Steed Webzell examines toolpath optimisation and the CAM technology required to ensure cycle times are maximised without sacrificing quality

When it comes to machined automotive components, cost and quality top the priority list. Machined parts must be produced in the shortest possible cycles, but with no compromise on quality. In years gone by, this responsibility would befall the machine tool programmer, but today the latest CAM software ensures the best toolpath is selected automatically – fast, error-free and without collisions.

High quality and delivery

A case in point can be seen at the West Bromwich, UK plant of Rimstock, where Delcam’s PowerMill CAM software has helped this wheel manufacturer boost its production to over 350,000 units a year. Both rapid delivery times and high quality are essential for Rimstock’s customers in the luxury and high performance car markets.

Rimstock uses two seats of PowerMill for all of its CAM programming. Andrew Colbourne, forge shop manager, previously had programs prepared externally for his machines or outsourced the machining work completely. The transition to PowerMill was prompted by Rimstock’s move into five-axis machining. The company today has six Haas five-axis machining centres that are used mainly for finish-machining, plus three Doosan models for finer threeaxis work.

“All our programming and machining is now completed in-house, which gives us much more control over scheduling and quality,” says Colbourne. “PowerMill allows us to get a level of finish by milling that was previously only possible using grinding operations. In addition, we can edit the leads and links so that the five-axis transitions can be positioned in areas of the surface that won’t be visible. Ultimately we have been able to achieve much lower cycle times by moving to five-axis machining and PowerMill.”

The story of success is similar at Progress-Werk Oberkirch (PWO), an automotive supplier from Baden-Württemberg, Germany, which is now using Siemens PLM Software’s NX CAM for its machining processes. Specifically, PWO selected NX CAM for its functionality and real-time simulation, enabling a reduction in processing times and error rates.

PWO has used Siemens PLM Software’s Solid Edge software with synchronous technology as its CAD solution for several years. Now, the combination of compatible CAD and CAM technology allows the company to integrate its processes on a single platform, ultimately increasing productivity and process efficiency, it says.

Software benchmark

Engineers evaluate CADCAM

Indicating the popularity of WorkNC in the automotive sector, more than 100 people attended a recent WorkNC and SolidWorks CADCAM seminar in Bursa, Turkey, sponsored by Walter Tools.

Automotive OEMs in Turkey using WorkNC include Fiat and Ford, and the event, which took place in the heart of the country’s automotive industry, focused on applications such as fi ve-axis machining.

A presentation of WorkNC V21 showed how the software’s parallel processing can calculate lengthy toolpaths quickly, taking advantage of the latest multi-core computer hardware.

Additionally, participants could see how WorkNC’s Auto5 module uses fi ve-axis toolpaths by automatically converting three-axis programs.

PWO develops and machines mechanical components from steel, stainless steel and aluminium for use in vehicle electrical and electronic systems, as well as in airbag safety components and steering mechanisms. The CAM software PWO used previously was no longer meeting the company’s requirements, so a benchmark was initiated among several software providers, it says.

“The result of the CAM benchmark was apparent quite quickly,” says Ralf Fischer, who is in charge of all CAx (CAD/CAM/CAE) systems at PWO. “The consistency of the Siemens NX solution and the reduced error rate makes our work so much easier. This helps avoid post-processing errors and duplication of production steps, which saves time and increases efficiency.”

The same advantages are desirable in toolmaking, as can be verified by another German company. Riemann is a specialist in stamping and forming tools for automotive customers, typically for components such as seats and exhaust manifolds. Based near Osnabrück, Riemann is now using WorkNC CAM from Sescoi, part of Vero Software.

“WorkNC was the only software that impressed us,” says company founder, Klaus Riemann. “We could easily select a range of milling strategies and automatically generate reliable NC code, and it was extremely easy to use.”

Riemann uses the latest 64-bit parallel processing version of WorkNC to program its multi-axis machining centres. These include several five-axis models from DMG/Mori Seiki, such as a DMC 75V, two DMU 200Ps and a DMU 600P with a six-metre long bed.

“We generally cut as much as we can in three axes at each five-axis inclined position – continually rotating our heavy workpieces would greatly slow down the machining process,” says Rene Luttmann, project manager. “Firstly, we machine the base of the tool and then change the set-up to machine all the other geometry and contoured 3D surfaces in one operation, significantly reducing our cycle times.”

The company’s WorkNC programmer, Mark Hildebrandt starts with CAD files from CATIA, using his expertise to optimise the WorkNC cutting paths for speed and quality.

“In particular, we find the rest material cycles extremely practical and efficient as they avoid air cuts and shorten machining times,” he says. “Furthermore, WorkNC makes it easy to fine-tune NC programs. I can edit milling programs and cut and paste elements, such as a proven milling strategy, into a new program.”

Recently, Riemann has added WorkNC’s automatic feature recognition for drilling.

“Automotive stamping tools have a considerable number of holes and we can cut these automatically in WorkNC,” says Rene Luttmann. “First, the software finds the hole features and coordinates from the CAD data. Next, it generates tailored machining strategies which use the tools that are actually available. This minimises the number of cutters we need to stock and eliminates the possibility of an error, delivering valuable cost and time savings.”

CAM software from NCG is also improving the efficiency of machining operations at Suzuka, Japan-based Mazakina, a manufacturer of large press tools and moulds for auto body panels. Customers include Honda, Toyota, Suzuki and Daihatsu.

Mazakina wanted to be able to successfully calculate toolpaths for body panel moulds as large as 1,000mm by 2,000mm in a competitive time. The company says its previous CAM system had problems in actually completing the calculation of large files, but this has been overcome with the adoption of NCG CAM.

Among the other advantages of NCG CAM cited by Mazakina are its ability to define the size of the toolholders and shanks, and input the minimum body length, allowing the use of shorter, more rigid tooling. This has further reduced machining time – clearly a highly desirable common denominator.

Vericut provides process integrity

CGTech’s Vericut machine tool simulation and optimisation software is designed to provide protection for both the component and the machine tool, say the company. Vericut takes the post-processed NC cutting tool path produced by all major CAM systems and checks the data for issues that may have catastrophic effects on process integrity. This may be a collision between the raw material or fi xture, or the structure of the machine tool, it says.

Through the simulation process, Vericut learns the exact depth, width and angle of each cut and it knows exactly how much material is removed by each cut segment, the company says. With this knowledge, the OptiPath module divides the motion into smaller segments. Where necessary, based on the amount of material removed in each segment, it assigns the best feed rate for each cutting condition encountered. It then outputs a new tool path, identical to the original but with improved feed rates. It does not alter the NC program trajectory.