![]() ![]() using this thing: [ or measuring by how much your walls tend to get to big).Ģ. Calculate and/or measure the increase of width due to these lobes (e.g. Instead, compensate for it from the beginning:ġ. So don't try to get rid of them by changing some arbitrary value such as flow rate, which controls much more important values, too. And these lobes will be bigger, the bigger you layer height gets. Though it is to be noted that dimensions were out of whack (probe height and width increased by ~ 0.2 mm).Įasy: Accept the fact that there WILL be lobes attached to the outer edges of your print. I can only guess that this is due to squeezing that extra bit of filament into the corners of the printed perimeters, leading to increased stiffness overall. ![]() Interestingly, with 110% flow rate, there was a significantly bigger E-modulus (increase to 120% to 140%). Also, the E-modulus was higher for the force being applied perpendicular on the printed surface. Naturally, these values are not reachable by a long shot.īut still: From 100% flow rate to 80% flow rate there is a significant dip in the stiffness, which by value is close to the actual flow rate (i.e. To show the impact more clearly, I decided to mock up a Three Point Flexural Test ( and for calculation of E-Modulus ).ītw: The base stiffness of PLA is reported to be 3.5 GPa ( see here). two areas will only touch each other at the most outer regions of those lobes. The impact of lowering the flow rate can be imagined by looking at the picture above: You are not putting one printed rectangle area to the next one, you are starting to put one rectangle with two lobes to the next one. Showing the impact of lowering the flow rate on the effective E-modulus (i.e. For my own printer (Folger Tech Kossel 2020), this was spot on.ģ. Please tell me how close I am to your actual results. Again, for 0.40 mm extrusion width and 0.20 mm layer height: b / bT = 91%. If you start to change your flow rate to match the measured width to the width set in software, you will end up with a value which should be close to tha calculation of b/bT. To give numbers: With 0.40 mm extrusion width and 0.20 mm layer height set in software, you should expect a single wall perimeter thickness of 0.44 mm. The result shows that bT will always be a little bit bigger than the slicer software thinks - approximately 22% the layer height is added. bc is calculated by rearranging the calculation of the area, which comprises both the reduced rectangle area (bc * h) and the two semicircles (pi * (h/2)^2). In reality, the actual width will be bT (T for total), which is comprised of a reduced width bc (c for circles) and two times the radius of the semicircles, which happens to be the layer height h, so bT = bc + h. The slicer software will extrude as much filament to fill up the area A = b * h of the rectangle (extrusion width b, layer height h). Let's assume these lobes are perfect semicircles (picture right hand side). In reality, you will print a rectangle with two lobes attached to both edges. But for a single perimeter wall this is not the case. to the left and to the right there are also perimeters printed. This would (approximately) be true if that perimeter was printed inside already existing perimeters, i.e. When printing a perimeter, the slicer software thinks you are printing a perfect rectangle with height h and width b (picture left hand side). Calculating the wall thickness in single wall printing Calculating the wall thickness in single wall printing.ģ. In the following, I will first show why (sections 1-3) and then give you advice on what to do instead.ġ. It seems quite common in FDM 3D printing to calibrate single perimeter wall thickness by adapting the flow rate (extrusion multiplier), e.g. Hey! I am not 100% on whether something like this has been discussed already, but I didn't find anything comparable.
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