How to Calculate Machine Requirements for Sewing Operations?

Sewing machines are the primary resources for a garment production unit. To make garments as per the daily target, a factory must allocate the right number of sewing machines and other equipment. For this reason, industrial engineers need to calculate machine requirements by sewing operations.

In this post, I will cover the steps to estimate machine requirements. You will also learn the types of machines you need to make garments in an assembly line. Keep reading this article and follow the steps.

How to Calculate Machine Requirements?

Prerequisite:
The following details are required to calculate machine requirements by sewing operations.

1. Daily production target of the line (A). This means the number of garments that need to be stitched per day.
2. Number of hours in a shift (B). How many hours do you plan to work each day?
3. SMV of garment operations (C). You need the SMV (standard minutes) of all sewing operations.
4. Present efficiency of the factory (D). Efficiency is required because production volume will depend on how efficiently workers may do their jobs.

Steps to calculate machine requirement:

Step 1: Prepare operation breakdown

Select a garment for which you want to calculate machine requirements. Analyse operations required to sew the garment and list down operations in a spreadsheet in a sequence. For example, see the operation breakdown of a Crew neck t-shirt in the following table.

Step 2: Identify machine type

Observe what stitch class has been used in the operations and according to those select machines against each operation.

Step 3: Calculate the SMV of each operation

Write down SMV. SMV is the most important part of calculating machine requirements. You can use SAM for each operation from your database. If you don’t have a database for standard minutes then calculate it. Read the article on how to calculate the SAM of a garment.

Step 4: Calculate the Theoretical machine requirement

Set your production target for the day (8 hours shift).
For example, the production requirement is 400 pieces per line. Use the present efficiency level of the factory. Now, calculate machine requirements using the following formula. It is called a 'calculated machine number'. Because the formula gives you a fraction of the machine but in reality, we can’t assign a fraction of machines to a worker.

Machine Requirment = (Target quantity x Operation SMV)/(8 hrs x 60 x Line Efficiency)
= (A*C)/(B*60*D)


Note: 60 is multiplied to convert hours into minutes.

Example#1: Let's say you need to find the machine requirement for the 'shoulder join' operation
Here,
Daily Target (A) = 800 units
Shift Hours (B) = 8 Hours (480 Minutes)
Operation SMV (C) = 0.45 minutes.
Line Target Efficiency% (D) = 70%

Machine requirement = (800 units x 0.45 Minutes)/(480 minutes X70%)
= (800 x 0.45 x 100) /(480 x 70)
= 1.07 Machines


Example#2: In case the Line Target is 1000 units per day and line efficiency is 80% then the machine requirement will be
= (1000 units x 0.45 Minutes)/(480 minutes X80%)
= 45000 /38400
=1.17 Machines

Normally, t-shirt lines work at 80% - 90% efficiency. For example, I have taken the line efficiency 70% and 80% in the above examples.

Step 5: Physical machine requirement

Now simply round off the machine number. Or you can club operations that use a similar machine class.

Example: Operation bulletin for Tee Shirt (Crew Neck).

Machine Requirement Summary:

• Single Needle Lock Stitch (SNLS): 2 Machines
• 4 thread Overlock machine (4TOL): 6 Machines
• 3-thread Flatlock machine (3TFL): 4 MAchines

Check out OCS's Online Calculators.


Also Read the Related Article:
Machines used for sewing garments for mass production
How to calculate the efficiency of the individual operators
How to calculate the efficiency of the sewing line or batch