This issue is a very common one for new 3D printer owners, but thankfully, it is also very easy to resolve! If your extruder is not extruding plastic at the beginning of your print, there are four possible causes. We will walk through each one below and explain what settings can be used to solve the problem.
1、Extruder was not primed before beginning the print
Most extruders have a bad habit of leaking plastic when they are sitting idle at a high temperature. The hot plastic inside the nozzle tends to ooze out of the tip, which creates a void inside the nozzle where the plastic has drained out. This idle oozing can occur at the beginning of a print when you are first preheating your extruder, and also at the end of the print while the extruder is slowly cooling. If your extruder has lost some plastic due to oozing, the next time you try to extrude, it is likely that it will take a few seconds before plastic starts to come out of the nozzle again. If you are trying to start a print after you nozzle has been oozing, you may notice the same delayed extrusion. To solve this issue, make sure that you prime your extruder right before beginning a print so that the nozzle is full of plastic and ready to extrude.According to the Loading Filaments section in your mostfunPro User Manual, reload the fliaments, and maker sure the extruder has a normal extrusion, then your extruder is ready to print.
2、Nozzle starts too close to the bed
If the nozzle is too close to the build table surface, there will not be enough room for plastic to come out of the extruder. The hole in the top of the nozzle is essentially blocked so that no plastic can escape. An easy way to recognize this issue is if the print does not extrude plastic for the first layer or two, but begins to extrude normally around the 3rd or 4th layers as the bed continues to lower along the Z-axis.When you find the first two layers can not be normally extruded, you should stop printing. When the extruder back to its original location, re-run the outo-leveling procedure as mostfunPro manual says. Make sure the machine is successfully leveling and you can start to print.
3、The extruder is clogged
If none of the above suggestions are able to resolve the issue, then it is likely that your extruder is clogged.Please see the Clogged Extruder section for instructions on how to fix this issue.