Sunday, May 09, 2010
Processing gcode instructions with the Rapman firmware
After running a variety of speed tests with the Rapman, I gained enough data to estimate the processing time for two kinds of gcode statement. The G1 statement processes in the Rapman 3.1 firmware at a rate of 17 msec/instruction. M108 instructions process at a rate of 19 msec/instruction.
Interestingly, the rate for the M108 instruction is actually significantly longer than for the G1. Given the floating point instructions necessary to interpret a G1 instruction this seems very odd. It would seem that much more time is spent reading off of the SD card than processing the information on a line of code. Either that or carrying out a M108 instruction in the Rapman firmware is more complicated that it would appear at first glance.
As a practical matter what this means is that if one wants to print a layer with 0.1 mm print road lengths you are looking at a maximum print speed of around 5.8 mm/sec. A print speed along a long road component axis of 16 mm/sec would imply that your average road segment would be no less than 0.3 mm.