This Small Business Innovation Research (SBIR) Phase I project will resolve key technical challenges associated with the commercialization of an innovative die-less sheet metal forming process, Double Sided Incremental Forming (DSIF). DSIF locally deforms a peripherally clamped sheet metal component using a small hemispherical ended tool on either side of the sheet, each moving along a pre-determined tool path. Current toolpath generation methodologies do not take into account the mechanics of sheet deformation during the forming process, resulting in unacceptably high forming time and unsatisfactory geometry accuracy. This research will create new automated toolpath design methodologies which account for the deformation mechanics of the sheet metal during DSIF to achieve part accuracies of 500 ìm or less while maintaining a user defined throughput. Additionally, a new DSIF forming center will be designed that can form large components using high strength alloys, where high machine stiffness and forming force are required. This work will provide a significant scientific and technological foundation towards commercializing DSIF for rapid prototyping and low volume production of sheet metal parts.
The broader/ commercial potential of this project is to significantly reduce the cost of rapid prototyping and low volume fabrication of quality sheet metal components by eliminating the need for expensive die sets. The inclusion of deformation mechanics into DSIF toolpath planning will establish a strong connection between the toolpath and the final geometry and stresses of the formed product in DSIF. Consequently, the iterative experimental procedure for optimum toolpath generation will be replaced by a structured, scientific and more robust toolpath generation methodology. The advantages of DSIF as compared to conventional forming include absence of expensive shape specific tooling (up to $1M each), higher formability (4 times higher) and reduced forming forces (30% lower). Greater formability in DSIF will allow light-weighting and enhanced fuel efficiency, leading to further energy savings. The cost of storing legacy die sets will be eliminated by DSIF, since only part models in the electronic format will be needed for re-fabrication of parts.
Double Sided Incremental Forming (DSIF) is a new manufacturing process that locally deforms a peripherally clamped sheet metal component using a small hemispherical ended tool on both sides of the sheet, each moving along a pre-determined tool path to deform the sheet. These local deformations accumulate to impart a desired global shape to the sheet. Sheet metal is widely used in automobiles, aircrafts, appliances, and other consumer products, due to low weight, and high stiffness. Low volume production and prototyping of sheet metal is typically prohibited by the cost of required tooling, with a die set costing roughly $1million plus long lead times for fabrication. DSIF technology will enable the rapid prototyping and low volume production of sheet metal by eliminating the need for these die sets and reduce lead times. In this SBIR Phase I grant, Scimplicity has developed new automated toolpath design methodologies which incorporate the mechanics of sheet metal deformation in DSIF to achieve increased part accuracies, while maintaining a user specified throughput. In addition, a new DSIF forming center was designed to meet requirements for larger components, and higher strength alloys. In this SBIR Phase I Grant, Scimplicity has achieved the following: 1. An increase in the throughput by up to 4 times as compared to the state-of-the-art in Accumulative-DSIF (ADSIF) while maintaining the unique advantage of higher geometric accuracy in ADSIF. 2. A new mechanics guided framework that uses a combination of FEA and metamodeling methods and integrates it with purely geometry based toolpath generation algorithms, for automatic and a-prior generation of Incremental Forming toolpaths. This framework allows for quick formability estimates using the DSIF Process. 3. A new hybrid two-pass toolpath strategy which uses ADSIF to create the majority of structure and then uses conventional DSIF out-to-in toolpath as a secondary finishing. This combines the advantages of highly concentrated deformation in ADSIF with the higher accuracy of the conventional DSIF out-to-in toolpath without causing the characteristic unwanted sheet deformation outside the forming zone. 4. A robust DSIF machine center, capable of applying required forming forces with minimal component deflection, while being able to form components of 2m x 2m x 1m, over a travel lifetime of over 9000km travel life. A further outcome of this work is an observation of the future work that needs to be performed to improve the process further. One observation is that the sheet may fail for freeform parts when using an ADSIF toolpath generated with the new toolpath strategies developed here. Therefore, future work in coupling the fracture mechanics in the process with the purely geometric based toolpath planning is required. Additionally, previous work at NU has shown that the fatigue life of parts formed with ADSIF is greater than that of the virgin material itself. Therefore, a comparison of the fatigue life of a part formed with ADSIF to a part formed with conventional forming processes will go a long way towards developing confidence in the operational performance of ADSIF parts as compared to conventionally formed parts.
