Fighting with computers

Computers are not always friendly.

Sunday, October 23, 2011

Calibrating RepRap Prusa

I thought my troubles were over once I've got all the parts for building my 3D printer, including the replacement for some defective parts.

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.





Thursday, October 13, 2011

Finishing my Reprap Prusa 3D printer

It's been a long wait to finish building my Reprap Prusa Mendel, to source all of the different parts and then to wait for some replacements of defective electronics. The building time has not been very long as I have had long waits in between, but I'd say it can be easily done over a weekend if you have all the parts.

Now I have to configure it and to master into the use of the system. My total cost is near 500€ and I have chosen some hardware to be better than average, so I guess cost can be driven down a couple hundred euros if you really push it to the bare minimums. I do not have yet any printed samples to show you though.

I can mention the companies I bought from that have given me a good service: XYZ printers (hardware), reprap-fab.org (plastic & extruder), RepRapWorld.com (electronics & PLA filament), Zapp Automation Ltd (stepper motors).

One of the things that have worked for me that can allow you to save so cash is to use both, the stepper motors and the belts, from two old EPSON printers for X and Y axis. They have enough torque to move the two axis well enough. Z axis, however, needs a more powerful motor. As I am using LM8UU bearings for my axis, I am not sure the same is true when using PLA printer bearings.

Anyway, I can recommend this project as a very entertaining one, but unless you are buying a full kit, I am afraid the process of sourcing all the parts may be time consuming. I know that MakerGear is selling a full kit in USA, but I was afraid it might become very expensive for people in Europe once you throw in shipping, taxes and customs.

All along the way, Reprap forums proved an invaluable source of information.