Kossel Mini problem not real MM in movement

Hi there masterminds of the 3d printing,

I have a very strange issue here with my Kossel mini, which I got from HKBAY back in 2015. I did build it, it worked then in 2016 i totally left it, as I have two more printers. Now the situation in 2017 is strange.

I have been working on the Kossel in the last week, updating software, putting the arduino on top of the printer with a FAN, I swapped the power supply to a proper one, I did get new nossle- yes I am having fun.
last night i noticed that the way i build the kossel back in 2015 wasnt right, the 3d printed slider part on the rails was spined 180degrees, so my rods were down on the slider, not up. And i have been printing so for loooong time. So today i decided, ok lets spin them as supposed on all Kossels. And voala- PROBLEM.

Now the problem is, when I home it, it goes only down. By yesterday everything was going well and G28 was giving a super result. Now thou its like reversed somehow. When I put it in manually by hand home, so pressing the end stops, it goes nuts. It thinks its not on 250.6mm, but on -250.6 and I do not understand what have happened.

Now there is other issue which i noticed yesterday when the printer was still homing and everything, the actual 250.6mm i write in Arduino for MANUAL_Z_HOME_POS wasnt coming out so. I did meassure again and the distance is 250.6, but when i give it to print it stays around 40mm above the bed. Which means that the printer is somehow not in MM? As a distance which in reality is 250.6mm for it its around ~290mm.

Please help here as I am a bit lost now,

I am running Arduino Mega with Ramps, Marlin RC8

Thank you!

Kind regards

Edited 1 time(s). Last edit at 02/13/2017 08:15AM by RadevDesign.

Ok, I did switch the stepper motors of X,Y,Z and now its running normal, but the second issue is still there.

Either your steps/mm is WAY out, or your manual home position is suddenly higher because you've flipped the carriages.

If your steps/mm is that far out then you'll have no chance of printing a flat first layer (assuming you've measured the diagonal rods correctly and put that value into firmware).

If you home, then put a caliper on a carriage, then command the effector to move down 100 mm, how far does the carriage move? If it moves 100mm or thereabouts, increase your manual Z home position.
If it only moves 86mm or thereabouts, multiply your steps/mm by 1.16.

Hi nebbian,

I did take in account the flipped carriages, and yes there was a 12mm difference, I did set this in Arduino, before I wrote the first post.

I have measured the diagonal rods and they are 215mm, standart all came ready assembled with the ends and exact length.

I did the 100mm test after G28 and it moved down with 80mm , not 100mm. Can you please explain me how to multiply the steps/mm?

Kind regards

Your steps/mm are probably set to 80 right now. You need to change them to 100.

In configuration.h, change this line:

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80, 80, 80, xx}

to:

#define DEFAULT_AXIS_STEPS_PER_UNIT   {100, 100, 100, xx}

(note that the xx depends on your particular extruder)

If using EEPROM, you can change the steps/mm by sending:

M92 X100 Y100 Z100
M500

I hope you aint shy, cause i wana kiss you right now ahhaah THANKS