Work unsafe for Humans

Robots carry out work in areas that would be unsafe for humans. Robots work in harzardous conditions where heat, pollution, radiation and other circumstances would have a negative impact on the health of humans. Please find examples below:

Reis, Germany - IFR-Partner

Laser welding - too Dangerous for Humans

January 2012

A Medium-sized manufacturer of hygienic furniture relies on laser welding to produce high quality products. Laser Welding cannot be done manually due to safety reasons. Thus, the use of a robot and a special welding cabin is necessary to protect humans. 

Friedrich Sailer GmbH develops and produces innovative and in many regards unique stainless steel furniture for use in the hygienic and clean-room area. For considerable time saving in welding and rework, the medium-sized company invested in an automated laser welding gantry from Reis Robotics in the year 2010. Despite small production piece numbers down to a lot size of 1, the gantry has from the beginning been more productive than all manual processes before.

Usually robot solutions in most cases are used if large numbers of the same products are to be treated or processed. This is different with Friedrich Sailer GmbH. "For years we have been producing mainly hygienic stainless steel furniture for the food industry, pharmaceutical manufacturers, and also for special requirements of the clean-room technology, such as microchip production", explains Christoph Mützel, general manager and grandson of the founder of the enterprise Friedrich Sailer who set up the company 85 years ago. "We have been using stainless steel as a material for many years already, because it is best suited for these applications and it is very robust. The concept of an automation solution with future-safe laser welding technology arose from the awareness that manual welding and the necessary time-consuming rework restricted the production capacity too much. With laser technology the heat input into the workpieces is minimized. So less distortion and hence, higher quality is generated from the very beginning. Besides this, most seams can be executed in such a way that they either require no or minimal rework. And the first test pieces already showed how successful this can be."

The investment in the laser welding gantry was the biggest system investment that Friedrich Sailer GmbH had ever afforded. Big, however, not only means the financial scope, but also the dimensions. The RLP16-FT laser welding gantry with a 3 kW fiber laser from IPG covers a space of 5000 x 2500 x 1000 mm, thus being able to process even very large parts. The beam guidance integrated in the robot arm improves the mobility of the robot hand to ensure optimum welding even in restricted positions. Since most of the workpieces are furniture that is completely welded to avoid joints and gaps, a lot of clearance was required. The same is also completed by an exchange sliding table system with lifting station (Demmeler) in the welding cell. Thus the complete work stroke of the robot can be used even for upright furniture like work tables with a height of 900 mm. For special applications there is also an RDK05 rotary/tilting part positioner available in the welding cell. If both fixtures are used, components with a length of up to 6000 mm can be clamped.

From the point of view of Christoph Mützel, however, it is not only the clearance that justifies the use of a gantry where no robot and the corresponding peripheral equipment like cable and hose packs are "in the way". The large work envelope and the much higher repeatability compared to a sliding unit where an articulated arm robot is moved on the floor were also of particular importance. "Despite movable tables on rails we achieve a repeatability of 2 - 5/100 mm. Therefore it is possible to preset the workpieces outside of the cabin or to perform manual prework then move them into the welding cabin for completion ", says Christoph Mützel.

Batch number of 1 and automation - a contradiction?

As sophisticated hygienic furniture has its price, it is usually custom-made to have as few gaps and joints at the application site as possible, thus avoiding a hygiene risk. Probably the gentle reader now wonders how a robot welding system pays off with small piece numbers and mostly without series production, since the robot first must be programmed for each workpiece. (Illus. 1) The general manager explains with an example how reasonable the solution is also from the commercial point of view. "Even with the intuitive teach-in procedure from Reis Robotics it can be that programming of a large cabinet takes approximately eight hours. This sounds a lot, especially as the welding process itself just takes approximately 19 minutes (illus. 2). However, an experienced TIG welder would be occupied for about 40 hours for the required 50 m seam. Rework of the seams to achieve a surface finish suitable for hygiene applications and an appealing visual appearance would take another 40 hours. Thus, the system has already proven its efficiency with the first workpiece." In a next step extension of the programming possibilities is planned. The use of the Reis programming system PROVIS allows an accessibility study and preparation of component programs offline on the computer. The busy time of the system can therefore be further reduced.

Illus. 1: The so-called teaching is done on the workpiece using the intuitive software from Reis

Illus. 2: After the teach-in procedure laser welding is performed automatically. By avoiding distortion rework is nearly superfluous

The advantages of automated laser welding can soon be recognized on the workpieces. Sailer for instance produces cabinets that are welded all around - and that even applies for inserted rack shelves - so that you get the impression it is solid material. The laser weld seams have a medium surface finish of < 0,8 µm which already satisfies highest hygiene requirements without rework.

To achieve best results, however, depending on material and geometry, corresponding trials are necessary at the weld position with the corresponding time required. To minimize the expenditure of time for this, Sailer GmbH developed a parameter data base - the so-called "Sailer FocusBase" - specially for their own requirements, where all information is filed and can be recalled any time.

Impressive quality

A picture paints a thousand words. As Sailer is also working as a subcontract producer for other companies, a sample case (illus. 3) was established containing a few small workpieces and weld samples. The quality that can be seen and sensed convinced every job orderer so far. Not only extraordinary fillet and corner welds can be marveled, but also examples of the quality of the weld seams. Two butt welded sheets were folded afterwards by 90 degree - in the seam and square to it. Then the sales team can convince each skeptic that something with a perfect look can also be perfectly solid. Speaking of beauty: With their highly developed hygienic furniture Sailer does not only impress customers. For the high-quality and likewise beautiful design the enterprise won the Red Dot Design Award and was nominated for the German Design Award 2011. (Illus. 4)

Illus. 3: The different patterns also convince job orderers always of the unique quality of the weld seams

Illus. 4: This is what a perfect hygiene sink looks like. Result: The Red Dot Design Award is due not least to the perfect weld finish

"Beauty, however, is only the part that can be seen with the eyes", adds Christoph Mützel. "Much more important for our customers is the high know-how we have worked out regarding the huge number of standards for hygiene. This is another unique selling point for us, because we take care of the regulations already during development and production, therefore also for fully welded furniture for clean-rooms. Some competitors besides stainless steel also use other materials and designs at some positions which cannot compete with a closed body in the long run.

Two partners - one solution

Sailer regards Reis Robotics not only as supplier, but as partner in development of an extraordinary solution. When the first inquiries to automation specialists were made in Mid 2009, the potential order for only one robot was not big enough for some of them. Christoph Mützel comments: "From the very beginning, Reis Robotics took us very seriously and we could make initial trials in advance already in the Reis test lab in Obernburg am Main. Another reason was the cumulative competence in Reis company, because we were looking for a general contractor for robot, gantry, and laser system. During the entire project which only took about six months from order placement up to commissioning, Reis acted very flexibly and customer-oriented."

Besides the gantry which required a close cooperation also with the supplier Demmeler for the sliding table unit, Reis also supplied the safety cell. The particularity is in the laser-safe, active safety cabin equipped with the patented Laser-Spy sensors from Reis Lasertec. The Laser-Spys monitor the hollow space between the walls of the double-walled aluminum cabin elements. (Illus. 5) As soon as laser irradiation enters into this hollow space with a "full penetration", the sensor elements of a Laser-Spy sensor will react and activate the safety circuit of the laser system within a few milliseconds. This equipment brings maximum safety for all the staff in the neighborhood of the welding cell where always other individually programmed cycles take place. Another individual particular feature - besides the large work envelope of the gantry - are the two doors of the cell. One of them was designed for very wide workpieces up to 3200 mm, the other one for very high workpieces to a height of 2600 mm.

Result

Not only Sailer's customers are enthusiastic about the technology. Also the staff members are enthused. The management of the company had four of the staff members who had been working as welders before trained at Reis. None of the approximately 40 staff members was dismissed. "The own initiative and creativity of our staff members gave rise to positive solutions within a very short time which we would never have expected. Today our experts are welding complex components successfully in the gantry that were not even destined for this yet", resumes Christoph Mützel. "Though the initial investment was high for a medium-sized company, the system is a full success very soon paying off even with very small piece numbers and individual items." Besides this, he is glad to be a pioneer of his industry with this future-oriented technology and the related quality.

The solution from Reis Robotics once more emphasizes that systems automation can be useful also without high volume production, provided that the programming effort for a task is proportionate to the desired result. This, on the other hand, requires an intuitive programming and teaching environment.

Components of the solution

  •  Laser welding gantry RLP16-FT with fiber laser IPG 3kW
  • Work envelope 5.000 mm x 2.500 mm x 1.000 mm
  • Modular welding optics (MWO) from Reis Lasertec with
  • digital distance measurement
  • coaxial and lateral inert gas nozzle
  • programming via camera and hair cross
  • lighting ring for camera
  • Components supply using processing tables on rails (Demmeler) with vertical stroke within a robot work envelope
  • Component positioner RDK05
  • laser-safe protection cabin with active monitoring of the walls by Laser-Spys from Reis Lasertec
  • laser prepared for upgrade to 4 kW

 

Author: Stephan H. Gursky