The machine is a simple structure repeat 3 times (with differents size), one for each axis: A table mount in a linear movement.
A fix gantry it's the best option in this case for the high weight of the materials.
The basic structure have: two rods and support, four linear bearing with a table attached, and a lead screw and bearing suports. The motor are a Nema 17 stepper motor.
The Y axis are mounted in the base,
The X axis are mounted in the fix gantry. And the Z axis it's mounted in the movil table of X axis.
Arduino Mega 2560 board for control, with ramps 1.4 for driving motors and Marlin (with little modifications), as firmware.
Simple, cheap, affective.