HOW TO CHOOSE A MICROFLUIDIC 3D PRINTER ?
Existing 3D printing technologies process explained
Every following technology is based on the same system of additive process, every object is built layer by layer after being sliced by an informatics system.
Types of Microfluidic 3D Printers
Microfluidic 3D Printer : 3D printing has multiple applications in various domains, particularly scientific ones
The 3D printing is an old factory process and is a declination of additive manufacturing. As their efficiency is growing they find applications in very different domains like microfluidics. They allow developing any disposable object for inexpensive costs, with many kinds of materials. Accuracy of 3D printing is high enough to create micro-fluidic system, 3D printers for such kind of things already exist on the market.
Microfluidic 3D Printer : Selective laser melting
Here the laser beam moves all over the print scheme and heats the powdered material until its melting point, the powder becomes a solidified structure, once the step is complete a roller comes to place powder above the piece which had moved a layer’s height down, and the process of laser sintering starts again. Selective laser melting is more used for metallic composition.
Microfluidic 3D Printer : Selective laser sintering
Works like SLM with one difference: the laser beam doesn’t heat at the melting point of the material, it stops just before, and creates cohesion between grains of the powdered material so the heat regroups grains between them and creates cohesion. Selective laser sintering is more used for thermoplastic composition.
Microfluidic 3D Printer : Fused deposition modeling
Fused deposition modeling is the most commonly used 3D printing process in the world, simple and efficient it finds many applications and developments. The principle of this process is to lay down heated plastic leaving the heating frame on a flat surface (corresponding to X and Y moves) and going up slice by slice (moving on Z axis). All those moves describe 3 axis of the space as well known as the Cartesian space.
Microfluidic 3D Printer : Stereo lithography Apparatus
Stereo lithography Apparatus has the same process than Selective Laser Melting and Selective Laser Sintering, a laser beam heats the resin with a parameter of exposure and the resin gets polymerized. Again the object is moving a layer’s height and the machine projects a new scheme corresponding to the slice of the object. The final product should get an UV radiation to consolidate it.
As we develop a FDM 3D printer the following parts will treat only this technology.
Microfluidic 3D Printer : Fused deposit modeling printers benefits of huge variety of materials
The diversity of resin is limited compared to the large choice of filament you find in the market: ABS, PLA, POM, Nylon, etc… There are many type of material : bio-degradable, food contact proof, corrosive resistant, each material has its own characteristics and functionalities. One thing that will be common to each material it is their way to warp when they cool down, some materials like ABS get high warping if it’s cooled down too quickly whereas PLA gets fewer problems like this. The warping characteristics depend on each material composition and recommendations of the filament’s factory.
Microfluidic 3D Printer : Different system and different precision for 3D printers move
For FDM methods we have to convert the rotation of the motors into a movement of translation, for this there is 2 most-known solutions:
- System of pulley plus belt provide a cheap solution, and allowing high speed printing in spite of losing accuracy so in resolution too
- System of screw : The system of leadscrew and nut offering high precision nevertheless there is a backlash when positioning, so it loses a little bit of accuracy.
The system of ball screws offering a much higher precision but reducing considerably the print speed, however there is a better accuracy than other systems with an extreme minimal backlash, under 50 µm, such system is more interesting for microfluidic and micro system fabrication.
You’ll choose the system in function of the quality required for your final product. Some of the printers combine with bolt belt for X and Y axis and ball screw for the Z axis.
Microfluidic 3D Printer : Hot head end and heat bed (specific to FDM printers)
The hot head end is really important. This is the part that makes your 3D printer a 3D printer; this part is heating the plastic at the right temperature of fusion, to finally depose it. The choice of the extruder is capital for the efficiency of the machine; as well there are 2 systems: one with thread nozzle and tap radiator, or bore nozzle and radiator. This last system is more efficient to prevent from leaks.
If you are heating up the material too much you’ll get viscous material which can leaks and clog your extruder, if you are under heating your filament won’t pass through the nozzle.
The heat bead is here to minimize the difference of temperature between the hot end and the environment so it prevents the heated material to get too high cooling rate and retract on itself and create the phenomenon called: warping. By warming up the plastic it keep it at a range of temperature where there is no deformation.
Microfluidic 3D Printer : Software, computer’s interface for the 3D printers
The software is generally built in 2 parts: Te first one allows you to place the object on your plate and choose different parameters like the height, infill, speed, a graphical interface and the second part “hide” is the slicer, this part cut any object in slice of the height you choose before in your parameters, then if you cut a cube of 10 mm high by slice of 100µm (0,1mm) the slicer will create 100 slices. In each slice it will analyze the “image” and decompose into coordinates and X and Y axis, so here is how we create a movement by telling motors to move this position from another. Those indications are listed in file called “gcode” it will also be the extension of your file here an example :
G1 : Telling the printer to move F: for feedrate in mm/min
Mechanical element that gives 3D printers’ accuracy : Step motor
Their rotation is segment by angle, in example a motor of 1.8°/step need 200 steps to make a revolution : 200×1.8°=360°, less the angle is big the more you get precision. Motors have to be coupled with a system to get translational movement and with a stepper driver; this global system will define the step need to move a given distance, however more the degree per step is smaller more your global system will be precise : if it needs 80 steps to move 1 mm, one step can move 1/80= 0,0125 mm or 12,5 µm whereas if it needs 320 steps to move 1 mm, by the same operation, 1 step move 3,13 µm, such precision is required for micro fluidic systems.
Stepper driver, electronics components that multiply the accuracy
Stepper driver offer an electronic precision, by interpolating the current function of the motor and segment it so it creates virtual step. Those virtual steps are multiplying the mechanical step of the system, but more the virtual step is high the lower the torque is. So it’s important to make a good compromise. The stepper driver can control the motor noise as well.
Fan, important to get better 3D printed results
Generally by 2 they are cooling the radiator body of the extruder to prevent too hot warming, and the second one is cooling of the piece when needed (like for the bridge structure, a high cooling is recommended).
3D printers’ interface for users
Interface is important to make the machine run by itself, make it autonomous and easier to use. Equipped of a SD slot you can run any loaded program with an easy to use interface, even change some parameters at your convenience.
Electronic capacitive sensor
This capacitive sensor allows interesting things, first of all it provides a good altitude of the extruder for the first layer, and allows to test different point of the flat surface and create a virtual normal vector of the surface and will multiply every point by this normal to get a better accuracy when moving and positioning !
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