Disclaimer: Never used a delta bot.
It sounds to me like your nozzle is moving vertically while trying to move horizontally. There are two things that could cause this. One is bad calibration. If your delta_radius is set wrong you will get the effector moving in either a cup- or dome-shaped pattern instead of flat. Check your calibration, and make sure the nozzle is a paper's width from the bed everywhere -- all sides and the middle.
The second possibility is that you simply have play in your machine. This is harder to fix, but easier to check: with the steppers turned on, and the effector away from the plate, grab the effector and jiggle it. It should be easy to tell if there's play in the vertical axis.
If neither of those is the cause, I'm not sure what it could be, but there's one way you could check. Find a video camera that can record at highish speed, put it close to the effector, and film moving the effector (printing or just jogging) and then play the video back frame-by-frame. You should see some sort of vertical motion in the nozzle, and by looking at how everything else moves, you might be able to figure out what's going on.
It sounds to me like your nozzle is moving vertically while trying to move horizontally. There are two things that could cause this. One is bad calibration. If your delta_radius is set wrong you will get the effector moving in either a cup- or dome-shaped pattern instead of flat. Check your calibration, and make sure the nozzle is a paper's width from the bed everywhere -- all sides and the middle.
The second possibility is that you simply have play in your machine. This is harder to fix, but easier to check: with the steppers turned on, and the effector away from the plate, grab the effector and jiggle it. It should be easy to tell if there's play in the vertical axis.
If neither of those is the cause, I'm not sure what it could be, but there's one way you could check. Find a video camera that can record at highish speed, put it close to the effector, and film moving the effector (printing or just jogging) and then play the video back frame-by-frame. You should see some sort of vertical motion in the nozzle, and by looking at how everything else moves, you might be able to figure out what's going on.