Power play for humans and robots

It would take about 15 employees, working three shifts, for a manufacturer of ventilation piping systems to grind internal and external welds on pipe elbows. An integrated robot solution with two stations, and a few employees for the less accessible points, ensure top quality at a competitive cost. Now the parts are produced in eastern Germany instead of eastern Europe.

As working and living standards have risen in formerly low-wage countries, their cost advantage has melted away, while problems with productivity and communication remain. At the same time, new, low-cost robotics and handling systems have, in recent years, become a real alternative for extensively automated production and assembly. More and more companies are bringing production back.

One ventilation piping systems specialist, which moved production of standard piping components to eastern Europe for a few years, has recently decided to return to Germany.

After an objective cost/benefit analysis, and renovation of a production site in eastern Germany, the decision was made to back a pragmatic combination of specialized technicians and a robotic system. The company expected to see an increase in productivity and costeffectiveness. In particular, concentrating at a single location reduced what had been relatively high costs for logistics, warehousing, investments, operations, quality assurance, and communications, some of which were even eliminated completely.

Robots weld and grind pipe elbows

The task that the robotic system had to perform included both welding and high-quality, fully automatic grinding of the outside and inside radii of two-part and three-part pipe elbows. Today, welding and grinding are particularly important, because customers have higher and higher requirements for design and quality. On the other hand, the global competitive pressure in the piping systems market is high, which has been addressed with as high a level of automation as possible.

The search for a capable manufacturer for such a combined robotic system, however, turned out to be not that simple. For example, producers of welding systems declined, saying that they were not responsible for grinding, or even that they considered it beyond their capabilities. It took „reversing“ this approach, namely by searching for a partner for robotic grinding, to come up with the current solution, a fully automated robotic cell for welding and grinding the pipe elbows.

Multifunctional robotic system

After thorough discussions and clarifications, SHL Automatisierungstechnik AG from Böttingen, specializing in robotic grinding and polishing systems, was awarded the contract to implement a robotic systems solution to integrate the following processes: receiving a two or three-part pipe elbow from a workpiece pallet, guiding and positioning the workpiece for welding a circumferential seam in the welding station, grinding the outside radius of the workpiece on belt grinders, setting the workpiece down in a transfer station, picking up the workpiece by another robot, grinding the workpiece on the inside radius on belt grinders, scotching the grind transitions on a polishing machine if needed, and finally placing the completed part in a waiting workpiece pallet.

The robotic welding and grinding system is designed to be multifunctional, not only with respect to its welding and grinding processes, but also in that it can process pipe elbows throughout a range of nominal sizes from DN 80 to DN 300. For these processes, which take different amounts of working time, the SHL robotic welding and grinding system was divided into two cells for capacity reasons. In Cell 1, the parts are welded and the outer radius is ground; in Cell 2, only the inner radius is ground and, if needed, the grinding transitions are scotched.

Complete process in two connected cells

Cell I consists of a double shuttle table that receives interchangeable workpiece pallets that can be adjusted to different diameters, a Kuka KR 140 industrial robot with a 140 kg payload, an insulated gripper with interchangeable jaws for handling pipes of 80 to 300 mm in diameter, a welding station with welding equipment and a protective housing, two SHL-FKS 250/450 belt and contact wheel grinders, a re-gripping station for additional positioning for outside finish grinding, and a station for transferring the parts to Cell II.

The second cell is also equipped with a Kuka KR140 industrial robot, a gripper with interchangeable jaws, two SHL-FKS 250/450 belt and contact wheel grinders, an adjustable grip transfer station for repositioning for inside finish grinding, and finally an SHL double shuttle table for receiving interchangeable workpiece pallets that can be adjusted to different diameters.

Problem areas are reworked by hand

The entire SHL robotic system, including the welding equipment, is enclosed by a safety guard enclosure with locked access doors, and equipped with exhaust ventilation systems. The workpiece pallets are loaded and unloaded with raw and finished parts at the accessible outside area, while the working areas are secured by a lock (lift doors: actuated pneumatically on the robot side, and manually on the operator side.) A special panel is also installed in the enclosure to allow observation of the welding process from the outside without the use of welding goggles.

The finished parts are then removed from the workpiece pallet, transferred to the „Manual rework“ area by transport cart, and finished there. This is where the teamwork between the robotic system for welding and grinding and the manually ground finish comes to bear. Robotic grinding is not possible at the less accessible
points, which is why a human takes over this part. The customer thus receives the result of a joint effort, a perfectly welded pipe elbow, with an appropriate surface, that can be installed directly.