Prusa i3 (first timer problems)

Hello Everyone!,

I am trying to build my Prusa i3 Einstein Variant, for the record I've never built any 3D printers but I have plenty of experience with a few. I wanted to build my own from scratch and I decided to use the Einstein Variant of the Prusa i3. It looked a bit complicated but hell, I like challenges. I was going to try and build it without asking questions, just checking forums and youtube videos but I have come to a stop for a few days now and I guess it's time to ask for help from experienced builders.

Here is my Setup:

- I'm using a hotend, thermistor, aluminum extruder assembly and stepper motor from a CubePro from work (the hotend broke and when I called customer support, they sent me the entire assembly so I ordered an extra hot end and now I have a free extruder which I inted to use), the stepper motor is model "M42STH47-1684S" [www.motioncontrolproducts.com]
- Ramps 1.4 w Arduino Mega 2560 (Marlin firmware)
- All other Steppers are Wantai 42BYGHW609L20P1-X1
- 500W Power Supply ATX

My Problems (right now)

- Extruder motor works when I wire it as if it was X motor, when I change the wires to Extruder in Ramps, then it just stutters as if there wasn't enough current, I calibrate the polulu board but still it won't move.
- Hotend won't reach 230 °C, it gets stuck at 183.3 and then ponterface kills it because it can't reach the temperature.
- I have a computer fan with 3 wires that I want to use as an extruder fan and I want to connect it to the RAMPS board, but I'm guessing it's not as easy as connecting just two wires, any thoughts?

I hope I can get this thing working soon. Thanks in advance.

You wont be able to extrude until you fix the temperature issue, it has to be hot before it will move.

What voltage is the heat cartage, it my be a 24v system and you have it on a 12v system

Check the resistance of the heat cartage with a multimeter (while unplugged)

The fan is just as easy as using two wires, just use +5v and gnd, its doesnt use the special PWM wire, it just PWM's the power

Thanks for the reply,

I managed to heat to 185 °C by doing a PID autotuning and changing the firmware and I'm testing the extruder again. It still doesn't work, I thought it might be because of a bad driver, so I changed the pololou for a new one, and it's the same problem. I'm starting to think that it might be the wiring. I might have missed something, because it turns right and left when the current is at max. I'll try to reverse the cables and see what happens.

I'll check the resistance of the heat cartage and let you know, maybe it should be 24v as you say.

I managed to connect the fan but it would bring havoc to my heating so maybe it's a 24v system as you say. I'll see if I can confirm that.

Tomorrow I'll test the system again and see what I can do. Hope this extruder works.

Ok so, I checked the Resistance on the heat cartdrige and its 15 Ohms. And the resistance on the thermistor is 100K Ohms. I don't know which brand is it since it's inside the ceramics.

I disabled PID tuning and I am using #define BANG_MAX 255, the heat goes up faster but it still won't reach 185°C unless there is no air current in the enviroment (I'm sweating here just to see it work).

It's strange, I mean, I'm sending all the current available and still it won't heat up. could it be that the thermistor be bad?

I'll work on the stepper motor later after fixing this. Any thoughts?

Edited 2 time(s). Last edit at 08/13/2016 03:49PM by neocorps.

I would say that is a 24v heater cartage... My 12v one is 3 ohms, sadly I don’t have a 24volt one to test

From another post "Ohms law. Your 40W 12V heater should have 3.6 ohms. Your 24V 40W should be approx 14.4 ohms."

Edited 2 time(s). Last edit at 08/13/2016 10:21PM by Dust.

Hey Dust,

Thanks, I've confirmed that online. So I took a look at different ways to convert my Ramps 1.4 to 24V and for my first build it's getting kind of complicated, so I ordered a 12v JHhead extruder, it has a 100k thermistor included and a fan so I guess that should be ok. I will print a new extruder assembly and see if I can make it all work.

Now I'm a bit worried about the stepper, It's making erratic movements, CW and CCW and I double checked the connections and I have calibrated the current of the driver.

Ok, so the J-Head 12v heater arrived and it works fantastic. no problem getting to 230°C.

Now I'm going to start checking the stepper motor to see what is wrong with it because it keeps moving erratically. Any thoughts on this?

Regards,

So I checked the Stepper driver and it keeps moving erratically.

I unplugged it and then plugged the extruder cable into the X stepper and it works great, extrudes and reverses correctly so I guess ether my stepper is broke or I need to configure it via marlin.

I looked into other forums and found that I could try changing this:

#define AXIS_RELATIVE_MODES {false, false, false, false}
#define INVERT_E_STEP_PIN false

To this:

#define AXIS_RELATIVE_MODES {false, false, false, true}
#define INVERT_E_STEP_PIN true

Because my stepper might need a low voltage for steps, but still no go. What do you think I should do?

SOLVED!!!

After almost breaking my head for many hours I found what was wrong with the stepper.

Turns out that the cables for the stepper were connected incorrectly. See I had to switch the cables for the wantai steppers because they wouldn't work as they were wired and since I saw the same diagram on the extruder stepper (same colors) I decided to do the same for this last stepper.

Out of a last try I switched the cables and voilá it worked. Now I need to check if I can speed things up and I'm done.

Thanks for the help.