3.2 - Engineering Concepts

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The following concepts are drawn from existing fields of engineering, or the sciences on which they are based:


Conservation of Flows[edit]

In the sciences and engineering we have the concept of Conserved Properties, which do not change as a closed system evolves. Under ordinary conditions, matter and energy are conserved properties, meaning the total amounts do not change. Another way of putting it 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. We can also write equations where the total now is equal to the total before, plus or minus any quantity that has entered or left the system in the interim. The equations can then be used to solve problems or answer questions about the design and operation of a system.

We can apply conservation rules beyond just matter and energy, to all types of resources, including such items as data or human labor. Thus, 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 design 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. A complete design will identify these waste flows, and try to make use of them rather than ignoring them.


Systems Approach[edit]

Figure 3.0-1. System diagram with boundary.

From the physics aspect, a system is 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 from an engineering design perspective 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 3.0-1). The boundary is a mental construct drawn around a collection of elements for the purpose of design and analysis. 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 to its existence, and will evolve over time. The Systems Approach tries to optimize the design not just at a single point in time, but across the whole time it exists. Thus 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, a part of the system known as a Functional Element can change inputs into different outputs. For example, a machine tool can convert raw bar stock + electricity into a finished part + shavings. 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 don't know ahead of time all the future needs for factory growth and the types of products it will make. Therefore we would prefer a flexible design which is able to change, rather than a monolithic fixed design that is hard to change. One way to provide flexibility is through the use of 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. 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, it 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

A defining characteristic of modules is using specific sizes and spacing so that items will fit together easily. 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. The "2.5" comes from the larger ratio between 2 and 5. This gives overlapping size ranges. Thus 5, 10, 15, 20, and 25 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. Spacing of mounting holes then follows the same system, with the holes a multiple of a module size apart. Then, for example, building a vehicle from a chassis, motor, and wheels does 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. This minimizes wasted space and allows placing of standard utility connections.

(An earlier version of this section started from 1, 2.5, 5, and 10, which in theory would work just as well, but has 2 minor differences from the standard R10" series in the current version of this section.)

  • 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. By comparison, the PCI standards for desktop computer expansion slots are 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 thus be worth the effort to automate.


Generalized Resources[edit]

The use of non-specialized resources was once a fact of life. High transportation costs made it too expensive to move most goods, and so people used what was available locally. New transportation methods like railroads and large ships dramatically lowered transportation cost. That made it feasible to extract high grade resources from the rare locations they could be found, and then move them 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, and 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. New discoveries of high grade concentrations can delay needing to turn to lower grades, but the Earth is finite, and thus at some point finding new sources will end. While it is efficient in the near term to extract concentrated sources of crude oil or metal ores, our example of petroleum is a major source of power for relatively cheap modern transportation. As the easy and cheap sources run low, the cost will go up, and all the other industries that depend on cheap transportation will be affected.

Thus we can see that the current mode of operation is not sustainable over the long term. Use of non-specialized resources, ones that can be found in many locations at lower concentrations, addresses this problem in two ways. First, since they are found in many locations, the average distance to ship them is smaller. 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 locations. 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]

Using finite generalized resources is 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, with most materials getting recycled many times. Some recycling of materials happens in our present civilization, most notably human and natural processes that return waste water to usable form. Other materials, such as fossil fuels, are currently single-use, and scrap metals have varying levels of recycling.

Material 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. The ultimate sources of solar, wind, and geothermal 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 resources.

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 our automated factory, there is even the possibility of taking wastes from outside sources and converting them to useful products, thus helping clean the rest of the world. This makes economic sense sense if the wastes can be acquired cheaply.


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 kit can be the opposite of distributed relative to conventional factories. They can concentrate more production steps and equipment types in a single place. At the other extreme you can have single machines spread all over the world, but coordinated. Where the control is located can be 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, there was no choice about having the human operators of production machines be in the same location as the equipment. The coordination of humans at a distance with each other was difficult and transportation costs were relatively high. Thus it also made sense to locate offices and multiple production tasks in one central location. This logic is why large centralized factories and office buildings were and are common. Modern 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 separate, but it is a new option made possible by the level of technology. The economics of remotely operated equipment depend on the cost of telepresence and remote control vs the cost of onsite humans. This includes parking, floor space, cafeterias, and bathrooms to accommodate humans, plus commuting costs. Remote access can save production floor space if the robots don't need as much as humans. The standard reasons for putting things in one place, like efficient transfer between production steps, still apply. The specific circumstances of a project will determine how distributed the design should be.

For example you might place 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. Therefore remote operation in this case would be more attractive. Another reason for distributed operation is if there are not enough local people with the right skills. Remote operation 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 is used for all long term spacecraft beyond Low Earth Orbit to date. Remote operation also is currently used for military drones, deep sea vehicles, and some types of mining, where the environment is hazardous or it is expensive to support humans. With recent improvements in electronics and network bandwidth 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 follow. Human presence is not an all or nothing situation. Temporary visits or a small permanent crew can supplement a larger operation mostly controlled remotely.


  • Self-Expanding Network

This concept envisions a distributed network of nodes that exchange data, physical resources, and products. What distinguishes the network 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 automation to coordinate tasks and payments. Nodes vary in complexity (how many tasks they perform) and output capacity. A specialty node may only do one or a few related tasks. An industrial node has a high output capacity. A general-purpose node has sufficient complexity to produce many of its own parts and materials. 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 closure than an individual node, because it includes a wider range of processes and products, and people with different skills. In particular, the products of the network purposely include designs, parts, and complete elements to establish new nodes, thus making the network self-expanding.

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.