Automating CAM

Zegla-plast Kunststoffspritzerei GmbH & Co. KG, Schwarzenbach, Germany, manufactures complex plastic parts in many variants for the automotive and processing industries. It also produces the required injection moulds in its own mould making plant. A significant contribution to the precision of the tools – and, therefore, of the plastic products – is made by Delcam's PowerMILL CAM software (0121 766 5544). Its open interfaces have enabled a novel CAM programming solution for electrode machining – the 'macrogenerator'. Image: Zegla-plast Kunststoffspritzerei GmbH & Co. KG uses Delcam's PowerMILL to support its Macrogenerator "At Zegla-plast, we often design very complex tools, for which 300 to 400 electrodes may be required," explains Hans Hacker, EDP operator and the 'intellectual father' of the macrogenerator. "To write the NC program for machining an electrode in PowerMILL, I would normally have to select the strategy for every single cutter, enter the speeds and feed rates, select the cutting tools, start the calculation and then repeat the entire process. This takes a lot of time, it's fiddly and a lot of work. So it was essential to find a way of automating the CAM programming of the electrodes." And the result is a much easier and quicker system. "First, you allocate article numbers to the electrodes in the data-entry dialogue of an Access database and then you can enter various predefined parameters – like offset, precision, material, etc," he explains. "Then I launch the macrogenerator, with PowerMILL running in parallel to it. In the background of the program, there is a small tools database, which holds all the necessary milling information. The macrogenerator reads in every electrode from the database and automatically checks the smallest radius of the workpiece geometry to be processed. Following this, the macrogenerator directly selects the most efficient machining strategy. If everything is okay, the electrode goes off to be milled and the macrogenerator checks or modifies the parameters for the next electrode. "What makes PowerMILL special, and the reason why the macrogenerator can function at all, lies in the open structure of our CAM system," explains Delcam GmbH sales director Ferdinand Hoischen. "PowerMILL offers the advanced user the possibility to create his own interface, through which he can have an influence on the calculation process, carry out editing and then see the effects of the changes." The automation of electrode programming has also been tackled in the USA, by the EDM Department, based in Bartlett, Illinois. The EDM Department provides EDM tooling and contract manufacturing, and has overcome the challenges of small batch (often one) EDM manufacture with the aid of ESPRIT CADCAM software (Somatech, 0871 218 3001). "The ESPRIT KnowledgeBase machining capabilities enable us to embed our machining expertise within the software, which substantially reduces programming time," explains Mark Raleigh, president of the EDM Department. "We are using knowledge-based machining to develop a storehouse of optimised machining operations that we use over and over again to ensure that each of our programs is as productive as possible." Image: The EDM department has automated its programming with ESPRIT The EDM Department previously developed CAM programs for producing sinker EDM moulds, using two-dimensional CAM programming software, augmented with manually written G-code to support 3D machining. In addition, the software did not support new generation machines, such as mill-turn lathes and four-axis machining centres, so the only way to program them was, again, to write G-code to support advanced machine functions. TEDIUM RELIEVED So EDM Department installed the solid-model based CAM software system. "We picked ESPRIT because of its unique KnowledgeBase machining capabilities," Mr Raleigh explains. "ESPRIT provides a wide range of features that embed machining and tool expertise into the software. This saves time by automating many tedious programming functions. The knowledge base also can help reduce machining cycle times by providing programmers with standardised operations that have been optimised by highly skilled and experienced programmers." Over time, the company has created a library of machining operations that handle the vast majority of its programming tasks. Today, when a programmer creates a new CAM program, he can simply drag and drop machining operations from the library, rather than creating them from scratch. Staying with automation in America, and Delcam's FeatureCAM knowledge-based CAM system (0121 766 5544) has reduced programming time for feature-intensive 2.5D parts by 50 per cent to 75 per cent and for less feature-intensive 3D parts by 25 per cent at Vector Tool & Engineering, Kansas City, Missouri. For the mould making company that generates an average of 240 new programs every month, time savings are substantial. In addition, machining time has been saved by the software's more efficient rest-machining and trochoidal-milling capabilities. While Vector Tool continues to see growth in new mould builds, the company also carries out extensive revision, rebuild and maintenance for its customers, both inside and outside the Peterson Group. This combination of work requires fast reaction times to keep customers up and running. "Our business has become more and more competitive, and CNC programming has always been a very critical factor for us," explains Randy Bennett, lead programmer for Vector Tool. "We felt that we needed a major improvement in efficiency that we were not getting from our previous software. The thing that sold us on FeatureCAM was its ability to automatically recognise features such as holes, pockets, bosses and slots, in 3D solid and surface models. This means that we don't have to deal with each individual surface, but can program features instead. This is much less time-intensive, because there are far fewer features and because the inherent commonality of features means that they can often be programmed from libraries." After the design phase is complete, the company's CNC programmers begin by importing the component. After the programmer is satisfied with the way that the features have been defined, the next step is to pick tools, and speeds and feeds, for machining each feature. The natural repetitiveness of features means that it is often possible to pick a tool and machining conditions from a similar example that has been machined previously and saved in the software's library. Many parts also have multiple copies of some features and, in this case, the relevant program can be copied easily to each location where it is needed. Box item What's in a strategy? Mastercam (4D Engineering, 01285 650111) recently introduced a new strategy, Dynamic Milling. The company has demonstrated the benefits via a worked example, comparing Dynamic Milling against a typical Zigzag Milling strategy. To highlight how the 2D high speed toolpaths can handle open pockets with islands and multiple entry points, an open pocket was selected for the experiment. Tools employed were high speed Steel 9.5 mm diameter, two-flute end mills; material AL 6061-T651. At a feed rate of 762 mm/min, the tool failed when both sides were engaged for an extended time in full material cut. At 381 mm/min, the tool cut the pocket successfully, but the tool was close to failure and the pocket took over four minutes to cut. The 'full depth-of-cut method' could be used for only two parts; the third part failed, due to excessive chip loading. Dynamic toolpaths (with dynamic core mill passes enabled) guarantee an efficient toolpath, with a consistent chip load that yields the best possible machining solution. The experiment tested the toolpath to failure and then the feed rate was adjusted to 1,000 mm/min. The toolpath produced a reliable pocket operation in less than 3 minutes! Additionally, the chips cleared consistently and reliably. See Dynamic toolpaths in action here First published in Machinery, March 2010