Well, I guess it's time to get this build thread started as we are a good way along on the table.
After looking at the Mechmate, Shopbot, and various 8020 builds we decided to go with a welded steel table and gantry. I wanted a stiff machine that could run at high speeds and aggresive cut depths. We will initially be using it for mostly cabinet work but did not want to be excluded from working with denser materials as we got more familiar with the tools capabilities.
Looking at the 8020 designs there just did not seem to be enough mass to control the forces of a large gantry working at high speeds. When finished, this build will weigh in around 750 lbs, which should be good to minimize the effects of the moving gantry and produce good clean cuts.
We started building thinking the table would be 48 x 96, but ended up at 66 x 120 so that we could work with 5 x 8 sheets of baltic birch; the cost difference in he raw materials to increase the size was minimal.
Just to set the bar, this is being built by my son and I (he is doing most of the manual labor, I am provding moral, monetary, design support). We both are familiar with welding and metal work, but are no more than weekend warriors at it.
So here we go...
I bought the Mechmate plans and spent a lot of time pouring over them, it closely resembles the Shopbot PRT style of router and the more I looked, the more I realized I wanted the more modern PRS style raised gantry. I looked at buying a Shopbot PRS and came to the conclusion that we would quickly be in the $20k range to get a working system; so I sat down with Turbocad and started drawing lines and sticking them together.
I decided to use 2x2 square tube and 2x6 rectangular tube for the X axis and gantry Y axis, mostly because it was readily available and relatively inexpensive. I chose to use 11 ga steel with the intention of using threaded inserts instead of tapping the bazillion holes where threads would be required (this saved a bit in material costs as it would have required the use of 1/4" steel to have enough meat to thread all of those holes).
So we bought 100' of 2x2 tube and 40' of 2x6 tube and started cutting....