The purchasing question
Procurement must purchase enough input for the required accepted output. Finished pack count, web width, repeat length, packs per repeat and GSM together define the theoretical film requirement. A gross-input waste assumption then converts that net requirement into a purchasing estimate.
Calculation method
Net length = good packs × repeat length ÷ packs per repeat. Net area = net length × web width. Net kilograms = net area × GSM ÷ 1,000. Divide by the usable fraction when the entered loss rate is a percentage of gross input.
Worked example
For 100,000 good packs, a 0.25 m repeat, two packs per repeat and 0.8 m web width, net length is 12,500 m and net area is 10,000 m². At 60 GSM this is 600 kg. With 4% gross-input waste, plan 13,020.8333 m, 10,416.6667 m² and 625 kg.
Round the order to supplier reel sizes after calculating the requirement. Whole-reel ordering may create stock beyond the process allowance. Keep that remaining stock visible rather than calling all purchased surplus production waste.
Checks before using the result
- Use approved machine layout dimensions.
- Account for fixed startup losses without double counting.
- Record reel rounding and carryover stock separately.
Common questions
Can finished pouch width and height replace the web layout?
Only for a clearly defined approximation. Gussets, seals, trim and lane arrangement can make finished dimensions insufficient for production purchasing.