Calibration for "Perfect" filament adjustment?

[MarkG]

The following is a somewhat long question, but I would be very interested in any replies, and as usual, it would help my understanding of the 3-D printing controls, and possible assist in troubleshooting the whole machine.

So, I am beginning this post through an intersection of observation and frustration at 3-D printing materials. There are many variables we all play with while trying to get our printing ‘Dialed-in,” and the temperature for different materials is one of the key variables. PLA, for example, works from 210 all the way to 245 degrees on my M2.

However, if the machine is calibrated and working well for some prints, it’s sometimes hard to find the right settings for a different roll of filament. This could be based upon material type, manufacturer, color and even the date of production. Measuring the filament diameter several places can help, but usually I have to use trial and error to see if adjusting the temp or extrusion multiplier results in a better print. I do this not by measuring something, but by printing a test print and either looking at it while printing or looking at the resulting print. I look at the bonding to the plate, and bonding between layers, and then the overall quality, if there are “zits” or stringing, or other artifacts. Sometimes, my machine is not working well, and I play with settings to get good prints due to slight clogging or even a poor thermister reading. After all, Joe suggests a print temp of 230 for the exact material I’m printing, but I have no way of knowing if it’s the same temp of my machine, due to the lack of thermister calibration. I regularly get a 10 degree difference between two V3b MH hot ends, on the same filament!

So, what if there was a way to have the printer extrude a test piece, and somehow measure it to determine how close it is to an exemplar, i.e. a perfect extrusion? I had been trying to get good settings for printing a PET product, and noticed that when I selected a 100mm extrusion from the tool window, it extruded only a short amount of filament, about 20 inches. I seemed to remember that PLA resulted in a much longer thread. I tried different temps and measured the results. (Below)
PLA:
Temp Thickness Length Mass

210 0.545 42 22.89
220 0.51 45 22.95
230 0.48 50 24
240 0.44 54 23.76

There is definitely a linear relationship in the thread extruded for PLA, and I am assuming that the extrusion motor is providing the exact same input each time. It also looks like there is conservation of mass, because the length times width of the data remains similar.

It got me wondering if, for a new material, I could actually “Sample” a material at one temp, measure the result, and then adjust temp (or other variables) to get my perfect setting! After all, the machine control does not know what material I have in the machine, the G-code is established based upon providing material at the nozzle at a specific location, and the machine controls the x, y, and z motors, and the extrusion motor. The extruder control calculations are based upon an assumption that if the extruder motor turns WW degrees, then LL amount of liquid material is deposited per second. Thus, even though PLA and ABS and PET and Nylon have different viscosity and materials properties when melted, the basic control principles are the same. Other variables such as retraction speed, distance and coast can help to clean up a print, but the machine control has to be basically the same for all materials: If I want an extrusion width and height of XX, the motor turns XX speed.

So, if that is true, shouldn’t there be a “Perfect” extrusion width and length for a sample 100mm extrusion request? And, further, if that is so, should I enter the physical measure of the filament, and then try to control my temperature to get a particular length of thread?

I would be eternally grateful for the observations, comments or answers to the above, Thanks.

Mark Gordon

[Capt. John]

Extrusion rate can depend on how consistent the diameter of the filament is and the size
of the particulate coloring the filament. Big time issues when you try to print glow.

While this is off topic, Seen a pinion gear in the extruder only has a few teeth in contact with filament.
Seen a drive gear that is semi dished out with a grove for the filament
where more teeth area grabs the filament that looks like a heck of a good idea.

Perfect in 3D printing is probably a few years down the road.

[MarkG]

As you say, extrusion rate can depend upon the filament diameter and other considerations. However, are we not all trying to get a specific rate of liquid filament coming out of the nozzle? If not, how can the machine control system expect to deposit the correct amount, per second of travel?

Independent of some settings that control the way that different filaments behave based upon viscosity (Retraction distance, speed, coast, start up) when the machine is STOPPING and STARTING extrusion. However, settings such as temp and thickness control how much material is actually extruding through the nozzle. The machine must ASSUME a specific amount, and if we could directly measure the amount in terms of something like length, diameter or number of seconds to extrude 100mm, we could actually calibrate materials instead of guessing (trial and error).


.. or at least it's an approach.

[Levi8than]

if we could directly measure the amount in terms of something like length, diameter or number of seconds to extrude 100mm, we could actually calibrate materials instead of guessing (trial and error).
.. or at least it's an approach.

I don't think the color/etc of the material affects flow rate, but the diameter of the filament sure does. Make sure you are measuring it yourself and not trusting the manufacturer. And the color/etc affects expansion/contraction, which absolutely affects flow rate since it expands in the nozzle and then may stay expanded when it cools (microscopic air/water bubbles remain I'm guessing). My natural pla roll measures almost exactly 1.75 mm diameter spot on, and extrudes like a dream, bridging better than any of my other rolls. It makes perfect prints. I set s3d's slicer to a .9 extrusion multiplier with the diameter pegged at 1.75mm, printing around 215C.

While of all of my colors, green is by far the worst. The filament measures closer to 1.68mm, and contracts as it cools, sometimes leaving little holes in the finish on the design. I find a get best results with the filament diameter set at 1.68, and the extrusion multiplier closer to 0.96. But even with these settings and a slightly cooler print head temp, this stuff still can't bridge worth anything.

Same brand, supposed to be the same stuff. Just colors are an additive and affect things. I don't know of a scientific approach that would really work except for tinkering with the settings until you find what works. A bunch of test prints with different settings sounds best to me.