For companies wrapping hundreds or thousands of pallets annually, determining the amount of stretch film usage and the average stretch rate is important to understanding costs. Below are two step-by-step stretch wrap calculations and a video to determine stretch film usage and stretch rates.
Determine Stretch Film Usage
We recommend figuring the amount of film usage per pallet and then multiplying the amount of stretch film used per pallet times the number of pallets per week.
To determine the amount of film being used per pallet, it is important to know the number of revolutions it takes around a pallet to secure the load. This is true whether applying by hand or machine.
In the video below we are using a pallet that requires a total of 11 revolutions to secure the load. The pallet dimensions are 48″x48″x63″.
Step 1 – Determine the amount of film used each revolution.
48″ per side x 4 sides = 192 inches of film used per revolution
Step 2 – Convert Inches of film used per revolution to ft.
192″ ÷ 12″ = 16 ft. per revolution
Step 3 – Multiple the number of revolutions by the amount of film used each revolution
11 revolutions x 16 ft. per revolution = 176 ft. of stretch film used per pallet.
The last step is determining the number of pallets going out per day or week and multiplying it by the amount of film used each pallet. The final number will give an accurate amount of stretch film footage needed per given time period.
Determine Stretch Film Stretch Rate
Grasping the amount of stretch rate consistently obtained by employees wrapping by hand or by machine application is essential in understanding stretch film cost. The step-by-step guide below will explain how to determine the stretch rate obtained.
Step 1 – Using an easily visible marker, make a 10-inch line on stretch film unraveled from the roll. Be sure to put the line at least 2-4 ft. away from the end of the stretch film.
Step 2 – Tie the film to a pallet and begin wrapping the pallet as normal. After a few revolutions, re-measure the line and write down the new length.
Step 3 – Use the formula below to determine the amount of stretch.
Line Size After Stretch – Line Size Before Stretch ÷ Line Size Before Stretch
Example: If the line size before stretching is 10 inches and after stretching is 22 inches the formula would be as below.
22 – 10 = 12 ÷ 10 = 1.2 or 120% stretch.
Step 4 – Use the formula below to determine the amount of ft per roll with an average stretch rate.
1 + Stretch Rate Obtained x Ft. per roll of film.
Example: Standard Machine rolls are 5000 ft. long and hand rolls are 1500 ft. see the two examples below.
1 + 1.20 = 2.20 x 5000′ = 11,000 ft.
1 + 1.20 = 2.20 x 1500′ = 3,300 ft.
Once the post-stretched roll length is determined and the film usage is known, purchasers can make accurate forecasts in film ordering and film savings. Below is the formula.
Formula to Determine Film Usage For a Specified Period
Number of pallets wrapped each week x Ft. of stretch film used each pallet
Example: 40 pallets wrapped per week x 176 ft. of film used per pallet = 7,040 ft. of stretch film used weekly
Stretch film footage used weekly ÷ Post-stretched Roll Length
Example: 7,040′ of stretch film used ÷ 3,300′ Hand Stretch Film Rolls at 120% stretch = 2.13 rolls used per week at a 120% stretch rate.
The amount of stretch obtained when applying the film is a massive factor in the overall cost of film and usage. Typically, most hand applications reach 100% – 150% maximum stretch. Stretch wrap machines with a pre-stretched head can consistently obtain 225% – 250% stretch. In the example above, the 3,300′ hand stretch film roll would have been 5,250′ long with 250% stretch.
If you have any questions about reducing stretch film costs or usage, feel free to call us at 1-800-441-5090 or shop online at www.uspackagingandwrapping.com.