Calibrating RepRap Prusa
As usual, I was wrong: Once I have finished building it and tested all the electronics it comes the moment to select a working firmware. There are several choices for RAMPS hardware but I selected Sprinter firmware as it includes acceleration control plus many people use it. But firmware alone is not complete till you've added all the different adjustment parameters so your hardware works together with the firmware the expected way (ie. a 10 mm move in the G-CODE causes a 10 mm move in your printer).
I was excited because once I tested with a thermometer that the hot-end heating and temperature reading was working nicely I thought it will be easy. I used RepSnapper for this basic tests, and next I tried to print a text object. Result was ok, but measurements were still a bit off. But when I attempted the design in the center of this picture the result were less than acceptable.
As many people suggested to use Skeinforge, and the recommended front-end was Pronterface I downloaded the whole thing and tried to go through a calibration process. I've found very useful the steps detailed here. Unfortunately my attempt at calibrating my printer faced two different problems. On one hand the default configuration I'm using for skeinforge 41 is feeding way too much PLA into the extruder (a big reduction in the feed speed in the Speed tab of SF41 seems to be helping). But the second problem is that I am having random lock-ups while printing. This problem appeared only now that I've moved the printer to my office, where I'm using a Linux PC. I can see that USB gets disconnected (only if RAMPS is powered) while printing. I guess it is an electrical problem, so I'll try both a new power supply and a better, shielded, higher-quality and shorter USB cable.
I am not very impressed by the end result of using LM8UU bearings. My x-axis is smooth only half way (I guess because the rods are not perfectly parallel) so I need to bump up the driver current for it not to lose steps (which gets the motor quite hot after a few minutes). Y-axis is smooth but less than I was expecting too. Z-axis is ok but still the motors need a good amount of current not to lose steps.
I've enjoyed the ride quite a lot, but I was expecting a better result. Still, I guess that as soon as I manage to get decent calibration I will start being happier with my Prusa that I am now.
By the way, I think what it is missing in the design is a LED light to lit the part being printed.