I need to convert the rotation movement of motor to a linear move (have to be in the same axis of the motor)

I made a 3d model on tinkercad consist of 2 parts:

- first part will monut on the motor and has a shape like screw inside 

[![enter image description here][1]][1]

[![enter image description here][2]][2]

- second part is a plunger that should move in linear direction when the motor rotate with the first part

[![enter image description here][3]][3]


[![enter image description here][4]][4]

[![enter image description here][5]][5]

I printed this model but the plunger stuck inside the first part and do not move 
So it fails 

I want a simple way to convert the rotary move to linear in the same axis of motor


Edit:

I broke part 1 from behind to see what happened inside i found it stucks as the part 2 jump above the screw shape 

[![enter image description here][6]][6]

I think this mechanism is hard to be done 

So i switched to scotch yokes mechanism 
Hope it works!!
The vertical gear will pull the horizontal gears to move the articulator in linear move

[![enter image description here][7]][7]


  [1]: https://i.sstatic.net/KyB3n.jpg
  [2]: https://i.sstatic.net/FR874.jpg
  [3]: https://i.sstatic.net/1jGhG.jpg
  [4]: https://i.sstatic.net/ZxDLa.jpg
  [5]: https://i.sstatic.net/CUSRY.jpg
  [6]: https://i.sstatic.net/ZkUvK.jpg
  [7]: https://i.sstatic.net/zEL29.jpg