I am always asked, ‘what sized die plate do I need’ for a certain diameter of pellet.
The quick answer is, ‘it’s dependent on the characteristics of your formulation’……
The general rule of thumb is; for a 1mm pellet you need a 1mm diameter die plate. By varying the thickness (depth) of this extrusion die, you can increase or decrease the density of the extrudate and subsequently the pellets.
The reason why the formulation characteristics have such an influence is largely due to the following:
The higher the water content, the higher percentage of shrinkage upon drying, thus meaning a 1mm wet pellet , may decrease in size by up to 30% when dry. However, a formulation with a lower level of water content, mixed with a variety of excipients and additives can see a much smaller percentage shrinkage.
My advice is to experiment with a selection of 3 different plates. First choose the target sized pellet for example 1mm, then choose a 200 micron +/- of the target size, i.e 1.2mm and 0.8mm . This will allow you to develop both optimum parameters and have the best chance of reaching an excellent particle size distribution per batch.
I can assure you that changing the diameter size of the die is much simpler than continually changing your formulation to suit the equipment.
We design and manufacture a wide range of different extrusions dies and screens from 0.5mm up to 8mm diameter, and in a variety of shapes so I am sure we can make your life a little simpler and increase both productivity and efficiency.
Feel free to get in contact to discuss your experiences too.
Tel: +44 (0) 1258 471122