Wholeseler's warehouse operations vs retailer's

A few weeks ago I had a chance to analyze jeans wholesaler’s warehouse operations like: inbound and outbound. A wholesaler has generally two main peaks: before spring-summer season and before autumn-winter season. Of course there are other peak periods but compared to these two main peaks they are small ones. In these peaks warehouse area increases a lot and man work power is needed much more than ordinary work days. Because of this wholesaler rented a warehouse which 2/3 of the year was almost empty and wholesaler employed much more warehouse employees to cover these two main peaks in his business. In addition to wholesale operations wholesaler has his own operated retail stores selling jeans under his own brand in different shopping malls and high street stores around the country. So a small part of the stock is kept in warehouse to feed these stores and for re-orders from wholesale buyers.

Because there are about 150-200 different models per season, there is no big need for WMS system in warehouse. There are barcode labels on products and inbound operation was done by scanning the products, making piles of 10-15 pieces of one model and putting them to the storage area right after the scanning. There is no addressing system so rows in the storage area are divided like man jeans area, ladies jeans area, ladies tops, etc. Every model’s all sizes are kept near to each other and are not mixed with other models unless the quantity is too small and there is no storage area for new delivery from supplier. Scanning is done just to know what received, but not to know where in the warehouse this product is kept.

The size range for jeans trousers products is too big compared to tops. Every jeans trouser has 20 different widths. Every width has 5 different lengths. So per one model there can be 100 different sizes.



Suppose warehouse has received 30 pieces of jeans of one particular model. They were scanned into five piles, every pile consisting of 6 jeans. Suppose 24-30, 27-32, 27-34, 33-36 are to be collected from these 5 piles. Finding these 5 piles among other 200 models would be a little big time consuming. Finding a particular size among these five piles will consume another time. 24-30 is on the third pile, 27-32 is in the 1st pile, 27-34 in on the last pile, 33-36 is one the 1st pile. On the 2nd and 4th pile there are no products to collect. The picker generally searches all 5 piles in order to find these 4 jeans, although there is no need to search 2nd and 4th piles.



Suppose there is an address for every pile. For example, these five piles are located in 101 numbered cell and 101 numbered cell is divided into five piles and each pile has a unique one digit letter within this cell. The picking list would be like this:

101-----a------33-36----- 1 piece
----------------27-32----- 1 piece
---------c------24-30----- 1 piece
---------d------27-34----- 1 piece

So the picker omits searching b(2nd pile) and d(4th pile).


If we somehow able to index the items in the pile while scanning them on inbound, we can increase the productivity of pickers a bit more by showing the exact location in the pile from the top. The picking list would be as following:

101---------a-------4------33-36--------1 piece
---------------------5------27-32--------1 piece
-------------c-------4------24-30--------1 piece
-------------d-------6------27-34--------1 piece

The picker counts 3 jeans from the top, takes the 4th one, checks if the right size. Then, takes the fifth jeans. So he omits the checking of the first 3 top jeans in the pile (a). Next, counts first 3 jeans from the top in the pile (c), takes the forth one, check if the right size and so on.

Suppose there is second order to collect(blue items). Suppose first order(red ones) is collected and after this collection the piles will look like below:


The picking list would look like this:

101-------a-------1--------24-34-----------1 piece
-------------------4--------27-32-----------1 piece
-----------b-------4--------36-36-----------1 piece
-----------d-------4--------30-36-----------1 piece

There is another way to collect these two orders. These two orders can be collected at the same time.

The picking list for both orders combined would be similar to this:

Cell number		Pile letter	Index		Size	1st order	2nd order
101		a	1		24-34		1 piece
			4		33-36	1 piece
			5		37-32	1 piece	1 piece
		b	4		36-36		1 piece
		c	4		24-30	1 piece
	d		4	30-36			1 piece
	e		6	27-34		1 piece

In this case the picker sorts these two orders at separate containers while picking.

The picking can be combined and order sorting can be done manually while scanning or an automated sorter can be used. The picking list would be as following:

Cell number		Pile letter	Index		Size	Quantity
101		a	1		24-34	1 piece
			4		33-36	1 piece
			5		27-32	2 pieces
		b	4		36-36	1 piece
		c	4		24-30	1 piece
	d		4	30-36		1 piece
	e		6	27-34		1 piece

The picking can be combined in a way so sorting at the end of picking can be omitted:

Cell number	Pile letter	Index	Size	Order number	Quantity
101	a	1	24-34	2nd	1 piece
		4	33-36	1st	1 piece
		5	27-32	1st	1 piece
		6	27-32	2nd	1 piece
	b	4	36-36	2nd	1 piece
	c	4	24-30	1st	1 piece
	d	4	30-36	2nd	1 piece
	e	6	27-34	1st	1 piece

The collected pile would be like this:

27-34
30-36
24-30
36-36
27-32
27-32
33-36
24-34

In the bottom of the pile will be located items from the top of the picking list. If the pile of goods collected is unstable the picker may start another pile but put a mark in picking list where the new pile begins from. After he collects all the goods in the picking list, he sorts the goods according to orders containers starting from the last collected pile. A separate container for every order in the picking list is created. This method is good for order picking between 10-30 orders at once.
In fact, there is another method of accomplishing outbound order without picking process and this method is called across-the-dock method (not a cross-dock).