Valk Welding: 2002

The Vermolen Groep produces among others a large number of traffic signs. In 2000, this manufacturer took over the production facility of Nederland-Haarlem in Haarlem, with the intention to produce all kinds of small and medium sized traffic signs as half-product for the complete group. However, the required production increase could not be realised with the existing production process. In close collaboration with robot integrator Valk Welding and other parties, the Vermolen Groep elaborated a new production cell that was not only flexible and user-friendly, but could also ensure faultless and unmanned production.

Although the production of traffic signs is not actually high-tech work within metal working, it is not an easy task to automate its production logistic. How do you integrate separate metal working, how do you capture the working forces in among others the robots, how do you get accurate and constant positioning and the most important, how do you maintain the flexibility to produce various products simultaneously? These were the questions, the Vermolen Groep had to deal with.

Unreliable
The production facility of Nederland-Haarlem, that was taken over by The Vermolen Groep mid 2000, already had a reasonable degree of automation with the use of one robot. The robot picked up a plate and brought it under an angle stamp, a rolling angle bender and a stomp to close the angles. Then, the product was put on a hook for the pre-treatment process. Concept and robot were designed for the serial size of the former owner of the traffic sign plant. With the take-over, the Vermolen Groep had far more ambitious plans with this Haarlem production facility,  that was mainly intended for the production of aluminium half products for all establishments of the Vermolen Groep. Therefore, not only quality requirements had to be increased, but also the welding duty of the existing robot cell. Manager Production & Logistic Ir. Bram Bruinsma: "When we started increasing the cell output, the problems with reliability and safety became apparent, and it became necessary to revise the existing automation."

Mass inertia
Bram Bruinsma himself monitored the development of a new robotised production cell and corresponding logistic and system integration: the construction of the peripheral equipment controls was done by an engineering firm and for the new robot he embarked with Valk Welding. This welding specialist from Alblasserdam has come so far with the integration of robots in the welding process, that as robot integrator he can also take care of production logistic in other sectors of metal working. That is why a Nachi handling robot was integrated in the production of the Vermolen Groep. This proved to be suitable to position the relatively soft product, with an extreme large mass inertia, exactly under the existing machining stations. The speed of the robot motion adjusts to the mass inertia of the product. Unique is that the product is being positioned in the rolling angle bender without using stops. The rolling angle bender (the radius with which traffic signs are being bent is very large) is a machine constructed specifically for this process. The required accuracy is reached by the high positioning accuracy of robot,  for which the rigidity of the applied suction cups plays an important roll.

Flexible
A touch screen is used to indicate to the control unit how many signs of what size and form must be made. In total, there are about 90 different forms and sizes, that makes 90 x 90 = 8100 different products. All sizes can be produced without any programming action. Hence, the production cell can be operated by untrained employees. Furthermore, the production can be interrupted for another form and size, after which the current production continues.

The complete production cell is enclosed in a fence, that cannot be opened without completely removing the hydraulic and pneumatic pressure. During a demonstration, the production of rectangular signs was stopped, and a triangular plate was put on the stack. Size and form were entered in the control, whereby changing the tool setting of the rolling angle bender automatically, and the product could be made. After that, the current production of rectangular signs continued. Bram Bruinsma: "It is exactly this possibility of 'breaking in' and automatic changing that makes the cell very flexible."

50% production increase
As with many robotised production systems, the production speed is not higher, but the increased production capacity is due to the continuous use. Because the cell continues after working hours, the continuity strongly increases and productivity was boosted with 50%. The complete production line is being used unmanned for longer periods and in the end it will run 24 hours a day. The robot reliability is no longer a limitation. Bram Bruinsma: "No, the bottleneck is the capacity of the material feeding and discharging, that has to be increased. In the meantime we also produce traffic signs as half-product for third parties, thus further increasing the total capacity. Due to the large mass inertia of the products, it is not possible for example to increase the fast speed of the robot. That is why we are thinking of a second robot within the production cell."

Special folding robot
The experienced gained at Vermolen with the use of a Nachi robot that will do much more than just 'handling', is according to Valk Welding the start of a broader application in plate machining. For example stop-free positioning of the folding press. Valk Welding will soon introduce a special folding robot that can be linked to existing and new angle benders. This folding robot is characteristic in that it requires minimum programming and follows the products during machining, resulting in minimum cycle times and maximum accuracy.