How machine safety boosts productivity

There is a real relationship between equipment safety and machinery output. Occupational health and safety codes and standards mandate that machinery that has exposed moving parts or in-running nip hazards — or anything that may endanger the worker – must have a protective device or guard to prevent access to the danger point.

If people place a box around a machine, although that makes it absolutely safe, it is totally user-unfriendly. Since that is a very impractical solution and it has a big impact on productivity, it would soon be removed. But then the exposure to dangerous moving parts remains.

As you know, there are consequences to non-compliance, and these can include accidents, human tragedies, fines, excessive costs and productivity losses.

However, there is a way of turning liabilities into productivity. It begins with benchmarking and overall equipment effectiveness (OEE). Let me explain how it works.

Overall Equipment Effectiveness (OEE) is a way to monitor and improve the efficiency of your machine using machine guarding arrangements. First of all, we need to measure the parameters of the machine, such as Availability, Performance and Quality.

Overall Equipment Effectiveness (OEE) in numeric terms looks like this:

Overall Equipment Effectiveness = Availability x Performance x Quality.

Availability is defined as Run Time/Total Time — the percentage of the actual amount of production time the machine is running compared to the production time the machine is available, or it can be calculated as the total run time of the machine after subtracting all unplanned downtime.

Performance is defined as Total Count/Target Count — the percentage of total parts produced on the machine compared to the production rate of machine, or how well a machine is running when it is running.

Quality is defined as Good Count/Total Count — the percentage of good parts out of the total parts produced on the machine, or how many good parts versus bad parts a machine has produced.

In a perfect world, reaching a goal of 100% OEE would require 100% availability, 100% performance and 100% quality. Since it is not a perfect world, there are losses in each of these criteria. What are they?

Downtime is a loss to availability. Here are some examples: Unplanned maintenance, machine changeovers, equipment failure, tooling damage, process warm-up and material shortage.

Speed losses relate to a loss to performance. Some examples include product flow stoppage, tooling wear, components jams, equipment age and material misfeeds.

Quality loss is a loss related to quality. Some examples are damage, rejects, reworks, tolerance adjustments and the warm-up process.

Curbing losses

The major goal behind an Overall Equipment Effectiveness program is to minimize or reduce the causes of inefficiency in the manufacturing environment. For example, by reducing machine adjustments/set-up and machine breakdowns through enhanced maintenance programs, we can reduce the downtime loss.

By reducing the number of machine stops and machine-reduced speeds through enhanced machine guarding design, as well as operator training, we can reduce the speed loss.

By reducing the number of rejects occurring during initial startup and full production runs through easy and safe access to the adjustment mechanisms of the machine, we can reduce the quality loss.

If you can improve your OEE numbers, you will improve your machine’s productivity.

Table 1 shows an example of real machine production data to help you understand the concept of OEE and the calculation of this data. This example shows the calculation of OEE and the OEE metrics of Availability, Performance and Quality.

Scrutinizing Availability, Performance and Quality, and reducing machine losses through locking in place the most effective methods of running the machine, by using machine guarding arrangements, will enhance Overall Equipment Effectiveness. Safety and productivity are truly two sides of the same coin.

Simon Fridlyand, P.Eng., of SAFE Engineering Inc., specializes in industrial health and safety concerns and PSR compliance. For more information, visit www.safeengineering.ca.