Number of problems with new Reprap Prusa i3

Hi all,

We recently bought a new Reprap Prusa i3 from Reprapguru on Amazon. After assembling everything and making sure all the connectors were correctly put in, we ran into the following problems:

1. Could not compile & upload the RepRapGuru Marlin v3 software - it complains about a missing u8glib.h library. Thus we are using the RepRapGuru Marlin v2 software. Could using the V2 instead of V3 software be the cause of the problems?

2. Stepper driver PCBs did not fit perfectly into their slots - they were about 0.5mm too long. After sanding them down, they now fit.

3. Heated bed thermocouple reports the ambient temperature to be 0 Celcius. Resistance across the disconnected thermistor is ~500 kOhms.
Edit: Forgot to mention, tried to swap thermistor from extruder and heated bed, tried to use 100 kOhm resistor in place of thermistor...but the ambient temperature is always reported to be 0 Celcius.

4. Hot bed does not heat. Extruder nozzle heats fine. Resistance across the disconnected extruder thermistor is ~100 kOhms. Are the extruder and hot bed thermistors the same?

5. Ambient temperatures do not refresh on the Repetier software. Heated bed temperature is always 0 Celcius. Extruder head only refreshes when Repetier is started, and stays at that temperature.

6. The Y-axis stepper motor does not work; it instead vibrates.

7. Although the Y-axis end stop is not triggered, the Repetier software seems to think it is triggered "Echo: Endstops hit Y:0.01"

8. Various other intermittent problems: sometimes the X-axis motor doesn't work (just vibrates), sometimes the Y-motor works again, sometimes the X-endstop gets inexplicably triggered, etc.

Could you please try to suggest what the problem could be? I am aware you can find people asking about some individual problems above but wondered if all these problems together point to a hardware problem.

Two experienced EE & mechanical engineers took a look at it the whole morning with multimeters, oscilloscopes, other NEMA 17 motors from working equipment, etc. to no avail. Their suggestion was to try to get the vendor to send replacement electronics. What do you think?

Thanks.

Edited 1 time(s). Last edit at 10/19/2017 07:52AM by blueskiesresearch.

What controller board does the printer have ?
What display does it have (reprap full graphic or alpha numeric)

Bed thermistor and hotend thermistor are usually 100K ohm types

Other problems sound more a configuration.h is not configured correctly

Hi, thank you for your reply.

The controller board is an Arduino Mega 2560 with a RAMPS 1.4 board sitting on top of it.

The LCD display is exactly as you see in the attached picture.

Thanks again for any advice!

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1. Could not compile & upload the RepRapGuru Marlin v3 software - it complains about a missing u8glib.h library. Thus we are using the RepRapGuru Marlin v2 software. Could using the V2 instead of V3 software be the cause of the problems?

You have set in the configuration.h that you have a glcd, when you do not. So its looking for a library to enable the graphical LCD

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2. Stepper driver PCBs did not fit perfectly into their slots - they were about 0.5mm too long. After sanding them down, they now fit.

Welcome to current quality control standards. Ie there are none

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3. Heated bed thermocouple reports the ambient temperature to be 0 Celcius. Resistance across the disconnected thermistor is ~500 kOhms.

thermocouples and thermistors are quite different things. That resistance is really high for a Thermistor, most are 100K at about 25c.

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4. Hot bed does not heat. Extruder nozzle heats fine. Resistance across the disconnected extruder thermistor is ~100 kOhms. Are the extruder and hot bed thermistors the same?

Bed will not heat if it cant read a temperature, safety feature. I would think both should be the same...

Hey Dust,

Thanks for your reply. I'm currently working on something else today so will take a look at your suggestions early next week.

Will go into the configuration.h and disable the glcd.

We tried to removing the thermistor that was reporting 500 kΩ, and stick a 100 kΩ resistor in its place. The temperature it was reporting was still 0 Celcius...although it may be reading the temperatures correctly but not updating it (it wasn't updating the temperatures for the working thermistor in the Repetier software either)

Have a great weekend everyone!

Hi guys,

I am using the Marlin v2 firmware instead of the Marlin v3 firmware.

y-stepper motor problem solved:
Furthermore I found the problem with the y-stepper motor - the plastic pulley on which the timing belt wraps around was over-tightened and not moving freely. Loosening the bolt across it and lubricating it with some WD40 fixed the y-stepper motor problems.

The remaining problems are:
1. The temperatures (for both the extruder and hot bed) are not updating at all. Extruder thermistor reports temperature to be 14.8 C even when it is heated (its heater works) and the hot bed temperature is reported as 0°C.
2. The hot bed's temperature is 0°C and does not change or heat at all.

Edit: More details:
1. Resistance across extruder thermistor: 120 kΩ
2. Resistance across hot bed thermistor: 580-600 kΩ
3. When the extruder temperature is set at 70°C in Repetier Host, the LCD panel correctly displays the set temperature as 70°C. The extruder's temperature rises to 80°C as reported by the LCD (why >70°C?). Meanwhile, the temperature reported in Repetier does NOT change at 15°C, even though the extruder gets hot to the touch.
4. I re-installed Repetier Host 2.0.5 and the temperature in the extruder now reports and updates correctly (agrees with LCD display).
5. The temperature in the hot bed is still reported as 0°C in both the LCD and Repetier Host.
6. I have tried using a variable resistor (from 0 - 130 kΩ) in place of the hod bed thermistor. The temperature in both the LCD and Repetier Host always reports as 0°C regardless of the resistance of the variable resistor.

Any suggestions?

Edited 4 time(s). Last edit at 10/22/2017 04:56AM by blueskiesresearch.

Post a link to this firmware you are using as this V2 and V3 doesn't correspond to anything standard
Post a link to what your brought also... so we know what you taking about.

Marlin, the real official marlin, is here [github.com] and is only at 1.1.6 at this time

Basically the firmware has to know about your hardware, if you just try any random old firmware, its like putting a dolphins brain into a dog, it might fit, but it never going to work

1) identify your motherboard, ramps and Melzi are the most common.
2) examine the configuration.h file... you have to edit that to match your hardware.

I'm somewhat surprised that it didn't already come with firmware....

Edited 3 time(s). Last edit at 10/22/2017 05:26AM by Dust.

Hi Dust, thanks again for your input!

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Dust
Post a link to this firmware you are using as this V2 and V3 doesn't correspond to anything standard

Firmware link: [goo.gl]

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Post a link to what your brought also... so we know what you taking about.

Vendor link:
[www.amazon.com]

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Marlin, the real official marlin, is here [github.com] and is only at 1.1.6 at this time

Yes I noticed. Is the Reprap that the guy is selling on Amazon a clone and not the original?

Quote

Basically the firmware has to know about your hardware, if you just try any random old firmware, its like putting a dolphins brain into a dog, it might fit, but it never going to work

1) identify your motherboard, ramps and Melzi are the most common.
2) examine the configuration.h file... you have to edit that to match your hardware.

I'm somewhat surprised that it didn't already come with firmware....

The instructional videos were linked to by a commenter on the vendor's Amazon page. The link to the firmware is on Video 19 of the instructional videos by another commenter.

I believe RepRapGuru in his video said it was a RAMPS motherboard.

This is most definitely just a clone machine... nothing official at all.
Real machines are made of aluminum, not acrylic

It does look like a ramps from the pictures (two boards on top of each other, with stepper drivers on a 3rd level

The firmware you have linked to is also for a ramps

now you asked earlier if the thermistor where the same

the firmware say
#define TEMP_SENSOR_0 6
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 6

So yes both type 6, they should be the same. So when disconnected from the board, the resistance should read the same for the same temperature.

You can also just move the hotend thermistor onto the heated bed thermistor plugs to check its reading correctly on your interface
T0 is hot end and T1 is the heated bed thermistor plugs

for full wiring see [reprap.org]

for connectors see [reprap.org]

Edited 1 time(s). Last edit at 10/22/2017 06:42AM by Dust.

Hi Dust,

OK - found out what the problem with the hot bed thermistor was. Silly mistake: It was plugged into the T2 slot and not the T1...Doh

Once it was plugged into the T1 slot, it started reporting the temperatures.

The temperature readings appear to be off by -10°C. It is reporting the room temperature to be 7°C instead of about 20°C. Is there a place where I can add a correction term to the thermistor resistance -> temperature conversions?

Thanks!

It's common for the low temperature readings to be off, because of the limited resolution of the ADCs and the lack of automatic ADC calibration on budget electronics. Don't worry about it, because the accuracy will likely be better at printing temperatures, and in any case it's less important to know the actual temperature that it is to know what works for your printer and filament (which you will only find by experimenting). Where high accuracy or high reproducibility between different instances of the same printer model is required, PT100 sensors are generally used instead of thermistors.

Edited 1 time(s). Last edit at 10/22/2017 11:22AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

OK thanks guys!