After several weeks in which we have given a review to all that implies 3D printing, we wanted to finish this series of special articles with a more practical, in which we are going to talk about the different materials available in the market to print and , Most importantly, where we can get them, their prices and their qualities, with a series of tests and measurements on them.
Setting test parameters
In order to carry out these tests, we have been in contact with several stores, and we have made measurements and impressions on the same products that they put on sale, so we can tell you first hand our experiences, both with the materials and with the Shops.
But the first thing that we are going to do is to establish the test parameters that we are going to realize. The first are the tools that we will use. In this case we will serve a foot of digital king for measurement of dimensions, a multimeter for conductivity and Mendel Tricolor RepRapPro printer to make the impressions .
Although with the filament normally can also perform tests of mechanical strength, these properties are given primarily by their composition, something that in most cases hardly varies. We are going to focus on its dimensions, of which basically at the time of printing we import two, the diameter and the roundness. Although for all practical purposes, the most important parameters to consider are the degree of variability of diameter and self – calibration of the printer , so that when we send commands extrusion material, the material coming out of the hot head is really the That we mark.
This is important because a great variability can not only create distortions and errors in the printed piece, but also serious problems with the 3D printer , such as jams head, cable that is split in the middle of printing, and a host of ” Horrors “that can cause from small inconveniences to catastrophic situations. Therefore we will make a series of measurements along the filament samples, we will obtain the average, standard deviation and final tolerances.
In addition to the filament itself, it is also important the coil in which it is coiled and as it is, as well as the packaging and sealing thereof. We will also check if there are storage defects, such as blows, excessive exposure to UV rays and if really, the amount of filaments that claim to have coils corresponds to reality.
Finally, we will perform several tests of printing, including one in which we will print the same piece with the different materials following their recommended temperature values. To do this, we will look for a 3D model of a piece in an open parts library and print it With all of them with the Mendel Tricolor, a printer also of open design, showing that the open solutions are as good as the proprietors.
In this case the chosen piece was a gear belonging to this part . The decision to take this piece is due to the fact that there are curves, roundings, straight lines, a small hole and a large hole, as well as a hole for a hexagonal nut, a gear and a separate edge of the central body. It is a perfect piece to check the different problems that can arise in 3D printing: warping, deformations, inconsistent and moving layers, deformed curves and lines, variation in dimensions, etc …
The different thermoplastic filaments
Explained already what we are going to do, we will speak to you very briefly of each of the types of filaments that we have taken into account and their properties. There is a great variety, although the market of the thermoplastic filament is in continuous development and new materials arise continuously.
ABS : Acrylonitrile Butadiene Styrene is the one of most thermoplastics used in 3D printing. It is not biodegradable, but is very tenacious, hard and rigid, with chemical resistance and abrasion, but suffers with exposure to UV rays. It is soluble in acetone and its density is 1.05 g / cm 3 . Requires a head temperature of about 240 ° C and tray of 110 ° C. For you to imagine, LEGO pieces are made of ABS.
PLA : polylactic acid filaments is another star of 3D printing. It is biodegradable and is usually obtained from corn starch, so that when smelling it smells almost to food and can be used for food containers. The texture of the pieces is not as soft as with ABS, but they are brighter and the corners come out better. Its density is between 1.2 and 1.4 g / cm 3 . The temperature required for printing is about 210 ° C with the bed at about 60 ° C.
In both cases we can find, in PLA as in ABS, all kinds of colors, ranging from natural crude, to golden and silver. But there are also varieties of these materials with special properties. We have for instance fluorescent colors that glow in the dark, or fluorescent glow when exposed to UV light. Also materials that change color according to temperature and to flexible varieties or conduct electricity.
HIPS : high impact polystyrene is very similar to ABS material and requiring the same temperature profiles. It is usually used in combination with ABS to make pieces with hollow spaces, using HIPS as a support that will then be removed with D-Limonene, with which it is soluble while acetone does not affect it. As the ABS supports bad UV light and its density is 1.04 g / cm 3 . We have used the same temperatures as with ABS.
PET : polyethylene terephthalate is one of the most used for bottles and other packaging materials. Its main property is its crystallization capacity, generating transparent parts with surprising effects. It is very strong and resistant to impacts. Its crystal density is 1.45 g / cm 3 . We have used the same temperatures as with the PLA.
Laywoo-d3 material which requires conditions similar to those of the PLA temperature, with the peculiarity that if we increase or decrease a few degrees, the color obtained is darker or lighter. After cooling, it has a wood-like texture and temperature variations, whether controlled directly, by fluctuations or type of cooling, will leave streaks more or less dark.
Ninjaflex: This is a revolutionary thermoplastic elastomer (TPE) for creating pieces with surprising flexibility. In itself, the filament has practically the consistency of a rubber cord, and the resulting parts can be deformed widely. The temperature is very similar to that of the PLA, with the head at 215ºC and the tray at 40ºC.
Nylon: Nylon is perhaps one of the most complex 3D printing materials. Its main problem is the lack of adhesion of the piece to the tray, which causes many failures besides a warping very difficult to control. In addition, it usually picks up moisture easily, so prior to 3D printing we must dry it in the oven for 3 or 4 hours. In exchange for all these difficulties, nylon is a very resistant material, little viscous, very resistant to the temperature and with different varieties that give him flexibility, transparency and other qualities.
We have found 9 types of different coils , which also appear in the table and all sorts of dimensions, so if your printer uses a special holder for coils or do you use your own yours, and requerís that the coil does not exceed a size Determined, you should take into account the types of reels that stores use to know if they will be compatible. In all cases the coils were in perfect condition and the amount of filament was adequate, but still we recommend that if you think to make a large order of many reels, always ask for a sample to know if it meets what you need.
After the measurements, we made the pieces, verifying that, although in some cases the variations and average value of the filament diameter are different from the nominal ones, with values that could theoretically offer problems when printing, with the appropriate calibration all this Is minimized and makes practically every type of filament. We have used, as we said before, a 3D Mendel Tricolor printer from RepRapPro and Cura software. The layer height has been 0.3 mm, the wall thickness of 1 mm and the bottom and top layers 0.6 mm with a density of 20%. The printing speed was 40 mm / s and that of the movements of 120 mm / s.
We successfully made pieces in all materials, and for this we tried different combinations of support surfaces, either with bare glass, Kapton tape, body tape, cardboard and use of lacquer. The best result obtained with PLA as Kapton, while with ABS was with lacquer (provided by Thingibox and following his advice) greatly facilitating printing. The only materials that was impossible to print the nylons were both Taulman as Chinese, we did not get that any material or temperature will stick.
In the gallery you have the pieces in the different materials, including samples of the thermochromic properties, phosphorescent and fluorescent, in that last case it must be said that red is the least noticeable. About Laywoo-D3 must say that its texture is quite surprising, besides the property of letting different shades according to the extrusion temperature , and the piece in transparent PET looks spectacular.
As for the materials with the most useful properties, the conductive ABS, but can not be used to print circuits has many uses for sensors, shields, etc … Of course, its resistance changes greatly with temperature and in our case, at 17 ° C environmental, we obtained values of resistance of 15,550 +/- 943 ohms / cm away from the 10,000 nominal. This value was obtained by making measurements in different sections with the same environmental conditions. To check the variation with temperature, we measured a sample of 10 cm at different temperatures, and then obtained the corresponding formula by a linear regression of these values, which gave us the formula R = 470 · T + 8.266 where the temperature (T) In ºC.
Special mention has the two flexible materials we have tested, the EcoFlex Flex of FormFutura and the NinjaFlex. The price is very similar, 34.95 € / 0.5kg the first against 36.95 € / 0.5kg the second, but the elastic properties of NinjaFlex are much greater , so much that it surprised. In addition we have verified that with both can be made to perfection “complicated” pieces like bellows with option of Z in spiral and walls of 0.5 mm of thickness.
Once you know an important variety of materials at our disposal, it is time to know where we can get them. We will point you to 4 Spanish stores, with the huge advantage of lower shipping costs and faster delivery time, and then some international stores with unusual materials.