Prusa i3 from Aliexpress...

Hello everyone!
So, I've been interested in 3d printing for quite a while now, and a couple of weeks ago I decided to buy a kit for a prusa i3. So I went online and went for one from Aliexpress. The kit arrived a few days ago and I've been trying to make it work ever since. So, I've got some issues.
First of all, even though all the cables were wired the right way, when I turned the printer on and tried to connect it to my PC the cable over-heated and made a spark. Result: the PC is unusable (something about the front panel I will have to figure out, since it doesn't want to turn on again D. The point is: the printer seems to work just fine, and I don't know which part of the main board (which is a Zonestar, BTW) has been damaged. The only problem I see is that the usb connector now looks broken. I haven't tried connecting another cable for obvious reasons. So I can't use my PC to make the first adjustments, and have to rely on the printer itself.
The second thing is, the motors for the z axis act funky. They sometimes work fine (but make a lot of ticking noise) and sometimes make a soft noise and not turn at all. They seem to do it without apparent reasons, and are not costant. The only thing I know is, they are wired together the right way.
Also, in the settings of the printer I can't find anything about the extruder motor, from the acceleration to the movement.
So, before short circuiting the usb cable, I tried putting in the micro-sd card that came with the printer, and contained two precompiled gcode test files. I tried printing them (even knowing that nothing good could come out) and I noticed two strange things: first of all, when the print job starts, the printer homes all, but then forces the Z axis down by about half a centimeter, which places the extruder in a lower position than the bed itself. This leads me to another (maybe more important) problem. On the board, when I manually move the axis, everything works fine with x and y. Z seems to be able only to go down. If i tell it to go up, it descends, even if the limit switch is activated (which seems to make sense... after all the printer thinks it's going up..or not?). This happened also in the test print: after finishing a layer, it tried to go down instead of up.
Last, no filament has been extruded so far. The extruder motor only seems to be able to tilt a few degrees in one direction and then come back.
Last thing to mention, all these problems took place even before the cable accident, so they shouldn't be related to it.
Any suggestions on how to fix this mess?
Thanks in advance!!!

Seems to me you need to adjust the steppers current. See the wiki for details. Oh, and btw, there is a Prusa i3 specific forum below...

So, I tried what you suggested... Now all the motors receive the right current, so they don't stop halfway through their processes. Still, there are other issues: the printhead only moves donward (both during simulated print and with manual instructions) and it still fails to go to the origin and stop there (it goes on for a few millimiters), and after that the two rods are in different positions.
Also, no filament is extruding (it never has) even if the temperature is right. The motor stays there and tries. Not even manually the filament moves (and it can't get out, either)
Can you give me some other advice?
Also, if a moderator sees this, can you please move this topic to the right place? I'm really not sure what it is...

Ok, I've been able to clear the extruder. Now I see that the extruder motor doesn't want to move at all, just to go back and forth by a small angle. Any ideas? Is the current still wrong?

Well, after some time.... I can clearly see what I didn't... I had swapped two cables! I should definitely not do electronics late at night... . Now the extruder works. Is there some software behind the z axis only going downwards? Thanks again!

If you have your printer communicating with your computer I would use the m119 command on the console of your host software to check your z end stop. You should be able to run the command and see what state it's in then keep it pressed and see if the state changes.

I would then make sure if it is in the right position to stop the Z axis before the printhead makes it to the bed.

If one of those two things doesn't correct the issue then I would suspect the pre sliced objects on your SD card. I believe it might be possible to use the slicer to set a negative z start value. This would also assume your firmware doesn't have protection against this.

Edited 2 time(s). Last edit at 07/26/2015 02:07AM by appdev007.

The problem is, when the USB cable overheated, it melted the USB module on the board, so I can't use it anymore. I can't even power the board from USB... (I had to change the current while the printer was on). I was wondering, though.... Can I somehow create a "fake" .gcode file that makes the printer do just what you asked? If so, what do I have to write in it? Or can I just generate it? Thanks again!

First I recommend that you go onto eBay and buy a ramps, Arduino Mega, stepper driver combo kit for about $35 and replace your bad board with that. Once you have that read the ramps page, link below, and triple check your wiring for applying power or connecting to your computer. Apply power first and make sure the thing doesn't smokebefore hooking it up to your computer. I suggest this board merely due to its commonality and low price. More common the board, the more people who will know it and know how to support it. There are many others out there to choose from.

[reprap.org]

While you're waiting on that to get here I recommend you read this page from top to bottom. Pay special attention to the toolchain section. At the risk of starting a debate, I recommend Marlin firmware and Slic3r. Whatever firmware you do pick you have to thoroughly read its page and learn how to configure it and whatever slicer you do pick you have to read this page and learn how to configure it for your printer. ( I'm talking about using a different firmware only if you're going to be getting a new controller board. Each firmware only support certain boards.)

[reprap.org]

Edited 1 time(s). Last edit at 07/26/2015 10:09AM by appdev007.

Ok! Thanks... I've now bought the Arduino Mega 2560 and Ramps 1.4 as a replacement. In a couple of days I'll be able to get them and see if everithing works! Really excited... Thank you very much for your help!

Good luck. I suggest lots of reading while your waiting on that board. Don't forget to triple check that wiring before applying power or hooking up USB. ; )

So... I've got my new board, which is RAMPS 1.4, and build everything and all. Now the movement is OK, the z axis moves both up and down. Still, there are some things I can't figure out... First: the stepper motor drivers overheat when used. This happened without me messing with voltages and screws. I don't know why it happens, but it bothers me quite a bit. Is it the wrong current? The other thing is, the extruder won't work. The extruder motor is OK, but when I try to extrude some filament nothing will come from the nozzle. I already checked the temperature is right, and tried running the motor alone. The strange thing is, when I tried to make it "extrude" 50mm of PLA, it extruded 430 instead. Which means... I should have to use a modifier of 0.116, but I don't know where to put it...

"the stepper motor drivers overheat when used"

This is because...

"without me messing with voltages and screws"

Who knows what level the are set at from factory. First thing you do with new drivers is check their vref.

==========

"when I try to extrude some filament nothing will come from the nozzle"

and

"it extruded 430 instead"

contradict each other. Is there filament coming out the tip of the hot end when you tell it to extrude or not? If there is and it's the wrong amount you need to set your esteps in the firmware. You need to run through this calibration guide from top to bottom before trying to do anything with your printer.

I didn't notice any questions about putting firmware on the board. Even though it may work for some things, the firmware for your old board may not be RAMPs compatible. Either verify that it is or just put a new one on there. I recommend Marlin. You can download it's official home. As far as I know the only way to get it off of there would be to use a GIT client like this or this. I would be wary about getting it from anywhere else (might be packing a virus).

Ok! Thank you for your help! I'm now halfway through the calibration process, and I hope everything goes well. What I was trying to say was that when I tell the printer to extrude, if the filament reaches the hotend it stops and can't be extruded (the motors seems not to be able to push it more), while the stepper can make it go near the extruder (I have the setup where the filament is fed from a tube connected to the stepper).
Still, thank you. Hopefully it will be all right, and I won't have to write here too soon

Glad to help. Don't be afraid to ask no matter what some a hole on this forum might say.

So if you haven't done VREF and Estep configuration I'm going to guess those will be the source of your issue. The motor probably isn't getting enough to push the filament and isn't being told the correct number of steps. I think by what you said that you have a Bowden extruder where the extruder motor is not mounted to the X carriage. As I understand it those require a little more to make up for the resistance of pushing the filament see the tube.

One other thing: It seems that everything is now working, except (once again) for the z axis. I went through all the configuration and calibration you suggested me, and the max feedrate I get is 1600 steps/mm. The problem is: when I run a test print (now with everything in place) the z axis is right on the first level but then moves up by too much and the filament gets extruded mid-air. Is there anything strange with my steps/mm? Or is it something else?
Thank you once again!

It appears that I couldn't count the number of threads and thought there was only one... Now everything works fine!
Just out of curiosity... Would it take long to hook up the display that I have (it was in the kit) to the new board? It has a flat cable connector with 10 pins, and I couldn't find any indications on how to connect them... even more because they also include the keypad on the front, with five buttons...

You need what is known as a "Smart Adapter" to Plug the LCD wires into the Ramps board and then enable your specific type in your firmware. The smart adapters are easily found on Ebay or if no adapter is made that takes the wires from the LCD to a Ramps, a LCD and adapter can be bought for as low as $10 USD on Ebay. Make sure that the adapter you get is compatible with Ramps as they vary shapes and sizes for certain boards.
Sample 12864 LCD Smart Adapter
LCD and Adapter

I'll be buying one of that for sure! Now... since I seem to be veeery noob... I had the machine working and allright. I left it for 30 minutes and now... it doesn't work anymore. Everytime I try to connect the USB cable to the port it creates little sparks. I checked and saw that there must be microcurrents. So I plugged in the cable. The pc simply doesn't recognise it. Still, I'm able to connect to the printer if the AC power cable is not in. I hope my RAMPS is still working, right? What could it be?

Sorry bud. You may need to unhook everything and check it for shorts. Are the leads of you thermistors and hot end heater insulated? You can't have any exposed wire anywhere. Did one of the insulated wires get pinched somewhere? Wire ties are your friend. You should probably go ahead and order another mega, ramps, and drivers. If you don't need them you can keep around as spare.