What is Pitch Time, Pitch Diagram and how to make a Pitch Diagram?

Pitch time: In industrial Engineering, Pitch time is a ratio of total SAM of garment and number of operations to be set for the style. Or

Pitch Time = Garment SAM/No. of operations.

Pitch time is used for line setting and calculating production target for the line.

Pitch diagram:

A graphical presentation of individual operation’s time (SAM) and pitch time on a same chart is called pitch diagram. For example see the following chart (Fig.1). At this chart on X-axis operations name and on Y-axis time value is depicted. The blue line is showing individual operation SAM and red line is showing pitch time.

Fig.1: Pitch Diagram (SAM Vs Pitch Time)

Usage of Pitch Diagram:

Pitch time is to calculating machine requirement in each operation.

Pitch diagram is used for line balancing in an assembly line. Pitch diagram is made on operator’s production capacity per hour and target quantity per hour in pieces for easy understanding.

How to make a Pitch Diagram

To make a pitch diagram on operator’s capacity Vs line target collect information as following. First conduct a capacity study for all operators and find out how many pieces operators are making at each operation. Where more than one operator is doing same operation, sum up their capacity for that particular operation. With the capacity study data make one table on spreadsheet as following table-1. 

For example, the line is making ladies blouse. Operations are listed in column B as per operation sequence (all operations are not taken). In column C number of pieces is listed according to the operations that can be produced by the operators. Add one more column ‘D’ and write target quantity (in the example -27) against each operation.

Suppose that hourly production target is 27 pieces for the line. So to meet the target at the end of the line you should get minimum 27 pieces per hour from each operation and for the preparatory operations capacity should be more than 27 pieces. Now draw a line chart with capacity and line target (Fig. 2). This chart is also called as “Pitch Diagram”. The blue line is showing actual capacity at each operation and Red line is presenting the target quantity.

In the chart, the blue line moves up and down. Where blue line is below the target line, you will get pieces which are less than target quantity. These operations are the potential bottleneck for the line. On the other way, where blue is top of the target line, it means operators have potential to produce more pieces on those operations if they are provided work. From the Pitch diagram, it is easy to understand which operations are bottleneck and where operator’s full capacity is not being utilized.

Table-1: Data shown in the following table and chart are assumed only for example. Follow above steps and make your own “Pitch diagram” with real data of a line. 

A	B	C	D
Sl. No.	Operations	Capacity/Hour (Pieces)	Target/hr (Pieces)
1	Collar run stitch	35	27
2	Back dart making	27	27
3	Sleeve slit binder	29	27
4	Front placket attach	21	27
5	Front placket finish	20	27
6	Front dart making	33	27
7	Shoulder Join O/L	30	27
8	Shoulder edge stitch	40	27
9	Sleeve attach O/L	50	27
10	Side attach	20	27
11	Cuff attach	17	27
12	Cuff  finish & Tacking	16	27
13	Collar  attach	24	27
14	Collar finish	24	27
15	Bottom Hem	27	27

How to calculate or check machine SPI ( Stitches Per Inches)

The abbreviation of SPI is Stitches per inch. In the Metric System it is expressed as Stitch per centimeter (SPC). It is very easy to measure SPI of the machine or seam. To measure it, take a fabric swatch of 12 inch X 2 inch. Sew the fabric length wise in a single burst with current SPI setting. Initially use contrast thread for bobbin and needle thread. Take out the stitched fabric and lay on a flat table. Remove all creases if present on the seam line by hand. Now, take one measuring tape, place it on the stitch line on the above fabric sample and mark line 2 inches apart. See the following figure.

Now count number of total stitches in between those two lines. Divide total number of stitches by 2. The result is the SPI of that machine or seam. For SPC measurement is taken in centimeters. If your SPI requirement is less or more than the current machine SPI then rotate SPI regulator accordingly (for basic machines). After setting check SPI again in the similar method. When you get correct SPI on the sample then go ahead for production.

Example: In the above figure, the total count of the stitches is 20 (in 2 inch gap). So SPI will be 10. 

What is line Planning

In this article, line means sewing production line or production batch. Each line contains a set of machines to make garments for mass production and set of machines vary depending on product category.


Line planning is scheduling and allocating of orders to production lines according to product setting (product is being made in the line) and due dates of production completion. A line plan defines when a style is going to be loaded to the line, how many pieces to be expected (target) from the line and when order to be completed. For example, please refer to the following Table-1, where a simple line planning has been shown in spread sheet.

Benefit of Line planning: It helps production manager as well as line supervisor with information such as what is the daily production target for line. They set their line (machines and manpower) accordingly. Line plan also provides information such as how many days style would run, what is the next style going to be loaded?

Table-1: Line Plan

	Line 1		Line 2		Total
Date	Daily Prod.	Cumm Prod.	Daily Prod.	Cumm Prod.	Daily Prod.
1-Dec	loading #2341A, Qty -3000 pieces		300	1200	300
2-Dec	200	200	300	1500	500
3-Dec	250	450	300	1800	550
4-Dec	400	850	200	2000	600
5-Dec	400	1250	loading #Polo , Qty -1500 pieces		400
6-Dec	400	1650	0	0	400
7-Dec	400	2050	100	100	500
8-Dec	400	2450	300	400	700
9-Dec	400	2850	350	750	750
10-Dec	150	3000	350	1100	500
11-Dec	loading #432K, Qty -5500 pieces		400	1500	400
12-Dec	100	100	loading #YK45, Qty -4500 pieces		100
13-Dec	250	350	200	200	450
14-Dec	500	850	250	450	750
15-Dec	500	1350	400	850	900
16-Dec	500	1850	400	1250	900
17-Dec	500	2350	400	1650	900
18-Dec	500	2850	400	2050	900
19-Dec	500	3350	400	2450	900
20-Dec	500	3850	400	2850	900
21-Dec	500	4350	400	3250	900
22-Dec	500	4850	400	3650	900
23-Dec	150	5000	400	4050	550

Daily Prod. – Daily production or line output Cumm Prod. – Cumulative production of the style till date