Virtual production
What is the configuration data in a RAPID Move instruction? Explain what could be influenced if you are not careful with the configurations.
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What does the expression "trash in trash out" mean in the simulation context? Explain how you would consider this in a simulation project.
Answer: "Trash in trash out" refers to that a simulation model can only represent a system as correct as the input data is. If data that is used for a simulation model cannot represent a system, the result from the simulation model will not provide any valuable information to the receiver. To consider input data and ensure that the simulation model is representative, are verification and validation important. When validating a simulation model, it should be ensured that the simulation model including its input data matches the real production system. The validation can be done by showing the model to the customer, do sensitivity analysis, and compare historic input with historic output data. Validation of the simulation model is also important for receiving acceptance from stakeholders. Another factor is to involve stakeholders thorough the project and identify them at an early stage of the project (during problem formulation).
b. Name and describe two contradictions you can face when trying to balance a problematic production line using Lean production as basis?
Answer: 1) reducing overproduction since balancing system losses means to even out the cycle times of equipment and 2) reducing stock levels and ques in the system which otherwise generates a high work in progress (WIP) and thereby tied up capital in production.
a. What does it mean that a robot has 6 degrees of freedom (DOF)? What is the configuration data in a RAPID Move instruction? Explain what could be influenced if you are not careful with the configurations.
Answer: 6 degrees of freedom means that the robot is capable of both translating and rotate the tool's coordinate system (TCS, TCP) relative to the X-, Y-, and Z-axis in a reference system.
A circular economy with several actors working together is evolving in society now. a. Why is a circular business model preferred when it comes to materials and sustainability?
Answer: A circular flow of materials that reuses the waste to make new products will not need virgin material and is, therefore, more sustainable. A circular model can also create a better connection between actors in the value chain and can promote better collaboration, for example, if the material is to be reused, the designers need to consider the choices and composition of materials in the product in order to enable recycling, reuse etc.
Describe a scenario where sustainability aspects are important for the design of a production system and exemplify with means for decision basis
Answer: A scenario should be described where sustainability aspects are important for the design of a production system. All four aspects of sustainability should be mentioned (environmental, social, economic, and ethical) and described how they impact on the scenario explained. It should also be exemplified how it impacts on decisions for the design for the scenario you explain.
In spot welding you could sometimes have a robot held welding gun and sometimes a stationary welding gun. What would be the major differences considering the coordinate systems used in the robot program.
Answer: A stationary tool is defined w r t the world frame and the robot is holding the workobject. The user frame is defined w r t the wrist coordinate system (toolframe - tool0). This means that the robot also carries the target frames since these has to be defined w r t the workobject (object frame).
c. In spot welding you could sometimes have a robot held welding gun and sometimes a stationary welding gun. What would be the major differences considering the coordinate systems used in the robot program.
Answer: A stationary tool is defined w r t the world frame and the robot is holding the workobject. The user frame is defined w r t the wrist coordinate system (toolframe - tool0). This means that the robot also carries the target frames since these has to be defined w r t the workobject (object frame).
b. Explain the meaning of warmup in a discrete event simulation model of a production system.
Answer: At the beginning of a simulation, the factory is completely empty. It is not representative of an ordinary day in production. Therefore, you should let the simulation go up in normal mode before you start logging what is happening and collect data from the simulation run.
A manufacturing company has a TAKT-time of 4 minutes/product with current customer demand. The available production time is 40 hours/week. What is the current customer demand per week? The customer demand is expected to increase by 20%. What will the new customer demand and the new TAKT-time be?
Answer: Available production time is 40h/week and the TAKT-time is 4 minutes/product. The customer demand is therefore: TAKT-time (minutes/product) = Available production time (minutes)/Customer demand 4 (minutes/product) = 40*60 minutes/ Customer demand Customer demand = 40*60/4 = 600 products/week (2p) When the customer demand increases with 20% will the new customer demand be 600*1,2 = 720 products/week (1p). The new TAKT-time = (40*60)/720 = 3,3 minutes/product (1 p)
Explain the meaning of the words cognitive automation, as it is used in production system context
Answer: Cognitive automation are technical solutions that can support an operator to perform the right task and take the right actions to ensure a high quality of the product. Within the Level of Automation (LoA) does this involve the "HOW to assemble (Levels 1-4) and situation control (Levels 5-7)." Examples of tools that can be used are smartphones and tablets to present information to the operator.
The difference between the words Effectiveness and Efficiency is described in chapter 7. Which of the words would you put at the start of the sentence below?__________________ describes the process from the customer's point of view: does the process deliver the expected cost, quality, and lead time required by the customer?
Answer: Effectiveness
Define Efficiency and explain the difference versus Effectiveness?
Answer: Efficiency (the internal view) considerations assess to what degree the process uses resources well. These metrics are generally based on the notion of productivity. The effectiveness (the external view) of a process can only be assessed by the customer and the customer alone. Effectiveness and efficiency are not perfectly correlated with each other; a productive resource is not necessarily an effective one. For more definition and distinction on these terminologies, see page 151 in course literature.
Describe systems and data flows in a modern production system.
Answer: Explain systems used in a production system and the purpose of them as well as the data exchanged between systems
Explain two benefits of using collaboration platform such as 3DExperience for virtual production planning.
Answer: First of all, by working with Virtual Production Planning you enable concurrent engineering, where different disciplines can work simultaneously on the platform towards the same source of data and information. Concurrent engineering will enable you to shorten the lead-time in process development to enable earlier "Launch-of-production" Moreover, working with 3D in the Virtual environment enables a much more intuitive view of data compared to using text-based solutions. Using databases, and not file-based will enable easier management of data (PDM), which enables version management, configuration management, and easy search for data. You will eliminate risk of redundant data.
A robot is theoretically controlled by calculating the forward kinematic and inverse kinematics. Explain these terms and the mathematical support as well as the procedure that is used to perform required calculations.
Answer: Forward kinematic describes the tool's position and orientation based on given axis values (1p). Through inverse kinematics can the axis values be gained when the tool's position and orientation are given (1p). Calculations are performed with the support of a transformation matrix. A transformation matrix is a special (4x4) matrix that describes position/orientation for a coordinate system in relation to the reference coordinate system (1p). These matrixes are placed in each joint and thereby is a kinematic chain created through the robot that is related to the base coordinate system with the tool coordinate system (1p).
b. Assume that you are programming a ABB Irbl400 robot offline. Explain what the robot does when the following RAPID-instructions are executed and how the single argument impacts the robot movement. MoveL penna_gr, v200, z50, PENNTCP\WObj:=REFRAM_PAPPER;
Answer: From the current position will the robot move the tool coordinate system "PENNTCP" linear against the goal position "penna_gr" with a speed of 200mm/s (1,5p). The goal position is defined relative "REFRAM_PAPPER" (work object) and together with the information zone data "z50" that is a passing position where the movement will be superimposed together with the next instruction given that it is a Move-instruction. This will then take place 50mm from "penna_gr" - otherwise it will become a stopping point (1,5 point).
How can buffers be used to identify bottlenecks in production flows? Exemplify how you used buffers in the DPS project.
Answer: Indications of bottlenecks when using buffers include large buffer levels and long waiting times in front of a resource, short ques after a resource, long/short mean times that a product is waiting in a buffer. Provide examples of how you used buffers in the DPS project.
Describe two possible setbacks with virtual training of operators
Answer: It is still challenging to ensure Motor skill learning process Skill knowledge is still challenging in a virtual environment for training operators. For these aspects is it still vital to physically interact with a tool and the product in the real world.
b. What do you need in terms of data to describe Mean Time To Failure for a NC machine.
Answer: NC is here referring to Numerical Control machine, the ones we use in the simulation project.In general, MTTF is the "up-time" between two failure states of a repairable system during operation. The "down time" is the instantaneous time it went down, which is after (i.e. greater than) the moment it went up, the "up time". The difference ("down time" minus "up time") is the amount of time it was operating between these two events. Since it is mean time, an average need to be calculated of the sum of failure time.
. What do you need in terms of data to describe Mean Time To Repair for a NC machine.
Answer: NC is here referring to Numerical Control machine, the ones we use in the simulation project.Mean time to repair (MTTR) is a basic measure of the maintainability of repairable items. It represents the average time required to repair a failed component or device. Expressed mathematically, it is the total corrective maintenance time for failures divided by the total number of corrective maintenance actions for failures during a given period of time.
c. Define Productivity and explain the difference versus Performance?
Answer: Performance consist of the two basic categories effectiveness and efficiency, where efficiency asses to what degree the process uses resources well and is the same thing as productivity. Productivity is the output in relation to input, the ratio between the output received from the production system in terms of product value delivered to customer and the input invested in producing a product.
Which one is probably best suited to achieve low unit cost at high volume production?
Answer: Product/Production-line Layout
b. Give an example of a circular system, which is sustainable over a foreseeable future, explain the materials flow and actors.
Answer: Production of curtain rods in one circle with manufacturer, sales users and a recycler. The manufacturer uses the used curtain rod material to manufacture new ones. As energy source in this circle all actors use wind, water or solar power
a. Explain two benefits for a manufacturing organization to use simulation tools.
Answer: Reduced time to market Flexibility when planning changes Saving development and implantation costs Easier for involvement by personnel in the design and development phase Digital documentation of the production system
Why does robot simulation result in a shorter time of production start when introducing a new product?
Answer: Robot code can be tested and verified offline while regular production is still ongoing.
Describe two mechanical constructs that can be used with an industrial robot
Answer: See lecture notes and laboratory pm. The described robot configurations are Cartesian, cylindrical, polar, articulated, spherical, SCARA and parallel.
Explain the meaning of the word sociotechnical, as it is used to describe systems (2p)
Answer: Systems and processes that are sociotechnical are a combination of human (social) and machine (technical), and their operation depends on both.
b. What are the two main goals when balancing a production line? (2p)
Answer: The goals of line balancing are to: -Evenly distributed work at the stations on the line. - Balance the capacity to match the desired takt time.
What is the quantitative value used in the SSLP method representing and why is it important to consider qualitative measures as well when selecting layout?
Answer: The quantitative value calculated for layout options according to the SSLP method provides an objective value for each layout to evaluate how well they fulfill the preset requirements of relationships between functions. The objective value is important for removing biases (1p). The quantitative value removes biases and represents in the best way how well-defined relationships have been fulfilled, but there could be other qualitative aspects that play an important role in selecting a layout. Therefore should also the qualitative aspects be considered when selecting a layout and not only relying on the quantitative value (1p).
The following is an example of an ABB robot RAPID instruction. Explain how it controls the robot motion and also explain each component of the instruction: MoveJ p3, v10, z10, tool1 \WObj:=papper
Answer: The robot should move the tool1 TCP to p3 in coordinate system "papper" at the speed of 10mm/s using a non-defined joint movement path. MoveJ p3 = robot should navigate to position p3, the movement is of type joint. v10 = sets the speed of the movement, here 10mm/s z10 = Zone size (accuracy). This indicates how close the robot must be to the target position before it can start to deviate towards the next position and thus corresponds to the radius in a fictional sphere around the target position - z10 means a radius of 10mm. This assumes that a new target position is given in the next instruction. If not, the robot goes all the way to the target position and stops. Tool1 = Defines the tool center point, which is what will be position at p3. \WObj:=papper = Defines the coordinate system in which p3 is given, in this case "papper"
The image below is a screenshot from a production system simulation in Visual Components software. Describe what you see in the image, both in terms of the objects and the situation.
Answer: There is a generator that feeds components onto a conveyor belt. The flow is then split into two parallel flows using conveyor belts, each leading to a process. After the processes the flows are reconciled into on flow again using a conveyor merger. One of the two processes is in a down state, blocking the flow and causing the products to queue up.
Why is there a growing need among manufacturing companies to work with virtual technologies?
Answer: There is an increase in the rate of product introductions in today's market. This requires companies to change their production systems accordingly to accommodate the new products. By working virtually, the changes can be verified offline before installation, which reduces changeover times and potential errors.
Explain how you can validate of a simulation model
Answer: Validation is the process of making sure that the simulation model, including the input data, matches the real system. Was of validating a simulation model include: Show the model to the customer Sensitivity analysis Historic input data - historic output data
Explain the difference between verification and validation of a simulation model. (1p)
Answer: Verification is the processes of making sure that the simulation model matches the conceptual model. Validation is the process of making sure that the simulation model, including the input data, matches the real system.
Explain the trade-off between volume and variant when designing a layout of a production system.
Answer: When a larger amount of variants are demanded from customers (customized, one-off products) higher flexibility is needed and layout organized around the product is more suitable. On the other scale, when you want a large volume of products, processes are more standardized and the layout is organized to enable high throughput. Then is a product workshop more suitable and the layout is designed to support the flow of the product.
Yield and Lead Time are two central concepts for a production system. Explain the meaning of the two.
Answer: Yield is the measure of what fraction of parts produced are acceptable. Low yield equals poor quality in a process. Lead Time is the time required from customer order to delivery of the product or service
Explain two examples of relations between humans (the personnel) in the system and the layout of a production system. Explain also how you would consider these relations when you are designing a layout (4p).
Creating a safe working place: aspects important for the design of the layout are for example to keep the traffic for forklift trucks and walking aisles apart, a good overview of the production area, placement of machines and assembly stations, good handling of material waste, etc. (2p). Ergonomic adapted workplace for personnel: aspects important for the design of the layout are for example the access to machines, adapted height to equipment when performing heavy lifts, access to tools, etc. (2p).
Name two typical application areas for industrial robots
Example Answers: Material handling Spotwelding
a. Explain how a production system is organized that applies cell layout and a real-world example representing the same principles. Mention two benefits and drawbacks with cell layout.
In cell layout are the required functionalities organized in the same cell to serve the needs of a product variant. A real-world example representing the same principles is a store for sports goods, with running and skiing equipment placed in the same area. Cell layout is suitable when there is a need for fast throughput and there is a need to organize the production according to product variants. Problems with this layout are the higher level of competence than for product layout, difficulty to balance, lower utilization of machines (1p). Benefits include a good trade-off between cost and flexibility, creating a "team spirit" and work fulfillment, and a better material and product flow compared to a functional workshop (1 p). Drawbacks include a demand for a higher competence level compared to product layout, it is difficult to balance because of an uneven flow which results in lower utilization and the utilization of machines is lower compared to a functional workshop (1p).
a. Productivity is output in relation to input. For the total productivity, explain what is included in output respectively input as well as how they are related to each other. (2p)
Output (the production result) is the value-added to the product and the input is the total amount of resources that have been required to realize a product. Productivity is the output divided by the input. High productivity indicates that the value added to a product is high in relation to the resources that have been required to realize a product.
what layout
Product/Production-line Layout
what layout
Project layout
What are two of the main benefits with virtual training of operators?
Reduced time to train Increased quality Safer and shorter ramp-up times Reduce training on physical objects/assets
Describe one aspect of an assembly operation that is especially positive to train virtually.
Reduced time to train Increased quality Safer and shorter ramp-up times Reduced training on physical objects/assets
Name and exemplify a suitable choice of product and the respective layout benefits for each of the below layout models: Project layout
Suitable for larger product that need one position, where material and products come to the product Problems: involved increased mobility of personnel, low level of utilization of machines, and high unit cost.
Product/Production-line
Suitable when a low throughput of the product is needed of a standardized product and when production can be organized based on the product flow. Problems: it is sensitive to disturbances, the pace is set by the longest operation time, sensitive to changes of the product, and it involves a higher level of investment.
Job shop/ functional workshop
Suitable when high flexibility is needed and for the product where time is not the critical aspect. Problems: increased material handling, total production time is longer, more planning is required, and internal storage is higher
Cell layout
Suitable when there is need of fast throughput and there is need to organize production according to product variants. Problems: higher level of competence than for product layout, difficult to balance, lower utilization of machines.
Mention one aspect of an assembly operation that is especially difficult to train virtually.
Tactile and skill-based aspects. Those are present mainly in the second and third phase of the learning curve
a. Will the system be able to produce 4800 products per week? b. Motivate your answer above by calculating the theoretical production rate of the illustrated system? c. In practice a production system will most likely perform differently from the theoretical. List four examples of things that impact production rate and that have been left out in the example above.
a. answer: no b.Answer: (calculated 40 hours) Station 1: 40*(3600/20)*0.98 = 7056 Station 2a+b: 2*40*(3600/45)*0.96 = 6144 Station 3: 40*(3600/25)*0.9 = 5184 Station 4: 40*(3600/33)*0.95 = 4145 Station 4 is the bottleneck and is only able to produce 4145 pcs per 40 hours week. Since there are no breakdowns or variation considered in the theoretical model, the system's production rate is equal to its bottleneck capacity, 4145pcs/week. c. Example Answers: Variations in operation times Breakdowns Setup times Material handling times Buffer sizes Etc...
what layout
cell layout
what layout
process layout
What are the general benefits for manufacturing companies to work in a virtual environment when developing a production system?
‒ Faster changeover of a production system since the new system can be tested prior to installation. ‒ Lower costs for changing the production system. ‒ Change to a design can be made at an early stage. ‒ The digital representation of the entire product lifecycle can be made available. ‒ The need for physical prototypes is reduced. ‒ The integration between product design and production can be verified. ‒ Lead times are reduced.
