A 3D object needs three axes to be represented within the 3D printing space and to be printed. Here, we explain the 3D printer axis system, how it works, and what aids its movement.
It’s a challenge to represent three physical dimensions on a sheet of paper, but any point in space must be represented by providing three coordinates, which are usually listed in the order X, Y, Z. Each coordinate provides information about a single direction, or axis, each of which is perpendicular to the other two. One coordinate would indicate position along a line, two in a plane, and three in space.
In 3D printing, printers use different mechanisms to maneuver in a particular axis. However, the two common systems are cartesian and delta. They both employ the FDM technology but have varying mechanisms of navigating the extruder within the printing space.
In fused deposition modeling (FDM), a hot end deposits polymer to create layers. This process is highly dependent on the 3D printer axes X, Y, and Z. Depending on the printer in question, the hot end will move in one, two, or all three of these axes.
The 3D printer axis system, therefore, enables a 3D printer’s operation and give the object depth and design. If there were only two axes, let’s say the X and Y axes, then your object design would be flat. It would be like printing with an inkjet printer as your print would have no depth. Normally, the X and Y axes correspond to lateral movement while the Z axis corresponds to vertical motion.
To avoid confusion, assume you are standing in front of your FDM 3D printer, the tool moving up and down is the Z axis. Your X axis is the tool moving left or right, and the tool moving in and out (from your standing position) is your Y axis.
The X-Y-Z-coordinate system most of us are familiar with is the Cartesian coordinate system, named after mathematician René Descartes. It plots points based on the X, Y, and Z coordinates. In 3D printing, the coordinates (x, y, z) determine the position of the extruder — in the 3D print space — which makes use of rails that transport both it and the print bed.
These printers rely on one or two motors along the axes and have a rectangular build area and a square print bed. A good example is the Lulzbot Mini.
Cartesian printers are the most available design among consumer desktop 3D printers, with two main variations. In the first, the print head moves side-to-side, along the X axis, and upwards in the Z axis, while the print ped moves in and out along the Y axis. A popular example is the Original Prusa i3, along with all its clones.
In the second, the print bed drops down layer by layer, along the Z axis, while the print head moves in the X-Y plane. Both the MakerBot Replicator+ and the Ultimaker 3 control the Z-axis deposition by moving the build plate up and down.
Even though they still work within a cartesian system, delta printers employ a unique mechanism for moving the extruder. These printers have three arms, with each attached to a vertical rail, that join at the center to suspend the printhead. None move in a single 3D printer axis, but instead, all three arms move in three dimensions in order to triangulate the nozzle’s position.
Your typical delta printer will move from one (x,y) point to another by changing the angles between the arms. A great example of a delta printer is the SeeMeCNC Rostock MAX V3.
Delta printers have a circular print bed (which is mostly immovable). These printers thus tend to be more accurate when working on circular prints, and because of their design, they are well-suited to printing taller objects.
The name “delta” comes from the extruder being suspended over the print bed in a triangular configuration. The fact that delta printers don’t employ familiar linear movement when depositing filament makes them unique.
The linear motion system is one of the most crucial mechanisms in most 3D printers. This is the system that moves the build platform or hot end along a particular 3D printer axis.
In a linear motion system, a motor turns electrical energy into rotational motion, which is then converted into linear motion. Let’s look at the main components that aid the linear movement.
Most 3D printers use a combination of leadscrews and timing belts for their linear motion systems. Leadscrews, or threaded rods, are usually used to accommodate the Z 3D printer axis. Cheap printers will often use simple threaded steel rods, while more expensive printers go for leadscrews to minimize backlash.
Leadscrews translate the rotational motion of stepper motors to the linear motion of the extruder or build platform. Most 3D printers use at least one leadscrew for movement along the Z axis. During the printing process, the leadscrew will lift the print head or build platform one layer at a time until the building process is complete.
There are different varieties of leadscrews, but the most used types are trapezoidal (ACME) leadscrews or ordinary threaded rods. A variation of leadscrews are ball screws, which give the best performance among the three, but are also the costliest.
The greatest advantages of leadscrews is that they deliver a significant force and are self-locking, meaning they will not move in the case that your printer loses power. This is one of the reasons they are preferred for the build platform. However, leadscrews are rarely used for the X or Y axes because they are prone to backlash.
Belts drive the X and Y axes of most 3D printers. A belt drive is mainly made up of a carriage attached to the belt, a toothed pulley (sprocket) connected to the motor, and a timing belt with teeth. When the motor turns, it rotates the pulley, which interlocks its teeth with those of the timing belt, rotating it in the desired direction.
A carriage, which is attached to the belt, moves with the timing belt. It is crucial to note that a timing belt requires a certain amount of tension, which is why many 3D printers have mechanisms for adjusting the belt tension.
Stepper motors are responsible for rotating pulleys and leadscrews. They are unlike DC motors because they rotate in increments, meaning they have precise control of their rotation. The most popular varieties used in 3D printers are NEMA 14, NEMA 17, NEMA 23, and NEMA 24.
Different printers have different movements. While some are single axis (single motor), others are double axis, which means they use two motors. Using two motors is common but it increases the possibility of losing synch, which is why some printers have the Z-axis screws connected with a belt and driven by a single motor.
Mendel-style 3D printers, like the Prusa i3, have a floating X bar that rises or lowers along the Z axis, while the print bed moves back and forth on the Y axis. Two leadscrews that are powered by two motors work in parallel to move the gantry up or down.
Such printers can have two Z screws and two motors, two screws and one motor, or one screw and one motor. In general, two screws and one motor offers superior reliability and user-friendliness.
Darwin-style 3D printers, like the Ultimakers, have a print head that moves in the X-Y plane. In this case, the X and y bars do not move up or down because they are affixed to the printer.
The X- and Y-axis movement of an Ultimaker is mainly facilitated by rods, GT2 gears, four belts, and of course some stepper motors. The Z-axis motion is rather straightforward and is aided by one leadscrew and two linear rails. Thus the build platform moves up or down on the Z axis.
License: The text of "3D Printer Axis – All You Need To Know" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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