For companies equipped with a laser system, a common worry is the management and recovery of sheet metal leftovers – those residues of previous operations that nobody wants to waste, and are commonly reused to create samples, complete urgent jobs in single batches of parts of different sizes, or replace any scrap from the manufacturing processes downstream of cutting.

Every workshop organises and solves the first steps of recovery – i.e. the logistics, storage and cataloging of leftovers – in the method that best suits the company’s production strategy and the materials available. Methods range from simple text files listing the parts available, to automatic software solutions for inventorying leftovers, and from storing the leftovers on sheet metal packs, to stacking on shelves, and on to more sophisticated warehousing solutions for more costly materials such as stainless steel. However, storage and cataloging affect above all the times and effectiveness of the recovery activities and the search among the leftovers. The last step in the recovery process is measuring the leftovers: the dimensions are required because the programmer, who is generally not in the workshop but in the office, has to refer to the formats available in order to generate the programs.

It’s clear, then, that the leftover recovery process has many steps and many activities that have a time-related cost. And the time devoted to managing urgencies, or producing single or small batches, has a greater weight and cost than those of the daily programming of production activities.

With a view to simplifying the process and making it more efficient, Salvagnini has introduced the SVS (Sheet/Scrap Vision System) option for its laser cutting systems. The SVS is an artificial vision system that enables sheet metal leftovers to be reused, producing a dxf file that serves as a starting sheet for nesting new parts to be cut directly on board the machine. The SVS option is available in two versions: the SVS1, which has a single camera focusing on the leftover and a working range of 1600mm by 1500mm, and the SVS2, which uses two cameras and has a much larger working range of 3000mm x 1500mm.


How does the SVS work?

The operator places the sheet metal leftover on the worktable and uses FACE, the Salvagnini human-machine interface, to indicate which is the reference leftover – given that there could be more than one on the worktable. The application acquires an image of the leftover, transforms it into a dxf file and enters it in the STREAMLASER On Machine database as a starting sheet. The operator proceeds to select the parts to be produced, and the application automatically creates the nest and completes the program. At this point, the actual cutting can start: the laser automatically checks that the leftover is positioned correctly on the worktable and then cuts the defined parts.

This option offers great potential in terms of process efficiency. With SVS it is possible to create nests on more than one leftover: several leftovers can therefore be placed on the worktable if, for example, a number of small leftovers are available – and this possibility enhances the performance of SVS2. Moreover, with a graphics application, it is possible to rapidly call up – visually – the parts belonging to nests that have already been produced and are repeatable with SVS.

This is a considerable simplification, above all when we think of the need to urgently produce parts machined only recently that may have been damaged during machining downstream, or for which greater quantities are needed.


SVS1 and SVS2: what are the differences?

SVS1 has a field of vision, and therefore a working range, of 1600mm by 1500mm. This means that it is possible to position one or more leftovers offcuts on the worktable, but these must always be arranged on the correct section of the table. SVS2, on the other hand, has a field of vision of 3000mm by 1500mm and, with its larger working range, offer greater flexibility: both small and large leftovers offcuts can be used, positioned in practically any area of the worktable.

SVS guarantees a wide range of economic and process advantages. Moreover, though the alternative applications available on the market have similar purposes, they are based on different technologies, which greatly limit their effectiveness. Vision systems that support laser cutting are generally applications in augmented reality: they do not transform the images of the leftovers into dxf files to generate a completely automatic nest. In practice, they take a picture of the leftover on the worktable and allow the operator to manually “add” the parts to be produced to the image taken. The disadvantages here are clear. On the one hand, the operator has to manually enter the parts one by one, without the possibility of creating a nest in automatic filling mode. On the other hand, and more importantly, the process is often completely manual and with no error control: without a dxf, the operator may risk positioning the image of the part to be produced outside the detected outline of the leftover.