Basics of 3D Printers
In this blog, I'll continue writing about the basics of 3D printers & components.
3D printers based on FFF technology will be discussed. RepRap community is the best resource for all design choices which will be discussed in this blog.
Basically, we need a 3-Axis CNC machine with an extra extruder to have a 3D printer.
So, lets do it.
Frame:
We need a frame to hold all axes (X,Y,Z) to be orthogonal to each other & rigid. An extruder (E-Axis) to be added later.
Frames must be rigid & withstand vibrations. Steel, aluminium, acrylic or even wood was used in the reprap community.
One example is a custom designed FFF 3D printer (V-Bot). I used V-Slot aluminum extrusions to assemble the frame which also serves as a linear guide for my motion system using belts, pulleys & V-wheels. Note how the assembled X,Y,Z axes are orthogonal to each other.
V-Bot FFF 3D Printer
Motion:
To have a linear motion, stepper motors are often used in the reprap project. Motion will be transmitted from the motor to a moving carriage using different techniques.
Lead screws, Ball screws & threaded rods are used by attaching the rod to the carriage and the motor. Couplers are used to attach the rod to the motor. By motor rotation, motion will be transmitted to the carriage based on the thread type used.
Fully Assembled Motion Axis
The other method to transmit motion from motor to a moving carriage is by using timing belts & pulleys. GT2, GT3, MXL are used regularly as a belt.
A pulley is attached to the motor shaft & an idler pulley is fixed at the other end of the axis. The belt will be connected through pulleys to the carriage.
GT2 Pulley GT2 Belt GT2 Idler
Belt loops around Motor Pulley & Idler
Linear Guides:
Guides are used to direct the carriage movement to one axis direction. It should be stiff & dead straight to guarantee exact straight movement.
Linear bearings (i.e. lm8UU linear bearing) slides into 8mm rod and connected to the moving carriage and fixed to the frame to act as a guide.
Aluminum extrusions (i.e V-Slot) is a linear guide for roller bearings (i.e V-Wheels).
Machine design & component vary from one to the other to achieve different goals, like speed, rigidity size, ...etc.
Electronics:
Stepper Motor: Wikipedia "A stepper motor or step motor or stepping motor is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can then be commanded to move and hold at one of these steps without any feedback sensor (an open-loop controller), as long as the motor is carefully sized to the application in respect to torque and speed."
Wikipedia stepper motor operation description:
Frame 1: The top electromagnet (1) is turned on, attracting the nearest teeth of the gear-shaped iron rotor. With the teeth aligned to electromagnet 1, they will be slightly offset from right electromagnet (2).
Frame 2: The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the teeth into alignment with it. This results in a rotation of 3.6° in this example.
Frame 3: The bottom electromagnet (3) is energized; another 3.6° rotation occurs.
Frame 4: The left electromagnet (4) is energized, rotating again by 3.6°. When the top electromagnet (1) is again enabled, the rotor will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example.
Stepper Motors comes with different sizes NEMA standard or non standard sizes. Geared or non.
Stepper Drivers: are the driver circuits used to control motor stepping speed, direction, power & brake. Famous drivers used are A4988, DRV8825, TMC210 ... etc.
A4988 DRV8825 TMC2100
Motherboard: This is the main board that controls the whole printer. Arduino MEGA2560 boards are the most used in the reprap project, however, they are outdated now since the arrival of the smoothieboard & the Duet wifi. The board has many roles to do, therefore it should use appropriate components that helps achieving its goals besides the brain "microcontroller".
We can evaluate motherboards by their capability to run fast motion, drive heated bed, control dual extruders or more, connectivity, price and many more.
Endstops: endstops are switches used to determine the limit of an axis. Mechanical, Hall Effect, optical switches are all used.
Mechanical Endstop Hall Effect Endstop Optical Endstop
Heated Bed: This is used to counteract first layer problems (warping & adhesion) by raising the temperature of the print surface slightly above the glass temperature of the filament used. PCB heated beds, silicone pads, power resistors or whatever source of heat is used. The goal is to have even heat distribution and high energy heat source to raise the bed temperature.
Bed Surface: Usually, either glass is used for precision levelness or aluminium for better heat conductivity.
Bed Material: This is a material that is applied to the bed surface to ensure better first layer adhesion. Different materials & techniques have been applied in order to find the one solution for all filamnets. Tapes such as Kapton Tape, Blue Tape, PET tape are always used. Glues also played nice with some or hair sprays. Currently, PEI material "Ultem" is one of the best choices that fits most materials. There are some materials like BuildTak, Fleks3D or PRINtTinZ plate ready for printing but I have tried only the BuildTak and had bad results.
Power Supply: DC power supply is used, either LED power supply or computer ATX PSU. I'd say to avoid cheap computer ATX and go for the LED power supply. 12V or 24V whatever the choice, electronics should be able to work with. 250W is what most regular size 3D printers consume.
LED Power Supply ATX Power Supply
Coolers: Fans are used to cool electronics, motors, hotend & printed part. Not always used & depends on components used & design. Water cooling has been used, but it is a bit overkill for our application.
The de-facto standard in reprap community is the combination:
Aluminuim Frame Prusa I3 style + Threaded rods for frame construction
Double M5 Threaded rod for Z-Axis
GT2 Pulley + Belt + Idler for X & Y axis as motion transmission.
LM8UU Linear bearing guide for X,Y & Z axes.
NEMA17 Motors + Arduino MEGA2560 + RAMPS 1.4 + A4988 Stepper driver + Mechanical Endstops + PCB Bed + 12V Power Supply
This combination gives a 3-axis CNC machine.
Extruder & Hotend are critical choices for 3D printers. That is why the next blog will be dedicated for discussing multiple designs,
Thanks for reading.
Note: My Custom made 3D printer (V-Bot) files will be shared once optimized.
No comments:
Post a Comment