Applying TRIZ for systematic manufacturing process innovatio

Available online at

Procedia Engineering 9 (2011) 528–537

TRIZ Future Conference 2007

Applying TRIZ for systematic manufacturing process innovation:

the single point incremental forming case

Joost R. Duflou *, Joris D’hondt

Katholieke Universiteit Leuven, Mechanical Engineering Department, Celestijnenlaan 300A, 3001 Heverlee- Leuven, Belgium

Abstract

Manufacturing processes are often based on physical principles characterised by a limited applicability window. Enlarging these windows is one of main targets of manufacturing process research activities. Technical and physical contradictions are typically encountered when conducting such research. This paper describes a case in which TRIZ principles were used to systematically identify opportunities for process innovation in the domain of emerging flexible forming methods. The TRIZ principles of physical conflict resolving have been applied to improve the performance of Single Point Incremental Forming.

© 2010 Published by Elsevier Ltd. © 2011 Published by Elsevier Ltd.

Keywords: Incremental forming; SPIF; Physical conflict resolving;

1. Introduction

Manufacturing processes, be they based on material removal, material growth or deformation principles, are typically characterised by limitations imposed by the underlying physical principles. Maximum achievable feed rates, maximum thickness or hardness of raw materials that can be processed, and achievable maximum accuracy levels are just some examples of such limitations. These boundaries in the multi-dimensional space determined by the relevant process parameters are often referred to as the process window. Overcoming process limitations, and thus expanding the process window, can be achieved by introducing totally new manufacturing principles. TRIZ can play an important role in such fundamental innovations. In reference [1] it is demonstrated how, for the domain of sheet metal cutting, the consecutive development stages correspond well to development trends recognized in TRIZ, illustrating that the methodology could be applied to systematically identify innovation opportunities. However, in an early development stage of a new technological S-curve, the core objective of most manufacturing engineering research is to enlarge the process window for a given manufacturing principle rather than to identify fundamentally new process technologies. The process limitations to overcome in this kind of research are typically corresponding to technical or physical conflicts that can also be systematically dealt with using a TRIZ approach.

* Corresponding author.

E-mail address: joost.duflou@mech.kuleuven.be . 1877–7058 © 2011 Published by Elsevier Ltd.doi:10.1016/j.proeng.2011.03.139

Joost R. Du ou and Joris D’hondt / Procedia Engineering 9 (2011) 528–537529

In this paper such a systematic process innovation procedure is illustrated by means of the case of Single Point

Incremental Forming (SPIF). This emerging flexible forming method is in an early state of development and a large number of process variants are currently being studied in the international manufacturing research community [2]. As will be illustrated in this article, applying TRIZ based problem solving, supported by Axiomatic Design (AD) analysis [9] [10] [11], allows to provide direction for this research effort, leading to significant performance improvements.

In the following sections the SPIF process is briefly explained (Section 2), the principal conflicts limiting the process applicability are identified (Section 3) and a possible process design solution is formulated (Section 4). The achievable performance improvements have been verified and are summarized in Section 5. 2. SPIF process description

2.1. Manufacturing principle

Single point incremental forming has emerged in the past few years as an innovative and flexible sheet metal forming technology, fulfilling the need for producing prototypes and small batch production of sculptured sheet metal parts. In this process a spherical tool moves along the contours of the part to be formed according to a programmed tool path, while forming the sheet metal blank, which is clamped into a generic rig, into the desired shape by localized deformation [2] (see Figure 1).

Figure 1: SPIF set-up with exploded rig view.

Unlike conventional sheet forming techniques, SPIF allows to form a wide variety of shapes in a short lead-time and at low cost by employing conventional CNC machinery and without requiring specific tooling. The clamping system used for holding the sheet metal blank is reusable. Where excessive unwanted deformations need to be avoided near the upper surface of the part being formed, a tailored backing plate may be used. This is however not a mandatory feature of the process. 2.2. Process limitations

The omission of a dedicated die significantly increases the flexibility of the process, since producing a die set typically requires approximately two months of lead time. However, this increase in flexibility comes at a price: the process is characterised by a relatively low accuracy, which limits the application range. Allwood et al. [3] investigated the impact of the process window on the applicability of the process, concluding that the limited accuracy forms a major obstacle for wide commercial use. Increasing the achievable tolerance levels therefore forms a major target for ongoing research dedicated to this process. Figure 2 depicts some typical dimensional errors to be expected from SPIF.

530 Joost R. Du ou and Joris D’hondt / Procedia Engineering 9 (2011) 528–537

>1.5mm

<1.5mm <1.0mm

Figure 2: Example of dimensional errors occurring in SPIF generated parts: cross section and top view with error indication.