July 19, 2017
Our tech support department answers hundreds of emails a week, and we find ourselves repeatedly describing the following concept: that of what is necessary for filament to flow properly. It might seem basic to the experienced 3D printer user, but for beginners or those with high-end printers that do the hard work for them, the concept can be foreign. At its core it’s really pretty simple, and we are eager to pass along this knowledge to you.
The most important elements to understand this are temperature and speed. The printer’s hardware plays a part as well, but it’s secondary to and in support of the first two. We’ll go through these one at a time, but it’s important to know that the first two, speed and temperature, are interrelated, and have a special relationship. Changing one will affect the other.
There are hundreds, if not thousands, of options for 3D printing filament, and it seems like there are new colors, polymers, and composites coming out every week. In general, the pigments used to color filaments have higher melting temperatures than the plastic itself. So, the more pigment in the filament, the hotter the nozzle temperature needs to be to melt it. If you’re having trouble printing some new filament, don’t be quick to assume that filament is defective before trying different temperatures and speeds; most of the time this isn’t the case, and a little experimentation will produce successful prints.
Temperature is probably the most important setting for your 3D printer. If your bed temperature isn’t correct, you won’t get your part to stick to the bed. If your extrusion temperature isn’t correct, you can get jams, improper layer adhesion, oozing, stringing, weak parts, or other failures. Each filament has its own range of temperature at which it melts best. PLA is from 190-220°C, ABS is from 220-245°C, etc.
These are ranges for a reason. They’re not one specific temperature because each spool of filament is different (different manufacturers use different polymer blends and pigments for their filaments), and there is also a wide variance in printer hardware. The location of the thermistor on your hot end, in relation to the nozzle, as well as the type and accuracy of that component, the presence of any cooling fans, and the ambient temperature of the print environment can all have a significant effect on the actual temperature of the melt zone. Even spools of the same batch made by the same manufacturer have been known to vary slightly in their melt temperature from one spool to another. This can be a source of confusion when trying to print with a filament similar to one you just printed with, only to find out it needed a little more heat to melt nicely. It’s not necessarily a bad spool-- it just may need a slight temperature adjustment.
The middle of the temperature range is usually a safe place to start when trying a new filament. From there, you want to start a print and OBSERVE. Watch as the printer prints the first layer, and note how well the filament flows. It might take some time to get the hang of what a good flow looks like, but once you learn it you’ll never need to do so again. Pay attention to how malleable the filament is immediately after it exits the nozzle. Does it bend like butter, or is it like trying to force a piece of half-cooked spaghetti to lay down at a 90-degree angle? If the filament puts up a fight before it comes to rest on the bed, it’s probably not hot enough before being forced out of the nozzle.
Sometimes the filament will stop extruding altogether; this is a sure sign that the temperature is too low, or as you’ll read in the next section, the speed is too fast for printing at the given temperature. It’s not necessarily that the filament won’t print at that temperature, but if you’re trying to force the filament to flow before it has a chance to melt, a jam is likely to occur. In that case, you’ll need to adjust the...
The other important part of the flow formula is speed. Temperature can be set as high as possible for the filament you’re trying to print, but if the print is going too fast, then it’s still not going to flow properly.
The speed must be based off the nozzle temperature: the hotter the nozzle, the faster the speed can be. Conversely, the slower you want to print (say, for better-quality parts), the lower the temperature can be, though it’s not really necessary to lower the temperature if you lower the speed. If you print too slow with certain types of filament (PLA, for one) and the temperature is too high, the filament can carbonize inside the hot end and cause problems. But typically, printing at a high temperature at a slow speed isn’t a problem.
If printing fast is your goal, then you’ll want to increase the temperature as much as possible. Maximum speed can only be achieved when the temperature is as hot as it can be for the type of filament, but be careful; print too fast and you can sacrifice quality, no matter what the temperature is.
Other than speed and temperature settings, the supporting hardware is the other factor that contributes to getting a good melt.
The extruder, for one, affects how well-controlled the extrusion is. Poor retraction can contribute to jamming issues, and if the extruder isn’t doing its job properly, issues can occur.
The hot end can also certainly be a source of jamming. Sub-quality heat sinks can exacerbate heat creep and cause filament to stop flowing.
The collets that hold both sides of the Bowden tube, if present on the printer, are common fail points if melting is not optimal. If the speed and temperature are not balanced, resulting in a healthy flow, the pressure can build up over time, and if the Bowden tube is the weakest link, it can pop out of one of the collets holding the ends in place.
Other print settings can also affect the melt. One important factor to consider is how close the nozzle is from the bed on the first layer. Ideally, you’ve calibrated your printer so that it’s perfectly level and extruding properly. When you print, say, a 0.3mm first layer, it comes out a perfect 0.3mm when measured with a caliper.
If the print bed isn’t leveled and the nozzle is too close to the bed at certain spots, or the print is level but the nozzle is just too close, the pressure being put on the filament as it tries to flow out through the nozzle can be too much for the physical components. We’ve seen Bowden tubes pop out from their slots, ruining prints, because of this. MatterControl has Software Print Leveling, which is handy for making absolutely sure that the print bed is level.
Always start with a clean nozzle and extruder.
We hope this has been helpful to you. Let us know if you have questions or comments below.
Get The Latest From MatterHackers
Please enter a valid email.