The zipper on my sweater broke so I sketched a new one. It works surprisingly well. This fits any sweater or jacket with a size 5 zipper. That means that the zipper teeth are ~5mm wide when zipped up. The zipper on your jacket will usually have the size on the back of the zipper slider.

I have created a new version of my zipper model which can be found at the link below.
Updated Zipper Model (+full assembly)

Printing Settings I Used:

• .1mm or .2mm layer height
• 1 outer wall
• 100% infill
• Printed in PLA

Printing notes:

• Printing at .1 will take ~30 minutes, printing at .2 will take ~15 minutes
  
  
• Use support to hold up the zipper tab, but make sure you don't generate support in the joint between the zipper mechanism and the zipper tab. That would make it harder to loosten. I have added a model with supports in case you don't have a slicer that lets you manage supports. 
  
  
• Use one outer wall and 100% infill to make sure the zipper tab is strong. It also helps to over-extrude a little bit, ~5% just to make sure it is all completely filled in and strong.
  
  
• Printing with ABS doesn't seem to work. The plastic is too soft and tends to bend when trying to zip, making the zip itself not hold. The only ones that worked for me were my PLA prints.
  
  
• This prints as one part. If the zipper tab is fused too hard to the zipper mechanism, be careful loosening it as it might break. It was designed with a .4mm gap on each side, but sometimes over extrusion or other things can cause issues.
  
  
• After you get it loose, wiggle it to smooth out the joint.
  
  
• If the zipper doesn't properly zip the teeth together, you can adjust the slider mechanism by lightly heating the top of it and bending both sides closer together. You don't need to adjust it too much, just enough that the teeth on your zipper can fit snugly through it.