How much quantity of printed foil or Lidding Foil & forming foil or base foil is required to blister a specific batch size?
This calculation is confusing for most of the professionals working in pharmaceutical industries because they don’t know how to calculate the quantity of foils required for blistering a tablet or capsule batch.
In this article, we will learn to calculate the quantity of the above-mentioned foils required for blistering by following two methods.
- Theoretical Methods
- Practical MethodÂ
Both these methods are equally important, you can apply any one of the above methods to calculate the foil quantity.
Case Study
Suppose we want to calculate the printed aluminum foil & PVC base foil for for given batch size,
Number of tablets = 500,000 Tablets
Tabs/Blister =10 TabsÂ
Number of blisters = 50,000
Now we will calculate the quantity of printed & base or forming foil for the above batch size, mean for 50,000 blisters first by using the theoretical method and then the practical method.
1. Theoretical Method
I am used to calling this method theoretical as we can use this method to calculate foils for any new product for which currently we have no tooling available. We can calculate the blister foil from the drawing of the blister using its dimensions.
Example
Suppose we have a blister drawing indicating the length & width of the blister as given below,
Length of Blister = 6cm
Width of Blister = 4 cm
The printed foil & base foil length for each full blister will beÂ
6×4 =24 cm²
Calculation Of Printed Foil
The concept is to cut the piece of printed foil according to the blister length & weight. In the above case, it is a 24cm² piece of printed or Lidding foil.
For more precise calculation we will take the length of printed foil for the theoretical dimensions of 6 blisters as below & weigh it
24×6 = 144 cm²
Suppose the weight of the printed foil piece for 6 blisters is 1.2 GM & weight of the foil piece for one blister isÂ
1.2/6 = 0.2 GM
Foil Quantity For 50,000 Blisters
As we have calculated that the weight of printed foil for one blister is 0.2gm so for 50,000 blisters we will simply use the unit rule
Weight of printed foil for one blister = 0.2 GM
The weight of printed foil for 50,000 blisters isÂ
50’0000×0.2 GM = 10,000 GM
Convert grams into kilograms
10,000/1000 = 10 kg.
Note
10.0 kg foil is required to blister 50,000 blisters. One most important point to remember is that this 10 kilograms of printed foil is Only required for perfectly cut blisters but we know that some scrape is also removed from the sides of the blister during its cutting.
Scrap Factor
The waste which is collected in the form of a web along with the empty rejected Blisters which are removed during machine adjustments is known as the scrap factor.
So we will add 1 or 2 % scrap factor depending on the efficiency of the blister machine.
Here we will add a 1% scrap factor so the total quantity of printed foil for blistering 50,000 blisters will be 10.1 kilograms.
Important Point
The base foil can also be calculated by using the above method.
This theoretical method calculation may have some variations which are discussed at the end of this article in the summary portion.
2. Practical MethodÂ
I named this method a practical method because you can perform calculations practically by taking the original samples.
How To Perform
These calculations are performed by taking the original pieces of the printed & base foil which are collected from the blister machine.
To take these samples first of all we install the required tooling & rolls of printed & base foils on the blister machine.
The dummy empty blister is formed on the blister machine in such a way that the blister is not sealed, meaning heat or pressure at the sealing station is not applied.
We get two separate pieces of printed & base foils when the blister is collected after cutting.
Separate the printed foil piece & weigh it & in the same manner, separate the base foil piece & weigh it.
Just like the previous calculation, we will take 6 pieces of each foil for precise weight calculation.
Calculation
Suppose the weight of 6 pieces of printed foil is 1.5 GM & and the weight of 6 pieces of PVC foil is 2.5 GM.
Take the average weight of each piece for one blister as below
For printing foil
1.5/6 = 0.25 GMÂ
For forming foilÂ
2.5/6= 0.41 GMÂ
Printed Foil Calculation For 50,000 Blisters
Weight of printed foil for one blister = 0.25 GM
The weight of printed foil for 50,000 blisters isÂ
50’0000×0.25 GM = 12500 GM
Convert grams into kilograms
12500/1000 = 12.5 kg.
Base Foil Calculation For 50,000 Blisters
Weight of base foil for one blister = 0.41 GM
The weight of printed foil for 50,000 blisters isÂ
50’0000×0.41 GM = 20500 GM
Convert grams into kilograms
10,000/1000 = 20.5 kg
Scrap Factor
In a practical method, we will weigh the actual quantity of scrap (web formed & empty blister during machine adjustments) & add it into the above foil quantities to get more precise results.
Summary
There may be minor variation in the weight calculations by the first method as foil shrinks after pocket formation & we are taking only length & width.
In the 2nd method, we are taking the actual weight of both pieces to give more accurate results.
Both methods have their own importance as the first method may be helpful for cost estimation in the case of a new product where we don’t have product tooling.
Image Credit
Image Source – Google | Image By – Jornen