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Help on CoreXY build

Posted by selva_tvi 
Help on CoreXY build
October 22, 2016 01:31PM
Hi everyone,

After building a crane style bot (with V-slot), now building a Core-XY with linear rods. Build size 100*100*100mm.

I am facing some issues when homing and while printing.

In the image 'Corexy.jpg ', the left side motor is connected to X motor connection in RAMPS, right side motor is connected to Y motor in RAMPS, left side endstop in X-carriage is connected to X-min endstop in RAMPS, backside endstop is connected to Y-min endstop in RAMPS.

When the X-carriage is at the front side (away from the motors), the X homing is done properly. The hot end moves to the left side and hits the endstop smoothly. (Refer 'HomeXatback.3gp')

Also Y homing is also done properly with the same condition (X-carriage is at the front side, away from the motors). X-carriage moves to the back side and hits the back endstop smoothly.

Now the problem arises when the X-carriage is at the back side (near by the XY motors). When I click 'X home', it is moving towards the X endstop, but not triggering it, stoping before the endstop.

And the same, when the X-carriage is at the back side, and when I click 'Y home, the hot end is moving strangely and not at all homing Y. (Refer Xhomingnotdoneproperly.3gp', Yhomeactingstrange.3gp').

I tried with motor wires swapping, X Y motors swapping, endstop swapping and tried with true and false values in Marlin also. (Configuration.h file attached.)

Also, after homing, if I move, Y axis by 90mm, X carriage is also moving along with Y. (Refer 'Xmoving90mm.3gp', 'Ymoving90mm1.3gp')

Same, when I move X axis by some value, Y is also moving with X carriage. Is it the normal property of Core-XY.

I am using Arduino+RAMPS with Marlin RC7. Using original E3d Lite6, MK8 extruder. I have attached the images, videos and config file also.

Also, I just printed a 20mm cube without filament. Instead of square movements, the printer is moving in parallelogram motion. (Looking like 15 degree inclined).

And how to get perfect tension with CoreXY. When I tighten the belt in the hot end mount, the mount gets inclined (X-carriage not perpendicular to Y-axis). But when I did the normal tight, X and Y are perpendicular.

Help me to proceed further.

Thanks & Regards
Re: Help on CoreXY build
October 23, 2016 12:09PM
Hi Everyone,

After continuous testing, I found the mistake is with me itself.

1. Stepper driver current was low, so that X and Y homing was not done properly. Adjusted the POT in A4988 and both X&Y homed super smoothly.
2. When I move X by given value, Y was also moving along with X and when I move Y by some value, X was also moving along with Y. Means the axes were moving diagonally.
Actually the problem was with stepper drivers. I used A4988 for X-axis and DRV8825 for Y-axis. But, forget to change the steps per mm value in firmware. Both was given as 80,80. Due to this the X and Y moved diagonally. Now, changed the Y stepper driver also to A4988. Now the issue of both axis moving solved. (I got idea about stepper drivers when reading this forum : [forums.reprap.org], in which Taz-dig suggested to check for both motors and stepper drivers)

X moves separately and Y moves separately.

Hope this may help some one.. Anyway thanks for the forum..
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