Tool Life Estimation Research Articles

Estimation of tool life in bulk metal forming based on different failure concepts

Abstract For an economic production with a high process reliability, an increased tool life is required. Therefore, the necessity exists to give a reliable estimation of the tool life during the design of new tool systems. Especially for cold forging processes, the failure caused by surface fatigue is characteristic. Different approaches are suitable to calculate the time period until the initiation of fatigue cracks. The aim of this paper is to assess the applicability of different failure concepts for a closed cold forging die. The critical, process-dependent load is quantified and localized by using a finite element method. Based on the resulting stress–strain distributions, the damage parameters are calculated yielding different estimates of tool life that are compared with practically experienced data.

Tool Life and Tool Quality in Bulk Metal Forming

Due to their intermediate position between the machine and workpiece, tools represent the interface of the manufacturing system to the process. Near net shape production, new materials and techniques are the new challenges in metal forming and especially in tooling. A significant economical effect can be achieved through an increase in the life of tool elements, as well as through proper tool management strategies. The greatest problem connected with the preliminary estimation of tool life is the large scatter of service life for a series of identically designed tools. The uncertainty in estimating the expected service life of tools and thus the tooling costs per piece is caused by the enormous variety and confluence of damaging factors, the factory-specific character of tool life and the stochastic phenomenon of tool failures. From the confluence of aspects influencing tool life it is clear that there is no general recipe for increasing tool life and tool quality. Each of the influencing aspects contains some possibilities for increasing the service time of tools. This paper shows some examples of tool design and tool manufacturing and points out that a knowledge-based approach imitating the activity and knowledge acquisition of human experts can be the bridge between computer aided (CA) techniques and human experience in predicting expected tool life.

Tool Life and Tool Quality in Bulk Metal Forming

Due to their intermediate position between machine and workpiece, tools represent the interface of the manufacturing system to the process. Near net shape production, new materials and techniques are the new challenges in metal forming and specially in tooling. A significant economical effect can be achieved through an increase in the service time of tool elements, as well as through proper tool management strategies. The greatest problem connected with the preliminary estimation of tool life is the enormous dispersion of tool lives for the same construction of tool. The uncertainity in estimating the expected service time of tools and thus the tooling costs/piece is caused by enormous variety and confluence of damaging factors, factory-specific character of tool life, stochastic phenomenon of tool failures. From the confluence of aspects influencing the tool life it is clear, that there is no general recipe for increasing tool life and tool quality. Each of the influencing aspects contains some possibilities for increasing the service-time of tools. Paper shows some examples in tool design and tool manufacturing and points out, that a knowledge based approach can be the bridge between CA-techniques and human experience in prediction of expected tool life.

Tool Life in Solid Forward Extrusion

Summary Tool life in bulk metal forming is limited both by wear and fracture. Due to the variation of life of Individual tools, the reliability of operation is low. For reducing tool costs a reduction of the absolute costs of tools as well as an increase of tool life should be achieved. Tool failure should either be avoided or it should be made predictable for reducing costs by Interrupted production. In cold extrusion, tool failure is often caused by fracture, especially in cases of complicated shapes of the workpieces. Until now, crack initiation and crack propagation (depending on the kind of heat treatment of the tool steel) systematically have not been studied. In the present work tool fracture in solid forward extrusion has been investigated. For this purpose mechanical properties of specimens of the tool steel were related to the tool life in extrusion tests under simulated production conditions. To understand the fracture behaviour due to fatigue, a fracture mechanics calculation was carried out using the weight-function method. The results of the investigation enable an estimation of tool life depending on the kind of heat treatment and hence, an optimized heat treatment for the special case of application.