Arduino Motorized SMT Solder Paste Dispenser

cults3d

This motorized solder paste dispenser for soldering SMT boards was inspired by this thing: http://www.thingiverse.com/thing:384680. The home directory of this project is on GitHub here https://github.com/zapta/misc/tree/master/paste_injector, which includes the hardware and firmware design of a compatible controller board that looks to the Arduino IDE as an Arduino Pro Mini. The schematic for this project can be found at https://github.com/zapta/misc/raw/master/paste_injector/eagle/paste_injector_schematic.pdf. The bill of materials (BOM) is listed at https://github.com/zapta/misc/blob/master/paste_injector/eagle/paste_injector_bom.csv. A discussion about this project can be found on the EEVBlog forum: http://www.eevblog.com/forum/reviews/solder-pasteflux-manual-syringe-applicator/150/. I successfully printed both PLA and ABS using standard slicing parameters (3 layer shells, 20% infill). Here are some hints to help with assembly and use: When printing the motor axis coupler, make sure your extruder temperature is high enough for good interlayer bonding. The step motor listed in the BOM can be found on eBay from many sellers; they usually come with a ULN2003 driver PCB that isn't needed here. To minimize free play along the motor axis when mounting the coupler, try to pull out the motor axis while pushing the coupler toward the motor before tightening the coupler screws. You can insert the threaded inserts using any standard solder iron that fits into their holes. It's best to get tapered inserts similar to those specified in the BOM; if not, you can taper them using a file or Dremel tool. When inserting the threaded inserts, don't push too hard – let the heat do most of the work. This will result in better adhesion. I programmed the controller board using an AVRISP MKII, but you can use whatever works for you; GitHub has the binary image file that includes the Arduino bootloader and a script to program the AVR fuses. If you want to hack the firmware, make sure to remove the two screws of the syringe holder and turn the syringe to screw it out of the motor mount (don't pull the plunger out, which may insert air into the solder paste chamber). To store the solder paste, remove the needle and close it with a Luer Lock cap. If you keep using the same needle, make sure to clean it after each usage by flushing it with IPA. The PCB design currently on GitHub (as of Nov 2015) was 100% auto-routed as part of the Autorouter Challenge discussed here: http://www.eevblog.com/forum/projects/the-auto-router-challenge-will-it-work/. The PCB currently on GitHub uses a 'reversed' micro USB connector; make sure to get the connector listed in the BOM or feel free to modify the PCB for your preferred micro USB connector. If you're looking for PCB manufacturers, check prices at http://pcbshopper.com. This is a 30x40mm two-layer board. I glued the two washers to the syringe holder using super glue so they don't fall off when removing the screws. Not a big deal though. The 3D models were designed with OpenSCAD, an open-source 3D programming package. If you want to tweak any dimensions, load the provided .scad file in OpenSCAD and regenerate the .stl files.