So not too long ago, a fellow 3d printer friend and I got into a discussion about calibration methods - specifically the feed & filament calibrations. I use one method, he uses another. He argued that it really doesn't matter what method you use (although, he insists that the method he uses is better because it is posted in the reprap wiki pages), the end results are what matters, and to a point, a can agree with that. My argument is that accuracy in the calibrations does matter.
The specific points of contention have to do with the feed rate and extrusion multipliers. The method of calibration he uses says to "get close to" feeding a specified amount of material, never touch the extrusion multiplier and fudge away any inconsistencies by adjusting the flow rate. The method I use says get the feed rate as close to exact as possible, adjust the extrusion multiplier to create the desired single wall thickness and there should be no need to mess with the flow rate. Since this discussion I remembered reading a forum post about the math involved in slicing a model for printing, and the calculations that the program must make in order to produce a recognizable object. The math backs me up. For those that are interested, the method my friend uses is Triffid Hunter's calibration guide. My method is outlined in my filament calibration posts found on this blog. The forum post that discusses the calculations of a slicer can be found here. You should read them and decide for yourself... ~~~~~~~~~~~~~~~ Time to go melt some plastic! All 3D printers and all hotends are not created equal.
We currently have four different 3D printers. Each one will run the exact same filament at a different temperature. One spool of filament - lets say white PLA, on each machine will print best at a completely different temperature on each machine. Machine 1 has an older hotend with the thermistor taped to the outside of the nozzle. Reported printing temp on this machine for the white PLA is around 165C Machine 2 has a generic J-head hotend with the thermistor installed in the heatblock. This one reports the printing temp of the same white PLA at 200C - 35 degrees more than the first machine. Machine 3 has an E3D lite6 hotend. Reported printing temp on this one, same filament, is about 215C - 15 degrees more than machine 2, and 50 degrees more than machine 1. Machine 4 has a full E3D v6. It and machine 3 are very close in temperatures (+/- a degree or 2 at most) because they share the same basic design. Fifty degrees difference from one end of the spectrum to the other, all with the exact same filament. So, when you enter the world of 3D printing, you need to be aware that there are no carved in stone rules about temperature. You have to find the temp that works best for your printer and hotend. Asking someone else what temperature they run a given filament at is, at best, a gamble. You might get lucky and they have the same type of hotend that you do and their temp range works for you, or, you may have complete and utter failure. ~~~~~~~~~~~~~~~~~~~~~ Time to go melt some plastic! So lately I have been seeing posts in Facebook groups of new folks trying to use layer heights that are too large, and some other common issues. There seems to be some misinformation floating around about these things and I would like to take this opportunity to hopefully clear them up
Knowing what size nozzle your printer has is very important. It is the nozzle diameter that several slicing settings are based on. Most 3D printers on the market today are using a 0.4mm nozzle size - it is a nice compromise between flow and detail. There may be a few out there that use slightly larger, or smaller diameters, so make sure you know what you have. Or, you may have an aftermarket hotend installed with a different nozzle diameter - again, knowing what you are using is a big factor in getting good prints. So, what are the settings that are affected by nozzle diameter?
For those that are interested, there is some great info posted over at soliforum.com about the math that slicing programs use (the write-up is based on Slic3r, but other slicing programs will have similar calculations): http://www.soliforum.com/topic/9551/soliprint-v11/page/2/ (look for the post by jagowilson about 1/3rd of the way down the page). Setting bed level is also critical to getting good prints. I see a lot of people wanting information about "auto-leveling" setups - which is the best one? The answer to that question is: The best "auto-leveling" system is the one that isn't needed. If you take the time to properly set up your printer (ie. calibration, calibration, calibration) then you should not have any need of "auto-leveling". Taking the time to do things right early on will save time in the long run. I rarely need to touch bed level on my favorite printer, even if I get a little impatient and pull parts off while the bed is still warm (very often seconds after they complete) the bed stays where it is set and I can turn the heater back on, load a new model, slice and print again within moments. Running an auto-level script for every print adds several minutes to print time, and frequently is not very accurate. In fact, I did away with the auto-leveling inductive sensor that came with my kossel kit. It was problematic from the start, and after adding the mirror tile (my typical print surface) to the bed surface, it became completely useless since it requires close proximity to metal to operate. Calibration of the effector is the critical component on a delta/kossel printer. Yes, it takes time and a lot of patience to do it right, but it is worth every second once it is dialed in correctly. |
AuthorA "Jack of all trades, master of none", I have dabbled in a lot of different things, but none have held my interest like these darn 3d printers do. Archives
May 2016
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