The build platform must be as rigid as possible yet still retain the ability to fold for storage. Two bearing blocks each hold two linear bearings for the 5/16″ diameter stainless steel rods to pass through. They are machined from 1 inch 6061 square aluminum stock. The platform is held in place perpendicularly by two arms which pivot on 1/4” bolts. The arms are in turn held with removable braces. This allows the platform to rotate down and lay flat for storage when the braces are removed. The aluminum plate for the build platform can be seen in the background of the following picture with a caliper resting on it.
The build platform consists of a 1/4 inch thick 6061 aluminium plate. The bottom was machined to lighten yet retain stiffness.
Because this milling machine only has 6 inches of travel in the Y direction and the final build platform is 8″ x 9.5″, the machining process was broken into two operations. First one side was machined as can be seen above. Once this was complete, the plate was then rotated 180 degrees, and taking care to square up and index the part using a dial indicator and an edge finder, the plate was reclamped securely and the operation was completed using a 3/16″ three flute carbide end mill.
And finally a view from the bottom, all bolted up. Four 8/32″ bolts are used to secure the plarform to the arms.
A cross brace can be seen in the photo above reaching from one bearing block to the other. The hole in the center is where the threaded rod for the Z axis will pass.