A big issue with the arms configuartion as they are is that there is no firmware support for end stops. What this means in real terms is that before a print is started, the arms must be manually placed in a specific location to a reasonable degree of accuracy. This is dificult and time consuming. The firmware choosen to run this printer was developed by a Reprap forum member named ttsalo. Unfortunetly , he is no longer an active member of the board, and so the fork of Marlin he was developing has stalled. Because I am not a programmer I have been forced to look at other options in order to get this machine fully functional. To that end I have decided to utilize the wonderful low cost design created by Quentin Harley, the Reprap Morgan. It too is a SCARA type printer, however it uses a central pole for a pivot for both arms.
The great thing about using this configuration is the firmware is far more developed. It supports both end stops as well as a form of bed leveling/ arm leveling. This will simplify the platform leveling needed to run the machine. To this end, new arms were machined, as well as the central post for holding the assembly.
Beside the old configuration.
Gears will be used to transfer motion from the stepper motors to the axels. First gears were printed to ensure the dimensions were correct.
Then all the gears were machined form aluminum.
Now, a test fit.
The arms will again be spring loaded. The springs, not yet built, will pull the arms back. This pulls the backlash to one side of the gear train in a similar manner as the previous arm configuration.