Update printhead.md

docs/hardware/printhead.md

@@ -330,6 +330,13 @@ The main difference here (from a hardware perspective) is that at the the **Go**
     If you can't load new filament, first of all check if you pulled the lever on the feeder gear.
     If you did so and were able to insert the filament but it seems that it's getting stuck lower down in the hotend, then you might hit the end of the nozzle with an edge of your filament. It helps when you cut the filament in a 45° angle and bend the part you're manually feeding into the hotend so that it's pretty straight.  
     If you still can't get your filament loaded, it's most likely that the PTFE tube inside of the hotend is clogged or deformed or that you have a clog in or above the nozzle somewhere. To clean, inspect and maintain it, you need to disassemble the hotend. Check the section ["Disassembling The Hotend"](#disassembling-the-hotend) further down below for more information.   
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+??? tip "Feeder Gear Pressure"
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+    When adjusting the pressure of the feeder gear, make sure you don't tighten it up too much as it could squeeze and deform the filament. On the other hand it shouldn't be too loose though as it should transport the filament reliably.  
+    When pulling out the filament of the extruder system, you should notice little dents on the surface of the filament from the teeth of the feeder gear, the filament itself shouldn't be squeezed and deformed though, it should still be "round" so to say. You don't want the feeder gear to "bite" too much into the filament as well though, as this may lead to inconsistentites of the filament flow. I personally like to extrude a bit so that the gear actually has to pull it in. Then I do a cold pull and check the marks of the gear on the filament itself. If you can see and feel little marks of the teeth of the gear on the surface of the filament, then it should be ok. If you don't feel and see any marks, then it's too loose. PLA is pretty hard, so the pressure can/should be a bit higher as well, but if the marks are pretty deep, then it already might be too much. If the filament is already a bit squeezed and kinda flat, then it's definitely way too much pressure (you'll most likely experience some weird artefacts, inconcisties and patterns at your prints as well then). 
+    The filament should be fed reliably, which especially comes into account while retracting. So keep an eye on the shaft of the motor by looking at the back of the motor - if you notice that it's slipping while retracting, you definitely need to increase the tension.  
+    As a rule of thumb you can keep in mind that the pressure should be higher when using hard filament like PLA and lower when using soft filament like TPU.    
 
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