How to Calculate Efficiency of a Line that Produces Multiple Styles in a Day?

Question: When a production line runs two or more styles having different SAM how can I calculate the efficiency of that line per day? ... asked by Alamrew Ayalneh

Not only you but many of others find problem calculating line efficiency on the day when one style is going to end and a new style is loaded to the same line. I am not clear when you face this problem
  • Is multiple styles are running to the line at the same time? or 
  • The previous style is over with some output and a new style is loaded at the back of the line? 
However, I am discussing this issue in details. I hope you will get the answer to your question from it. There are two ways to find line efficiency like,

Line Efficiency% = (Total line output * Garment SAM *100) / (Total operators * shift hours * 60) or

= (Total SAM of produced garments / Total worked hours*60)*100

Line Efficiency% = (Sum of SAM produced by individual operators / Sum minutes attended by each operator) * 100 or

= (Total SAM produced by the line/Total worked hours * 60)*100

Most of the factories follow formula#1 to calculate line efficiency. As because
i) It is easier to calculate, 
ii) Most factories do not have the facility to record operator wise output (SAM produced) and 
iii) factory is concerned about line output not about the WIP in the lines.

I have earlier post method of line efficiency calculation using this method. Click here to read it.

Coming to your problem, I guess you use formula#1 to calculate your line efficiency.

When two or more styles are running together in a line. How to use formula#1 to calculate line efficiency? Here is the formula -

= {(Total output of Style#1 * SAM of style#1) + (Total output of Style#2 * SAM of style#2)}*100 / (Total operators * shift hours * 60)

For example: In a line, 20 operators worked for 8 hours and line produces 200 pieces of style# A and 200 pieces of style# B. SAM of style# A is 15 minutes and style# A is 20 minutes.

Line efficiency %= ((200 * 15 + 200 *20)*100)/ (20 * 8 * 60)

= (3000+ 4000)*100/9600

= (7000/9600)*100

= 72.9%

Note that though this is widely used methods for line efficiency calculation you don't get an accurate efficiency of the line. So to get accurate line efficiency figure use formula#2. You can use this formula for single style also.
To calculate line efficiency that runs more than one style you have to measure production of each operation/operator irrespective of styles and measure actual attended minutes by each operator to the work. Then calculate operation wise total produced SAM by multiplying operation SAM to output at each operation. 

For example, an operator makes two different operations of two different styles. SAM of operation#1 is 0.50 minute and operation#2 is 1 minute and she made 400 pieces for operation#1 and 200 pieces for operation#2. So Total SAM produced by the operator is equal to 400 minutes (400*0.5 +200 *1). 
Similar way calculate SAM produced by each operator and sum up to calculate total SAM produced by the line. Calculate the sum of individual operators working hours.

Finally, calculate line efficiency% by using formula#2.

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