Fabric Roll Allocation In The Apparel Industry

concept & importance

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What is fabric roll allocation or fabric roll planning?

Roll Allocation or roll planning is simply associating fabric rolls to lays so that the least possible number of end bits are left behind.

*End bits are the small fabric pieces that are left from a roll post spreading. Being smaller than the lay length, they cannot be utilized in the lay and hence end up being wasted. You can move to the end of this article to understand the concept better.

The main objective of roll association is, therefore, to minimize the end bit wastage.

Let us take a practical factory case to understand this better:

Say, we have 2 lays of 10 m and 11 m respectively.

Lay 1 needs 25 plies and Lay 2 needs 24 plies.
Lay 1= 10 m and Lay 2= 11 m

The fabric rolls to be used are:Roll 1= 150m, Roll 2= 100m, Roll 3= 165m, Roll 4= 99m

According to the concept of roll allocation, we need to associate each roll with the lays to minimize wastage.

For this, we need to calculate the wastage produced by each roll while spreading.

Lay 1 calculation
Lay 2 calculation

Through the above calculation we achieve a roll combination that can give us the minimum possible wastage:

Lay 1= 25 plies and Lay 2= 24 plies

So, instead of picking any roll from the fabric store, like done in the usual process of laying, if a certain combination of rolls is selected, it can drastically reduce end bit wastage to ensure better utilization of the biggest cost: fabric.

You can also check out the video here to understand this.

What are the benefits of roll allocation?

Roll allocation is needed to ensure optimal fabric utilization that minimizes the fabric wastage. To understand the benefits of roll allocation, let us take a small case. This will compare the normal method of picking random rolls for laying with the calculated method of roll allocation.

We have the following cut plan, where the total fabric required is 130 meters. We have 2 rolls: R1 and R2 of length 68 m and 62 m respectively.

Total fabric needed= 130m
R1= 68m, R2= 62m

The “general industry trend” is to pick up the first available roll and use it. Once it is exhausted, we move on to the next roll and the process goes on.

If we follow the general laying trend, the case will be:

For Lay 1 (10 m), we pick roll 1 (68 m). We can spread 6 plies and are left with 8 m fabric in the process. We use the second roll, R2, to spread the remaining 4 plies. So, we have 22 m from R2 left at the end of Lay 1.

Now, for Lay 2 (3 m), we can use the 8 m fabric left from R1 to spread the 2 plies, leaving an end-bit of 2 m. Then, using R2, we spread 7 plies, leaving 1 m fabric from R2.

We have exhausted both the rolls and are left with a total 3 m end-bits. Moreover, we are short of 1 ply in Lay 2.

Lay 1 and Lay 2 calculation

So, in this process, we have wasted 3 m of fabric and our lay is still incomplete.

Now, let us take a look at an alternative approach using Roll Allocation:
Through roll allocation, R1 is used to spread 5 plies for Lay 1, leaving 18 m of fabric. Then, using R2, the remaining 5 plies are spread, leaving 12 m of fabric in R2.

For Lay 2, the remaining fabric from R1 is used to spread first 6 plies and the remaining fabric from R2 is used to spread 4 plies.

Check this table below for a clearer understanding:

Lay 1 and Lay 2 calculation

The above calculations clearly show that using roll allocation, we could complete both the lays with no end-bits left, i.e. no wastage.

The above case is again a very simple situation. On the cutting floor, the results are further magnified.

Hence, we can establish that Roll Allocation is necessary to reduce wastage and optimize fabric utilization on the floor.

How easy is manual roll allocation?

Now that we have established the importance and advantages of using roll allocation, the next question that arises is whether manual roll allocation is possible or not.

Manual allocation might sound very simple but, is actually a very tiresome and complicated task. All the permutations and combinations involved in a real on-floor situation can be exhaustive and prone to errors if done manually.

Let’s assume we have 3 rolls (A, B & C) and 3 markers (M1, M2 & M3):

3 Rolls3 markers

Roll-marker combination

Now, the total number of roll-marker combinations that are possible for 3 rolls and 3 markers are 3 *factorial times 3 factorial, i.e. 36.

Out of these 36 possible alternatives, only 1 solution is going to give us the best results that minimize fabric wastage.

This means that the probability of finding the best solution out of these 36 alternatives is just 2.8%.

And this example is just a very small case. In actual apparel manufacturing scenarios on the cutting floor, the number of rolls and markers are immense.

Probability of best solution reduces with increase in number of rolls and markers

As we can see above, if we increase the number of markers and rolls, the probability of getting the best solution decreases.

What is the need of the hour?

In the boom of technology, the need of the hour for manufacturing facilities is to deploy automatic systems that automatically evaluates all the roll-marker combinations and ensure the best fit to reduce end bit wastage.

Do you know of any alternate methods to reduce end bit wastage? Do let me know in the comments below.

 

 

*End Bits: End bits are the small fabric pieces that are left from a roll post spreading. Being smaller than the lay length, they cannot be utilized in the lay and hence end up being wasted. They add up to the fabric wastage in apparel factories and thus act as one of the biggest obstacles for achieving optimal fabric utilization.

You can look at the example below to understand how every fabric roll leaves behind an end bit:

What is end bit?

End bit wastage is the main reason where the concept of ‘Roll Allocation’ comes into the picture.

Check this article to know about the fabric losses that prevail on your factory’s cutting floor.

*Factorial: The factorial function (symbol: !) means to multiply a series of descending natural numbers. Know more about it here.

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