Like all areas of automotive manufacturing, powertrain assembly plants must respond to the demands of multi-model production, rapidly changing technologies and fluctuating capacity demands.
Indeed, the more quickly a powertrain plant can rectify bottlenecks on the line – or changeover from one model to the next – the more profitable it will be.
In any assembly operation, the key to optimal performance depends on the efficient distribution of automated and manual workstation tasks. Ideally, each task flows seamlessly to the next – with no operators idle or overtaxed at any point in the process.
But on powertrain lines that can extend a quarter mile and include 150-250 discrete operations, achieving an optimal workload balance can be a challenge.
Identifying the Bottleneck
A variety of factors can cause even a well-designed line to become imbalanced. For example, changing line speed or customer demands on daily output – or switching model years – can impact workstations in disproportionate ways.
Of course, the first step to rectifying load imbalance is identifying the bottleneck. And for decades, time studies have been the tried and true method of choice.
During my years in powertrain plants, I was involved in many time studies that relied on observation and “stopwatch” methods of data collection. Needless to say, this approach can intimidate workers on the line – and impact work habits while information is gathered.
The result? Data collected may not reflect typical operation.
Today, job monitoring software can work behind the scenes to provide real-time task status and time – as well as overall station cycle time. With this data in hand, plant process managers can analyze and reassign workstation tasks in a more impactful way.
The Problem with Zone Control
Next comes the work of rebalancing the line to conform to the more efficient process. In plants with conventional zone control architecture, line rebalancing can be an arduous and costly undertaking.
In typical assembly, each zone has just one PLC that controls its section of the conveyor and all associated manual workstations. Each automated workstation has its own PLC, running unique logic for its functions and integrated with the zone controller.
To reassign or change a manual task, a controls engineer must obtain and analyze the current PLC program for the zone – and modify it. This activity is followed by hardware retooling, code debugging, testing and validation.
The total time to reprogram and balance a line can extend to two weeks – with much of the work occurring after hours or on weekends when overtime rates apply.
More Distributed Control + Configuration System = More Flexibility
A more distributed approach to assembly line control is the first step to streamlining this process. In a highly distributed architecture, each manual workstation has its own PLC – independent of the conveyor controller(s). Each automated workstation also has its own PLC running independent logic for all functions.
This more distributed architecture opens the door for configuration tools that enable manual workstation load rebalancing without reprogramming.
How Does it Work?
First, every manual and automated workstation must contain the same PLC core structure. The logic for all manual stations is exactly the same, with all available functions available in every manual workstation. Since the definitions for all possible tasks reside as a standard library in the master file, only the parameters change with each new task selected or reassigned.
No programming is required.
A configurable powertrain line can also include dedicated stations for specific operations, which can be either bypassed or used depending on the build sequence for the product run. The ability to select or deselect entire workstations minimizes the need for hardware retooling on the line.
Using a design and configuration tool, like the Rockwell Automation® Production Performance Builder (PPB), enables a powertrain line to be rebalanced in a fraction of the time. In fact, lines can often be reconfigured during scheduled work or lunch breaks.
For powertrain assembly plants, a configurable line translates to lower overall operational costs. And for powertrain equipment suppliers, a design and configuration tool helps enable design repeatability and appropriate system sizing from the outset.
Learn more about how to enable flexible powertrain production and assembly systems.