Hey Pankaj,
This looks like a bad case of warping, but you’ve said the z axis moves slowly to begin with. I’d advise applying a little bit of grease to the area which it moves slowly on. Maybe it is gripping the axis to much.
Hi!
I agree with GIFT3D in that this basically looks like a terrible case of warping. Maybe look into that? However, if you are concerned about the Z-Axis, make sure it is securely fastened. My Lulzbot Axis actually became loose and I had a similar problem. You could try grease in areas, and see how that works.
Good Luck!
Jackson
can you show the under side of the parts?
Material?
Bed and Extruder Temp?
Bed surface material?
A video on YouTube or such of the first row of cubes printing would be immensely helpful.
Check all the connections on your z-axis. Loose couplers, misaligned gantry, bent screws, plastic or dirt in the z-screws, steppers not aligned in the frame, loose frame or gantry screws could all cause motion to have backlash or bind at the bottom of the z-axis and then loosen up once the z-gantry gets a few millimeters up the shaft.
Printing PLA with ABS bed and nozzle temperatures, or using the wrong surface could also cause such problems.