Modern controllers driving continuous plant improvement

Many companies are getting far from their best value out of their controllers. They largely limit their use in the main to that of the pure engineering function and miss out totally on their additional use as a key component in the drive for process improvements in the plant. As such they are sub-optimising the value that they are receiving from their investment and making it harder for their continuous improvement teams to show significant progress.

Many modern plants have PLCs or other controllers that are able to generate performance data for the equipment which could be used for problem solving and process improvement purposes.

A batch processing organisation that is driving continuous improvement has four fundamental best practices which underpin its progress:

Effective teamwork
This is the best practice of getting the organisation to work together in striving to achieve the teams' short-term objectives and the organisation's strategic goals.

Visual management
This is the best practice of providing the required performance measurement data to those who require it, in the most appropriate format and at the right time, in order for them to monitor and then drive the improvements into the process. This is the key area where efficient utilisation of controllers can have a material impact.

Best practice development
This is the best practice of identifying the optimum methodology for conducting key operational tasks in an inclusive way, documenting them and ensuring that the methodology is the way that task is conducted, by all shifts, every time. Examples of key operational tasks are machine set-ups and shift changeovers.

Structured improvement
This is the best practice of using visual management to identify improvement opportunities and other opportunities identified directly by the teams, combined with the use of formal problem solving techniques to progress these opportunities and hence improve throughputs and reduce losses.

Manual performance measurement issues
It is interesting how in this day and age many manufacturing companies have state-of-the-art controllers managing critical parts of their manufacturing plant, yet they often resort to requiring operators to fill in manual log sheets to record downtime and other process losses.

This data is then manually entered into a spreadsheet or similar and then circulated to line management and process improvement teams for action.

It has been found that for various reasons manual systems frequently record inaccurate data and the cycle time until that information is available to the factory floor teams, in a useful format for driving improvement, is just too long.

If this information is available 24 hours after the event then it would be considered reasonably efficient, as some manual systems can take up to a week. This means if an adverse trend starts at 10.00 am on day one it may not be noticed until the start of day two, 24 hours later. If this data was available in real-time then it would have been possible to bring the process back into control by, for example 11.00 am on day one, resulting in only 1 hour of additional waste, compared to 25 hours of waste with one of the more efficient manual systems.

Controller supplied software issues
Most modern controllers also have software that is able to produce reports, so why is it that a lot of manufacturers do not make use of them. The main reasons would appear to be two-fold.

Firstly, the software, which is often imported from Europe or the US, is frequently very expensive, with recurring annual costs. Secondly, it also tends to be written by people who may be very competent at designing controllers but who may not necessarily understand what information is required by a company on the leading edge of continuous improvement.

Best practice for performance measurement
Many of the leading companies operating in capital intensive environments are using a metric called overall equipment effectiveness or OEE.

OEE has one component that measures downtime losses, another that measures speed losses and another that measures yield or quality losses. These are then combined to calculate the OEE.

Where Availability Rate = AR = Total Planned Production Time "“ Total Downtime

Total Planned Production Time and Speed Rate = SR = Total Product Output

Potential Product Output at Rated Speed and Yield Rate = YR= Total Good Product Output

These are then multiplied to give OEE,

So OEE = AR x SR x YR

It is frequently reported as a percentage, where 0 <= OEE <= 100%

One of the strengths of this metric is that it provides a snapshot of the machine's performance against the theoretical maximum for that period, so an OEE of 50 per cent would indicate that the machine only produced one half of what it theoretically could have during that period. The three component parts then indicate which of the big losses need to be investigated further. The operator or continuous improvement team member should then be able to drill down to the root cause or causes of the problem and take appropriate action either to bring the process back into control or achieve even higher standards of performance.

When organisations start to measure OEE they frequently discover that the initial values are in the order of 25"“35 per cent, giving opportunities for significant improvement in output and reduced costs without further capital expenditure.

In an example of the real-time feedback one would want to drill down and look for causes of the downtime and the speed losses as they are both significant.

Are we making the most of our controllers?
If there are controllers on equipment, in particular bottleneck equipment, and operators are recording data manually where this data is available electronically, then it is a waste for the operators and sub-optimising the effectiveness of the investment in the controllers. If the organisation is getting reports from the controllers but they are either not used or they are in a format that is not useful to drive improvement, then it is similarly sub-optimising the investment.

If the software that was supplied with the controllers is inadequate for the needs of the organisation in driving continuous improvement then it is recommended that the organisation investigate alternatives that can interface with those controllers via OPC or other methods to ensure that it is gaining the full benefit of its investment.

If the information available from controllers is not available for use or not used, as discussed above, then the organisation is probably not making full use of its current assets in the pursuit of its improvement goals. This is one area where a large number of companies can benefit significantly from further investigation as the potential financial ramifications can be significant in terms of improved efficiencies, outputs and reduced losses.

Proventus Consulting Pty Ltd
49 Hancock Drive, Cherrybrook 2126

"Many modern plants have PLCs or other controllers that are able to generate performance data for the equipment which could be used for problem solving and process improvement purposes."

"If there are controllers on equipment, in particular bottleneck equipment, and operators are recording data manually where this data is available electronically, then it is a waste for the operators and sub-optimising the effectiveness of the investment in the controllers."