With productivity being a hot topic at the moment it’s important to know how to calculate the productivity of your machinery and factory to enable you to implement and track productivity improvements.
This article covers two productivity calculations. The first is a Basic Productivity Calculation based on output and input, whereas the second is a more comprehensive productivity calculation based on Overall Equipment Effectiveness.
Basic Productivity Calculation
Basic productivity is calculated by comparing the amount of goods and services produced by the inputs that were used in production. This results in a basic productivity formula of;
Productivity = Output/Input
This basic productivity formula can be used to calculate the productivity of your complete production process, or of a particular process or machine within your production process.
Output must be expressed as a numerical value, and is the finished value of goods or services produced by a person, machine, or process.
Input must also be expressed as a numerical value and is the value of input that was used to produce the output, such as labour, materials, machine time.
The widget making machine produces 100 units a day, the finished value of each unit is £10.00. This means that the output of the machine is £1000.00 per day.
The total cost to make 1 widget is £2.50. This cost includes £1.50 of materials, £0.50 of labour and £0.50 of machine time. This means that the total input cost for 100 units is £250.00.
So the basic productivity calculation is £1000/£250 = 4. Therefore the productivity for this machine on this particular day is 4. Having established a productivity factor for this particular machine, it is then possible to use this same formula to compare the productivity of identical work stations, or to monitor the productivity of this particular machine over time.
For more detailed information on this basic productivity calculation, read this clear guide by Accel: http://www.accel-team.com/_pdf/atpdf_08_extract.pdf
OEE (Overall Equipment Effectiveness) Calculation
For a more comprehensive productivity calculation OEE should be used. OEE takes into account the speed at which the machine or factory runs, the quality of the finished products produced and the actual machine operating time versus the available operating time. OEE is best calculated per machine rather than across the whole factory as it is then easier to identify where improvements need to be made to help improve productivity. OEE is calculated as:
Performance x Availability x Quality
Performance is the speed at which the machine or work station runs expressed as a percentage of the speed it is designed to run.
Availability is the asset operating time expressed as a percentage of available operating time.
Quality is the total number of good units produced expressed as a percentage of the total number of units that were started.
Availability – The widget making machine is capable of producing 100 units every hour. The production day is 8 hours, so the machine is capable of producing 800 units per working day. But, today there is a downtime of 1 hour due to maintenance and a shortage of materials so this means that the machine will only be working for 7 hours.
Actual Operating Time (7 hours)/Available Operating Time (8h hours) = Availability of 87.5%
Performance – During the 7 hours of operating time that were available today, the machine produced 625 units. The amount of units the machine is able to produce within an hour is 100. So the theoretical time need to produced 625 units is 625/100 = 6.25 hrs. The performance of the machine is;
Theoretical time (6.25 hrs)/Available time(7 Hrs) = 89% Performance
Quality – Of the 625 units produced today, only 600 of the units were of good enough quality to be sold. The other 25 units need to be reworked before sale or scrapped. This means that the good units expressed as time is 600 units/100 units per hour = 6 hours. So the quality is;
Good Units expressed in time (6 hrs)/Performance time (6.25 Hrs) = 96% Quality
So our final OEE calculation is
Performance (89%) x Availability (87.5%) x Quality (96%) = 75% OEE
This calculation shows that the total losses during the day for this machine were 25% which equates to 2 hours of lost production time. Over time, this adds up to a large amount of lost production time, therefore decreasing the profits that could be made if the productivity of the machine was higher. It is therefore very important to identify the root causes of this loss and to then implement the necessary measures to reduce or eliminate the losses.
There are many ways of improving performance, availability and quality, some of which are outlined below.
- Performance of machinery can be simply improved by production monitoring systems that enable you to quickly identify, track and rectify faults or bottlenecks in the process. They also motivate workers associated with the process to hit targets.
- Performance and availability can both be improved by automating your machinery and production process. Automation helps to increase available working hours as machinery is not dependent upon an operator for it to keep producing products.
- Quality can be improved by using vision inspection throughout your production process. Vision inspection during the production process enables you to identify and eliminate faulty products earlier in the process.
If you would like to discuss the productivity of your machinery or factory with one of our automation consultants, contact us on 01223 499488.