If Im planning to go with the min z height of 3.25" does it make sense to do a drop table to make the legs as short as I can? On top of that if it doesnt offer any rigidity benefits does a drop table offer any other benefit?
If I was to set up a drop table to make the legs as short as possible, what would the conduit length be for the legs?
The drop table allows you to cut the top of thicker pieces of material.
If you have a need to cut larger items (like facing a thick piece of wood), then the drop table makes sense. If you intend on only working with 3/4" to 1" material, then there is no need.
An alternative to a drop table, and what I do, is that I setup my MPCNC with legs long enough to cut/face the top of a 3" object. When I cut thinner items, I just stack a few layers of 3/4" mdf to raise my object close to the x/y gantry.
The idea to both of these approaches is to reduce how far down the Z axis has to travel to get to your material. The farther the Z has to lower, the more horizontal forces the cutting material has on the bit and causes the Z to rotate.
One other question I have. When using the calculator and setting a z workspace of 3.25" like it defaults to. Does that mean the z axiz with the router but without the endmill has 3.25" of travel? So if I throw in an endmill that sticks out 2 inches I will have 1.25" of work space below the end mill but could still travel 3.25" correct?
So If I did use a drop table and didnt have enough shim material to raise my piece to be within that normal 1.25" work space, the z could still go low enough to work that piece? Or am I understanding the z workspace in the calculator?
The calculator assumes 1) that you mount the feet of your MPCNC at the same level as the spoil board, and 2) the mount you have for your router correctly places the bottom of the nut for the router flush with the end of the Z axis. With this setup, working space is the distance between spoil board and the face of the nut when the Z axis is in its highest position. In that space must fit the end mill, the work piece, and any clamp clearance. There is enough travel on the Z axis for the nut to rest against the spoil board, so there is no need for shim material.
Note that your 3.25" of Z axis will allow you to mill material up to about 1 1/8" in all situations, and somewhat thicker material in some situations.