Critically appraise a systematic approach with lean thinking and apply it into analysis, planning, design and performance evaluation of a complex production system.

Assignment Brief

ENG770s2 – Virtual Systems Design and Simulation for Production
Coursework

Instructions for completing the assessment: The work involves a design of a complex production system in a virtual environment with solutions developed and submitted in a report via Moodle. The length of the report is suggested no more than 4000 words.

Aims of This Work

1. To develop a systematic understanding and critical awareness of sustainable manufacturing systems, system design approaches, and manufacturing planning techniques as applied in industry.

2. To enhance the acquisition of analytical knowledge and practical skills for analysing complex manufacturing processes or systems, through the development and integration of virtual product design, virtual assembly, and virtual prototyping systems using advanced computer-aided design and simulation tools.

3. To explore modelling and simulation techniques that support the rapid creation, evaluation, and improvement of innovative system designs, particularly within constraint-based production systems in a virtual environment.

4. To develop expertise in managing system uncertainty, analysing random system behaviour, refining system designs, and formulating alternative operational management strategies, using a virtual prototyping system applied to a real-world industrial case study.

Unit Learning Outcomes

1. Critically appraise and apply a systematic approach incorporating lean thinking to the analysis, planning, design, and performance evaluation of complex production systems.

2. Identify and evaluate advances in discrete event simulation techniques and modelling methods for the development of constraint-based production systems, aiming to provide optimal or near-optimal solutions with the aid of computer-aided design and simulation tools.

3. Enhance virtual prototyping systems by integrating key system characteristics such as flexibility, reconfigurability, and responsiveness, to create an efficient, cost-effective, and environmentally sustainable manufacturing plant in a virtual environment.

Assessment strategies & instructions

The overall assessment strategy is designed to test problem solving capabilities through a case study including a design of a complex production system in a virtual environment using computer-aided design and modelling simulation tools to satisfy LO 1, 2 and 3, with solutions developed and submitted in a report. Each student is expected to develop their own computer models, which will be checked and questioned by the supervisor in week 10 and 11 as part of the overall assessment.

The report should include the following information:

• Unit Title – Virtual Systems Design and Simulation for Production
• Unit Code – ENG770s2
• Your Student ID Number
• Unit Lecturer: Dr Qian Wang
• Date/Month/Year

1. Introduction/Background (refers to page 2-4 and your own research work)
2. Main work (refers to page 5-6)
3. Discussions and conclusions
4. References (if applicable)
5. Appendix

Assignment

(Coursework)

Background

In order to be competitive, modern products must be designed with a view to production methods in which a production system should to be designed in a cost-effective way and the system is able to operate at optimal or near-optimal conditions. Nevertheless, design of a production system can be a complex process and any small change of the system design often makes a significant impact on the overall system performance. In the real-world industry, implementation of the entire production system is often very expensive and cost of ‘getting it wrong’ can be very high. For these reasons, both system and product designers need to work together to ensure a ‘right first time’ scenario. Virtual prototyping techniques offer a potential solution to the major difficulties involved in design, analysis and performance evaluation of a product and a production system providing a fast delivery of alternative solutions at a minimum of cost. Nowadays, virtual prototyping techniques are commonly used in manufacturing sectors involving some form of computer-aided design and modelling simulation activities.

Assignment & Tasks

This assignment is based on a case study of assembling loudspeakers on a production line that needs to be investigated. A loudspeaker manufacturer has just upgraded its loudspeaker design by incorporating some forged parts with improved magnetic characteristics for the unit, which has additional benefits of reduced part count and part features to facilitate automatic feeding as well as ease of manual assembly.

Figure 1 shows the basic structure of a loudspeaker and Figure 2 illustrates what is known as the motor unit assembly together with the voice coil. Figure 3 shows a cross-section through a typical loudspeaker. The assembly of an entire loudspeaker is illustrated in Figure 4 and 5, respectively.

The parts in the whole assembly can be grouped into two different types namely:

• The ‘soft’ parts.

These are the dust cap, the diaphragm, the spider and the coil.

• The ‘hard’ parts

These are all in the ‘motor unit’ sub-assembly including the pole piece, the magnet and the top plate, together with the frame.

The proposed manufacturing facilities should as far as possible incorporate automation, however, it is still anticipated that some of the ‘soft’ parts may be assembled manually. The aim is to produce one loudspeaker every 20s over an 8hr working day and a 5-day week (1440 units/day, 7200 units/week). The speakers can be sold at £5/unit, giving a potential turnover of £36000/week and £1800000/year.

After an initial investigation of the system, data collection and analysis, the following system parameters have been identified and determined:

• Conveyors will be used and it may be 5, 10, 15 or 20 m long.
• Each frame arrives randomly and is loaded in position (manually) in NegExp 18s.
• Each pole plate can be fed/assembled in LogNormal 17s, STD: 5-15%.
• The magnet can be fed/assembled in LogNormal 19s, STD: 5-15%.
• The top plate can be fed/assembled between 15-18s in a uniform distribution.
• Manual assembly of the spider and coil by a worker takes a time of 35-45s in a uniform distribution
• Assembly of the diaphragm takes an average time of 18s.
• Manual assembly of the dust cap takes an average time of 16s.
• At the magnetisation station: 20s.
• At the automated test machine (ATM): 10s.
• Fork-lift trucks may be used at the end of the production line and it may travel at 2m/s.

Each finished loudspeaker will be individually bagged by a worker (s) after the ATM (automated test machine). A robot might be used to pack the finish products into a container. Each container should hold 36 loudspeakers and filled containers should be stacked and wrapped together in groups of 4 before being taken away by a fork-lift truck (s) to the warehouse.

Feeders/hoppers can be replenished automatically inside/outside the normal working hours (you decide this). This process involves unpacking parts manually and placing them on a single long conveyor that runs to a centrally located robot which can intelligently pick up correct parts and place these parts on short conveyors running to each feeder. The robot can run with a cycle time of 1.2s. Each worker can place individual parts on the conveyor in NegExp 4s; it needs to keep the number of workers to a minimum. The operating time of this conveyor must also be kept to a minimum since it involves the additional cost of overtime and/or part-time workers.

Fully assembled loudspeakers are passed through an automated test machine (ATM) where 1% of inspected units do not comply with specifications and are removed for rework – rework is not part of the study.

An eco-friendly and safe shop floor/workshop design is encouraged.

Equipment Reliability

The following information is known about the breakdown and repair of equipment:

Item MTBF MTTR

• Feeders 40 hr 0.5 hr
• Robots 180 hr 2.0 hr
• Stacker/Wrapper 300 hr 1.5 hr
• Conveyors 4000 hr 3.0 hr
• Fork-Lifts 300 hr 2.0 hr
• Magnetiser 3000hr 4.0 hr
• ATM 2000hr 4.0 hr

Others

Manufacturing and design constraints of the product are advised:

1. 1. The magnets are fragile and must not be subject to any sudden shock or impact.
2. 2. The central hole in the top plate has been manufactured within a tolerance of ±0.02 mm. The top plates` outer diameter has a tolerance of ±0.1 mm. The positional tolerance when assembling the central bore of the top plate over the pole plate is ±0.05 mm (in order to maintain the critical gap for the coil).
3. 3. You should determine all the nominal dimensions for the loudspeaker parts and incorporate the stated tolerances for your design of the loudspeaker if applicable.

Tasks

You should attempt to complete the following tasks:

1. Provide a background/knowledge of the loudspeaker-related product and production through a literature study.
2. Create a process plan for assembly of a loudspeaker using ‘pre-manufactured components’. Suggest suitable assembly sequences that would benefit from automated and/or manual operational processes.
3. Produce a drawing incorporating your proposed facility layout design based on the logic sequences of assembly within a boundary (with assumptions in Note) and justify your design by considering  constraints such as space utilisation; ease of operations and services; reduction of temporary storage areas or buffer zones, transport/human operator motions; safety; costs etc.
4. Build a full system model using Enterprise Dynamics (ED) software by incorporating 3D objects (if applicable) and all the necessary statistical values; test and verify the functionality of the developed ED models.
5. Design and run suitable experiments with the developed ED models; collect, analyse and interpret the generated simulation data including graphical simulation results to be presented in the report.
6. Evaluate system performance making any improvement that would be most beneficial to the system design and explain why you consider these changes, which may be advantageous.

Note

Make your own assumptions due to any necessary data which may not be given or should not be included in your particular case study. This may refer to such as the availability of factory space, location of stores and so on. You may also consider how your system design may be able to cope with an increase in demands as well as product variances in future.

Your work must be presented and illustrated in a written report. The report should be structured as indicated at page 1 and it should include your own work with the relevant context, drawings and screen-captures and other materials. Please keep your report concisely below 4000 words.

Sample Answer

Virtual Systems Design and Simulation for Loudspeaker Production

Introduction

In modern manufacturing, virtual systems design and simulation play a vital role in planning efficient, cost-effective, and sustainable production processes. This report focuses on designing a virtual production system for assembling loudspeakers using Enterprise Dynamics (ED) software. The aim is to create a production line that can meet high output targets while integrating automation, lean principles, and sustainable practices. The loudspeaker assembly process combines manual and automated operations, and requires careful planning to ensure precision, particularly due to strict tolerance limits on certain components.

Background and Literature Review

Loudspeakers convert electrical signals into sound and consist of both “soft” and “hard” components. Soft parts such as the diaphragm, coil, spider, and dust cap require delicate handling, often involving manual assembly. Hard parts include the pole plate, magnet, top plate, and frame, which can be more readily automated.

Modern production methods increasingly use virtual prototyping and discrete event simulation (DES) to test production line efficiency before physical implementation. According to Sanchez et al. (2021), DES allows manufacturers to model complex systems, analyse bottlenecks, and predict outcomes under different scenarios. Similarly, lean manufacturing aims to minimise waste, reduce non-value-added activities, and ensure continuous improvement (Womack & Jones, 2003).

Simulation tools such as Enterprise Dynamics are effective for modelling systems with random or variable behaviours, like assembly times and equipment reliability. These simulations reduce the risk of costly design errors and allow for real-time data analysis and optimisation.

Continued...