This is part two. Here’s part one.

Before we start, let’s dispel any potential rumors that I’ve got it in for this yahoo. My reasons are, as I stated in part one, that I don’t like misinformation being used to push an agenda. I neglected to mention something else, which is that while math was honestly never my best subject at any point in my life, I absolutely love geometry. I may struggle a little bit these days to recall the formula for calculating the surface area of a sphere, but that’s only a recent phenomena for something I learned literally 20 years ago and only needed maybe once thereafter.

“you not think in volume terms”

You mean like you didn’t when you first offered your mathematical proofs? The calculations you gave were for the area of a two-dimensional cross-section of a piece of filament. If volume truly was your definitive proof of your initial claim, why not lead with that instead? Either you didn’t realize your initial maths disproved your claim or you knew but assumed I wouldn’t understand the implications for volume, which is rather condescending, like those little ad hoc explanations parents give to children when they question the logistics of Santa’s gift economy.

“and do casual counts”

What were you saying before about simple calculations?

“… ok .. try in other way … we suppose that the error is similar / equal … but the tolerance is distribute not only on diameter but also on length … same wire length extrude from 1mm of (2.85) require 2.7mm of (1.75)”

Okay, trying this other way isn’t going to really help your case. Between the scattershot delivery and slight drop in your ESL coherency from before, it’s obvious you’re more than a little flustered at this. I mean, I get it, I challenged your expertise, showed flaws in your interpretation of simple data, and now you don’t want to look like some kind of charlatan. Of course, no one would assume that; as you said, you’ve got personal experience to go along with your claim. While anecdotes aren’t empirical, it’s like I said in my last entry: If you’re getting good results from your setup, then have at it, Hoss. My issue is that you’re trying to tell me it’s because 2+2=5, with the 5 meaning the first 2 is five times worse than the second 2. Numerology has pretty low standards for validation to begin with, but this is almost comical. Adding another axis to your argument isn’t going to augment any sort of authoritative answer on the algorithm.

Anyway, I’m going to give you the benefit of the doubt and assume you meant 1 *centimeter* of 2.85mm and 2.7cm of 1.75mm since those are the units you use later when referring back to the same data. So, a 1cm tall cylinder (10mm) with a 2.85mm diameter is going to have a volume of 63.79mm³.

If we shrink that diameter down to 1.75mm but want to keep the 63.79mm³ volume, our height is now 26.52mm, so you’ve got that part of the proportion right (keyword: proportion). Before we go any further, let’s apply a 0.10mm tolerance to our stumpy tower. That gives us a new radius of 1.375mm (to get a 2.75mm diameter) and with that comes a new volume of 59.4mm³. The difference in these volumes is 4.39mm³, which is 6.881% of that total volume.

Going back to our 26.52mm tall tower, if we apply the 0.10mm tolerance to our diameter of 1.75mm, we get a radius of 0.825mm, which gives us a volume of 56.71mm³. Our difference is 2.69mm³. That is 4.53% of that total volume. You may say, “Case closed.” as it’s a lower percentage compared to our stumpy tower, but as we’ve established, that’s not being fair to the data because it ignores how proportions work (though we’ll get to this in a moment). 0.1mm is 5.7% of 1.75, but it’s 3.5% of 2.85. That’s where you would say then that 5.7% being almost twice 3.5% means 1.75mm is “twice as good” even though it means you’ve got more drastic deviations in the diameter compared to the 2.85mm.

It’s the same issue here. 0.1mm is not actually a ratio or a proportion (certainly not an exponent). It’s an absolute figure applied to two different numbers.

Take 1 away from 10 and you’ve got 9.

Take 1 away from 20, and you’ve got 19.

9 is not a factor of 19.

Now take 1 away from 10 and 2 away from 20.

Now you’ve got 9 and 18 respectively.

9 is a factor of 18.

This is because of proportions and ratios.

If the proportion is the same, it’s not going to make a difference. Even with your revised proportion you bring up later about the tolerance differences, you’re still showing at best a negligible difference between the two standards.

if suppose that the tolerance is long 2.7mm (for simplicity) on both filaments, and from 2.7mm (1.75) you have 1cm of wrong extrusion … then .. from (2.85) you have 2.7cm of wrong extrusion … What is the piece with best finish? … one with 1cm line error or one with 2.7cm line error.

I have to put my hands up here and admit this statement baffled me at first, and not just because you’re further losing your grasp on your own communication skills. Throwing out terms like “wrong” and “best” as qualifiers to the number doesn’t help as these don’t add to the empirical values of the numbers. It’s putting the cart before the horse… and then putting the horse on its back after smashing the cartwheels with a mallet.

What’s being described here is a pair of cylinders with tapering diameters… wait a minute, if the 2.85mm filament is 1cm tall as you already said, then how can it have 2.7cm of “wrong extrusion”? If it’s now 2.7cm tall, then how can the entire length be wrong? You’re comparing two cylinders of equal volume with different diameters, and now you’re changing the height of one without accounting for what that’s going to mean for the new volume.

I take it back; this statement is baffling all over again. I can maybe see what you’re trying to get me to visualize, but you’re playing fast and loose with cherry-picked dimensions for an unqualified hypothetical scenario. If both sizes of filament are going to be of equal length now (2.7cm/27mm) then we’ve got two radically different volumes. Furthermore, where do you get the 1cm (10mm) of tolerance? Why would it be 1cm for one and 2.7cm for the other? If they’re both the same length now why would the tolerance be the same vertical height for them? In fact, in the next “sentence” you say that only one will have 1cm of a differing diameter while the other will have 2.7cm. Are they the same or are they different? Is the tolerance a ratio or an absolute figure you’re applying to both volumes? If the tolerance is a proportion, then the error is evenly distributed. If the tolerance is an absolute figure, then there’s going to be a minor difference for the larger diameter compared to the smaller. The problem is that you’re treating it as the former in some cases and the latter in other. You’re just mixing up the data until you get something that could be vaguely mistaken for a proof positive for your case.

“The finish of 1.75 is 2.7 times better than 2.85 filament.”

Again, the quality of the finish is going to depend on the size of the nozzle, the layer height of the print, and the overall speed of the printing process. This factor of 2.7 you’ve come up with is based on a proportion you set up and promptly ignored in the very scenario you derived it from. It’s an utterly meaningless factor in the context of the equation and now using it as a marker for the quality of a finished product is equally meaningless.

and PS: typically 2.85 has 0.1 tolerance and 1.75 has 0.05 .. another big difference.

A big difference you ignored (forgot?) in your first set of mathematical proofs. You’re right, though, it is a very big difference. It’s such a big difference that it further shows how invalid and misinformed your claims are.

0.05 is half of 0.1, but 1.75 is not half of 2.85 (as that would be 3.5). Referring back to our 26.52mm tall tower of 1.75mm filament, with its volume of 63.79mm³, we’re now going to apply that tolerance of 0.05 to our diameter. A 1.70mm diameter now means a 0.85mm radius. That gives us a new volume of 60.2mm³. That’s a difference of 3.59mm³, or 5.63% of our total volume. Our stumpy tower doesn’t change from before because we’re still applying the 0.1mm tolerance to its 2.85mm diameter and getting a 6.881% difference. Now there’s only 1.251% difference between the two cylinders. Lastly and purely for giggles, if we apply the 0.05 tolerance to our stumpy tower, our radius of 1.4mm gives us a volume of 61.58mm³. Let’s lay out all our figures on a table and even add in some different heights for our cylinders.

but now sorry .. I not have time for these discussions, I’ll not do other reply, regards

(sigh) Look, I get it. You run multiple sites, including a YouTube channel, offering your opinion and insight into a disciplinary field you’re clearly invested in. You’ve got credibility to think about; if people don’t think you’re on the level, there’s no shortage of other places to go for more information on a topic. It doesn’t help that this is such a relatively young field (as far as us hobbyist/prosumer/startup/semi-pro/maker/what-have-you’s are concerned) and there’s so many factors to consider that it’s easy to miss the forest for all the trees. However, it doesn’t help anyone to double down on fallacious claims backed up by misreading data and flip-flopping between subjective aesthetic judgments and objective truth claims.