Extrusion Width - Auto: All it does it take your nozzle setting and multiply that by 1.2. Nothing magic here. For best print results, it is often recommended that your extrusion width be at least 1.2 times your nozzle width. This sets the width of the plastic printed for your model to be 0.48 mm for a 0.40 mm nozzle, sets it at 0.60 mm for a 0.50 mm nozzle, at 1.20 mm for a 1.00 mm nozzle, etc. So that's what this setting does. It doesn't affect anything other than the width of the plastic lines the printer extrudes.
Extrusion Width - Manual: This is the settings I always use. I never use Auto. I almost always use either 0.50 mm or 1.00 mm, depending on what I'm printing. I like numbers that easily divide by 1 or 0.5 and so I design my models that way. You get best results normally when your model's dimensions line up well with your printer's dimensions. For example, if I design a wall that's exactly 1 mm thick, this will print well with an extrusion with of 0.5 mm, but won't print well with an extrusion width of 0.48 mm, because you can't evenly divide 1 by 0.48, there will be a remainder, and than remainder will be difficult to print.
Extrusion Width is just like Layer Height, only it deals with width and not height. Extrusion Width only tells the printer how wide to make lines. It doesn't affect anything else except print speed. A wider line means more plastic per mm, so you'll need to lower your print speed. For example, if you double your width, you need to half your print speed, because twice as much plastic is printed per mm. The Extrusion Width should always be at least 1.2 times larger value than Layer Height. At slicing time Simplify3D will warn you if it's not at least 1.2 times larger. The reason for this is that the plastic will adhere better if lines are printed so that they are wider than they are tall. If the width and height are equal, then the amount of space that touches between each layer is too small, and results in very poor prints. By making the width bigger than the height, the lines are smashed together more, so they adhere better.
Extrusion Width should not be confused with Extrusion Multiplier, Nozzle Diameter, or Filament Diameter, because those affect how much plastic to extrude, and shouldn't be used to change the width of your print line. Any adjustments made to those can dramatically screw up your print. Only adjust those when you're having problems with prints not extruding properly. For example, if too much plastic is extruded and walls are overlapping, or not enough plastic is extruded and walls have gaps between them, that's when you start playing with these other adjustments. Don't use these to make your print lines thicker. That's not what they are for. They control how much plastic is printed per mm according to your Extrusion Width and Layer Height settings, not how wide or high to print your line. Only Extrusion Width tells the software how wide to print your lines. Only Layer Height settings tell the software how high to print each line.
It's true that adjustments made to Extrusion Multiplier, Nozzle Diameter, and Filament Diameter end up producing the same results, either more or less plastic being extruded per mm. They are different ways to tell the software how to adjust how much plastic to extrude, that's all. These affect the width of the line being printed, but DO NOT affect the horizontal spacing between the center of each extruded line. If you make a line very thick using these settings, then lines will overlap each other horizontally because the space between the center of each line doesn't increase when you adjust these, only the width increases, causing overlaps if too thick. Extrusion Width and Layer Height don't work like that. Extrusion Width tells the printer to print lines with X amount of distance between the center of each line horizontally, and Layer Height tells the printer to print lines with X amount of distance between the center of each line vertically. Width and height are automatically adjusted so lines touch each other, normally. If they don't touch properly then you need to adjust Extrusion Multiplier, Nozzle Diameter, and Filament Diameter.
To clarify that further, think of Extrusion Width and Layer Height as the print RESOLUTION. If you want higher resolution, you use smaller values for these. If you want lower resolution, you use higher values for these. Don't use these to fix extrusion issues. They are for changing print resolution only.
If lines are printed so thin that there's a gap when their shouldn't be, adjusting either Extrusion Width or Layer Height will NOT fix the problem. For example, if you have a 20% gap between walls that should be solid without a gap, and you make your Extrusion Width larger, your gap will still be 20%, but will now be a larger gap because the lines are now larger and further apart from each other (the print resolution is lower). You didn't get rid of the gap, you just enlarged the lines, and the line spacing, so the 20% gap appears wider, but is still there at 20%.
Likewise, If lines are printed too thick and are overlapping each other, adjusting either Extrusion Width or Layer Height will NOT fix the problem. For example, if you have a 20% overlap between walls, and you make your Extrusion Width smaller, your overlap will still be 20%, but will now be a smaller overlap because your lines are now smaller and closer together (the print resolution is higher). You didn't get rid of the overlap, you just shrunk the lines, and the line spacing, so the 20% overlap appears thinner, but is still there at 20%.
You adjust Extrusion Multiplier, Nozzle Diameter, and Filament Diameter when you need to address gaps or overlaps in printed lines. For ease of adjustment, Nozzle Diameter, and Filament Diameter should match your real nozzle and real filament diameter. Only change Nozzle Diameter to match the actual nozzle diameter in use. Don't use other values. Likewise, only change Filament Diameter to match the actual filament diameter in use. In most cases you'll keep the value of Nozzle Diameter the same unless you change to a different nozzle size. It's possible, that over time, your nozzle diameter can increase from use. That's the only time you might want to change the Nozzle Diameter value if you haven't changed nozzles. Filament Diameter can change from spool to spool. Some spools, although stated at 1.75mm, can be thicker or thinner than stated. In such cases, changing the Filament Diameter to match the current spool's real filament diameter is necessary to get good print results. This setting should NEVER be off from the actual filament diameter in use. If it is off, it will throw off extruder calculations. Extrusion Multiplier is the best setting to alter if the other two already match what's in use but prints still have either lines that overlap or lines with gaps.
Put another way, Extrusion Width and Layer Height adjust print resolution. Extrusion Multiplier, Nozzle Diameter, and Filament Diameter adjust print extrusion ratios according to print resolution, but have no effect on print resolution. The Extrusion Multiplier setting in particular is similar to an inkjet paper printer's ink level setting. On an inkjet printer if you set the ink level higher, the print darkens and the dots in the print start to bleed into each other because more ink is used per dot; if set lower, the print lightens because less ink is used per dot. The ink level doesn't effect the print resolution though. The Extrusion Multiplier is used like that, for fine tuning how much plastic is used per line, while not affecting print resolution per line.
Last edited by BaronWilliams
on Sun Mar 08, 2015 3:40 pm, edited 2 times in total.