Case Studies Of Industrial Robots

Robots in action can be found everywhere. Robot Manufacturers give examples of robot applications in different industries.

Dürr, Germany - IFR-Partner

State-of-the-Art Control Engineering - Simpler, Faster and more Effective

The computer technology changed our life at a fast speed. Particularly the production technology is not imaginable anymore without its use. In this connection, science speaks of the third industrial revolution. Also in painting technology, formerly a rather manual production and empirically dominated manufacturing area, the computer entered massively and made the processes more economical and more environmentally friendly. Latest developments in the field of computer and control systems show that some potential is still available here with regard to effectiveness increase. That does not have to mean that the complexity must increase at the same time. Quite the contrary.

Painting installations, in particular robot stations, need a high amount of control equipment for their function. This is usually subdivided into a station controller, a safety controller, the individual robot controllers and where appropriate the controllers of the application equipment. The station controller on PLC basis (PLC: programmable logic control) coordinates all processes in the station and communicates with the outside world. It receives the information about the motor vehicle model to be painted and the colour and instructs the painting robots correspondingly. It evaluates the signals of the periphery, such as the conveying and booth equipment for example, as well as the fire protection and converts it into corresponding actions. In the safety PLC, as the name already says, all safety-relevant information merges. Basically, this is the personnel safety, realized by light curtains at the inlet and outlet of the station as well as by door contacts at the painting booth and by emergency off switches. If one of these signals is released, the station must be brought into a safe state immediately. Ideally, it should continue where the stop occurred after elimination of the cause. The robot controller is mainly responsible for the movement of the robot and the setting of triggers. An application part makes the parameterizing of the application technique possible. In specific cases, a separate control is used for the application, for example during the seam sealing and for the underbody sealer application. Here, standard robots which do not have any functionality for the process in the robot controller are often used. Below the line, a lot of control hardware stands around a robot station today. Two examples are supposed to clarify this: A station for the inside painting with four robots and six handling devices for the opening and closing of hoods and doors requires one PLC and ten robot controllers. A station for seam sealing with four robots also requires one PLC as well as four robot controllers and four application controllers. A similar expenditure. And not to forget: In both cases, a so-called vision system is needed for the determination of the car body position. And this does not manage without separate hardware, either.

 

Doesn't it suggest itself to simplify the whole system in the sense of complexity and cost reduction? The contemporary computer technology makes this possible. The new control system EcoRPC (Robot and Process Control) for Dürr robots is based on an industrial PC and is multikinematics/multiprocess-capable. What does this mean? With this control, it is possible to operate up to four robots or four different processes simultaneously. If you look at the represented robot station for the inside application of engine compartment and trunk with two painting and two handling robots, you only need another two instead of four robot controllers if the new technology is used. That is a halving of the required hardware.

 A painting station for the interior paint application
A painting station for the interior paint application of engine compartment and trunk. The hood openers are arranged suspended on an elevated rail. The advantage of this solution is that the station is by far shorter with a higher flexibility compared to conventional layouts. Robot and hood opener can "overtake" each other.



The secret of the increased capability lies in the cycle time of the processor that is by far shorter. Next to the multikinematics/multiprocess capability, this feature entails even further important advantages. The process scanning times are considerably shorter now. This achieves a higher safety of the application system. If for example an increase of pressure is detected in the paint line, the dosing pump can be stopped before the paint line will burst and an exchange, combined with a time-consuming cleaning, will become necessary. The installation components can be synchronized with each other better. This affects in particular processes with a very high application speed or processes that require a very high accuracy with regard to movement and material dosing. As examples, sealing processes are mentioned. Here, the application speeds are in the field of 1000 mm/s with simultaneously high demands on the accuracy of the application. In the first illustrated example, the seam sealing in the field of the rear light, the specifications for seam width and height must be met exactly, since otherwise the rear light would not fit during the assembly. The second example shows the double-flanged seam sealing of doors in the closed state. In this procedure, a special nozzle is inserted in the door fold and seals the double-flanged seam from the inside of the door. The demands on the visual quality are exceptionally high here. Since the seam runs at a very small distance to the door rim, even minimum deviations in the situation and shape of the seam are noticeable for the eye. These two examples show that such processes would be hardly controllable without an optimum alignment between process and robot movement. And yet another advantage: The EcoRPC yields a higher productivity. Since the car body is now tracked in the robot controller and not in the PLC anymore like up to now, programs and application data can be loaded providently. Thus the time needed for the loading up to now directly before the application is omitted.

 
Simulation and application result of the seam sealing in the rear lamp field. Here, an exact positioning and geometry of the seam is required to avoid manual smoothing.


Double-flanged seam sealing with closed doors requires an exact synchronization of robot movement and process


The new control technology has already passed its fire test in several projects. In the seam sealing sector, robot installations equipped with the EcoRPC are in operation at various manufacturers and control robots and application on one platform each there. The first project where the robot application of a new paintshop was equipped with the EcoRPC in all fields was recently finished successfully. In this factory of a known Italian car manufacturer, a vehicle is built which already enjoyed great popularity in its original version in the sixties. The robot and application technique for PVC and paint material was supplied by Dürr. In total, two robots for the underbody sealer application and 20 painting robots for the primer, base coat and clear coat application, outside and inside, are in use there. In the inside painting, which is carried out in the stop-and-go mode, the robots are besides supported by ten handling devices. By the way: the looming success of this vehicle also made a capacity increase of the painting installation already existing for quite some time necessary. There, a new primer station with six painting robots and additional robots for the base coat and clear coat application was supplied by Dürr.

A modern, strong robot controller would be unconceivable without a convenient programming system. With the EcoScreen 3D-OnSite system, Dürr offers an indispensable aid for programming, parameterizing and visualizing of the robot application in 3D display. This can happen directly at the installation, therefore "onsite", and of course parallel to the current production, or "offsite" at an office workplace. By means of an Ethernet connection, the communication with the robot controller for the upload and download of the data is guaranteed. This way, the functionality of the system will be, however, not exhausted for a long time yet. Functions are available that are only known from offline programming systems: a robot simulation in accordance with the RRS standard (RRS: realistic robot simulation), collision monitoring, multikinematics simulation of up to 16 robots, video recording, to only mention the most important ones. In addition, the programming system offers an automatic generation of painting paths as well as extensive data management possibilities with the aid of a database manager. And last but not least, as an important aid for the maintenance, a diagnosis module is available that can record and file all signals of one or several robot controllers simultaneously at a very high sampling rate. For the graphic analysis of the data, the diagnosis module contains extensive tools. A long-term filing of the data in a SQL database is also possible.



T
he EcoScreen 3D OnSite vision system offers an extensive functionality for the optimum programming and parameterization of robot installations for the painting and sealing process




The contemporary computer performance makes it increasingly possible to simulate processes. The driving force here is the circumstance that product cycles are getting increasingly shorter and the building of preproduction models is increasingly omitted for temporal, but also for financial reasons. A robot programming by means of data models is possible with so-called offline programming systems for quite some time. This functionality could meanwhile, as mentioned above, also be integrated into the programming system of the robot installation. Today, process simulations answer important questions such as for example: Is the flow in an immersion basin optimal, so that "fresh" process medium is available at each place of the vehicle body? Is the heating of the body in a dryer regular and is the temperature needed for the networking of the paint material reached everywhere? Is the flow of a painting booth laminary or are turbulences created which might lead to a soiling of the painted vehicle and the system? In the planning of paintshops, a flow of materials simulation cannot be refused on anymore. It confirms important planning premises (such) as capacity, machining time, design of car body stacks. These possibilities described here can to some extent today, at the latest in the near future, however, be linked with each other to a 3D model. By means of suitable display programs in connection with a "Power Wall" the customer can enter his paintshop. And this long before the laying of the foundation stone. The time has come: The Digital Factory becomes reality.



Process simulation of the warming of a driver's cab in the paint dryer


Finally, a marginal note for historically interested people: The first industrial revolution was heralded with the introduction of the steam engine in 1776 by James Watt. The second industrial revolution gained momentum with the decentralization of the machine drives, for which the invention of the alternating current motor by Werner von Siemens in 1879 was authoritative. The third industrial revolution mentioned in the introduction were the introduction of the microprocessor technique and the decentralization of the "intelligence" combined with that. This microprocessor was introduced in 1971 by the Intel Company.


Author
Dr.-Ing. Pavel Svejda
Dürr Systems
Rosenstrasse 39
74321 Bietigheim-Bissingen
Germany
Phone:  + 49 (0)7142 78 2290
Fax:      + 49 (0)7142 78 2107
E-mail: pavel.svejda@durr.com
Internet: www.durr.com