Automotive development has major implications for aerospace manufacturers
Automotive development has major implications for aerospace manufacturers
Maurice Hanley
Keywords Aerospace industry, Assembly, FANUC, Robotics
Flextool is a radical new concept in fixture design developed by FANUC Robotics initially for the automotive industry. It promises even greater benefits for the aerospace industry.
Before looking at the Flextool in detail, it is worth examining why the concept can potentially make an even greater impact on production costs in the aerospace industry than its original market.
Briefly, Flextool is a flexible fixturingsystem that employs robot technology to create a fixture that can automatically adjust so that different car bodies can be assembled on the same line (Plate 1).
It is a telling observation that the pressures that led to the development of Flextool for assembly exactly parallel those that led to the rapid acceptance of CNC in the machine shop. This augurs well for the future.
Plate 1 Two FANUC Flextools are used as a flexible fixture for a spot welding assembly
First and foremost was the need to introduce flexibility. In an uncertain world with shorter product life,flexibility is paramount. Flexibility on existing tooling systems was limited and only achieved at the expense of unacceptable levels of downtime between changeovers.
Having six assembly lines for six different models rather than one has two detrimental effects;under-utilization of equipment and excessive use of expensive floor space.
Without Flextool a body assembly line would be required for each model. Producing two bodies on one line shows a saving over conventional hard fixtures cost. Produce more than two, then the savings are enormous.
In the automotive industry production runs are measured in the high hundred thousands, if not millions. Fixture costs can be amortised over one million units.
Contrast this with the aerospace industry where production runs are measured in hundreds if you are lucky.
Tooling and fixture costs are, therefore, a much higher percentage of the final product cost in the aerospace industry than the automotive.
The obvious conclusion from this is that major savings in production tooling can make a correspondingly greater contribution to reducing unit costs.
That in a nutshell is what Flextool promises.
Hardware and sophisticated software
In essence Flextool is a load bearing horizontal faceplate approximately 250mm square that can be positioned anywhere in a cube approximately 500mm square by 220mm high. The faceplate may be adjusted to any angle within the cube. What makes Flextool is a combination of hardware and sophisticated software.
The hardware uses proven robot technology while the software is designed with an intuitive graphic interface that eliminates any need for specialised programming knowledge. The terminology to move the positioner is self-explanatory "in/out", "up/down" and slightly nautical "fore/aft".
Beneath the faceplate that carries the fixture location are six servo-drive units that can position it with six degrees of freedom of movement (three linear and three angular) anywhere within the working envelope.
On the faceplate can be mounted location points, clamps and other tooling likely to be used on any conventional fixture to position components for assembly.
Initial costing studies on auto assembly lines carried out by FANUC Robotics indicate that Flextool costs are higher for a single assembly, but as soon as two are produced Flextool shows a cost benefit. If five plus versions are produced on the line then the capital investment is reduced to 50 percent of conventional fixture costs.
Even for a single assembly there are significant benefits that could justify the premium which is around 10 percent.
Risk management is a factor that concentrates the minds of senior management today.
Unlike hard fixturing,Flextool can be redeployed on to new models with minimal costs if sales fail to reach projections. But ignoring this "worst case" scenario, what about other,more likely occurrences?
Design changes can be incorporated with minimal cost and, just as important, minimal downtime.
During set-up shim adjustment of fixtures is an unavoidable, time-consuming part of the process. To adjust datum locators in conventional fixtures, shims or spacers often have to be removed and ground to correct, then replaced. For Flextool this is simple. Any off-set is achieved by entering the amount and direction of the adjustment.
Shim software is an important element of Flextool. It uses shopfloor terminology and makes adjustments in seconds rather than hours. Corrections are made in directions aligned with the assembly co-ordinates. For multiple assemblies passing down the line, the system maintains a complete set of off-set corrections for each assembly.
Features included in the shim software include an undo sequence and a historic log of previous shim movements. During prototype development or pilot-production when adjustments are most likely to be required temporary adjustments can be made, then undone.
The shimming software records all moves with a date and time stamp. An entire tooling set for a line can be returned to any position in the historic shim log.
All this adds up to a massive 90 percent reduction in the time for set-up and theodolite verifications when compared with conventional tooling. By any yardstick the "risk" element of a major project is significantly reduced with Flextool.
Flextool also promises to reduce ongoing operational costs. Simpler tooling requires less maintenance,while the high reliability of the robot-based servo-mechanisms ensures maximum availability.
The construction of the Flextool units is simple. There is a base, the faceplate and six servo-actuated legs. The legs are paired into triangles to create a geometry with maximum rigidity.
The units can carry maximum loads of 140kg vertically and 75kg horizontally. This can be sustained at the maximum off-set of 250mm. One standard FANUC robot control system can control two Flextool positioners.
The potential for Flextool is only beginning to be explored. Although conceived as a positioner, it has already been tested as a robot in its own right. For difficult to access locations such as under a wing, the Flextool can reach up inside the assembly. The dynamic load capacity is 36kg.
