What is 3D printer - Anatomy of a 3D printer

What is 3D printer - Anatomy of a 3D printer

To get the most out of your 3D printer, achieve optimal quality, make repairs, or troubleshoot any issues, it is important to know the components of your 3D printer. Here we will focus on the mechanical and electrical core components of the most common type: FFF (Fused Filament Fabrication) or FDM (Fused Deposition Modeling) 3D printers.

Mechanical

Frame

The structure of the printer. Frames in the past have been made from laser cut wood, now though most are made from sheet metal, aluminum extrusion, or plastic. Many components of the frame can also be 3D printed themselves. Regardless of the material, the more rigid the frame is, the more precise the movement, and the higher movement speed can be. Its critical the frame be as strong, sturdy,and stable as possible.  

Enclosure

Enclosures for your printer can offer many advantages. Safety is the primary function. There are moving parts, electrical components and wiring, heating elements, belts, the build plate, etc. are some of of the elements you will need to be protected from. An enclosure will also help you maintain an ideal printing environment for optimal print quality by protecting from air flow, and/or loss of heat. Some materials need a heated and controlled environment for success. Your enclosure can be as basic as a cardboard box large enough to completely cover your printer through its full range of motion, or can be a custom made cabinet designed for your specific machine. 

Print Bed /Build Plate

This is the surface you are printing on. It can be made up of multiple components, but all will serve the same purpose. 
  • The base of your print bed will usually be an aluminum plate with a heating element attached (most commonly, though there are some non-heated beds out there). This heating element will aid in adhesion of the printed part, while PLA can be printed without a heated bed, other materials require heat. Heat can also help prevent or reduce warping of the printed part due to thermal contraction. Different materials require different bed temperatures and experience varying severity of thermal contraction. 
  • Bed Surfaces - There are many options available. Some are more beneficial for some materials over others, especially more advanced engineering grade materials. Most printers with include some type of printing surface, glass, PEI film, "BuildTak" or something similar are the most common all purpose. It is always important to make sure your bed surface is compatible with the material you are printing with.  
Bed Leveling: Many printers include one of many types of automatic bed leveling system to make sure the bed is always a consistent distance from the nozzle throughout the entire bed surface. More accurately this is Bed Tramming, as it is not actually leveling in the basic sense. An automatic bed leveling system will measure the distance from the nozzle to the bed at multiple points and make any adjustments needed within the print settings. If your printer does not include an auto leveling system you will adjust the bed to nozzle distance manually. This is a critical step for successful printing. 

Motion Control - X, Y, Z Axis:

Delta:
Delta printers have 3 arms that come together to suspend and control the effector. The motors controlling each of the 3 arms all work at different rates for movement in each direction. Delta printers utilize a circular build area, and generally need to be twice the height of the max build area. Delta printers can achieve higher print speeds, this is achieved by having the build plate, heavy motors, and other parts being stationary, only the print head moves. While it can be faster, the printed part will be indistinguishable from a delta printer vs. a cartesian printer.

Cartesian:
Most common. Configured in a cube, each axis is controlled by one or two motors. They normally have a rectangular build area.

Leadscrews:
Commonly used on the printers Z axis, as the leadscrew rotates it raises or lowers the bed or the printers X axis assembly above the print bed.

Belts/Pulleys:
Belts and pulleys are used on most machines to control the X and Y axis. A toothed gear on the motor will drive the belt to move the X axis and the Y axis. Tension is usually adjusted using a smooth pulley or bearing. 

Electrical Components:


Stepper Motors:
Stepper motors rotate in incremental steps instead of continuously like regular DC motors. These steps are needed to achieve the precise control over their position. Stepper motors are used on all 3 axis as well as the extruder. The most common is the Nema 17 motor with 200 steps per full revolution.

End Stops:
Most common are mechanical switches used to let the printers controller know where the starting point is on each axis. Some printers use optical sensors instead of mechanical switches, but their operation and use the is same.

Control Board:
The control board is the brain or motherboard of your printer. Each motor, sensor, fan, end stops, and all other electrical component is connected to and controlled by the control board. Many printers use 8 bit boards though 32 bit are becoming more common, especially for delta printers. The control board translates your print settings along with the model to be printed into mechanical commands for production. This is achieved via G-Code. Many control boards also contain a USB port, SD card slot, Network connectivity or other communication methods.

Stepper Drivers:
Integrated on some boards, removable and changeable on others, these chips are responsible for running each stepper motor. There are several stepper drivers available, each different driver will allow each step of the motor to be further divided into "microsteps" to achieve even further precision. These drivers also allow for adjustment of each motors current. More power will make the motor run stronger, but will also make it run much hotter. Adjusting the current on the stepper driver is extremely precise, it is very easy to burn out the driver, the stepper motor, or the entire control board if you are not careful.

Screens:
Almost all printers will include a screen of some type, along with buttons or a knob to control your printer settings. Touchscreens, and full color displays are becoming more common, but many still use basic LCD screens.

Extruder & Hot End

Extruder

The extruder is the main component of what makes your printer actually print. It is what feeds the plastic to get melted and pushed out. There are 2 primary 'zones', the cold end, and the hot end. The cold end has a stepper motor that drives the filament in and pushes it through. The hot end is where the filament gets melted and deposited.

Direct Drive Vs. Bowden Extruders:

  • Bowden - With a Bowden system, the hot end and cold end are seperate. The stepper motor and filament drive system are remotely mounted with the filament traveling to the hot end through a PTFE tube. This reduces the weight of the moving print head which can increase print quality in some cases. It can make fine tuning the print settings to be more critical as well. 
  • Direct Drive - A direct drive system as the cold end mounted to the hot end directly. This creates a straight, short path for the filament which can be an advantage for some materials and print quality tuning. The extruder is mounted vertically above the hotend  as one compact package. 

Extruder Gear/ Hobbed Gear

This is what physically feeds the filament. It is mounted to the stepper motor shaft and has "teeth" cut into it to grip the filament to push it through the hot end. There are many types and styles, some with advantages or limitations depending on the extruder type.

Idler Gear

The idler gear is used along with the extruder gear to feed the filament through the hot end. This is spring loaded pulley, bearing or wheel that pushes the filament against the extruder gear. Ideally your printer has a way to adjust the tension on the idler against the extruder gear so that it neither pushes too hard, or too soft.

Hot End

There are 2 primary hot end types; All metal vs. a lined hot end. An all metal hot end doesnt use a plastic liner or insulator. By not using any plastic the hot end can achieve higher temperatures and print a wider range of materials. They do rely  on active cooling for proper operation. A lined hot end will use a PTFE (or PEEK) liner or insulator. This reduces friction along the filament path, but limits your printing temperature based on PTFE breaking down at temperatures above 240 degrees celsius.

Hot end heat sink & hot end fan:
This is the largest component of the hot end. It is a large radiator that houses the filament path, it ensures that heat does not travel up the filament path and melt it prematurely. This issue is called heat creep, it can cause filament jams, and inconsistent extrusion. This is an especially big issue with PLA. The hot end fan  should be running at all times when the hot end is heated. For proper extrusion, the heat must be isolated only to the needed area.

Heater Cartridge, Heat Break& Heater Block:
The heater block holds multiple components; the heater cartridge, nozzle, thermistor/thermocouple and heat break. The block itself can be made from brass, copper or most commonly aluminum. The heater cartridge is as the name suggests a cartridge that heats the heater block. It is nothing more than a high power resistor. The heat break separates the heated and cooled portions of the filament path within your hot end. The heat break can be made from different metals, its primary function besides providing the filament a path to the nozzle is to create a precise temperature change point between the cooled heat sink, and the heater block.

Thermistor / Thermocouple:
There are various types of sensors for monitoring the temperature of the hot end. They are all essentially electronic thermometers for your control board. Thermistors are the most common, but for extremely high temperature printing your printer may utilize a thermocouple.

Nozzle:
Nozzles are essentially a piece of metal with a small hole that the filament is pushed through. Nozzles are interchangeable, there is a variety of metals they are made from, and available in a variety of sizes. The metal the nozzle is made from will dictate its lifespan, especially with more abrasive materials. Brass is the most common metal, but nozzles are also commonly made from stainless steel, plated steel, and plated copper among others. Nozzles are available in a range of sizes with .4mm being most common. You can use a smaller nozzle to achieve higher detail, this will increase total print time, and can be more prone to clogging. Clogged nozzles are one of the most common issues encountered with 3d printing. Choosing the right nozzle depends greatly on the material you intend to use, the detail you hope to achieve, and the speed you intend to print.

Layer cooling fan:
This fan cools off the extruded plastic immediately after it leaves the nozzle. The printer control board will turn this fan on and off under the circumstances set up in your slicer settings. Different materials utilize this fan very differently. While it can help your print hold its shape very well with PLA, used the same way with ABS can cause delamination. The layer cooling fan or print cooling fan should not be confused with the heat sink fan which cools the hot end itself, and not the printed object at all. 

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