Why is the object not moving along the curve path? Yet again, I am have problem with the curve-modifier. So I did exactly (or at least I believe I did) as what others told me in my last question:
set origin of the curve to its geometry &gt; set cursor to the curve &gt; set origin of the tube to its geometry &gt; move the tube to the cursor
And then I applied the curve-modifier and move it along the Z-axis. But for some reason, the tube ran out of the curve and they were not aligned any more. The same happened to the cylinder array that is supposed to run along the curve as well. I tried rotating the tube and change the axis, but it still didn't work.
Could anyone please point out what I missed in these steps? The file is attached as follows: the tube and cylin_array are the application of curve modifier, whereas the tube.001 and cylin_array.001 are after the application.
What you need to do when you want an object to correctly follow the curve is to put both the curve and the object origin at the exact same place. So here:

Select the curve, press ShiftS &gt; Cursor to Selected
Select the object (for example tube) and press ShiftS &gt; Selection to Cursor
Give your object a Curve modifier, find the right Deform Axis (here -Z)
The object is a bit shifted, it's because you've rotated it and didn't apply the rotation, you need to apply (ShiftA)
If you want the curve to go in the opposite direction, switch to Edit mode, right click and Switch Direction