Our recommendation is to design an HB core.
Good products have core with a tridimensional shape. It means that a core with uncompressed fluff show a tipical increased thickness (it means more absorbent material) in the crotch area and especially in the front side. See simplified core design on the right. You can see there is a first layer along the whole core and a second one positioned in the center/front area. These two layers can be two distinct cores but generally it is a single core with a 3D profile (usually it is obtained through a profiled mould filled by absorbent material).
You can identify 3 different zones
* shallow zone: it is the lightest area mainly teh back of the core
* deep zone: it is the heaviest area and it is located where you need more absorbency
* transition zone: it is the area between shallow and deep
Typical basis weights vary from 100 to 200 for shallow zone and fro 400 to 700 for deep zone. As you can easily understand depending on what deep zone shape and basis weights you choose for your core you will have a specific distribution of absorbent capacity from front to back. Pic shows a graph of capacity profile for a specific product obtained through a xls software developed by iResolve named PocketShape
Since we choosed to design an HB core it means SAP will follow fluff distribution (if our equipment is able to do it!!). More SAP we add more absorbent capacity you have distributed along the core with same “capacity diagram” that fluff defined.
A simple spreadsheet like PocketShape will help you to obtain the proper “capacity diagram” and modify your core geometry accordingly.
Of corse you can design a more stylish cores, rounded and narrow at crotch area but the basic rules we have described here above are the same.
Just their application requires more sophisticated tools to predict core performances.