The MecaStack calculations for a baseplate are based upon the following publication, which assumes a donut with the hole cut out in the middle.
What is the basis for the MecaStack baseplate analysis?
You can not enter an ID of 0 in the software without causing a problem; however, you can enter a very small number. The problem is that when you enter a small number for the ID that the bearing pressure is assumed to act across the entire baseplate. This tends to cause a very large bending moment acting on the ID of the baseplate and causes it to get thick. Our opinion is that this is not a reflection of reality, it's just that the calculation is assuming you have a donut style baseplate and the calculations break down when you deviate. We recommend the following:
1) Enter a small ID and see if it causes a problem with the calculation. If it's not really an issue, then this is sufficient.
2) If # 1 causes a problem, then enter normal ID. For example, if the projection from the OD of the stack to OD of the baseplate is 4 inch [100 mm], then I make sure the projection on the inside is the same 4 inch [100 mm]. This will give a reasonable bearing pressure on the baseplate and design it accordingly, and then the excess baseplate inside should just be extra that is not really needed.
On the drawings we will show it as a solid plate, but for analysis purposes use the above procedure to prove the design.