Despite years of supporting research, commercial use of the Single Point Incremental Forming process remains very limited. The promised flexibility and lack of specific tooling is contradicted by its highly complex deformation mechanics, resulting in a process that is easy to implement but where workpiece accuracy is very difficult to control. This paper looks at geometry compensation as a viable control strategy to increase the accuracy of produced workpieces. The input geometry of the process can be compensated using knowledge about the deformations occurring during production. The deviations between the nominal CAD geometry and the actual produced geometry can be calculated in a variety of different ways, thus directly influencing the compensation. Two different alignment methods and three deviation calculation methods are explained in detail. Six combined deviation calculation methods are used to generate compensated inputs, which are experimentally produced and compared to the uncompensated part. All different methods are able to noticeably improve the accuracy, with the production alignment and closest point deviation calculation achieving the best results

The envisaged flexibility of Single Point Incremental Forming is contradicted by its highly complex deformation behavior, making the process easy to implement but difficult to fully control. This paper describes a regression method that uses Gradient Tree Boosting to predict the deviations for a given input geometry, which can replace the physical part production needed for the optimization of generating toolpaths. This paper elaborates on the calculation of the geometric features used by the regressor and the selection of an appropriate training dataset. The method is validated using a generated dataset of fully freeform ellipsoid workpiece geometries.

Single Point Incremental Forming owes its flexibility to lack of dedicated tooling needed to create a variety of different geometries. This is possible because of its computer controlled nature: the toolpath that is executed will determine the shape of the produced part. By altering the toolpath in a smart way, the process can be optimized towards different criteria: speed, accuracy, surface quality. This paper describes a new methodology to automatically create toolpaths based on feature geometry. It can be used to add local features to a preformed shape, or to improve the surface quality of complex freeform parts. The paper describes the slicing algorithm and toolpath generation. The robustness of the procedure is demonstrated and a first test case shows an increase in surface quality without compromising on accuracy.

Single Point Incremental Forming is a flexible process that is well-suited for small batch production and rapid prototyping of complex sheet metal parts. The distributed nature of the deformation process and the unsupported sheet imply that controlling the final accuracy of the workpiece is challenging. To improve the process limits and the accuracy of SPIF, the use of multiple forming passes has been proposed and discussed by a number of authors. Most methods use multiple intermediate models, where the previous one is strictly smaller than the next one, while gradually increasing the workpieces’ wall angles. Another method that can be used is the manufacture of a smoothed-out “base geometry” in the first pass, after which more detailed features can be added in subsequent passes. In both methods, the selection of these intermediate shapes is freely decided by the user. However, their practical implementation in the production of complex freeform parts is not straightforward. The original CAD model can be manually adjusted or completely new CAD models can be created. This paper discusses an automatic method that is able to extract the base geometry from a full STL-based CAD model in an analytical way. Harmonic decomposition is used to express the final geometry as the sum of individual surface harmonics. It is then possible to filter these harmonic contributions to obtain a new CAD model with a desired level of geometric detail. This paper explains the technique and its implementation, as well as its use in the automatic generation of multi-step geometries.

ESAFORM is an association with the mission to stimulate applied and fundamental research in the field of material forming. Its annual conference, the International ESAFORM Conference on Material Forming, is used to achieve one of the main goals of ESAFORM: to spread scientific and technological information related to material forming within academic and industry. The next conference will be held online on 14-16 April 2021.