Small batches produced by welding robots
Valk Welding has completed a unique project for the Czech supplier VOP, in which 21 types of fuel tanks for forklift trucks are welded from a warehouse system 24/7, virtually unmanned, on Panasonic welding robots. The project is an example of extensive automation, Industry 4.0 style with a large degree of flexibility. VOP has raised its capacity by 60% and shortened its turnaround times by 40% compared to the existing IGM welding robot. VOP is aiming to meet the production target of 35,000 fuel tanks a year with this system.
As well as manufacturing vehicles for the Ministry of Defence, VOP supplies articles such as fuel tanks for forklift trucks and agricultural vehicles. When the company became a certified supply of Caterpillar last year, the production target of 22,000 items was sharply raised to 35,000 a year. For that purpose, some items that were still being manually welded and some that were being welded on an existing IGM robot would from that point onwards have to be welded on a completely new production system. Engineer Mr. Horník: "We were therefore looking for a solution that enabled us to do this production-technically in the same area."
Ample robot experience
VOP already had over ten years' experience with robots when it took its first Valk Welding robot systems into use in 2006, and since then it has had Valk Welding convert two existing IGM welding robot systems with Panasonic welding robots. Based on that relationship, Valk Welding was also asked to develop a new welding production system. The project engineers of Valk Welding CZ set up the project entirely under their own responsibility and also worked with local parties in the tendering phase. Only the welding robot cells were supplied from Valk Welding in the Netherlands.
Large degree of flexibility
Despite the substantial production volume a large degree of flexibility was one of the most important items on VOP's wish list. A total of 21 different types had to be welded on call and per batch, also with the ability to process single items. The solution was found in using a central storage buffer for the pre-assembled tanks. Each tank can be transported with an unmanned conveyor system from the warehouse to the welding robot, welded and then delivered to an output station by the same conveyor.
In order to be able prepare sufficient tanks in 2 day shifts for welding production during the night, the cell is equipped with seven tacking stations where the tanks are assembled and clamped onto a pallet. The conveyor stores each pallet in the warehouse, which provides 2 floors of space for a total of 72 pallets. The advantages of this setup are that the pallets can be quickly changed, each pallet is immediately available and there are no longer any loose tanks in the workplace.
Two identical robot cells
To meet the required welding capacity two identical welding robot cells have been provided, each of which is equipped with a drop-centre manipulator. This makes it possible to position the tanks in such a way that the Panasonic TA 1900 welding robots can reach all points at the best possible welding position. The average cycle time was thus reduced to 12 minutes. Up until that time the manual welding had taken 51 minutes, and the welding on the IGM robot almost 18 minutes. These time gains made it possible to achieve the higher annual capacity. The welding programmes for most of the tanks had already been prepared by Valk Welding's software programmers.
The tanks were assembled and loaded in two shifts, and welded during the night time. This is done entirely unmanned. The welding robots therefore no longer have to wait for an operator.
40% time gain
The entire system was first tested for 3 months and went into full production last summer. The use of the latest Panasonic WG3 arc welding technology ultimately reduced the cycle time even more than expected. A cycle time of 11 minutes means that VOP has achieved a time gain of 40% compared to the former IGM welding robot. Engineer Mr.Šturala: "Because of their speed and quality the use of Panasonic welding robots is at anyhow a neccesisty for achieving this production volume.
Flexible response to market demand
VOP regards having a production system such as this as a absolute necessity, not only to achieve the required production volume but also to be able to respond flexibly and quickly to market demand. Mr. Horník:”From our warehouse we can prepare a large number of tanks and weld them on call, which enables us to supply our customers quickly and just-in-time.” With this flexible welding production cell VOP is well ahead of its time and VOP will keep its production facility in the Czech Republic. www.vop.czRequest for information