How to determine maximum diameter & length of Roll Film with core 3 inch using Tim's Diameter Calculation

Why it will be the important things for an Engineer or Packaging Development people ? When an Engineer and Packaging Development people starts to develop a new packaging, there are not enough information about how length of the packaging roll to be determined and how weight of the packaging roll to be determined. In fact, The Packaging Development must optimize the length of the roll film to reduce down time by changes roll and the otherside, not exceed the specification of the packaging machine like a maximum outer diameter unwind unit and maximum load capasity of unwind unit.

Maximum diameter unwind unit is a maximum diameter unwind unit at certain packaging machine that varies from one another to ensure the packaging roll rotate in normal condition at unwind unit.

Maximum load capasity for unwind unit is a maximum load of the packaging material that can handle by unwind unit to ensure no damage happen causing overweight at unwind unit.

If said, Your packaging machine has a maximum diameter unwind unit is 350 mm max and max load for unwind unit is 25 kgs, for an example the packaging material that you must develop having structure like : BOPP20/ink/adh/CPP40, width of film = 160 mm, core 3 inch, thickness of core is 9 mm. From this information, you can determine how length and how weight the roll must be by following this steps and using my formula named TIM'S DIAMETER CALCULATION below.

Step 1. From the structure of film, you can get some information like :

• Total thickness = 20 + 1 + 1 + 40 = 62 microns
• Density of BOPP film = 0.91 g/cm3
• Density of CPP film = 0.91 g/cm3
• Gsm adhesive = 2 gsm ( commonly )
• Gsm ink = 1 - 2 gsm ( commonly ), 2 gsm for Full Block Design
• Weight of core 3 inch ( thickness 9 mm ) = 195 g/100 mm

Step 2. Using my formula to determine maximum length of Roll film allowed :

TIM'S DIAMETER CALCULATION FOR CORES 3 INCH :

Max length(M)={[max.diameter(mm)exp.2 - 8836 /[thickness(microns)x1.274]}

= [(350)exp.2 - 8836]/[62 x 1.274 ]

= 113664 / 78.988

= 1439 meters tolerances 1% in length

So, The Engineer and Packaging Development must determine the length of packaging roll must below 1439 meters, for an example 1300 or 1250 meters/roll.

Steps 3. The next steps is to ensure that the weight of the packaging roll not exceed the max load capasity of unwind unit. For this case, we choose 1250 meters/roll for an example from previous steps. Then, please using this formula :

For film(Kg)=[length(M)xwidth(M)xthickness(microns)xdensity(g/cm3)]/1000

For Adhesive or Ink(Kg)=[length(M)xwidth(M)xGsm(gsm)]/1000

For Cores(g)=using extrapolation for this data :

Weight of core 3 inch ( thickness 9 mm ) = 195 g tolerances 5 % in weight

For this cases :

• For BOPP Film(Kg)= [1250x0.16x20x0.91]/1000 = 3.64 Kg
• For CPP Film (Kg) = [1250x0.16x40x0.91]/1000 = 7.28 Kg
• For Adhesive (Kg) = [1250x0.16x2]/1000 = 0.4 Kg
• For Ink (Kg) = [1250x0.16x2]/1000 = 0.4 Kg

Width of cores must wider than width of film, for this cases 160 - 0 + 2 mm. We choose 162 mm.

• For core (Kg) = [162/100]x195 = 315.9 g = 0.316 Kg
• Total weight (Kg) = 12.04 Kgs

So, The Packaging material roll for 1250 meters can be applied because the weight of the roll = 12.04 Kgs, not exceed the max load 25 kgs, and the maximum outer diameter roll not exceed the maximum outer diameter unwind unit. Good Luck !!

Adding information for density of the packaging material :

Material Density (g/cm3)

Aluminium foil 2.72

PET 1.4

PVC Shrink 1.2

Nylon 1.15

LLDPE 0.92

BOPP 0.91

CPP 0.91

PVdC 1.7

Note : For next articles, I will give another formula to determine the same cases like it, but using different diameter cores such as core 4 inch and 10 inch. Commonly used in Pulp & Paper Industry.

From the author :

Hopefully, this articles usefull for You. Well pleased to sent this FREE information to any people and let Anytime, Anywhere, and Anypeople using this site : http://www.interpak.blogspot.com/ as a references for Packaging & Printing Issues.

Regards,

Mr.Timothy