I have Prusa i3 derivative with MK8 extruder and Marlin 1.1RC8 as firmware. I already reduced the default speeds as well as the accelerations. But sometimes when trying to print with BQ PLA filament (220°C), mostly during filling areas, my extruder clicks. The below screenshot of Slic3rs Layers view shows the clicking "lines".
What settings I need to change to avoid the overextrusion in this case?
Extruder 'clicking' is an audible indicator that the teeth on the hobbed gear are slipping... determining if this is a symptom or a problem is where things get tricky.
Not so sure about adjusting feed rate - as this will impact the entire print and may introduce other problems. Measuring the dimensions of a sample print with a set of calipers is a good way of identifying over/under extrusion.
General maintenance items perhaps?
Thermistor: Nozzle temperature measurement is dependent upon the precision of the thermistor and how well it is attached... 5% drift at 220 degrees may be as low as 210 degrees or as high as 230 degrees. Use a thermocouple on a multimeter, non-contact probe, etc. to verify your nozzle temperature.
Temperature: Nozzle temperature 'sag' of +/- 5 degrees is normal. Monitor nozzle temperature during a print to see if it stays within this range (see: Speed below).
Speed: Printing fast is awesome... when you have a hotend that can keep-up with the demands of melting incoming filament. Too fast, and the filament may not be properly melted; increasing the pressure needed to force it through the nozzle. Support material and infill typically print faster than the rest of the model - you mentioned hearing clicks "...mostly during filling areas."
Alignment: Make sure the hobbed gear, idler bearing, and filament are properly aligned. Filament that wanders around in the feed path is much more likely to slip and/or buckle.
Teeth: Make sure that the teeth of the hobbed gear are clean and clear of debris. 'Gunk' in hobbed gear teeth reduce grip on the filament.
Tension: Increase the tension between the hobbed gear and idler bearing if possible; worn hobbed gears may need a little extra help holding-on to the filament.
Stepper: Heat generated by the stepper motor can be passed down to the hobbed gear... softening the filament and causing it to slip. Stepper quality, capacity, and duty cycle can greatly effect how much heat is generated; 200+ degrees is entirely possible. Passive cooling (heatsink) is a good idea, active cooling (fan) is better.
A loose heat-break, nicks in the filament path, variations in filament width, etc. are all possibilities as well.
Also, Simplify3D created a great reference for solutions to common 3D printing problems (if you haven't seen it already).
https://www.simplify3d.com/support/print-quality-troubleshooting/
Try reducing to just two perimeters, and let that blue area be calculated as infill. This may give you a zig-zag infill instead of a straight, oversized bead.
The only time that I've observed clicking from the extruder on my Anet-A8 is on the first layers when I have the head height set too low - the nozzle is unable to extrude at a high enough rate to allow the filament to progress as requested.
If you have a somewhat repeatable scenario, you could try reducing the filament feed rate to 90% or so, and see what effect that has. I have already observed with one of my reels of filament that 90% feed rate gives me a less over-filled solid area, so maybe the default feed rates are a little on the high side (or this filament is of excessive diameter).
I've tried to reduce the "Extrusion multiplier" from 1 to 0.95, but that caused gaps. Now I've minimized the clicking by setting the Slic3r option "Infill before perimeters" on the "Print Settings > Infill" page.
One trap I've seen that causes the extruder to click, and over or underextrude is that the extruder control is in the wrong mode.
The extruder can be set into relative or absolute mode. If absolute extrusion values are sent while in relative mode, then the system will be trying to push more through than the nozzle or hot end can handle. You'll get blobs, clicking, ooze and it will damage the extruder and hot end.
Have a look at the G-code - and see what the "E" numbers look like - it they look relative (the same or close numbers repeatedly) or absolute (numbers slowly incrementing). Cura defaults to absolute - but initially was NOT sending the G-code to put my controller into absolute extruder positioning.
Note also - this is separate from the XYZ absolute/relative positioning modes.
M82 will put the extruder in absolute mode.M83 will put it back into relative mode.
I had this issue and it turned out to be the extruder cog rubbing on the inside of the hole in the heatsink, causing the stepper to slip.
