Daniel Walczyk

Design and analysis of reconfigurable discrete dies for sheet metal forming

Abstract Discrete dies have been investigated for sheet metal forming since the early part of the 20th century. The reconfigurable nature of these dies lends itself well to flexible manufacturing systems; unfortunately, the state of knowledge on how to design and analyze discrete dies consisting of densely packed pins is very limited, thereby hindering industrys acceptance of this type of tooling. This paper addresses the design and analysis issues involved with movable die pins, turning a matrix of die pins into a rigid tool, and the pin matrix containment frame. A generalized procedure for designing discrete dies is developed and then applied to the design and fabrication of a pair of high-resolution sheet metal forming dies. These dies are set to shape and then used to stamp benchmark parts out of steel sheet.

The Impact of Culture and Individualism–Collectivism on the Creative Potential and Achievement of American and Chinese Adults

ABSTRACT: This research explored the relation between culture and creative potential in highly educated adults. It was hypothesized that culture would influence creative potential and achievement, largely through how individualistic (citizens serving themselves) or collectivistic (citizens serving society) the society of origin was. To this end, 55 American and 56 Chinese doctoral students were surveyed concerning their creative potential, their sense of individualism or collectivism, and their Graduate Record Examination quantitative subtest scores. Americans displayed significantly higher scores on a measure of creative potential than the Chinese. As expected, Americans showed greater individualism. Chinese were more collectivistic. Chinese had significantly higher skill mastery in the domain of mathematics. Theoretical and practical implications of these findings for understanding cultural differences in creativity are considered.

Development of a reconfigurable tool for forming aircraft body panels

Abstract To significantly cut the time and cost of tooling development, a reconfigurable discrete die (that is, matrix of individually actuated pins) is being developed for aircraft fuselage parts made by forming sheet metal or molding of composite materials. Each pin in the die is a simple hydraulic actuator outfitted with an in-line NC solenoid valve to control its vertical position. Pin positions can either be set in a closed or open-loop fashion. Once the pins are “set,” then the entire matrix is clamped into a rigid tool. A single pin was constructed to resolve several design issues, including the removal of trapped air in the hydraulic circuit, prevention of hydraulic leakage, motion control, and quantifying the dynamic frictional forces. Because the performance of the single pin was deemed acceptable, a 4 × 4 test die of similar design has been constructed to establish the frictional interactions between adjacent pins, the workability of the pin matrix clamping scheme, and the feasibility of closed and open-loop control of pin positioning.

Rapid Tooling for Sheet Metal Forming Using Profiled Edge Laminations—Design Principles and Demonstration

Sheet metal forming dies constructed of laminations offer advantages over more conventional tooling fabrication methods (e.g. CNC-machining) in terms of tooling accessibility, reduced limitations on die geometry and faster fabrication with harder die materials. Furthermore, the recently introduced Profiled Edge Lamination (PEL) tooling method improves upon other lamination-based tooling methods. Adoption of this promising rapid tooling method by industry is being hindered by the lack of formal analysis, design principles, and manufacturing requirements needed to construct dies in such a manner. Therefore, the propensity for delamination of the die is discussed and preventive measures are suggested. The basic machining instructions, i.e., an array of points and directional vectors for each lamination, are outlined for both compound and planar profiled-edge bevels. Laser, AWJ and flute-edge endmilling are experimentally identified as the most promising methods for machining bevels. Development of a stand-alone PEL fabrication machine is suggested over retrofitting commercially-available 5-axis machines. Finally, the general procedure for creating PEL dies is implemented in the construction of a matched set of sheet metal forming tools. These tools are used to successfully stamp a sheet metal part out of draw-quality steel.

Bending of Titanium Sheet Using Laser Forming

Abstract Laser forming, a novel manufacturing method for bending sheet metal first reported in 1985, has been investigated as an alternative to hot brake forming (industry standard) of titanium sheet parts for the aircraft industry. Laser forming involves scanning a focused or partially defocused laser beam over the surface of a titanium workpiece to cause localized heating along the bend line and angular deflection toward the beam. The main advantage that laser forming has over conventional brake forming is increased process flexibility. An experimental investigation of this process (primarily designed experiments) met the following objectives: identified the response variables related to change in geometry (bend angle) and material microstructure; characterized the influence of process variables (scanning speed, beam diameter, laser power) on these response variables; determined the degree of controllability over the process variables; and evaluated the suitability of laser forming for the aircraft industry (most important), all with respect to titanium sheet. It has been determined that laser forming with an Nd:YAG laser is a controllable, flexible manufacturing process for titanium sheet bending. Unfortunately, these advantages over traditional hot brake forming are overshadowed by the fact that, with regard to forming with titanium, laser forming is significantly slower and more labor and energy intensive, and results in unacceptable material properties at the bend line according to aircraft industry standards. These findings cast doubt over the assertions of some researchers that laser forming may be a viable manufacturing process for parts made in small batches. Instead, it appears that it may be best suited for rapid prototyping of sheet metal parts.

Using Reconfigurable Tooling and Surface Heating for Incremental Forming of Composite Aircraft Parts

The application of composites in the aircraft industry has increased significantly over the past few decades. With traditional composite laminate shaping, each layer is made to conform to the mold surface by hand before subsequent layers are added. This is a very labor- and time-intensive process. There is a great deal of interest in developing an automated process for forming composite parts with compound curvatures. The proposed composite forming process utilizes a computer-controlled, reconfigurable discrete element mold to incrementally form a compound curvature part shape from a flat lay-up, thereby facilitating process automation. An elastomeric interpolating layer called an interpolator, is placed on top of the hemispherical forming ends of the die elements to prevent dimpling of the composite lay-up. The process employs vacuum to pull a single diaphragm (top), composite, and interpolator into contact with the mold surface. Through an experimental investigation, this new composites forming process with active tooling has been successfully demonstrated. Heating of the composite is accomplished by uncontained, forced convection using a matrix of heated air jets mounted above the composite. However, low-powered conduction is shown to be the best heating method in terms of both composite heating time and minimization of through-thickness temperature. Using vacuum to conform both the composite and the interpolator to the mold, and choosing sufficiently stiff diaphragm and interpolator materials, undimpled and wrinkle-free composite parts have been formed in an incremental fashion.

A comparison of rapid fabrication methods for sheet metal forming dies

The need for rapid, low-cost die fabrication and modification methods is greater than ever in the sheet metal forming sector of industry. Consequently, three fabrication methods, suitable for rapid die development schemes, are being compared experimentally based on cost, lead-time, shape resolution and flexibility issues. The candidate methods include CNC-machining a solid billet of material (standard method), assembling and clamping an array of profiled-edge laminations (PEL), and configuring and clamping a matrix of closely-packed pins (discrete die). A matched-set of forming dies was made using each of the candidate fabrication methods for stamping an FEA-verified benchmark part out of steel sheet. Based on the stamping experiments, a PEL die is shown to be similar to CNC-machined dies except that most tooling accessibility problems are eliminated, die geometry limitations are reduced and faster fabrication is possible for harder tool materials. When compared with CNC-machined dies, the discrete die method limits part shape fidelity, maximum forming loads, die geometry and blankholder incorporation. However, the discrete die method excels over the other two methods in terms of lower cost and faster fabrication time. The results of this study make a strong case for the sheet metal forming sector of industry to actively implement the PEL and discrete die methods in their manufacturing operations.

Fixturing of Compliant Parts Using a Matrix of Reconfigurable Pins

Commercially-available reconfigurable fixtures, used for holding compliant sheet metal, composite and plastic parts during secondary machining operations, are extremely expensive and overly-complicated devices. A computer-controlled, reconfigurable fixturing device (RFD) concept for compliant parts, based on a matrix of individually-stoppable pins lowered by a single rigid platen, has been developed as a simple and low-cost design alternative to commercially-available devices. Two different approaches to stopping and clamping individual pins have been investigated: a combination electromagnet assist and gas springs compressed with a toggle mechanism, and a pneumatic clamp. Simple mechanical models have been developed for predicting the stopping and clamping performance of both designs including pin positioning accuracy, vertical load-carrying capacity of a pin, and deflection of a pin subjected to lateral loads. An RFD prototype, consisting of a single pin actuated by a servoed platen, has been designed, built and tested. It has demonstrated the feasibility of this new RFD design.

Development of a computer-aided manufacturing system for Profiled Edge Lamination tooling

Profiled Edge Lamination (PEL) tooling is a promising Rapid Tooling (RT) method involving the assembly of an array of laminations whose top edges are simultaneously profiled and beveled based on a CAD model of the intended tool surface. To facilitate adoption of this RT method by industry, a comprehensive PEL Tooling Development System has been proposed. The two main parts of this system are (1) iterative tool design based on thermal and structural models and (2) fabrication of the tool using a Computer-aided Manufacturing (CAM) software and Abrasive Water Jet (AWJ) cutting. CAM software has been developed to take lamination slice data (profiles) from any proprietary RP software in the form of polylines and create smooth, kinematically desirable cutting trajectories for each tool lamination. Two cutting trajectory algorithms, called Identical Equidistant Profile Segmentation (IEPS) and Adaptively Vectored Profiles Projection (AVPP), were created for this purpose. By comparing the performance of both algorithms with a benchmark part shape, the AVPP algorithm provided better cutting trajectories for complicated tool geometries. A 15-layer aluminum PEL tool was successfully fabricated using a 5-axis CNC AWJ cutter and NC code generated by the CAM software.

A Comparison of Pin Actuation Schemes for Large-Scale Discrete Dies

Abstract Reconfigurable discrete die tooling is attractive for reducing the lead time, initial costs, and recurring costs associated with stretch forming of sheet metal parts such as aircraft body panels and wing skins as well as automotive and marine components. Current tooling for the stretch forming process requires substantial lead time for fabrication and is inflexible and expensive. To develop discrete die tooling for stretch forming, three different discrete die designs have been proposed, and small-scale prototypes of each have been built. In this paper, the three designs are compared to each other in terms of performance criteria, including pin positioning accuracy and repeatability, setting speed, suitability for a production environment, fabrication costs, manufacturability and maintainability, and maximum forming load capacity. The advantages and disadvantages of each design are also discussed.