A method was developed for obtaining proper fluid distribution through parallel gun-drilled passages and for being able to inspect the actual drilled passages to guarantee that the designed minimum wall thickness is not violated. This invention uses one feature that addresses both issues mentioned. By machining a “trough” in the center of the cold plate that intersects the gun-drilled passages where they meet in the center, the area where the two drilled passages intersect is removed and any mismatch is eliminated. This allows access for direct inspection of the drill wander. An integral cap, which incorporates orifice features to address the fluid distribution, is then inserted into this trough. This method can also work in a two-layer cold plate where every other fluid passage is for the alternating fluid layer.

A Comparison between Regular and Vibration-Assisted Drilling in CFRP/Ti6Al4V Stack

2014-01-22369/16/2014

As aircraft programs currently ramp up, productivity of assembly processes needs to be improved while keeping quality, reliability and manufacturing cost requirements. Efficiency of the drilling process still remains an issue particularly in the case of CFRP/metal stacks: hot and long metallic chips are difficult to remove and often damage the surface of CFRP holes. Low frequency axial vibration drilling has been proposed to solve this issue. This innovative drilling process allows breaking up the metallic chips in such a way that jamming is avoided. This paper presents a case of CFRP/Ti6Al4V drilling on a CNC machine where productivity must be increased. A comparison is made between the current regular process and the MITIS drilling process. First the analysis and comparison method is presented. The current process is analyzed and its limits are highlighted. Then the vibration process is implemented and its performances are studied. Both processes are compared according to the following criteria: chip morphology, thrust force, power consumption, tool life, cycle time, holes quality and manufacturing costs. Results show that the vibration drilling process is more productive and reliable, while maintaining the quality as well as reducing manufacturing costs. The paper also shows that the vibration drilling allows simplifying cutting tool design and reducing lubrication.

Lonfier, Julian, De Castelbajac, Côme

A New Robotic Vibration-Drilling Process

2014-01-22589/16/2014

In today's aircraft assembly process several new features make drilling operations very challenging according to production requirements. Parts are made of thin or thick multi-material stacks with a large scope to cover and complex assembly sequences. In addition, the current ramp-up in aircraft programs involves to improve productivity while keeping process quality and reliability. In this context robotic solution meets perfectly all these requirements as it is flexible, reconfigurable, fast and agile. Among the possible end-effectors, the Barrel Multi-Function End Effector (BMFEE) appears to be the most flexible solution to allow many different process configurations. The latest developments have been focused on the drilling equipment of this BMFEE. In fact the drilling process efficiency can be constantly improved especially in terms of reliability, quality and productivity. Therefore vibration-assisted drilling system has been integrated into the BMFEE drilling module. This innovative drilling process allows breaking up the metallic chips in such a way that jamming is avoided. Thus peck-drilling cycles are avoided and the global process offers more reliability and productivity while fulfilling quality requirements. This article presents the work of this integration. Benefits of this new robotic vibration-drilling process are shown on the basis of an industrial example.

Laporte, Sylvain, Gueydon, Etienne, Auffret, Alain, De Castelbajac, Cosme

Characterization of Flow Drill Screwdriving Process Parameters on Joint Quality

2014-01-22419/16/2014

A state of the art proprietary method for aluminum-to-aluminum joining in the automotive industry is Resistance Spot Welding. However, with spot welding (1) structural performance of the joint may be degraded through heat-affected zones created by the high temperature thermal joining process, (2) achieving the double-sided access necessary for the spot welding electrodes may limit design flexibility, and (3) variability with welds leads to production inconsistencies. Self-piercing rivets have been used before; however they require different rivet/die combinations depending on the material being joined, which adds to process complexity. In recent years the introductions of screw products that combine the technologies of friction drilling and thread forming have entered the market. These types of screw products do not have these access limitations as through-part connections are formed by one-sided access using a thermo-mechanical flow screwdriving process with minimal heat. The friction drilling, thread forming process, hereto referred to as "FDS," is an automated continuous process that allows multi-material joining by utilizing a screw as both the tool and the fastener. The process uses the friction caused by the rotating screw to pierce and extrude the material. Threads are then created in this formed extrusion which allows the fastener to be screwdriven into the parts. A final torquing then securely clamps together the sheets of material. This study explores the quality design space as represented by resultant joint geometry as a function of the critical process parameters of fastener force and drilling speed. Feasible design space regions are explored to determine how process parameters affect joint geometry, and strength testing performed to validate the findings.

Skovron, Jamie, Mears, Laine, Ulutan, Durul, Detwiler, Duane, Paolini, Daniel, Baeumler, Boris, Claus, Laurence

Practical and Portable Automated Machining

2014-01-22759/16/2014

The utilization of new materials and tightening of desired tolerances has driven the advancement of Practical and Portable Automated Machining. Increased demand in volume within the aerospace industry not only requires minimizing the amount of manual operations, but also applying automation inside existing manual fixtures. In the past, manual labor, with drastic limitations on achievable accuracies, has been utilized in areas that machine tools cannot either access or the limited amount of work does not justify the expense of additional machines. Assemblies requiring critical hole alignment or drilling through stack materials often are difficult to achieve using manual operations. The solution is a practical and very portable machining unit that is small enough to fit into otherwise difficult areas and is lightweight enough to be either moved into position by small machines or quickly disassembled/assembled with each subassembly capable of being positioned manually. The criteria for the developed machine were that it be; Lightweight - Under 250 lbs allowing for manual positioning or easy mechanical positioning Accurate - Maintain accuracy achieved with current PKM technology Rigid - Capable of drill/mill/orbital of titanium Flexible - Can be mounted in any orientation and is adaptable to rail, vacuum, fixed leg, gantry, etc. Inexpensive - affordability should be compared to high-end manual tools instead of machine tools The XMINI Parallel Kinematic Machine developed uses the major benefits of Parallel Kinematics which presents an excellent rigidity to weight ratio, high accuracy, very flexible. This was combined with the new construction of the PKM, redesigned to reduce the size weight of the unit by scaling the unit down in size as well as replacing previous heavy components with aluminum and carbon fiber components. The XMINI has an expandable work envelope by combining mechanical methods of moving the machine (i.e. - tracks, rails, etc) along with the utilization of cross lasers, cameras and/or probes for accurately establishing the new position. Applications for the new XMINI are currently underway with multiple major aerospace manufacturers. These applications take advantage of the portability as well as the flexibility in the mounting orientation. All of the programs included requirements of being manually portable, and drilling/milling. Highly accurate holes in aluminum/titanium/Carbon Fiber stack materials are being achieved for many of the projects. Exploration is continuing on other potential uses in welding, laser cutting and fastening.

Neumann, Karl-Erik, Reno, Robert

Dry Drilling of Stackup Composite: Benefits of CO2 Cooling

2014-01-22349/16/2014

The use of composite materials and composite stackups (CO-Ti or CO-Al) in aerospace and automotive applications has been and will continue to grow at a very high rate due to the high strength and low weight of the materials. One key problem manufacturers have using this material is the ability to efficiently drill holes through the layers to install fasteners and other components. This is especially true in stackups of CFRP and titanium due to the desire of drilling dry for the CFRP layer and the need for cooling when drilling the high strength Ti layer. By using CO2 through tool cooling, it is possible to protect both layers. Through work supported by the National Science Foundation (NSF) and Department of Energy (DOE) it is shown that CO2 through tool cooling productivity can be significantly increased while maintaining required hole tolerances in both the composite and Ti layers. Improvements in tool life have been demonstrated when compared to either emulsion or dry drilling. By providing dry CO2 cooling through the tip of the drill, resin binders in the CFRP don't soften, and cool Ti chips don't degrade the composite at either exit or mid-levels. The summary of this paper is that when drilling stackups of composite material, oil-free, CO2 through tool cooling provides significant benefits over other types of cooling or lubrication.

Sorbo, Nelson W., Dionne, Jason J.

Implementing Determinate Assembly for the Leading Edge Sub-Assembly of Aircraft Wing Manufacture

2014-01-22529/16/2014

The replacement for the current single-aisle aircraft will need to be manufactured at a rate significantly higher that of current production. One way that production rate can be increased is by reducing the processing time for assembly operations. This paper presents research that was applied to the build philosophy of the leading edge of a laminar flow European wing demonstrator. The paper describes the implementation of determinate assembly for the rib to bracket assembly interface. By optimising the diametric and the positional tolerances of the holes on the two bracket types and ribs, determinate assembly was successfully implemented. The bracket to rib interface is now secured with no tooling or post processes other than inserting and tightening the fastener. This will reduce the tooling costs and eliminates the need for local drilling, de-burring and re-assembly of the bracket to rib interface, reducing the cycle time of the operation. Ultimately, self-indexing components mean that the there is more flexibility as to what point in production the bracket can be attached to the rib. This allows for a reduction in cycle time and cost, whilst increasing production flexibility. This research has improved the design for wing manufacture capability of the company.

Irving, Lucas, Ratchev, Svetan, Popov, Atanas, Rafla, Marcus

Production Optimization of Automated Fastening Systems with Efficiency Software and Machine Remote Access in the Airframe Industry

2014-01-22659/16/2014

The demand of fulfilling increasing Prime Customer requirements forces Tier 1 suppliers to continually improve their system solutions. Typically, this will involve integration of “state of the art” tools to afford the Tier 1 supplier a throughput and cost advantage. The subject “Production Optimization Approach” addresses the machine and process optimization of automated fastening machines in operation at customer factories. The paper will describe and focus on the main aspects of production optimization of existing machines to meet and exceed the required customer production and reporting criteria. Furthermore, the paper will present existing examples based on use of the established diagnostic tools

Neugebauer, Lutz

Flex Track One Sided One Up Assembly

2014-01-22749/16/2014

The Boeing Company is striving to improve quality and reduce defects and injuries through the implementation of lightweight “Right Sized” automated drill and fasten equipment. This has lead to the factory adopting Boeing developed and supplier built flex track drill and countersink machines for drilling fuselage circumferential joins, wing panel to spar and wing splice stringers. The natural evolution of this technology is the addition of fastener installation to enable One Up Assembly. The critical component of One Up Assembly is keeping the joint squeezed tightly together to prevent burrs and debris at the interface. Traditionally this is done by two-sided machines providing concentric clamp up around the hole while it is being drilled. It was proposed that for stiff structure, the joint could be held together by beginning adjacent to a tack fastener, and assemble the joint sequentially using the adjacent hole clamp up from the previous hole to keep the joint clamped up. This process would significantly decrease the costs and complexity that is usually associated with two sided equipment involved in One Up drilling and fastening. This paper will examine the equipment and testing completed to prove out the process of using adjacent hole clamp up to achieve One Up Assembly.

HansonSmith, Riley, Merkley, Alan

Advanced Multi Axis Trim and Drill Cell for Low Volume, Multiple Part Configuration in a JIT Environment

F-0070-2014-9558

5/20/2014

The aerospace manufacturing arena is a constantly evolving challenge to all of the participants. The conjuncture of continual cost-cutting pressures and product changes have created technical and system challenges to implant a manufacturing infrastructure that can cope and deliver widely different parts. All this in a climate of shorter delivery schedules and more complex parts geometries produced by advanced CAD systems. The challenge for equipment configuration is to create highly flexible robust machine configurations that can be adapted to multiple part configurations in the most efficient manner. This paper will research the inherent challenges in implementing automation into a highly manual operation where the technologies have to facilitate the flexibility yet ensure strict control of part variation. It will explain the technology mix required to integrate into an optimized machine configuration to process flow of parts in a JIT environment where hundreds of different parts have to go through a similar process in the minimum amount of time with maximum reliability

Laird, Andrew

Innovative Sprays and Particulate Reduction with GDi Injectors

2014-01-14414/1/2014

Innovative nozzle hole shapes for inwardly opening multi-hole gasoline direct injectors offer opportunities for improved mixture formation and particulate emissions reduction. Compared to increased fuel pressure, an alternative associated with higher system costs and increased pumping work, nozzle hole shaping simply requires changes to the injector nozzle shape and may have the potential to meet Euro 6 particulate regulations at today's 200 bar operating pressure. Using advanced laser drilling technology, injectors with non-round nozzle holes were built and tested on a single-cylinder engine with a centrally-mounted injector location. Particulate emissions were measured and coking deposits were imaged over time at several operating fuel pressures. This paper presents spray analysis and engine test results showing the potential benefits of alternative non-round nozzle holes in reducing particulate emissions and enhancing robustness to coking with various operating fuel pressures.

Kazour, Joseph, Befrui, Bizhan, Husted, Harry, Raney, Michael, Varble, Daniel

The Digital Image Correlation Technique Applied to Hole Drilling Residual Stress Measurement

2014-01-08254/1/2014

The residual stresses found in components are mainly due to thermal, mechanical and metallurgical changes of material. The manufacturing processes such as fabrication, assembly, welding, rolling, heat treatment, shot peening etc. generate residual stresses in material. The influence of residual stress can be beneficial or detrimental depending on nature and distribution of the residual stress in material. In general, the compressive residual stress can increase the fatigue life of material because it provides greater resistance for crack initiation and propagation. A significant number of improvements for residual stress measurement techniques have occurred in last few decades. The most popular technique of residual stress measurement is based on the principle of strain gage rosette and hole drilling (ASTM E837-01, destructive). Although this technique is effective for some applications, strain gages provide the localized or averaged data and cannot capture the peak or high resolution data when this technique is applied on high strain gradient areas. The measured strains are also highly influenced by the position of strain gages around the drilled hole. The improved measurement technique of 3D-Digital Speckle Pattern Interferometry (DSPI) with hole drilling can capture the full-field, high resolution and high accuracy in-plan and out-of-plan deformation data. However, DSPI is easily affected by environmental noises and it cannot measure in-plane and out-of-plane deformation simultaneously. The needs of Digital Image Correlation (DIC) techniques from industry have been increasing, especially in micro- and nano-scale mechanical testing applications mainly due to its relative easy implementation and utilization. Although DIC has a lower sensitivity than DSPI, it is more robust on spot measurements. Full field contour, displacement and strain data of specimens in any shape can be easily evaluated by DIC. This paper presents a new comprehensive residual stress measurement technique using 3D-DIC and hole drilling mechanism. In this, the residual stress measurement is performed in a full-field and no contact approach.

Chen, Yi-Hsin, Chen, Xu, Xu, Nan, Yang, Lianxiang

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