At the time he designed the 4x4 Hybrid, Joe had become well-known in the world of home-built CNC routers for his earlier work
Joe's 2006
This machine was constructed mainly of MDF and HDPE and had a cutting area of about 2x4 feet. Joe's Hybrid design was a significant improvement over the 2006 machine in its use of aluminum and steel for increased rigidity yet was still relatively easy for an advanced amateur to assemble in their own garage or basement workshop.
After several years of successful 4x4 hybrid builds forum members began experimenting to improve the machine. These modifications are discussed in our members forum. The culmination of many different modifications was a revised designed called the Joe's Evolution (often shortened to "Evo")
Joe's CNC 4x4 Hybrid machine (below). It continues to be built using easily available material, electronics, and software.
Hybid parts are still available. There are many of these machines that have been built and still are.
Hybrid MDF parts could flex under high cutting loads and the mdf was susceptible to moisture.
The Evo design builds on many of the elements of the earlier Joe's Machines and is the culmination of a decade of refinements
The Evolution: The machine design is an evolutionary refinement of an earlier design Joe's 4x4 Hybrid .
Of course, parts of the name are often dropped and it has become more common to call the machine a Joe's Evo or just a Evo
The main difference with the Evo machine is that the Y and X/Z carriages are made of 3/4" aluminum plate. This design change addresses one of the Hybrid's main weaknesses, the MDF carriages. 
Joe sells a kit of aluminum parts needed for the carriages and bearing adjusters or you can make them yourself.
The CAD files are available for members wishing to cut their own aluminum parts.
Another change was to use a larger 3" x 6" 80/20 extrusion for the gantry or X axis. This change added significant stiffness to that axis. The extrusions used on the Y axis are the same 2" x 4" 80/20 parts as were used in the Hybrid. Becasue these are supported by the base the smaller size provides adequate stiffness.
While it's technically possible to build an Evo using leadscrews, almost all current builders are using rack & pinion instead. Leadscrews limit the size of the machine and are more finicky to keep running well.
The suggested base for new Evo builds is a welded steel design that has proven to be more rigid than the old Unistrut base used on the Hybrid.
There are many vertions of steel bases done by our builders This is a bolted steel base
There are designs for a very cool folding base by a talented builder in our forum.
Unistrut Bases of all kinds have been made
Aluminum Extrusion
Wooden Bases are a good alternatives, many designs have been built from wood
Many types of Z axis can be used and have been adapted or built to be used on all of our machines.
Stepper motor and controller options for the Evo are similar to those used for the Hybrid. Some builders are using larger NEMA 32 motors to take greater advantage of the Evo's increased strength. Controllers based on The Gecko G540 continue to be an excellent option for new builders.
