How to Calculate OEE in the Garment Manufacturing Industry?

You are measuring the common garment production KPIs for many years. Today let's learn OEE, a new perfromance matrix. OEE is a global standard for measuring manufacturing productivity. OEE covers all the primary perfromance matrices such as productivity perfromance, quality perfromance and availability of resources.   

In this article, I will show you how to calculate overall equipment effectiveness (OEE) in the aspect of the garment production. 

What is OEE?

OEE stands for Overall Equipment Effectiveness.

Overall Equipment Effectiveness (OEE) is a performance metric measuring how well a piece of equipment or manufacturing process performs. It's a common benchmark for identifying the percentage of truly productive time. The OEE measure is a combined analysis of production performance, quality performance, and equipment availability for production. 

OEE is calculated by multiplying three factors together:

• Performance 
• Quality and
• Availability

OEE is one of the KPIs used to measure the performance of the equipment in industrial production. OEE is also measured as one of the plant KPI metrics in the garment manufacturing industry. When measuring OEE for the garment production line, we modify the variables for calculation purposes. The reason for the changes can be understood from the following reasons.

The sewing floor is labor intensive and overall production performance depends on the employees' performance instead of machine and equipment performance. Quality production depends mostly on operators’ skills instead of sewing machines’ problems. Same way unavailability of the machine is caused by human factors rather than machine downtime. 

On the other hand in textile mills, looms, and spinning machines are big and automated. In such plants, OEE is dependent on the machine and equipment rather than employees. 

How to calculate OEE for a Production Line? 

To calculate the OEE of a production line, you need to capture information needed to calculate these 3 variables - Line Performance, Quality production rate, and Availability of machines. In this section, I wil show the calculation formula and calculation method with examples.

1. Availability: 

In generic terms, availability is the percentage of planned production time that's actually used. This factor considers equipment breakdowns, scheduled maintenance, and changeovers. Formula for calculating avalabity:

Availability= (Total planned time - Downtime)/Total Planned Time

In garment production, (sewing floor) availability is calculated as shift time minus the downtime. Then it is converted to availability percentage. Let's calculate machine availability on a line of 30 sewing machines. In a single shift, all machines are normally available for 8 hours. Due to various reasons, some machines were idle during the production shift. 

Example: 

Available hours in the line (A): 8 x 30 Hours = 240 Hours 

Line Downtime (B): 20 Hours  (Assume it)

Availability = ((A-B)/A 

= (240 - 20)/240 

= 220 /240 

= 0.9166

Therefor, Availability of the machines is 0.9166

2. Performance:

How well the equipment is performing compared to its maximum potential. This factor considers equipment speed, minor stops, and idling time. 

In garment manufacturing, line performance is calculated from produced SAH and Hours Worked (Utilized hours). The Utilized Hours are calculated from the total available hours for the line minus the total downtime in the line. 

Performance = (Line output * Garment SMV)/(Hours Worked*60)

Hours worked by Line = (Number of operators * Planned Hours) - Total Donwtime Hours of the Line. 

Planned Hours = Shift Hours (if Overtime approved Planned Time = Shift Time + Over Time Hours)

Example:

Shift hours (A): 8 Hours

Downtime (B): 20 Hours 

Line Output (C): 400 pieces 

Style SAM (D): 30 Minutes

Manpower in the line (E) : 30 

SAM produced (F) = (C x D) = (400 x 30)=12000 minutes =200 Hours

Hours worked (G) = (240 - 20) Hours =220 Hours

Performance = (Hours Produced / Hours Worked)

= (200 /220) =0.9090 

3. Quality:

The rate at which "good quality" products are produced without defects or rework. This factor considers scrap, reject, and rework. 

Here is the step for calculating the quality performance of a production line. At the end line inspection, keep record of right first quality garments. You can record total checked garments and total defective units found. From these two data you can derive right first time quality production of that line.  

Example:

Total production quantiy: 400 pieces 

Defective units : 15 Pieces

First-time good quality production quantity = (400 - 15) = 385 pieces. 

Quality performance = (Good quality garments /Total production) 

= 385/400 

= 0.9625

4. OEE Calculation:

Now you have claculated 3 variables and you have data as followings 

Availabity = 0.9166

Perfromance = 0.9090

Quality = 0.9625

OEE of this Line = Availability * Performance * Quality 

= (0.9166 * 0.9090 * 0.9625) *100

= 0.80194 * 100

= 80.19

So, OEE of the Line is 80.19

In the daily OEE report you can show all these 4 matrices as the following by Line. 

Image: example of an OEE report of a Fashion unit

We can simplify the calculation formula to reduce double data entry or going through all the processes of calculating availbility, performance and quality separately. Please refer to the handwritten calculation formula in the attached image. 

OEE = (Hours Worked / Planned Hours) X (Line Output X Style SMV / Hours Worked X60) X (Line output - Defective units) / Line Output

= (Line output - Defective Units) X Style SMV / (Planned Hours) * 60

= ((Line output - Defective Units) X Style SMV)*100 / (Shift Hours x Number of Operators ) * 60

Image: OEE formula simplified

OEE Calculator:

Based on the above simplied formula, I have made one online OEE calculator. You can use this OEE calculator to calculate OEE of your production lines. 

Image: OEE calculator screenshot

Conclusion:

The calculation of OEE is easy and provides the overall factory performance. If you can include this KPI in your monthly plant performance, it will be a good addition to management reporting. The critical part is data availability. Keeping a record of downtimes in the line, and capturing quality data by line and by employees is not possible without the use of technology solutions. 

There are a couple real-time production and quality systems that can help you provide such data to calculate Line OEE. Even some factories get OEE reports automatically by date. OEE is measured by industrial engineers and the MIS team.