anycubic i3 mega with non-standard "Steps per unit" settings?

Last weekend I acquired a used anycubic i3 mega 3d printer which somehow only prints correctly if I set the so-called "Steps per unit" to the double value. So with gcode, from following original setting

Code:

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M92 X80.00 Y80.00 Z400.00 E92.60  <--- (Default settings)

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I had to issue following gcode command/setting:

Code:

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M92 X160.00 Y160.00 Z800.00 E185.20 <--- (My changed value)

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Is this normal? I have not found anyone on the internet with this non-default setting.

Is there another way to get the same result, while keeping the original default setting?

Any help would be appreciated.

Some background:
With the latter setting the manual moving of the X-, Y-, and Z-directions in each 0.1, 1 or 10mm steps works as expected. With that also the printing of a 10x10x10mm block has the correct dimensions. Without that change, everything shrinks to half the distance, so manual moving in steps of 0.05mm, 0.5mm or 5mm. Also the 10x10x10mm block comes with some imagination (Since the filament smears and does not stick) out as a 5x5x5mm blob. I find this strange because this setting looks like the factory default setting. (When comparing output of other users on the internet.)

Does someone have an explanation why the settings for the steps per unit need to be doubled?

The stepper drivers are still the original DRV8825. The steppers themselves are still the original ones (BJ42D20-11V03) with 1.8?/step rotation. Also all spindles are unchanged.

Firmware is V1.1.2 ( V1.1.2_20181008 ), controller board is the trigorilla1.1

As follow up from previous posting, some information about how to read out and change values in EEPROM:

I issued following commands:
* M501 to read from the EEPROM
* M92 command from above, verified with the
* M503 command to verify the settings
* M500 to write settings to EEPROM.

Since (Ubuntu linux) minicom does not support serial speeds higher than 115200, I had to use following solution for the communication with Linux:

Download mysetbaud script from the Stackexchange forum, (search for mysetbaud and 250000) and set speed for ttyUSB0 accordingly to 250000

Then I opened two terminal windows:

# Window 1:

Code:

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tail -F /dev/ttyUSB0

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# Window 2:

Code:

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cat > /dev/ttyUSB0

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In Window 2 I was able to issue the commands. Interestingly I noticed that before issuing any command from above, I had to start Cura at least once shortly. Otherwise the 3d printer would not accept the commands. It looked like Cura initializes the 3d printer somehow for serial communication. Something I do not understand fully yet.

DRV8825 drivers : 1/32 with the same jumper settings the A4988 drivers : have 1/16, this means twice as many steps

A4988 drivers Use
#define DEFAULT_AXIS_STEPS_PER_UNIT { 80, 80, 400, 92.6 } // 1/16 Step settings

DRV8825 Drivers Use
#define DEFAULT_AXIS_STEPS_PER_UNIT { 160, 160, 800, 185.20 } // 1/32 Step settings

You may have to change the jumpers to get to the original 1/16 Step

Fantastic! You hit the nail! I was wrong in assuming that the DRV8825 was the original driver ic.

Originally the anycubic i3 mega has the A4988 drivers, which can be verified on http://thingiverse.com/groups/anycub...al/topic:27064

This also means that the correct way to handle the DRV8825 driver is to build the application from scratch with using the correct define from above. The M92 command from above also works but is a workaround for this.

Thanks!

This great info. I just got an Anycubic i3 Mega and kept having poor print quality. I'm new to 3d printing and this was a setting I was missing which has fixed my crappy prints!!