Testing mechanics without extruder

Hi!

I'm making an H-bot 3d printer and I just finish the mechanics. So now, I want to test it without extruder. I'm using Marlin Firmware and Repetier as a Host. I tried to set #define TEMP_SENSOR_0 0 but It gives me an error: #error "TEMP_SENSOR_0 is required." So how can I do this?

Thanks!

I made a dummy thermistor from a simple resistor in the range of 50-100k ohm.

Edited 1 time(s). Last edit at 11/20/2016 05:13AM by o_lampe.

have a look at m302 cold extrusion

Oh, thank you. So in Repetier I upload the file that i want to print, i slice it, i write M302 S0 at g-code box, hit send and then hit print? And after this what command should i send to reverse to the initial state?
M302 S170? Thank you!

Quote
jinx
have a look at m302 cold extrusion

Does that really work without thermistor/dummy attached?

Apperently not..........

oops missed the no thermistor part
with marlin at least on line 226
//#define DUMMY_THERMISTOR_998_VALUE 25
//#define DUMMY_THERMISTOR_999_VALUE 100
just have to uncomment those!!! never tried it

Ok, so now I have another problem. I connected my thermistor to the board. And the value that he reads is 957.5 celsius degree. And off course the command to the printer is MAXTEMP triggered. System stopped!

That temp was with thermistor 11 from Marlin. When I changed with thermistor 1 repetier is reading 0 celsius degree. And again, system stopped! What is happening? ))

So I know that the majority of thermistors are NTC. So without thermistor connected to the board everything is fine. When I connect the thermistor I have MAXTEMP triggered. I measured my thermistor with a multimeter and it's about 1.6 ohm. I don't know why it s so low. It should not be like 100K?

if your thermistor is reading 1.6 ohm when cold it is probably a ptc type that increases in value as it heats up(not what you want for testing your printer.
just fit a normal resistor of about 75k ohms and select 100k thermistor type in the config.h (this should simulate a reasonable temperature)

MAXTEMP is usually a sign for a shortcut. 1.6ohm could be contact resistance of the probes.
A shortcut often happens, when the grubscrew is tightened too much, or the teflon tubes are not pushed up to the sensor.

Ok, so now I'll write for all the people witch will come with the same question and want to test the mechanics without thermistor, extruder etc. And after this, the admin can close the topic but leave it on site so others can read it.

Here is how I solved the problem:

First, most of the extruders from 3d printers have an NTC thermistor witch means resistance degrease with increase of the temperature. I measured the thermistor resistance with my multimeter and it was like 1.6 ohm witch is very very low(like a shortcut). A good thermistor should be somewhere like 100Kohm at room temperature. So clearly, when I connect the thermistor to my minirambo board and I opened repetier it showed me something like 900 degree celsius. That's becouse as long as the resistance of thermistor goes down reading temp by software increase. When I pulled out the thermistor from the board, repetier showed me something like 35 degree and that's because the resistance of air between pins from board is very high. So clearly my thermistor was broken. When I took it off from extruder I saw it was broken.

Next, How I tested the mechanics without extruder , thermistor connected to the board:
Go to Marlin configuration.h and you must to modify the next lines:

In the Thermal settings part:

from: //#define DUMMY_THERMISTOR_998_VALUE 25 make it: #define DUMMY_THERMISTOR_998_VALUE 40
from: #define TEMP_SENSOR_0 0 make it: #define TEMP_SENSOR_0 998

In the PID > Bed Temperature Control part:

from: #define EXTRUDE_MINTEMP 170 make it: #define EXTRUDE_MINTEMP 20

And these are all the settings witch you must to change in Marlin. Now go to Repetier and modify( If you use another host, try to find the compatibility of files to your host and do the same thing):

In Config->printer settings-> and set Default Extruder Temperature at 40 degree Celsius
Next, go to Slic3r->Configuration, and make a total new configuration of how do you want the object to be printed but with the only condition to introduce in Filament Settings->Filament->Temperature->Extruder->First layer: insert 40 degree ->Other layers: insert 40 degree

Don't forget to save it. Then upload a STL file into the printer, slice it, go to manual control, inser M302 in the G-code command and hit send. Then go to Print Preview and hit print.

And that's all. Your printer should be able to start moving.

I hope this topic will help some makers when they will be in the same situation. Thank you guys for everything!