  • Modular Automation

Factory automation is a well known technology, but usually it means using automated machines and robots to make an end product, with some amount of human labor to assist. These type of machines are inherently flexible. You can choose to make a single part or a whole production run, or change products with a simple software change. For Modular Automation we envision a more advanced version that considers the factory itself as part of the product. If the assembly of the building, and setting up of factory equipment locations, storage, and other items can itself be automated, then the entire factory can become configurable and flexible according to changing needs. We do not expect 100% automation of these tasks, especially at first. To the extent we can implement it, though, it can dramatically improve productivity and self-expansion. With standardized factory modules, the tasks would be repeated many times across different factories, and therefore be worth the extra effort to automate.

Local Resources[edit]

The use of locally available resources was once a fact of life. High transportation costs made it too expensive to move a lot of goods. So people used what was available nearby. New transport methods, like railroads and large cargo ships, dramatically lowered the cost of moving bulk goods. It became feasible to extract high grade resources from the rare locations they could be found, then move them long distances to where they are wanted. A prominent example is petroleum, which is only found in abundance in certain locations, and is shipped around the world.

Such high grade resources are by definition finite: they are the peak of the abundance distribution. They tend to be exploited first because they are the easiest and bring the most reward. Once the peaks are used up, if the resource is still in demand, then people must necessarily turn to lower grade sources. Counteracting this to some extent is the fact that not all the resources are discovered at once, and extraction methods improve over time. These effects can delay needing to turn to lower grades, but the Earth is finite, and so at some point finding high grade sources will end.

It is efficient in the near term to extract concentrated sources of energy like crude oil, but this cannot last for the reasons just stated. In addition, fossil fuels deposit CO2 in the atmosphere, which has major unwanted side effects. Both difficulty of extraction and side effects encourage us to move away from these sources. Since petroleum products are the major source of power for relatively cheap modern transportation, we must find alternative methods. As the easy and cheap sources run low, the cost of production will go up, and all the other industries that depend on cheap transportation will be affected. This includes delivering petroleum products where they are needed.

We can see from the petroleum example that the current mode of extracting the highest grade resources first is not sustainable over the long term. That's in addition to the waste problems they create. Use of lower grade resources, that can be found in many locations, helps address this problem in two ways. First, since they are found in many locations, the average distance to ship them is smaller, requiring less transportation energy. Second, the lower concentrations are more abundant and less prone to run out. For example, iron ore in concentrations above 25% are needed at present to be worth mining, and only occur in certain places. However iron makes up 5% of the entire Earth's crust, so learning to extract it from the common minerals in which it is found would vastly increase the sources.

Cyclic Flows[edit]

Even lower grade resources are still not ultimately sustainable if mass flows are linear. Linear means matter flows from a source such as a mine, is used one time within civilization, and then is disposed of as waste. In that case the resource, no matter how abundant, gradually gets depleted and wastes accumulate over the long terms. The alternative is to use cyclic flows which follow how nature operates, where most materials get recycled many times. The most notable examples are the human and natural processes that return waste water to usable form. Already used materials have some advantages over newly extracted raw sources. They often occur near where new products are wanted, since that's where old products were used and discarded. Therefore transportation distances can be short. Their quality as ores can be quite high, and in fact recycling of metals and some other materials are well-developed industries.

Materials recycling is enabled by sufficient energy, which, unfortunately cannot be reused. So-called renewable energy actually only arrives on a regular basis from a human perspective, so what is renewed is the daily or seasonal supply. The ultimate sources of solar, wind, hydroelectric, and geothermal energy are nuclear fusion and radioactive decay, which are finite linear processes. The time for them to run out, however, is measured in billions of years. This is much longer than current human time horizons, so from an engineering design perspective we can treat them as unending sources.

Including recycling in the original design of a location should be more efficient than adding it after the fact. Items can be designed with recycling in mind from the start, and factory processes can be integrated to make use of wastes from other processes. It should also bring some cost benefits by reducing the need for mining and processing of raw materials. For example, a rusty iron pipe is still a much higher grade of ore than most iron mines supply. This is why a lot of iron and steel scrap gets fed back into making new products. Recycling also reduces the need for waste disposal. If recycling is efficient enough within an automated factory, there is even the possibility of taking wastes from outside sources and converting them to useful products, thereby helping to clean the rest of the world. This makes economic sense sense if the wastes can be acquired cheaply enough.

Distributed Operations[edit]

Distributed operations are characterized by tasks and processes happening in more than one location. We can categorize types of distribution by where the equipment is, and by where the control is. The former is easy to understand. A given location either has all the equipment, or some subset of the equipment. In fact, integrated factories grown from a starter set can be the opposite of distributed relative to conventional factories. They can concentrate more production steps and equipment types than is usual in a single place. At the other extreme you can have single machines spread all over the world, but coordinated electronically. Where the control is located can be any combination of local vs remote, and manual vs automated. The possibilities are therefore direct human operator at the equipment, remote operation by humans, local computer/automation operation at the equipment, or remote automated control.

  • Remote Operations

Before the electronic age, only one of the four options was practical: manual human operators of machines in the same location as the equipment. The coordination of humans at a distance from each other was difficult and transportation costs were relatively high. So it made sense to locate offices and multiple production tasks in centralized locations. This logic is why large centralized factories and office buildings were and are still common. Modern electronics-based technology like cell phones, broadband networks, and remote controlled robots with vision and force feedback, enable operating in a more distributed way, with people separated from each other and from the equipment. It is not required that people and equipment be separated, but it is a new option made possible by the level of technology. Modern electronic controls and software also add the options of local and remote operations of some tasks without needing people at all, i.e. automation.

The economics of remotely operated equipment depend on the cost of telepresence and remote control vs the cost of onsite humans. Onsite workers require things like parking, floor space for access, cafeterias, and bathrooms. Travel to work has significant overhead in commuting time and costs. Remote access has the potential to reduce the cost of supplying the items people need. For example, rather than parking spaces for a large number of daily workers, the land area and construction cost for parking could be reduced to just what is needed for occasional maintenance staff. The standard reasons for putting things in one place, like efficient transfer between production steps, still apply. So the specific circumstances of a project will determine how distributed the design should be.

An example of remote operations is placing a solar panel factory in the Sahara desert, where you have plentiful sunlight to run it, and sand (silicon dioxide) as the raw material for the silicon cells. The human operators, though, might not want to live in the desert, and the costs to support them there would be relatively high. So working remotely in this case would be more attractive. Another reason for remote work is if there are not enough local people with the right skills. Remote work expands the candidate pool to the whole world (or at least the part with fast enough broadband). A third reason is multiple people in different time zones can operate the same equipment by remote control, using it around the clock and making it more productive. A fourth is job flexibility. You may not need a full time person at a given factory, but you can assign them to work in different factories and switch locations electronically.

When moving to more difficult locations on Earth, and eventually into space, sending the equipment ahead and operating it remotely is a relatively more attractive option. At first, the new location is not able to support people from local resources or provide comfortable living space. The difficulty of supporting people is why remote control has been used for all long term spacecraft beyond Low Earth Orbit so far. Remote operation is also used for military drones, deep sea vehicles, and some types of mining, where the environment is hazardous or it is expensive to support humans. Continuing improvements in electronics and network bandwidth mean remote operation can be effectively applied to more tasks than before. The more difficult and distant the location, the higher the incentive to operate remotely.

Once local support capacity is in place at a given location, the humans can then follow. Human presence is not an all or nothing situation. Temporary visits or a small permanent crew can supplement a larger operation which is mostly controlled remotely.

  • Self-Expanding Networks

Self-expanding networks are a particular kind distributed operation, consisting of multiple nodes that exchange data, physical resources, and products. What distinguishes such networks from the general background of modern industry is the elements are designed to work together and make items for each other. The network also uses some level of automated software to coordinate tasks and payments. Individual nodes vary in complexity (how many tasks they perform) and output capacity. A specialty node may only do one or a few related tasks, while a general-purpose one could perform many tasks. A general-purpose node may have enough flexibility to produce many of its own parts and materials. A local personal or commercial node would have smaller output capacity, while an industrial one would have a high output capacity. These are not sharp categories, but rather descriptions of types within a spectrum of different nodes.

The network as a whole can provide a higher level of self-expansion and self-production than an individual node, because it includes a wider range of processes and products, and more people with different skills. In particular, the products of the network can purposely include designs, parts, and complete elements to establish new nodes, so helping the network to grow.

A large conventional factory, like one for assembling automobiles, is normally dedicated to one task. When demand for that particular item falls, the equipment is under-used and people get laid off. Separating production tasks into smaller, more flexible nodes can make it easier to change what they do as demand fluctuates. This requires more computers and software to re-direct tasks as needed, but computers are relatively cheap compared to re-purposing a conventional factory. A flexible network may therefore have higher utilization and be more efficient overall.