Design and Development of a Tailored Blank Manufacturing System for Stamp Forming Process

Lightweight high-performance structural parts are increasingly becoming more
important in many industries. Composite materials with their high strength-toweight ratio have proven to be among the best solutions to achieve such parts. In recent times, thermoplastic composite materials combined with the stamp forming process has been an interest of study. In this process, an input two-dimensional blank profile is thermoformed into a shell-like three-dimensional part. The conventional blank profile preparation process for the stamp forming results in non-optimised blanks and high material waste. To tackle this challenge, a new blank manufacturing technique called Tailored Blank Manufacturing System (TBMS) has been developed by various machine suppliers. In this technique, the two-dimensional blank is produced using short strokes of pre-impregnated thermoplastic tapes to the required thickness and orientation angle (also called stacking sequence).

From market analysis, it is identified, that most of the developed systems fall short in one or more limitations which are material deposition rate, the accuracy of tape placement, cost of the system, material waste, and finally, sensitivity of the system to tape imperfections. In addition, these systems use continuous tape placement systems such as Automated Tape Layup (ATL) or Automated Fibre Placement (AFP) limiting to use of single input tape width for blank manufacturing. Moreover, the use of laser, infrared and ultrasonic heating to weld one layer of tape to another, makes the system complex and expensive. Besides, most of the high material deposition rate systems are designed to produce large auto-clave parts such as aircraft wings and not specifically designed to produce blanks for the stamp forming process.

In this PDEng design project, a dedicated TBMS for stamp forming process is designed. A cheaper yet accurate welding system is tested and used as the primary tape welding technique for developing concepts. Using the preliminary requirements set by the consortium of companies and the knowledge obtained from the trial runs, two TBMS design concepts for the stamp forming process were proposed. The proposed concepts are validated against the requirements and one concept is chosen for further development in the preliminary design stage. The preliminary design of the concept is virtually tested for its feasibility. The designed system has proven to have a higher material deposition rate to cost ratio. However, it does not meet the required accuracy requirements. Therefore, the design is iterated for further improvement using the suggestions provided by the consortium members. The original design and the iterated design are compared against the machineswith similar material deposition rates and tape width variation levels. From the comparison, it is identified that the designed system indeed have a higher material deposition rate to cost ratio compared to the machines that are currently available in the market. Moreover, the designed system eliminates the sensitivity of the system to tape imperfections and provides reasonable levels of tape placement accuracy.

In order to validate and support the design choices, a "proof-of-concept" lab-scale demonstrator model was constructed. The demonstrator uses a pick and place strategy to build blanks from pre-cut uni-directional tapes. The blanks produced from the demonstrator with simple inexpensive welding system are compared with the blanks produced using other machines with different welding sources. It is identified that the blanks produced at various machine suppliers and the blanks produced using the demonstrator after being heat pressed under the same conditions into laminates revealed to have similar quality. Proving, that it is possible to produce good quality blanks using the designed low-cost blank manufacturing system.