Here are couple of images to help demonstrate the size differences.
We used Optimal Junior and Optimal Bluegill to make an image we used on our Facebook page.
The other picture is the actual die inserts we use on the extruder to manufacture the two lines. The inserts are pieces that go on the end of the extruder to mold the shape and size of the final product. I added a ruler (in mm's) to help show the difference in size.
On manufacturing: I try to keep expansion down to between 0.5 and 1.0 mm. The Optimal Standard die plate opening is 3.0 mm and the Optimal Junior is 2.0 mm. Expansion is the result of many inputs, but a large component is from heat and moisture. Adjustments in these variables (even minor ones) can change expansion dramatically. For example, I've seen 6+ mm pellets come off of a 2 mm die!
Some feed manufacturers use the actual die size to label their feeds. Because floating feeds require expansion, people often notice pellets are a bit larger than the bag label claims. As part of our quality control, we measure the pellets coming off the extruder and adjust parameters if necessary to keep the final pellet size within spec.
