Extrusion multiplier and weight of final part

[drummerdimitri]

So I've been wondering if it was good practice to increase/decrease the extrusion multiplier until the final printed part weighs as much as what the software expects it to weigh since I have no other way of "calibrating" how much plastic my nozzle lays down.

[darKing]

Why not take a look at the part and then decide if it's good or not?

[wirlybird]

Have you tried weighing a part to see if it is even close the the slicers estimate, which is what it is, an estimate?
The amount of filament used is a calculation so I imagine if you change the extrusion multiplier the calculation could change.

It might be workable but I think the value given by the slicer is not accurate enough. Consider the estimated time. It isn't even close sometimes!!

[joaojoao]

first of all, we have to be aware that we are working with microns..the tolerances used by a simple caliper average measure of the filament used, for example, won´t be accurate enought to properly calibrate the extrusion multiplier..and our printers (99% of all) don´t have all variables covered by the correct type of tolerances..so..
It´s a go point of view, but you do need at least a weighting process with a specific tolerance range, with a small margin of error..and thats it´s for your printer only..

[darKing]

Have you tried weighing a part to see if it is even close the the slicers estimate, which is what it is, an estimate?
The amount of filament used is a calculation so I imagine if you change the extrusion multiplier the calculation could change.

It might be workable but I think the value given by the slicer is not accurate enough. Consider the estimated time. It isn't even close sometimes!!

You'd also have to setup the density of the filament and sometimes you don't have these numbers. But I consider the weight still more accurate than the time (for obv. reasons).

Still I don't get it why someone would want to tune the extrusion rate by weight. What's the point?

[dkightley]

Let's do a test to see if the OP's theory holds water.....

Run 1
EM = 0.99
Est Wt of prod = 14.65gm

Run 2
EM = 1.09
Est Wt of prod = 16,13gm

Run 1
EM = 1.19
Est Wt of prod = 17.6gm

So....changing the Extrusion Multiplier changes the estimated weight by exactly the same multiple...and hence...

So I've been wondering if it was good practice to increase/decrease the extrusion multiplier until the final printed part weighs as much as what the software expects it to weigh

..is not going to happen!

So let's look at the real problem here....

......since I have no other way of "calibrating" how much plastic my nozzle lays down.

Q - What do we want to calibrate?
A - The amount of plastic being extruded.

Q - What changes if the amount of plastic changes?
A - The weight of the product....but also something else that can very easily be measured - the width of a single extrusion.

So....why not print a test cube with no infill and a single perimeter and measure the width of the wall. If it matches the extrusion width setting, then all is okay. If it doesn't then adjust the extrusion multiplier up or down and repeat the test print until you get the right width. Your extruder is calibrated......

[joaojoao]

of course the estimated weight by S3D varies when changing the extrusion multiplier..we want to calibrate using the weight, so we set the extrusion multiplier to, lets say 1.0, then we compare the estimated weight with the real weight, and then we ADJUST the extrusion multiplier for real, not looking again to the estimated weight by S3D..

It could be a way to go..since filaments diameter varies along the filament lenght..and instead of printing calibration cubes time to time, using a precision balance can save time..and who know, could be more accurate?

[darKing]

Well, considering that an extrusion Ratio of 1 isn't always the right amount (over / underextrusion), that density and weight differs depending on Filaments... it seems like a pretty strange Idea... especially if precision is what you want to achive. If you want to achive a 90 / 60 / 90 body it's very unlikely to only watch your weight.