At its headquarters in Ichenhausen, Germany, Scheppach manufactures about 300 products, including machines and accessories. Today the 150 employees of the Scheppach Group generate over EUR 52 m in turnover annually. With its comprehensive range of high-quality, stationary woodworking machines the international specialist targets ambitious DIY and professional users. This quality requirement is also reflected in its modern machine pool – a winning combination of laser punching machines, powder coating facility, various CNC machines and, last but not least, a new robotic welding cell.
“Our complex portfolio would not be cost effective to produce without the welding robots we have had in operation for over 20 years. By investing in the Yaskawa innovative welding cell we wanted to achieve the state of the art in terms of quality, flexibility and programming options,” says Jürgen Niederwieser, Sheet Metal Processing Team Manager at Scheppach.
The wide product range calls for maximum flexibility from the welding system. The Yaskawa system must be able to handle all assemblies of the full Scheppach product range. These can vary from A4-size items weighing only a few kilograms to 150 kg components of two metres in height. Material thicknesses range from 1.0 to over 15 mm. The only common feature is that all parts are made of mild steel and welded by the MAG method.
A convincing system concept
The many years of experience and welding technical know-how of Yaskawa Europe, formerly known as Motoman robotec, have paid off in the design of the innovative welding system. The layout of the cell clearly demonstrates the expertise of the design engineers. A Motoman MA1900 welding robot, suspended from a gantry with a three-metre linear servo axis, introduces flexibility to the system. The six-axis robot with a maximum range of 1.904 mm can be moved along its traversing axis to an optimum position at any conceivable welding point. With its ingenious wire feed and integrated cable routing, the precision welder guarantees top seam quality and maximum availability.
Additional flexibility is provided by the accurate twin-station RWV2 series positioner with a distance of three metres between the face plates and a handling capacity of 1,000 kg per station. This design enables the system to be subdivided into a welding and a loading area. The servo positioner has a horizontal rotational axis for station interchange and an infinite rotating axis at each station to convey the assemblies to the optimum welding position. The entire system is controlled by the modern high performance DX100 controller, also from Yaskawa. This controller can coordinate up to 72 fully synchronised axes and makes light work of the ten axes in this system.
Jürgen Niederwieser is also impressed by the user friendliness of the DX100: “The programming of the new system was for us the advent of a new era. Following training at Yaskawa we were able to create our own programs quickly and easily with the DX100. And if we encountered a more complex program problem in the starting phase, the Yaskawa service technicians in Allershausen were always available by phone for instant support. Programming has meanwhile become routine.”
System operation amounts to no more than loading parts, for which welding programs are stored in the control system. All welding is performed by the robot. This is a positive development for the operators, whose working conditions have substantially improved. The operator can concentrate on the easier task of loading parts on the clean side of the system without the need for protective clothing. Manual handling of parts is no longer necessary. Which of the tasks – loading or welding – is cycle time critical, depends on the respective parts spectrum. The objective is to maximise utilisation of the welding robot and minimise its downtimes.
Exploiting the full potential
The creative potential of the new system at Scheppach is demonstrated by the welding sequence for a completely new product, the jigging device for the Wox 700 Duo double log saw: “We break the voluminous assemblies into various sub-assemblies and weld two pre-welded items and one main welded assembly in a single operation. This enables us to reduce the complexity of this component and greatly simplifies jigging. The method allows the robot to move to any desired position with optimum orientation, without conflicting with the various clamping elements,” explains Niederwieser, adding: “Sometimes we have different assemblies on the system simultaneously for a variety of final products.”
Even when loading the system with heavy parts weighing up to 150 kg there is no interference with the precision work of the welding robot on the other side. The extremely sturdy design of the positioner prevents vibrations occurring, even when such high forces are being exerted, ensuring consistently high welding seam quality. This is particularly important to welding specialist Niederwieser: “It goes without saying that the quality of the welding seams is critical in our products, as it is a decisive factor for ensuring reliable functioning. Furthermore, most welding seams remain visible, even after powder coating of the final product, so the buyer also sees this as a quality feature. The new robotic welding system satisfies our quality requirements perfectly in this respect.”
It is not only the quality of the welding seams that meets with approval – the overall performance of the system achieves the highest possible ratings. Since it was commissioned in July 2011 the welding cell has been running in 2-shift operation without outages of any kind – a confirmation for the decision-makers at Scheppach, for whom the decision in favour of Yaskawa was not an easy one: “We had shortlisted several suppliers and inspected reference installations from each of these companies. In the end we were convinced by Yaskawa’s expertise and their partnership approach. Today we know we made the right decision. The system fully satisfies our ambitious requirements in terms of quality, flexibility and reliability,” says Niederwieser.