Saturday, June 3, 2023

How to choose a 3D printer


Over the years, 3D printers have evolved from expensive exotics to devices that are quite affordable and easy to use. They are actively used for production and medicine, but their popularity is growing among ordinary users. Many people are deterred from buying only by a lack of knowledge about a new type of technology. How some 3D printers differ from others, what characteristics and options they have – in this guide.

There are many types of 3D printers, differing in both the printing principle and design. But the most widespread are two types: filament and photopolymer, which differ in the technology of layer formation.

Layer formation technology
DLP/LCD/SLA are photopolymer printers that use a special plastic that hardens under ultraviolet light. The printer contains a tray with a transparent bottom, a print head with a UV lamp located under it, and a work surface located above the tray and capable of moving along the Z axis.

When working, a liquid photopolymer is poured into the bath, and the working surface descends to the transparent bottom, leaving a minimum clearance of one working layer thick. The head, acting on the necessary points with an ultraviolet beam, forms the first layer, after which the working surface rises to the thickness of the new layer. And so – until the product is printed. During operation, the printer seems to “pull” the inverted figure out of the bath.

Photopolymer printers are more expensive than filament printers, have a low print speed, the choice of materials for them is small and the materials themselves are more expensive. But the printing accuracy of photopolymer printers is much higher – individual dots and layers are almost indistinguishable.

Photopolymer printers are used to build figures with high precision and high detail. They are used by jewelers to make casting molds, by dentists to make dentures, and also for modeling.

PJP / FDM / FFF – filament printers that print a figure with plastic, fusing it layer by layer onto a work surface.

Filament printers are cheaper and faster than photopolymer printers. Filament printers offer a variety of plastics of various characteristics:

undemanding to the settings of the basic parameters, allowing you to quickly switch to printing.
durable, for the manufacture of loaded parts.
colored and multi-component, for the manufacture of artistic products, incl. with imitation of various materials (wood, metal, etc.).
The main disadvantage of filament printers is their low print accuracy. Firstly, on a freshly printed figurine, layers of printing are clearly visible. Secondly, the figurine and its elements can be deformed due to uneven temperature effects, this must be taken into account when preparing for printing.

By design, filament printers are of several types:

Prusa (“stolodrygi”). For these printers, the head moves along a horizontal frame, in the same plane along the X and Z axes. Instead of moving the head along the Y axis, the table itself moves.

The design is inexpensive, but not the most accurate – the separate movement of the head and table adds its own errors. Such designs usually have an open body, which often contributes to uneven cooling and deformation of the figure. There are also problems with high massive figures – when the table moves, inertia can skew the model. However, the latter is “treated” by reducing the print speed.
Prusa ½ (console). In this model, the frame is replaced by one vertical stand. The model is very compact, but has all the disadvantages of “Prusha” with virtually no advantages. Printing accuracy is even lower due to worse head positioning.

H-bot, Core-XY, Makerbot, Ultimaker. In all these subspecies, one principle is used – the table moves only along the Z axis, i.e. up and down, and the head is in a horizontal plane along the X and Y axes. Between themselves, they differ in the complexity and accuracy of mechanics – the simplest for H-bot, the most difficult for Ultimaker. In general, the design is largely spared from Prusa’s shortcomings: printers have high accuracy and speed, they are often located in a closed case – a thermal box, which ensures uniform cooling of the model and the absence of distortions. Cons – a complex device, high price, large weight and dimensions.

core-XYZ. In this model, the table is stationary, and the head moves along all three axes. The most expensive and sophisticated models, which nevertheless provide the best print quality.
Number of extruders
In filament printers, the plastic is melted and extruded out through an extruder, which can be compared to the print head of a conventional printer. Most 3D printers have one extruder, but there are models with several. This gives the device three additional capabilities:

Print complex composite figures with supporting inserts made of easily soluble plastic.

On a conventional printer, it is impossible to print parts with “hanging” elements – the melted plastic will have nothing to hold on to when printing and it will simply fall.
Multi-color printing – each extruder prints with plastic of its own color, resulting in a color model.
Simultaneous printing of several identical figures – each extruder prints its own figure, as a result, the printing speed increases significantly.
heated platform
In a filament printer, the figurine, when printed, must fit snugly against the table substrate, if at some point a part of the figurine base comes off the table, it can be skewed. The tight fit of the figurine is facilitated by the table cover, its material, as well as its temperature. Heating the table ensures better adhesion of the plastic to the table and greatly reduces the risk of premature “sticking off” of the figure. A heated table is an important option that should not be neglected.

working material
Both the process of printing the figurine and its future characteristics largely depend on the material used. Before changing media, make sure your printer supports it.

PLA is one of the most common base plastics. It has a low melting point, adheres well to the table, is easy to print, is environmentally friendly, and has little to no odor when printed. PLA is quite strong, but does not like high temperatures (above 50º C) and is brittle (it does not bend well). Most PLA plastics are easily abraded, so loaded parts (gears, levers) should not be made from it.
ABS is another common plastic. It is durable, resistant to abrasion, quite flexible and is not afraid of temperatures up to 150º C. ABS plastic, for example, is used to make LEGO parts.

But it is more difficult to print with it, since it shrinks when cooled, it needs a high printing temperature (200-210º C) and a heated table. It is necessary to print in a closed case – the evaporation of ABC plastic is harmful to health, in addition, uneven cooling leads to its deformation.
PETG is a modification of the well-known food-grade plastic from which most plastic bottles are made. Similar in performance to ABS. It also requires high printing temperatures, but shrinks much less and bakes better, making it easier to print than ABS. Environmentally friendly and not afraid of ultraviolet (unlike the above).
HIPS. Similar in characteristics to ABS, it was developed as a support for complex models printed in dual-extruder printers. Soluble with limonin (D-Limonene). Rarely used alone.
Nylon is a flexible, strong and durable material suitable for the manufacture of heavily loaded parts. Shrinks when cooled, so it’s best to print in a closed chamber.
Carbon Fiber – Nylon with added carbon fiber, designed for use in heavy duty applications. Durable, resistant to abrasion. Shrinkage is lower than pure nylon, making it easier to print.

PVA, like HIPS, is designed to support the elements of complex parts, but is much more convenient to use, as it dissolves in ordinary water.

Flex, NinjaFlex. The material is elastic and flexible. Melting point 200–210º C, tends to shrink when cooled, so it is better to print in a closed case.
BronzeFill, Conductive, CopperFill, LayBrick, StainlessSteel, Woodfill – plastics with fillers. Characteristics depend on the material of the main plastic – it can be PLA or Neylon or some other. Fillers can be used to give a decorative look: figurines made from BronzeFill, CopperFill, LayBrick, StainlessSteel, Woodfill look like bronze, copper, ceramic, steel or wood respectively.

In some cases, the filler is used to give an additional characteristic: for example, Conductive plastic is able to conduct electricity.
photopolymer resin. Used in photopolymer printers. The material is quite hard, but brittle and is not suitable for the manufacture of loaded parts. There are special resins for dentists, for making molds, etc.
Characteristics of 3D printers
Height, depth and width of the workspace
Working space dimensions are one of the main parameters of the printer, which determines the maximum size of your future creations.

Proceed from the dimensions of the products that you are going to make – for small works with high detail, a working space of 100x100x100 mm will be enough. For domestic use – the manufacture of various parts, models and toys, a printer with the most common working space standard – 200x200x200 mm will suffice. For the manufacture of large-sized products, printers with a working space of 400x400x400 mm are produced, but they are already much more expensive.

Build speed
The parameter is measured in mm / s and implies the maximum speed of the print head. The actual speed depends on the set print accuracy, the complexity of the figurine, the printer model, the material used and other parameters. For example, the following 14x4x10 cm tablet stand prints in approximately 6.5 hours at 50mm/sec and 4.5 hours at 100mm/sec.

Minimum layer thickness
The minimum layer thickness is analogous to resolution. The larger the value of this parameter, the rougher the product will turn out, and the more forces will be required to bring it to a finish look.

On the other hand, the thinner the layer, the longer it will take to print. For most applications, a minimum thickness of 0.1 mm is sufficient.

Maximum layer thickness
It is not always necessary to have high precision in the manufacture of a part; for rough large parts, the surface quality is often unimportant. In this case, the thicker the layer, the faster the print will be. Increasing the layer thickness by 10 times will increase the print speed by the same amount.

Nozzle diameter
The diameter of the nozzle affects the detail of the product and the quality of smooth surfaces on it. The standard size is 0.4-0.5mm, a smaller diameter nozzle can provide better detail and sharper edges on the product, but the smaller the nozzle diameter, the slower the print speed. Therefore, many printers have the ability to replace the nozzle for a specific task.

Main working program (“native”)
To print, information about the object to be printed must be loaded into the printer, and a regular model created in a 3D editor is not suitable. 3D printers have their own specifics – the model must be “cut” into layers and for each layer there must be information about the movement of the head. The program that “cuts” the model into layers is called a slicer (from the English slice – layer) and the quality of the product depends on it no less than on the characteristics of the printer.

Pay attention to the possibility of working on “non-native” programs for the selected printer – if it is, you can always use a proven quality third-party program. If the printer only works with “its own” program, be sure to find as much information about it as possible, find out everything about the convenience of working with it and its quality.

Jewelers, dentists, and modellers will love the accurate and easy-to-use photopolymer printer .

To get acquainted with 3D printing and make simple figures, an inexpensive filament printer will suffice .

For printing parts from a wide range of plastics, choose from models with a heated bed .

If you are going to make small items – gears and other parts for household appliances, miniature models, etc., an accurate filament printer with a small working space is suitable for you .

To produce large items – cases, large models, decorative items – you need a 3D printer with a large amount of working space .


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