Now that we have the filament diameter and feed rates calibrated, we need to calibrate for flow. Again, too much or too little will affect print quality and accuracy.
Flow rate (how much plastic is coming out?)
We will be printing a single wall test cube, but only about 8-10mm high. We don’t need to do the whole cube. There are a multitude of test cubes on thingiverse, and other sites, the size doesn’t really matter much - a basic 20mm x 20mm cube will work fine, it is the settings that matter here.
In Slic3r, under the Filament Settings tab, set the extrusion multiplier to 1
In the Print Settings tab of Slic3r, in the Layers and perimeters section, we want to set layer height to 0.3, we want a single perimeter, 0 top layers, and 2 bottom layers
For Infill, we need to set it to zero
And lastly, in the Advanced section, we need to set the default extrusion width. This typically should be 120% of the actual nozzle diameter. For a 0.4 nozzle it will be 0.48; for a 0.35 nozzle, it would be 0.42, and so on. My printers all currently run 0.4 nozzles.
I like to set the first layer to 100%, but you can set it to more for better adhesion if you like.
Make sure you save your settings!
Print one copy of your test cube, approx 8-10mm tall (roughly 25 layers) - it should look something like this when done.
Get out your calipers and measure each wall of the cube after it has completely cooled (if it is still warm you could deform the plastic when measuring and not get accurate readings), near the center of the wall. Try to grab only the top 1 or 2 layers of each side as shown below.
Make a note of each measurement and take an average of the wall thickness.
The number we are looking for here is the same number as our default extrusion width - in this case 0.48.
More than likely, your first run will be larger than this, so we will need to make an adjustment to the extrusion multiplier to correct it.
The math is simple: desired measurement / actual measurement = extrusion multiplier
Say our wall thickness averaged out to 0.5075, our math would be 0.48 / 0.5075 = 0.9458...
So we want to enter 0.94 in our extrusion multiplier box (i have found that rounding down usually works better than rounding up and 2 decimal places is usually sufficient, 3 if you are having difficulty getting it to come out right).
Don’t forget to save your changes!
Re-slice your test cube with the new settings and print another test box and measure the walls again. You should be pretty close to the desired 0.48 wall thickness. If not, you can tweak the extrusion multiplier by hundredths up (if too small) or down (if too big) until you get the desired wall thickness
Now you are ready to print amazing projects!
Keep in mind, this will need to be done for every roll of filament you use - every roll will be slightly different - even 2 rolls of the same color, from the same vendor, will be different.
Slic3r is great because you can save the filament profile for each roll/color you have. It makes switching materials as easy as selecting the correct profile before slicing your model.
Yes, I really have that many profiles saved, LOL.
Once you get the hang of doing these calibrations, you can accomplish them in about 15 minutes, and it really does make a difference in how your prints will turn out.
Next time we will explore making changes to our slicing profiles to get good infill in small areas.
Time to go melt some plastic!