A new laser-hybrid system: super technology, but too fast for the process.

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How close curse and blessing of modern technology can lie together is show in this example. A state-of-the-art hybrid laser welding system improves quality and cycle time significantly but is simply too fast for the downstream processes.

The system replaces several old welding plants (submerged-arc welding plants and MAC manual welding) and delivers much higher quality as well as drastically reduced processing times.

However, the advantage of the faster process quickly turns into a problem in the production flow. That's because the downstream tack and welding processes for attaching components, referred to collectively below as "assembly", are quite simply overwhelmed even though they theoretically have the capacity to cope with the customer takt time. They become a bottleneck. Due to the over-fast laser hybrid unit, the process is driven by a push system. Intermediate inventory builds up. Because of the size and weight of the workpieces (approx. 10 m long, weighing 1 to 2 tons) and the limited space in the hall, this leads to a collapse in production.

Where exactly is the problem?

It should be perfectly simple: The entire process is timed according to the customer takt time. Because the corresponding assembly capacities are available, it should all work smoothly.

But

the work processes that go into the approx. 80 different workpieces have a spread of up to 25:1. Process and safety considerations mean that this imbalance cannot be compensated for with multiple personnel at the workplaces.

The solution comes in three steps:

1. Cluster formation (small, medium, large) reduces the spread to about 3:1. For each individual cluster, the capacity required in assembly is re-calculated.
2.This shows it's necessary to install several new assembly stations.
3. Intelligent control using an EXCEL-based KANBAN system.

The EXCEL-KANBAN system maps the entire shift schedule with rest breaks and days off, and takes account of the widely varying processing times in assembly. It also takes account of the varying times of the work processes to be done between the laser hybrid system and assembly. Unplanned extra work can be included as the situation requires.

The production programme implemented by the ERP provides the option of freely accessing an assembly station that becomes available. This free choice is only limited by technological framework conditions which are determined by an EXCEL algorithm when the order is received.

The pacemaker in each case is one of the assembly stations. It activates the KANBAN at the start of an assembly process, releasing pre-manufacturing in the laser hybrid for the subsequent workpiece.

Now the blessing and the curse are very close together. The extreme speed of the laser hybrid process determines that this machine can only start pre-production when an assembly workplace is about to become available.

The only drawback is that the expensive laser hybrid system sometimes has to wait and assembly equipment sometimes stands idle. However, it is not possible to compensate for over-dimensioned plant by increasing capacity utilisation.