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Vol. 7
May Issue
Year 2006
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Articles


in Vol. 7 - May Issue - Year 2006
Robot-Aided Shotblasting Technology: Flexible Speedy Processes For Castings



With the R


A mini version of the Roboblaster is already in use


RDGE 2: The wire-mesh continuous-flow system is a multifunctional system for high productivity. It can be fully automated with one of two robots for loading and unloading.


RDT 100-So: The rotary table system has been firmly integrated into a diecasting manufacturing cell. The robot places the component to be shotblasted on the mandrel in the centre of the rotary


Aluminium cast part, treated in the rotary table system


RDT 150 S-5: Gearbox components are descaled and compressed (shotpeened) in the robot-aided satellite rotary table system.

Castings are an important production item in many industrial sectors.  Diecastings in particular have become indispensable, particularly in the automotive industry. The most highly automated casting processes enable streamlined and environmentally-friendly manufacturing. However, in view of the hard fight on the international front for low manufacturing costs, it is no longer enough to only automate some areas of manufacturing.  Integrated automation concepts, which cover the whole production process, are in demand. Great significance is attached to all area of production besides the actual casting process. Compared to manual processing, automation offers considerable optimisation potential, particularly with regard to throughput, productivity and manufacturing costs. Not only product quality and manufacturing consistency are increased by fully automatic, reproducible processes. Safety at work and the working environment also experience improvements. With shotblasting systems, which can be fully automated by modern robot technology, Rösler Oberflächentechnik GmbH, Untermerzbach, offers a wide range of specific solutions which assist economic and successful production in a difficult environment.

Specific customer solutions for the automation of shotblasting processes are part of the core expertise of Rösler, whose customers are well known and respected companies, in amongst others, the automotive and automotive supply chain. Solutions for the deburring and shot peening of sophisticated castings are a particular strength of Rösler Surface Technology.  These include fully automated, robot-aided or robot-based shotblasting systems such as the Roboblaster. "The deciding factor in the design is always the level of technological creativity", says Dipl.-Ing. Frank Herbst, Manager of the Shotblasting Technology Sales Department at Rösler.

Roboblaster - the system of the future

With the Roboblaster, Rösler demonstrates how the benefits of the robot can be used for very ambitious shotblasting tasks. This highly efficient processing system is very suitable for utilisation in complex manufacturing environments and can be integrated perfectly into fully automatic production lines. The basis of the “Roboblaster” concept is a shotblasting system as the main body, and a robot co-ordinated to the size of the plant, tasked as production assistant. Depending on the technical concept, the robot conveys the component into the machine and moves it in the shotblasting media stream produced by several heavy-duty shotblasting impellers. Shotblasting can be carried out on general areas, or only on part of the component by separate switching-on and off of each individual shotblasting impeller.  With a compressed-air shotblasting technology concept, the component is already in the machine and can be shotblasted on specific areas with a shotblasting nozzle held by a robot. The cabin interior and the component gripper unit are made completely of manganese steel or hardened tool steel.

The main body of the shotblasting system is decided by the component size, geometry and processing task with regard to design configuration, clearance, and number of shotblasting impellers or compressed air output. The design weight of the robot and the type and size of the patented grippers depend on the component weight. In principle, all conceivable shotblasting technology processes are possible with the Roboblaster: from rust removal, descaling or paint removal, through deburring to shot peening. "The Roboblaster, with its extremely wide utilisation spectrum, is a successful system", explains Frank Herbst. "Where there is an unmanned production line and very large component series, it is significantly superior to other shotblasting systems."

The "Roboblaster" concept has already been implemented by Rösler in several variants. For example, for the deburring and surface finishing of aluminium diecast cylinder heads. Two Roboblasters, equipped with separate 6-axis robots, have been integrated into the production line of a car manufacturer. The gripper unit of each Roboblaster collects the cylinder heads from the infeed roller conveyors in a cycle time of 23 seconds and feeds them into the shotblasting machine. Here the components are processed on all sides by four heavy-duty shotblasting impellers. Process security and optimum shotblasting results are achieved through the rotating and oscillating movements of the cylinder heads.  Upon completion of the shotblasting process, which lasts only 15 seconds, the robots remove the components - with closed shotblasting impeller partition - from the shotblasting chamber and feed them to the next process. The partitions enable the shotblasting impellers to continue to run during loading and unloading without downtimes.

A Roboblaster with six shotblasting impellers is used for processing magnesium transmission casings. The robot has been equipped with double grippers in this system concept in order to pick up components from two parallel lines and feed them into the shotblasting machine.  Each case is set individually in a rotating and oscillating motion.  Rösler has developed a Mini-Roboblaster, whose main body is about as big as a manual shotblasting cabin, for use by an aircraft manufacturer. Very small turbine blades are shotblasted completely and automatically in this machine. The shotpeening process used by the airline industry in accordance with strict regulations increases the fatigue strength and the robustness of each individual component. 

Flexible  handling

In view of the increasing cost pressure on manufacturing companies, robots have long been the ultimate answer to many different rationalisation problems. An automotive supplier was looking for an automated shotblasting system for deburring and surface finishing  aluminium diecast oil sumps for cars (each weighing 4.5 kg), which would offer high production rates without having to sacrifice flexibility due to rigid production requirements: a system which simultaneously offers top and reproducible quality to meet the special requirements of the automotive industry. A wire-mesh continuous-flow system RDGE 800-4 with 4 heavy-duty shotblasting impellers and with twin-track infeed and outfeed conveyor belts has been laid out and set up for loading and unloading using two robots. This system however can be easily loaded and unloaded manually, and the client uses this facility specifically for processing special bathes. In fully automatic operation, the first robot takes the oil sumps for processing from a wire-mesh cage and places them alternately on the two tracks of the conveyor belt. After the shotblasting process, the components leave the shotblasting chamber via a discharge conveyor with a wedge-shaped receptacle at the end of the belt. This special detail ensures the exact positioning of the components (with up to max. 5 mm margin of error) so that they can be removed specifically by the second robot. A light barrier is triggered as an aid to ensuring that the robot grips the component at the correct time.

Compact solution for diecasting manufacturing cells

The same diecasting manufacturer uses another Rösler robot-aided shotblasting system besides the wire-mesh continuous-flow system. The rotary table system RDT 100-So, on which aluminium diecast ladder frames (weighing 2 kg each) are processed, is designed in order that it may be integrated directly into a completely unmanned diecasting manufacturing cell.  This integration provides the opportunity for reworking on the production line so that the castings do not have to be transferred onto a separate line, which is a time-consuming operation. Within the completely self-contained manufacturing cell, one robot manages the complete handling between the individual workstations, from the casting plant via the punching machine, in which the frames are pre-deburred, through to the shotblasting machine and subsequent placing into a wire-mesh cage.

Every 40 seconds the robot removes a component from the casting plant. The shotblasting machine is co-ordinated exactly with this indexing cycle. The robot grips the ladder frame and places it onto a specially located mandrel in the centre of the rotary table. The locating device tips grip exactly in the component recesses. The position of the mandrel and the size of the door opening had to exactly match the shape of the grippers and their function. These factors constitute important interfaces for interaction between shotblasting machine and robot control. The robot requires 10 seconds for each loading and unloading operation. The shotblasting process and the opening and closing of the door last 20 seconds. The stopping point of the rotary table is accurate to within a  millimetre so that after the shotblasting process the component stops exactly in the position required for removal by the robot.

High optimisation potential

A further example proving that almost every shotblasting system can be automated successfully with robot support is demonstrated by the use of a satellite rotary table system, RDT 150/S-5 fitted with two heavy-duty shotblasting impellers which Rösler Surface Technology has developed and built for a car manufacturer. High-alloy special-steel toothed gearbox components (toothed components, gears) are descaled and surface-compressed (shotpeened) on the outside in this compact, space-saving machine. Shotblasting must be very specific and intensive in order to penetrate down into the root of the tooth. The machine is incorporated into a production line and is loaded and unloaded by a robot. Automatic feed and removal units enable linking with other production machines. 
This satellite rotary table system manifests extraordinarily high optimisation potential for the production process with regard to effectiveness and throughput by reason of its special technical design. The continuous loading and unloading carried out from outside during the continuous process is a significant detail, which produces short cycle times. The rotary table is divided into five segments of equal size, which are separated from one another by partitions. The outside area is sealed safely from the shotblasting area by these special partitions. In each segment there is a satellite with a component locating mandrel, onto which the robot places the toothed components.  More and more gears are placed on top of each other so that the inside areas, which must not be shotblasted, are masked. During the shotblasting process the components pass two shotblasting stations, where they are set in counter-rotation. Different blasting angles and the one hundred percent uniformity of the shotblasting effect required for shotpeening can be achieved by changes in the direction of rotation of the shotblasting impellers.
 
Quality can be planned

There are almost no limitations in the use of robots in conjunction with shotblasting systems. The engineering and system control requirements however have increased. At the start of planning a system, Rösler have movement analyses with animated 3D simulations for layout optimisation. The individual work stages are assessed, examined for snags and evaluated for cycle times. Furthermore, processing times and costs for manual and fully automatic processing are compared in a comprehensive process analysis in order to clarify efficiency and the cost-benefit aspect. Finally, the Rösler Test Centre is used in order to establish and test the shotblasting process concept. All systems undergo an extensive test programme for quality assurance. The package is rounded off with professional commissioning of the system by experienced engineers.




For Information:
Rösler Oberflächentechnik GmbH
Tel.: +49.9533.924-802
Fax: +49.9533.924-300
www.rosler.com