All of this information is provided AS IS, with no warranty or guarantee of accuracy. A good-faith effort has been made to ensure this document was accurate at the time it was written, but YOU ASSUME ALL RISK BY FOLLOWING ANY ADVICE BELOW.
Nylon is a strong and impact-resistant thermoplastic that is used weed-trimmer line. With the proper printer settings, some of these weed-trimmer lines can be directly used as a 3D printer filament, often with surprisingly good results.
Additionally, these filaments come in several colors and are generally less expensive and easier to obtain than 3D-printing-specific nylon filaments, easily less expensive than PLA.
This document is an attempt to summarize the various tidbits of information I have discovered when printing with trimmer line. Some of the advice also apply to 3D-printer-specific nylons.
Trimmer line in amounts less than a kilogram rarely come on spools. Instead, they often come in clamshells designed to have the line pulled from the center of the container. Don't try to feed this directly into your printer, or an epic tangle will result!
In order to print with the trimmer line, you will need to either re-spool the filament onto a spare spool (which takes forever and can cause epic tangles if you aren't careful), or print out a spool specifically intended for this purpose and place the bundle on the spool without rewinding. The later approach is preferred.
If you are buying one of the larger spools, know that they are not the standard sized 3D printing spools: they won't fit in a typical filament desiccator like the one from Sunlu. You'll either need to make a custom one, or use an oven.
If you are using a 1.75mm-based printer, the closest standard diameter for trimmer line seems to be 0.065" (~1.65mm). To account for this, you will need an extrusion factor around 112% (1.65mm).
The equation to calculate the extrusion factor is:
100 * 1.75^2 / diameter^2
Here is a quick table describing the extrusion factors for given diameters:
| Diameter | Factor |
|---|---|
| 1.75 | 100% |
| 1.70 | 106% |
| 1.67 | 110% |
| 1.65 | 112% |
| 1.62 | 117% |
| 1.60 | 120% |
A heated bed plus glue stick (or even dried elmers glue) seems to work best. For the first layer, using a true 80°C surface temperature on the bed seems to work well. The surface temperature on the bed can be dropped to 70°C or 60°C after the first layer.
Warping is a problem, especially with the harder nylons. I've found nylons to warp more than ABS. Without a warm enclosure, parts can start to peel off of the build plate after 4mm or so, starting at corners. A brim can help prevent warping a little, but for larger parts an enclosure is really needed. With the softer nylons, I've had no trouble printing smaller parts without an enclosure. Even warming up the room with a space heater will help considerably, especially in winter.
The reasons these things warp is because of thermal expansion. If you need accurate-sized parts you will need to figure out what the shrinkage will be and then adjust your model accordingly. Printing at 101%-102% size is a good start, but you should print a test part first to dial it in exactly.
Delamination is a common problem when printing with nylons. To get a good layer bond, the following factors need to be taken into account:
- Extrusion pressure
- Cool-down rate for new layers
Nylons need some pressure/compression to form good layer bonds, so I usually set my extrusion width to 0.1mm larger than my extruder nozzle size when printing nylon. That is a 0.5mm extrusion width for 0.4mm nozzle and a 0.7mm extrusion width for a 0.6mm nozzle. This seems to help form strong layer bonds.
Also, a good bond between layers will not form if the nylon being extruded cools down too quickly or the previous layer is too cold. This means that the fan should be off almost all of the time. An exception to this no-fan rule is when the time to print a layer ends up being less than 10-8 seconds. At this point you need to start turning up the fan to avoid globbing.
If you are printing fast, you may also need to increase your printing temperature to ensure a smooth flow of plastic and that the extruded plastic is hot enough to bond well with the previous layer.
All nylons are hydrosorbic, but how much so depends on the type of nylon. "Soft nylons" like nylon-6 are extremely hydrosorbic and must typically be desiccated (dried-out) before use.
Some recommend leaving some moisture in the trimmer line so as to leave a rougher surface on the previous layer to create a better layer bond. However, if you get your printing settings right this should not be necessary. I recommend always printing with the filament as dry as you can get it.
That being said, moisture acts as a plasticizer for nylons. If you are printing with completely dry nylon, your printed part will not have full impact resistance and flexibility until it it reabsorbs some amount of moisture from the air, which could take as much as a week or two depending on the humidity.
If you print with non-desiccated (wet) trimmer line (which is typically the state it is in when you get it) it will tend to foam and expand in the nozzle. This is usually undesirable. If you want to minimize foaming but don't have time to desicate, one trick is to print fast: 80mm/sec or faster. This somehow reduces the amount of foaming. You can use this as a trick for making parts look "frosted" print the walls slower than the top/bottom infill with a blue trimmer line. When doing this, the parts seem to retain their moisture and are more flexible immediately after printing compared to printing with properly desiccated filament.
Dry nylon also has significantly less odor while printing and likely emits fewer ultrafine particles.
Dry trimmer line has little odor while printing. Wet trimmer line will have a plasticy odor, but still nothing compared to printing ABS or ASA (which is utterly noxious).
But just because you can't smell it doesn't mean there is nothing there, so a minimum precaution if you are printing lots of nylon is to:
- Print in an enclosure.
- Print in a room that...
- Is not occupied continuously (i.e.: not next to your desk while you work, or in your bedroom)
- Can be easily ventilated (like with an open window) when the print is complete.
- Keep the door closed while printing.
I have found the fumes to be tolerable for short periods, but prolonged exposure to substances with a slight inflammatory response could cause an allergy to be developed, at which point the symptoms could get dramatically worse.
This section describes the different kinds of nylon used in trimmer line and their different properties.
The vast majority of trimmer line that is suitable for 3D printing is made of what I call "soft nylon". These trimmer lines are almost certainly pure nylon-6. Any filament that I describe as a "soft nylon" can generally use the same printing settings as any other "soft nylon".
- Flexible, somewhere between a really hard TPU and PETG.
- Highly hydrosorbic. If not desiccated before use, it will foam at slower printing speeds. At faster printing speeds (80mm/sec+), foaming seems to be less of a problem.
- Difficult to sand.
- Highly impact resistant.
- Excellent layer bonding when printed correctly.
I use the following print settings when printing "soft nylons" at 80mm/sec:
| Property | Value | Comment |
|---|---|---|
| Extrusion Factor | ~114% | for ~1.64mm |
| Extruder Temp | 260°C | |
| Bed Temp | 60°C-80°C | |
| First Layer Height | >= 0.3mm | Helps ensures a solid first layer bond |
| Layer Height | 0.2mm | |
| X/Y Scale | 101% | Just a starting point. |
| Layer time fan-on | 7sec | Point at which fan should turn on |
| Minimum layer time | 4sec | At this point the fan should be maxed out |
| Brim? | Depends on part | Sharp edges will need brim |
| Fan? | OFF unless layer time <7sec |
"Hard Nylon" is a bit less common in Trimmer Line, but still easy to get. I'm not sure exactly what kind of nylon these trimmer lines are made of, but it is likely a nylon co-polymer of some sort. It is a tad more transparent than "soft nylon".
- Harder than "Soft Nylon", but still a tad flexible. Similar hardness to PETG.
- Warps/shrinks significantly more than "Soft Nylon".
- Hydrosorbic.
- More transparent than "Soft Nylon", but still a bit milky.
- Easier to sand than "Soft Nylon".
- Still impact resistant.
- Excellent layer bonding when printed correctly.
- First layers will tend to delaminate unless you take specific action to prevent this, see first layer print settings for more details.
I use the following print settings when printing "hard nylons" at 80mm/sec:
| Property | Value | Comment |
|---|---|---|
| Extrusion Factor | ~114% | for ~1.64mm |
| First Layer Extruder Temp | 270°C | |
| First Layer Bed Temp | 100°C | |
| First Layer Height | >= 0.3mm | Help ensure solid first layer |
| Extruder Temp | 260°C | |
| Bed Temp | 80°C | |
| Layer Height | 0.2mm | |
| X/Y Scale | 102% | Just a starting point. |
| Layer time fan-on | 7sec | Point at which fan should turn on |
| Minimum layer time | 4sec | At this point the fan should be maxed out |
| Brim? | Depends on part | Sharp edges will need brim |
| Fan? | OFF unless layer time <7sec |
All of these trimmer lines are 0.065" with a round diameter. All items listed have been test printed and work fine.
- MaxPower 333665 RoundCut Trimmer Line, 1800’
- Color: Blue
- Note: This line is powdered with talc, you will need something like a paper towel clipped to the filament as it enters the printer.
- Availability
- Amazon $29/1800' ($9/lb, $20/kg)
- Ace hardware brand
- Color: Natural/Translucent
- Availability:
- Ace Hardware: $10/200'
- "Fepito" trimmer line
- Color: Blue
- Availability:
- Amazon $10/328'
- Oregon-band trimmer line
- Color: Fluorescent green (Purty!)
- Availability:
- Amazon: $20/lb ($44/kg)
- ForestDepot: $11/lb
- BlueNatHxRPR
- Color: Natural/Translucent
- Availability:
- Amazon $13/lb