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Thursday, 20 September 2012 04:48

Zero waste wings for sanitary napkins

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At first look sanitary napkins seem all very similar. They are all made of a central chassis, usually straight or slightly contoured, and a pair of "wings" to position the product on the user's underwear.

State of the art design wants the full product cut from a single web. The outcome is 30% of your material goes in trim. Is it possible to find another way to produce it and save all that raw materials? Of course the answer is yes. Other manufacturers found a solutions and now their patents are on the way to expire. 

How to innovate your sanitary napkin design?

Many types of sanitary napkins exist on the market. But all of them can be divided in 2 big categories: “shaped” and “winged”. The latter is the most appreciated by women because they are equipped with lateral tabs, commonly called "wings", that help the positioning of the product on the underwear and protect the underwear itself from the contact with body fluids that might not be immediately absorbed by the sanitary napkin.

The wings extend from the longitudinal sides of the sanitary napkin and can be attached to the underwear folding them on the external part of the garment, thus enveloping completely or partially the part of the underwear on the opposite side of the sanitary napkin.

Generally these wings are integrally formed by one or more layers constituting the sanitary napkin itself, and particularly by the union of the lateral edges of the inner material and the outer material.

A mechanical cut, usually of rotary type, is used to shape outer profile from a single web although consisting of multiple materials laminate.

This very standard process has a major drawback: material scrap.

The waste is in some cases from 20 to 40% of the total material used, due to the fact that the wings are present only in the central part of the product. This results obviously in a very significant cost.

Among other drawbacks there is also the fact that the tool for cutting the profile is closely connected to the profile itself. In fact, being the outline rather complex to be drawn, the cutting tool is generally delicate, expensive and must be replaced periodically when worn out. This represents a cost since the replacement of the tool, which involves a machine stoppage, is often long, even in case of product change over on the same production line, and is often not a simple activity. 

To produce sanitary napkins of different sizes or with a different wing design is mandatory to stop the machine and replace the cutting tool according to the new product profile, and this results in an increase of production costs. Moreover the strict link between tool profile and product leads to an important cost increase of the whole production line because for each product size it will be needed at least 2-3 tools to keep line running with spare tools while worn tools are regrinding.

It is more and more common develop alternatives processes to save as more material as possible.  According these new methods wings are manufactured from a separate web and attached to the main product body in a later stage along the process. In this way you can shape wings reducing to zero (or almost to) material trim.

A new smashing technology can be applied to production of sanitary napkins in order to further simplify the whole process and reduce capital investments. It consists of the following steps:

- cutting at least one sheet of suitable material in order to form the absorbent product wings, with a non-rectilinear profile in such a way as to create, on a single web, two identical specular sequence of wings;

- putting alongside the two wings sequences in phase so that said profiles look specular, thus forming a sequence of pairs of opposed and symmetrical wings sequences;

- linking pairs of opposed wings with a release paper;

- cutting said web along a transversal line in order  to isolate a pair of opposite wings including release paper patch;

- transferring the wing pair and release paper patch to absorbent product central structure for a following seam.

The manufacturing process according to this system here described allows the significant reduction of the scrap material, in particular for the production of the wings, resulting therefore less expensive.

But the process above described, providing phases (in particular cutting) simplified compared to standard processes, significantly reduces the complexity of the production equipment. Some patents are present around this construction. Take care to design it properly or acquire a valid license.

Read 1413 times Last modified on Monday, 01 April 2013 21:45
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