Retraction Jamming Problem! Recently I had this problem where I needed to change filament from PLA to PET-G or similar. And... filament jam. After playing around with different settings and speeds and still getting the same results I had to clean everything. And again during a print, it jammed.

I brought a new nozzle, heating cartage, Teflon (PTFE) tube and some additional components(fans, new wires and so on) but still was the same. Now I'm waiting for a new set of hotend Mk8Design Needed kit. 

A week after the order and still waiting, I played with retraction a little. By default, it was set to 0.8&nbsp;mm on Sli3er but I had set it to 4-6&nbsp;mm because it gives the best results and no stringing. I changed it again to 1.5-2&nbsp;mm and... no more jamming at the cost of getting stringing. I'm using PLA which I never had experienced strings before.

So, in summary, the problem occurs due my retraction setting. Either I have to live with strings and no jam problems or no strings but jamming problems during printing.

Have someone had same problem as me? How did you fixed it? 


Printer AlfaWise U30(bowden type) but it's no longer the same. 
Motherboard: MKS 1.4 Gen A4988 + DRV8825 Stepper drivers(no problems here)
PID(Autotune), Calibrations and so on done correctly.
Firmware latest marlin 1.1.9 (Tried bugfix but the same)
Sofware for slicing PE Sli3er (Tried Ultimaker Cura with same model and same problem)
I had problems with jamming PETG due to retraction.  My model had many retraction moves, such that the amount of filament used during a printing move was less than the retraction distance.  I found that several trips through the feed gear flattened the filament, which caused two problems.  


The flattened (or ovaled) filament had trouble fitting through the round holes and tubes, and
Since it was thinner, the filament was not gripped as tightly so there was less force pushing it.


I reduced my feed gear pressure and the problem stopped.

PETG is not as stiff as PLA.  The multiple trips through mangle flattened it.