Brief History of 3D Printing filaments
The materials using in Fused Deposition Modeling (FDM) or just plainly 3D Printing have greatly evolved over the years.
The FDM technology was employed for decades in an industrial setting, but it was only around late 2008 when a couple of enthusiast started DIY’ing open-hardware and open-software controlled 3D printers when this technology became available for the pro- and consumer.
These early days, the “ink” for these printers, which we now call filament, was mainly crude ABS plastic rod, normally used for industrial plastic welding. There are also anecdotes of plastic lines used in weed trimmers being tested for their suitability in the early days of Home and Office 3D Printing.
The last 5 years a lot has happened on the market for 3D Printing Filaments. The plastic injection moulding industry which originated at the event of low-cost, mass-produced consumer products back in the 40s, has developed a plethora of polymer compounds or more generally referred to as plastics. MatWeb, a renowned Material Properties Database used by many engineers and scientists alone lists over eighty thousand of these commercially available polymer variations for different applications.
When I started looking into 3D printing materials for my own prototyping use back in 2011, mainly ABS was available for purchase – One of the most common polymers in use in the consumer and automotive industry. Soon after, individual makers and the industry discovered PLA (Polylactid Acid). Until then PLA was mainly used in the medical field as well as for food packaging and shrink films. It’s beauty is, that unlike ABS, which is made from fossile resources, it’s synthesized from starches and sugars. This means it’s a renewable resource, compostable and less harmful to the environment.
Used in 3D printers, it adheres well to many surfaces, processes easy and does not require a heated print bed or enclosed build chamber to avoid warping of larger volume prints.
Unfortunately, the physical properties of standard PLA prints often don’t meet application requirements when it comes to exposure to higher temperatures, physical durability and exposure to the elements. Which often are requirements of functional prototypes or small batch manufactured parts.
Composite Filaments to the rescue ?
Shortly after, the industry started experimenting with PLA composites. Some recent ones for example include PLA filaments that are mixed with Carbon fibre dust/cut-offs. While Carbon, which is used a lot in the car or airline industry, has a nice ring to its name, its strength is reliant on it being processed as a fiber. Mixing Carbon dust with polymers, while sounding cool and looking quite nice, will not noticeably strengthen 3D printed objects. Also, Carbon is extremely abrasive and will ruin standard issue 3D Printer nozzles after just printing very small quantities.
Nylon also is a good alternative for prototypes. It’s sturdy and flexible to a degree. But again its difficult to process as its highly hygroscopic and absorbs humidity very fast, causing tiny steam bubbles while printing, requires a high print temperature, and also does not easily adhere to normal print surfaces. In addition, it’s high degree of flexibility might not be desirable for mechanical parts.
How are mechanical properties of polymers actually quantified?
To really be able to evaluate a good choice of material for a specific application, just following one’s gut feeling is often not enough.
There is a large number of parameters that are usually specified on polymer manufacturers data sheets. These values can be quite confusing at first sight. Let’s have a look at some of the common ones:
This indicates how a specific material will react when it is exposed to sudden impacts. In other words, it’s a test for brittleness. The higher this value, the more the material will resist breaking on a sudden impact. It is usually expressed in J/m2 or ft-lb/in2. For impact strength tests a flat sample plate is notched and suspended in a vice. Then a large, heavy “hammer” is swung against the sample. The result is the amount of energy the sample absorbed when the hammer swung through and broke the sample piece.
Tensile and Flexural Strength
Tensile Strength measures how much you can pull or stretch a material before it breaks. Flexural Strength how much a material can be bent until it breaks. The results are closely correlated with Flexural Strength Values typically a little higher.
The stretching in this test is done with slowly increasing strength and the resulting value measured in Psi or Pascal (also N/m2) indicates the strength. For this a sample with a fixes cross-section diameter is used. Again Higher values indicate materials that withstand higher force. It is important to differentiate Yield Strength and Ultimate Strength (UTS is also called Tensile Strength at Break) values. Yield strength indicates the point until the material does not significantly deform. Ultimate strength is the point at which the material will be close to failure. Which leads us to Elongation.
Elongation is related to the Tensile Strength. It measures the percentage change in length of the sample before fracture and is usually expressed in %. Practically it means, how far a material can be stretched before it breaks. Nylon or TPE materials for example will have a high Elongation value, even multiple 100%, whereas ABS or PLA would have a low one in the single or double digits. The combination of a high Tensile Strength and Elongation would indicate a very “tough” and hard wearing material.
Heat Deflection is an indicator of the temperature sensitivity of the Polymer.
While PLA for example is very hard at room temperature, a 3D printed phone holder used in a car in Summer won’t keep its shape for very long.
Heat Deflection is measured in degrees Centigrade or Fahrenheit. The Sample is fixed at two ends and a defined pressure is exerted on its mid-point. Then temperature is increased, and when the sample starts deforming by a certain margin, the test is complete.
Obviously, the heat deflection characteristic required depend on the application. But the Heat Deflection Temperature of standard 3D Printing PLA you find in the market is around 60-80 C, which does not really make it suitable for applications in which the part will be exposed to direct sun, a fan shroud used close to a 3D Printing extruder, or a vessel that is supposed to hold hot liquids. Obviously, the higher the Heat Deflection, the higher the print temperature will be. This will increase the processing difficulty in standard 3D Printers.
Desirable Properties specific to FDM 3D Printing
We have quite a few customers using our materials for small batch manufacturing and prototyping. Our products are also often used in University and Research Settings.
In addition we work closely with Material Scientists at National Taiwan University to look at suitable alternatives of current polymers used in the 3D Printing Industry.
Based on aggregated feedback, here some examples of desirable properties good, general prototyping material could have:
- Impact resistant (High Impact Strength)
- Strain Resistant (Good Tensile Strength)
- Temperature resistant, while still being able to process on most 3D Printers (Heat Deflection > 100C)
- Good Solvent Resistance
- Strong layer bond characteristics to avoid breakage along print layers
- Easy processing, without requiring heated beds or chambers (low/no warp)
- Safe processing, no/very little fumes
- Non-destructive on Brass nozzles most printers use
- Preferably made from renewable sources
- Cost effective – value for money
There probably are more, and I would be keen to here from you what your thoughts are. I would appreciate if you could leave a comment below.
Let’s have a look how some common materials stack up. As there are many, many different variations of these materials, the values below represent some averages from the above mentioned MatWeb Database for the different Material families:
|Tensile Strength at Yield||+||o||++|
|Elongation at Break||24.9 %||23.1 %||76.9 %|
|Heat Deflection at 0.46 MPa||94.7 °C||81.2 °C||164 °C|
|Nozzle Temp||224 °C||197 °C||247 °C|
|Water Absorption||<1%||<1%||4.91 %|
In general, our customers seem quite satisfied with PLA for standard applications. They like it’s convenient processing properties. However, it’s low temperature deflection values and relative lower impact strength often require the use of ABS for many applications.
This together with the other requirements listed above was input for our R&D efforts over the last eight months. We discussed them with the Polymer Material Scientists as well as some of our raw polymer suppliers to investigate on a new type of polymer blend optimized for 3D Printing FDM purposes.
It’s a lot of fun, but also very time intensive to blend, extrude and test all the different variations. A lot of things can be determined theoretically, but real-life testing is still indispensable to ensure the filament really will meet our high expectations. Below the first spool of EVO-17.4 fresh of the extrusion line. EVO is just the working name we use internally for now to designate our 17th blend tested in its 4th variation. I believe we are pretty close to having a optimized, general-use FDM polymer which will combine most positive properties of the many filaments out there, while still being cost effective enough so one does not have to think twice using it on a daily basis.
Your opinion matters to us
We would love to get some samples of “EVO” in the hands of some serious beta testers to get unbiased opinions and feedback. If you are interested in participating, send us a brief email at [email protected] with a bit of background about yourself and we will send you samples in return for your valued feedback. EVO samples process on any 1.75mm FDM printer at about 215 C.