LONGBOW APACHE HELICOPTER
Design for Manufacturing and Assembly Application on the design of the AH64D Helicopter.
This study examines the effectiveness of Design for Manufacturing and Assembly(DFMA) methodology used by the design, manufacturing, quality, and supporting engineers for the development of the Longbow Apache Helicopter. Data were obtained through the Integrated Product Development (IPD) team for several redesigned areas of the Longbow prototype Helicopter Crew Station. Results of the study show that DFMA can be an effective approach, as indicated by a significant cost and weight savings.
Design for Manufacturing and Assembly (DFMA) is a design philosophy used by designers when a reduction in part count, a reduction in assembly time, or a simplification of subassemblies is desired. It can be used in any environment regardless of how complex the part is or how technologically advanced this environment may be. It is gaining popularity where manufacturing costs are a concern. DFMA encourages concurrent engineering during product design so that the product qualities reside with both designers and the other members of the developing team.
DFMA is utilized by hundreds of domestic and international companies in an effort to cut down concurrent manufacturing and assembly time. Domestic companies like Allied-Signal, Motorola, Hughes Aircraft, and McDonnell Douglas Corporation have already implemented the DFMA philosophy throughout their product lines. The DFMA implementation process may be done at two different stages: when a new design requirement is established or when an existing design requires product optimization, such as the case of the Longbow Apache Helicopter. At the initial design stage, the designer develops a simplistic conceptual design by envisioning an assembly that requires a minimum of parts to perform the requirements previously established, and is easy to install. In the second stage the designer redesigns existing assemblies or designs new assemblies in order to implement design optimizations to ease manufacturing, and installation. This also meets reliability and maintainability requirements, moving the design towards cost reduction and customer satisfaction. In order to maximize the benefits of DFMA the designer must have a good working knowledge of the manufacturing processes available, and process capabilities to produce the parts. The design and manufacturing elements must work closely to determine the best manufacturing approach. A review of the State-of-the art manufacturing processes which increase the effectiveness of DFMA provides a means to understand this synergism, as well as the availability of Statistical Process Capabilities (SPC).
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|Fabrication Time (hours)
|Assembly / Installation Time (hours)
149 / 153
8 / 153
|Total Time (hours)
|Table 1. Pilot's Instrument Panel Estimate Summary
|Subsequent analysis yielded data indicating that the fabrication time could be reduced to 20 hours. The total manufacturing and assembly time would be reduced from 697 hours to 181 hours, weight reduction would be to 2.74 Kilograms, and the total cost was reduced by 74%. The pilot's instrument panel DFMA concept is shown, and Table 1 provides a summary of the estimated comparison for the Pilot's Instrument Panel.
In addition, data were obtained for three other areas: The Co-Pilot Gunner (CPG) instrument panel was a good candidate for DFMA due to its assembly complexity, number of parts and rivets required to assemble it. It included the Up-Front Display (UFD) tray and the Multifunction Display (MFD) tray. These last two sub-assemblies of the CPG instrument panel made it very difficult to assemble and require extensive labor for the assembly activity and the final installation.
The total original part count was 87 parts. Presently it has been reduced to 12 parts, where 7 are machined parts and 5 are sheet metal/composite parts. The original instrument panel is a combination of sheet metal parts representing more than 90% of the total parts and a few machine parts being fastened mechanically. Bench tooling is required to perform the sub-assemblies of the UFD and MFD trays, making the task very difficult.
With the simplified DFMA instrument panel, sub-assembly is minimal, representing a considerable amount of time and cost savings, as well as weight savings. The DFA Summary of Results show part of the DFMA assessment done by utilizing the BDI software analysis on the Instrument Panel Top Assembly Drawing, 7-511171010-1. These tables provide data indicating what it takes for manufacturing to produce, and assemble the CPG instrument panel, substantiating the numbers of parts, hours, processes and cost to complete the task
The BDI software does a complete analysis of all the tasks required, providing a summary of results. A general overview of how long and how much it takes to build and assemble specific components or parts is done. Also, an analysis profile is provided with suggestions to improve the current design.
This software is used by the manufacturing team members to estimate and predict the savings that can be obtained. Data are entered and the system does its analysis in different areas. A complete listing of all the activities required to perform an assembly, including the count of tasks, figures the minimum items required for assembly, and the item(s) cost. This provides a complete overview of the task to be performed.
The BDI software does an assembly analysis profile on a set standard format where it theorizes the number of tasks to be performed, fasteners required, connectors to be installed, candidates for elimination, acquisition of items not in reach or on stock, acquisition of tools not on hand, standard operations, library operations, and reorientations. After all these activities are numbered and plotted, it automatically provides suggestions for improvement.
The system provides suggestions for design and for assembly, by giving instructions, and indicating every task with its time saving, and its percentage reduction. It indicates specific instruction to perform the related tasks in order to obtain the suggested savings.
It also lists, under what is called Design for Assembly Analysis Totals, all the parameters used for the analysis such as total assembly time, total assembly cost, total assembly weight, number of parts and sub-assemblies, theoretical minimum number of parts or unanalyzed sub-assemblies, and the hourly labor rate.
All the suggestions and comments included within the computer generated tables are automatically provided to aid the designers and manufacturing engineers to obtain a better view of the job.
Design for Assembly Suggestions for Redesign provides detail analysis of the UFD Tray Assembly (-13), MFD Tray (-57), MFD Tray (-49), Bracket (-119), Closeout Assemblies (-29 and -31), UFD Tray Assembly (-3), and Tee (-125) which are installed on the copilot's instrument panel, and the pilot's instrument panel. It gives suggestions for hardware reduction such as rivets by incorporating integral fastening elements into functional parts, or by doing a different securing method. Part reduction is recommended by combining parts with others. Hardware can also be reduced by the addition of chamfers, lips, leads. Assembly redesign is suggested to provide unrestricted vision for Bracket (-119), Closeout Assemblies (-29 and -31), UFD Tray Assembly (-3), MFD Tray (-57), and MFD Tray (-49). Detailed time saving and percentage reductions are provided.
There was a considerable cost, weight, and schedule savings of approximately 74%, 8%, and 74% respectively in the areas where applied.
There are many lessons from which the aircraft industry and, in this case, MDHS can fruitfully benefit. From the experience of other companies, it seems that various attitudes and practices must be nurtured for DFMA to be fully implemented. Many commercial companies attribute their world-class competitiveness to DFMA. John Deere and Company says, "the first companies to implement DFMA will be the leading world-class competitors, the last companies to implement DFMA won't have to worry about it." So, applying DFMA can help make MDHS a world-class competitor in the helicopter manufacturing industry, adopting a trend that has already been started by McDonnell Douglas in St. Louis and that has proven to be very successful.
The utilization of DFMA has not been extensive. Indications are that DFMA can successfully contribute when cost, weight, and schedule are the prime drivers for the development of a program.
It is suggested that DFMA has been successful in the Longbow Apache Program, even though its utilization was limited to a few components only. If it could have been used across all the design activities, it would have been more helpful in reducing the parameters indicated previously (cost, weight, and schedule). The part count was reduced by 87%, the fabrication time was reduced by 93%, assembly time was reduced by 94%, the weight was reduced by 10%, and the cost was reduced by 74%.
Training is a must. DFMA could be more successful if all the team members understand what it is about and what are the ultimate goals. The management commitment to DFMA can bring the success of the Program by making the decision on educating the employees. It is understood that every professional individual possesses a basic training and that it will give an easier transition towards the goal of the project, but, if these professionals are not provided with the adequate tools, the success of the program could be in jeopardy. That is why training is a key item for the success of any program.
It is clear that for DFMA to be effective, the design team must understand the capabilities of the production process that will be used to produce their parts and set requirements within those limits.
During the course of this study it was found that the Design for Manufacturing and Assembly utilization by the aircraft industry can present great advantages. Still, there are areas that could not be covered due to the study's scope. Areas like designing for disassembly where designs also consider the future dismantling of assemblies for environmental purposes.
DFMA was applied on structural, and ECS designs only, but it can also be used in areas like flight controls, engines, transmissions, hydraulics systems, and electromechanical components used to house and support electrical and avionics components. These areas have not been studied, and may be topics for further future studies.
Implementation of DFMA is not an easy task. It takes the correct attitude in order to successfully use it and overcome all barriers created by people used to work under a different approach. Additional study in this area may be beneficial.
For a successful DFMA implementation, more management participation and concern are needed, as well as providing more empowerment to the different team members so that they consider themselves as participants in the development of the program as any others within the organization. Management involvement and commitment may be a good topic for study, given the results and successes of DFMA implementation in the general and aircraft industry.
A closer look at process business reengineering tools should be considered. Dimensional Management (DM) is one of the tools that can help this process. DM is an analytical and quantitative approach used to manage assemblies through disciplined techniques such as the proper identification of control datum, prediction of allowable variation, definition of key interface characteristics (KC), part count reduction and/or clearly defined product acceptance criteria established early within the product definition life-cycle. While listening to the voice of the customer, DM can provide a set of associative concepts and structural tools utilized within a disciplined Integrated Product Definition (IPD) process that establishes product characteristic requirements that ultimately yields ease at assembly, driving reduced operating costs and a reduction in non-conformance parts and tools.
The author wishes to express that the views and findings are those of the writer and in no way intended to reflect the official opinion of McDonnell Douglas Helicopter Systems (MDHS).
Author: Alfredo Herrera,
Dimensional Management Technical Lead.