To process its work pieces, the end customer from the automobile industry needs loading gantries with very high holding times. These must operate quietly and simplify processes. This works at notably higher dynamics. The OEM supplier supplies low-wear roller energy chains for this complex new development. These can have a smaller configuration, but can also operate very quietly and will stand up to the high accelerations and speeds over the long-term.
"We have redesigned our gantry system from the ground up", explains Grad.-Eng. Peter Vogl, Director Design & Development at GROB-Werke GmbH & Co. KG in Mindelheim. "We based our efforts on the market developments, the needs of our customers in the automobile industry, and the respective machining processes of their work pieces. "This relates to all manufacturing steps that can occur on castings or forgings.
The underlying focus is always the issue of how the various work pieces can be machined in the fastest, most cost effective, and therefore most productive manner possible, without compromising work piece quality or machine holding times.
The company has developed a new linear gantry, also called transfer machine, which was presented very successfully at EMO. Its key features are that it is notably smaller and more compact than previous solutions. "Our objective was to create uniform, simplified loading processes", Peter Vogl elaborates. "This can only be achieved with dynamics." This then quickly leads to the issue of a matching energy supply. We tested a host of solutions and ultimately decided in favor of our long-standing supplier of energy supply systems. “
The linear gantry employs roller energy supply systems. The advance tests compared the performance of magnetic chains and plastic energy chains. The decision left no doubts: internal test results showed, among others, that magnetic chains can neither meet the requirements for quiet operation, nor stand up to the high speeds over time. "Our linear gantries generally run 6 days per week in a three-shift operation. This calls for extremely rugged components in all areas", emphasizes Peter Vogl. "We simply cannot afford machine and system downtimes. “
"The development and design departments alone employ approximately 360 people at the Mindelheim facility", Peter Vogl reports. The total employment at the main facility is about 2,500 people. "Our order backlog is very good. We believe that we have good future prospects and are therefore once again significantly expanding our production capacity. We are also concurrently investing into our staff. The employment level will continue to increase until the end of 2012. The product spectrum of the family owned company, founded in 1926, encompasses flexible manufacturing systems for the automobile industry. This includes machining centers, special purpose machines, and the automation of these. The core competencies are machining up to a completely ready-to-install condition, including precision machining, sub- or complete assemblies, as well as inspection activities required for quality control purposes. This primarily relates to components for the drivetrain field, including engine and transmission components. With its four factories in Germany, Brazil, USA and soon also in China, the company is ideally positioned to address the local demand for its machining solutions.
The new linear gantry, or transfer machine, is notably more compact and smaller than the manufacturer's previous solutions. The height of the X-beam above the building floor is only approximately 3.20 m, and is therefore significantly lower than before. "Problems with building heights are a thing of the past with the new system", Peter Vogl notes. "Building cranes are no longer in our way. “
A novelty is the vertical suspension of the travel carriage, which can carry loads up to 80 kg, and that of the loading arm on large caster wheels below the X-beam. The already proven parallel kinematic technology of the loading arm was also updated and improved. The gripper can be retrofitted with a pivot axis in the A or C direction.
The reduction of the inert mass permits significantly higher travel speeds and acceleration. "The speed is at 6 m/s, the acceleration at 6 m/s2. The travel distance can be as much as 40m", Peter Vogl elaborates. "The speed and acceleration are therefore twice as fast as the previous model." The significantly improved dynamics of the linear gantry now permits loading of linked single and double spindle machines with a single action gripper.
A complete production line consists on the one hand of the linear gantry, and on the other hand of one- and two-spindle machining centres for the workpieces. "For reasons of occupational safety, the sum of all noises must be relatively low," Peter Vogl puts an important requirement criterion in a nutshell. In addition, there are the requirements for dynamics, wear resistance and service life. In the new transfer unit, the P4.32 profile roller energy chain has proven its worth from the very beginning.
Michael Offner, igus® Sales Manager Southern Germany, comments: "With 'rol e-chains, you can generally assume a three to four times longer service life than with gliding chains. “
In addition, the pitch of the chain links is the same with or without the roller, which means that, radially, the moving energy chain is especially quiet and vibration-free. In addition, there is a damping profile in the trough that further minimises noise generation. "In advance, we made some modifications to the running surfaces and the crossbars, so that today the required operational smoothness is definitely met," says Michael Offner. Peter Vogl can only confirm this: "In our internal measurements, the operating noise of the systems is 72 dBA overall, which is well below the maximum 75 dBA permitted by some customers."
Energy-efficient work processes are increasingly becoming the focus of plant operators. The P4.32 profile roller energy chain (inner height 32 mm) also meets this requirement and is consequently being used more often in automation. Compared to sliding friction, rolling friction is basically 75% lower. This means - in terms of the energy chain alone - a reduction in drive power of up to 57%. In addition, due to the high push/pull forces, a gliding energy supply system must be designed to provide much greater strength, whereas with rolling friction it can be much smaller and lighter without having to compromise on speeds, accelerations or the noise level. "However, it was clear from the start that only a rolling solution would be considered due to the high dynamic values," explains Roland Singer, Technical Sales Consultant at igus®. "Otherwise, the wear and tear is simply too high in these extreme operations."
The energy supply system is supplied as a pre-assembled ready-to-connect readychain® system that can be installed simply by "plug and play". Especially in the gantry area, the plant manufacturer has been relying on pre-assembled system solutions for many years. "It pays off," confirms Peter Vogl. "We have not had a single return in this long period. " To summarise, the tribo-optimised plastic chains and the chainflex® cables help to design and operate machines and systems in an energy-efficient and cost-efficient manner.
In the past, the P4 profile roller energy chain has mainly been used in crane applications such as container handling or bulk material loading with travels of up to 400 m. In both areas, extreme robustness is the most important factor. Noise generation plays a subordinate role in this environment. The situation is quite different in manufacturing. Smooth and quiet operation plays an important role here. "But we also solved this task in a spirit of partnership," Michael Offner looks back. A collaboration has been going on for almost twenty years. During this period, the most diverse energy supply problems have been solved.
This is reflected in the linear gantry in a number of other technical details of the loading and automation concept. The horizontal sliding changer, which replaces the pivoting changer during loading and unloading, also uses robust plastic energy supply systems.
"These ensure the required machinery and system availability, which we guarantee to our customers world-wide", Peter Vogl summarizes. "New engine and transmission generations, and new drivetrains have been driving the increased demand for flexible and highly productive manufacturing installations with nearly all automobile manufacturers and their suppliers. We are able to address this demand with our proven systems. “