James Lowrie

Micro-Tube Hydroforming System Based on Floating Die Assembly

Micro tube hydroforming system based on floating a micro-die assembly in a pressurized chamber is an innovative system which can allow fabrication of complex micro tubular products. In this system, the fluid pressure inside the chamber which surrounds the die and punches is the same as the pressure required to hydroform the tube. The unique features of this system are its capability to hydroform complex micro tubular parts irrespective of whether the material require material feeding, the ability to hydroform very small tubing because material feeding can be achieved by employing non-hollow punches, and the ability to hydroform multiple parts with ease because the fluid intake to the pressurized chamber is independent of the number of micro tubes to be hydroformed.

Scalability of conventional tube hydroforming processes from macro to micro/meso

Due to the increasing demand for small, complex parts, researchers are putting a great deal of effort into applying the metal forming process to the micro and meso world. However, the tube hydroforming process is yet to be fully realized on this small scale because of the difficulties which arise in scaling the conventional tooling to the microscale. This article discusses the difficulties that arise as a result of simply shrinking the traditional hydroforming tools to the microscale. A simple mathematical model is then proposed as a way to help designers determine the limits of the conventional punch with a tapered nose commonly used in tube hydroforming. The model is then validated by performing a finite element analysis of the punch, and the results of the model are discussed in relation to the scaling concepts posed at the beginning of this article. It is determined that as the punch shrinks down, the stresses on the punch rise significantly as a result of changing aspect ratios of the workpiece and the inability to accurately machine very small holes through the punch body. A nonconventional tube hydroforming method may therefore be required to perform micro-tube hydroforming operations, especially on harder materials.

Novel Extrusion Punch Design for Improved Lubrication and Punch Ejection

The extreme surface expansion and pressures observed during the backward extrusion process can have adverse effects on the surface of the workpiece and the life of the punches used in the process. After the forming process is complete, the ejection of the punch can further damage the part surface and reduce tool life because the pressures on the land of the punch remain quite high. The research presented in this investigation aims to reduce or eliminate the galling and surface damage for the backward extrusion process by creating a new class of punch which can create the opportunity for lubrication transport to the area underneath the punch and lessen the damaging conditions during punch ejection. The proposed tooling divides the traditional punch into two pieces, a hollow punch body and an insert with micro channels for lubrication transport. The tooling was developed and used in a series of tests to determine the benefits of the new punch. Preliminary data shows that the extrusion loads for proposed punch are similar to the conventional punch, but the surface finish is significantly enhanced using the modified punch design and the galling is minimized. Furthermore, there is a marked reduction in the ejection load required to remove the punch from the part after forming.Copyright