Using DFA to Enhance VE/VA Workshop Outcomes

Richard F. Johnson
Manufacturing Engineering, VE/VA Group
MAGNA INTERIOR SYSTEMS — SEATING GROUP
19700 Haggerty Road, Livonia, MI 48152
Presented at the International Forum on DFMA

Introduction

In the automotive industry, the pressure to reduce prices is present at all levels, from the vehicle manufacturer (OEM) through to the lowest level of the supply base. Most first and second tier suppliers are faced with contractual performance or productivity clauses which require annual downward price adjustments of 3 to 5% on the products they provide to the OEM.

Faced with these pricing constraints and continuing cost pressures, the suppliers and OEMs alike have resorted to a multitude of formalized techniques designed to meet the challenge. These include GFD, TQM, VE, VA, and DFM/DFA. Some of these techniques have met with success while others have been tried briefly and dropped. At the Magna Interior Systems Seating Group, we have found the most powerful combination by a wide margin has been the melding of the disciplines of DFA and VE/VA.

This paper describes the means by which the Magna Seating Group VE/VA team has employed the Boothroyd Dewhurst DFA method to enhance the outcomes of our Value Engineering Workshops, resulting in significant savings in materials, design costs, tooling, and processing of parts and assemblies.

Value Engineering/Analysis as a Full-Time Activity

Because of the continuing requirements for maintaining downward pressures on all costs, it has been found productive to establish and maintain a small department within Engineering whose only purpose is to concentrate on the broadest areas of cost reduction through the Value Engineering/Value Analysis approach. This department is made up of experts in each of the disciplines required to develop and manufacture the products of the supplier company. Personnel were selected for their demonstrated skills in the areas of product development, manufacturing, tooling, and processing as well as their overall industry experience. In many organizations, it would be difficult to take people with these skills out of the mainstream of product development for an extended period of time for this effort; however, the fact that some of the best and most experienced personnel have been assigned exclusively to this program at Magna speaks to the level of commitment required to achieve success.

Once the commitment is made, we have found that the payoffs can be several times the cost of supporting the group. Further, properly equipped with the latest computer equipment and software, and trained to use every available means to spot cost reduction targets, it is easily demonstrated that a full-time VE/VA group can have a major impact on the bottom line.

At Magna Seating, we have used the DFA technique to strongly enhance our cost reduction efforts, not only in the area of metal parts, but also in the analysis of cut & sew products such as seat and armrest covers. We believe this second application of DFA is an industry first. We have developed our own formulas for each sewing operation and have verified the accuracy of the outcomes by comparing them with actual observations during visits to the various facilities. DFA is now the standard tool used to target our VE/VA efforts.

Correlating Product Design with the Manufacturing Process

Effective design for lowest cost and fewest components can only be accomplished by a product design and engineering staff that understands the manufacturing capabilities of the plant(s) in which the assembly will be made. Unfortunately, in today’s working environment, the design team is often not conversant with the processes and procedures of the manufacturing facility. Further, program time constraints frequently seem to force the design to be initiated without thought of how the final product will be made. Time for analysis is usually not scheduled into the program, and the design proceeds to a point of no return before a realization is made that tooling and processing of the parts, subassemblies and assemblies have not been considered adequately in light of plant conditions.

In order to minimize this problem, the training of product engineers and their design counterparts must include continuing exposure to the plants charged with manufacture of the products for which they have technical responsibility. Visits to plants for orientation and training should be for a minimum one-week period with as much floor exposure as can be practically included. In some cases 3 to 6 month plant assignments may be considered for newer members of the product design and engineering staff.

The payoff for this type of training is the ability of the engineers and designers to visualize the manufacturing process during the preliminary design stages of new products, including direct knowledge of process layout when conducting the initial baseline DFA analysis. This procedure minimizes false starts, redesigns, issuance of Design Change Notices and the accompanying cost of tool changes later in the program.

When conducting the baseline DFA it is important to include inputs from the entire product team. Insights into potential production and assembly problems by those who live with the plant environment on a daily basis are invaluable in assuring the accuracy of the DFA outcome. Minor design changes which may vastly improve the processing of the assembly and its components can produce a major cost impact on the final product.

Purchasing, Sales, and Quality Assurance personnel will enhance the knowledge base of the team and bring independent ideas to the DFE–VE/VA process which could easily be missed by the technical staff because of their close contact with the product being considered.

Targets for Change — DFA as a Tool for Focus

The usual way to attack a high-cost part or assembly is to wait until after the design is released, tooled and in production and then discover that the expected margins are not being generated. Obviously, by this time a lot of engineering and design cost is already burdening the product; often it is discovered (usually by the CEO) that “we’re shipping this thing with dollar bills wrapped around it.” Clearly, early analysis of new designs using the DFA technique is crucial to the commercial success of each and every product. A strict regimen needs to be imposed providing for DFA analysis as soon as the first concept layouts and illustrations are sufficient to define the product in all its functions.

The early review at concept stage will reduce parts count and processing steps by highlighting possibilities for combining parts, reducing extra screws, bolts, and washers, and reducing or eliminating extra or superfluous reinforcement achieved by parts layering (common in the automotive seating industry). Major development, tooling and gauging costs are saved by the lowering of parts count, and all are familiar with the high cost associated with making changes later in the product development cycle.

A review of operations will reveal other opportunities for cost savings in processing. In automotive seating systems, many parts are covered with foam or fabric, or are otherwise not visible. In the JIT environment, parts aren’t stored for long periods prior to final assembly and, once assembled, are shielded from corrosion; thus many covered/non-visible steel parts need not be coated.

Wire welding is another process which often can be minimized or eliminated.

Baseline DFA and preliminary design reviews often expose small weld-on parts (gussets, trim tabs, etc.) that could be made integral with the primary component. Eliminating these saves handling and welding time (observed savings of 30–60 seconds per assembly are common).

Rethinking how to achieve a function can also reduce parts dramatically—for example, guiding moving parts (folding seats, latches) with pierced slots in the main bracket instead of welded guide features.

Manual lubrication with brushes or rags can be automated to reduce headcount, material use, and exposure to hazards—typically with rapid payback.

Designers often specify many screws, rivets, and small fasteners that are hard to handle. Caught early, alternate constructions deliver the same function with fewer components. Magna minimized these and automated the remaining essentials, using DFA “Suggestions for Redesign” to target opportunities.

Automate error-prone assemblies. Parts detection can ensure rivets/washers are present; cartridge-fed thin washers prevent omissions; press-fit rollers can be automated for ergonomics and error reduction.

Multiple reorientations drive cost. Baseline DFA documents the penalties and guides redesign to single-axis, stack-from-one-side assembly.

Other assists include palletized assembly fixtures and direct feed of parts from press/rolling mill to assembly in straight-line flow.

Method and Approach

Before any VA/VE workshop, an engineer runs a baseline DFA analysis (with team assistance) on the target products. The baseline is peer-reviewed and revised; if already in production, DFA outcomes and assumptions are checked against actuals.

Next, the baseline is saved aside and a Phase 1 analysis applies “reasonable” low-risk changes that are likely to be accepted by design, plant, and customer.

If time permits, a Phase 2 analysis explores more radical, minimum-parts/minimum-steps solutions while preserving function.

In the workshop, DFA outcomes target product/process improvements from the outset. During brainstorming, Phase 1 and Phase 2 reports spur ideas. DFA is updated in real time to quantify time and cost impacts, creating positive momentum and stronger executive-review buy-in.

Example Program — Jump Seat for Extended-Cab Pickup

A strong example of DFA’s power to reduce parts and operations costs involved a jump-seat for a major automotive OEM. Drawings and sample assemblies of the current product were provided, with the option to tool as-is or redesign while keeping features and functions. Profitability would be marginal without change, so DFA guided a rapid redesign within timing constraints.

Baseline

DFA on the current assembly (first from illustration, then from tear-down) revealed 105 separate parts across four material types, multiple manufacturing methods, and joining via welding, riveting, screws, snaps, and swaging. Many parts were hidden until cut apart (tubes-in-tubes, multi-piece plastics). Calculated assembly time exceeded 1,440 seconds (excluding paint); six major subassemblies; extensive MIG welding; numerous small tabs hand-welded to mount trim; >4 reorientations just for the seat base bracket; long tube insertion, flattening, slot piercing; and obstructed/hidden operations.

Phase 1 “Reasonable” Changes

Applying the “Reasonableness Criteria,” low-risk changes combined or eliminated parts and simplified processing/assembly while preserving essential functions. Many weld steps—especially small, hard-to-handle pieces—were eliminated. Multi-layer parts were replaced by slightly thicker gage material. Cams/rollers were changed to slides guided in pierced slots.

Results: parts cut from 105 to 19; major subassemblies from 6 to 5; assembly time from ~1,445 seconds to ~258 seconds. See Figure 2.

Phase 2 “Anything Goes”

Phase 2 assumes any change is possible if functionality is preserved. Goal: minimum parts and single-axis assembly; welding minimized; only essential screws/rivets retained. Parts count reduced to 9; major subassemblies to 2; assembly time to <100 seconds. Tubes deleted; functions integrated into cushion and back support stampings; base bracket in one piece (no welds); stops/guides integrated; plastic sliders replace two-piece rollers; seat-belt anchors integrated; separate brackets/weld-nuts eliminated; seat/back cushion combined with parallel sew lines to form a flexible hinge; hinge via shoulder rivets/screws with plastic-coated bearing to eliminate bushings.

Coordination of DFA with the VE/VA Process

Baseline DFA targets combinations and eliminations, plus removal of costly handling/insertion/assembly steps—affecting not just part cost, but also tooling, gauging, fixturing, and capital. Worksheet totals guide the team to the richest opportunities. Subassembly Worksheets visualize complexity and reorientation penalties; “what-if” weight reductions can be iterated and summarized.

Using DFA as described has reduced typical VE/VA workshops from 3–4 days to ~2 days, improving participation and documentation quality while increasing idea volume and impact.

Cautions — Use Your Reality Check

Not every good idea will ship. Achieving 25–30% implementation is solid; 40–50% is outstanding. In the jump-seat example, final parts were 68 vs. 105 (strong, but not the 19 of Phase 1). Often the limiter is that DFA/VE weren’t scheduled early enough.

The solution: institutionalize early DFA and VE in the development process and keep demonstrating bottom-line results.