Engineers and makers who routinely design custom PCBs and circuits would benefit significantly from having a PNP machine on hand that could manage all the monotonous, repetitive soldering of SMDs. Unfortunately, most PNP machines can cost a fortune, which is why some choose to go the DIY route, including software developer/circuit maker John deGalvina, who created a PNP machine around a Smoothieboard controller.
“This PNP build pulls ideas from many different machines that came before this one. I used the OpenPnp OpenBuilds as a starting point. I wanted to have a usable machine without spending thousands while being able to add things (like auto feeders, and a nozzle changer) as needed.”
deGalvina designed his PNP machine using the open source Smoothieboard 5X CNC controller, which packs an Arm Cortex-M3 LPC1769 (512Kb of Flash, 64Kb of RAM), 5X Allegro A5984 stepper drivers, three large FETS for controlling large resistive loads, and three small FETS for managing add-ons. It’s also equipped with Ethernet, USB-B, micro SD card slot, six end-stops, four thermistors, and extra I/Os (SPI, UART, I2C).
For the frame, deGalvina went with a pair of V-Slot Mini V linear actuator bundle for the X-axis, and Mini V gantry set for the X-axis, and Nema 8/17 motors and Juki nozzles for the Y-axis and vacuum head, along with a host of hardware from OpenBuilds.
Additionally, he used 3D-printed 0816 SMT automatic feeders, a desktop PNP material stack block, a surface mounting PNP head (dual, with linear rails), and a USB microscope and Teslong portable multi-function soldering magnifier camera, giving the machine double camera vision for accurately placing SMDs.
Initially, deGalvina used Ethernet for transmitting commands using the Smoothieboard, and found the PNP machine wasn’t up to speed in part placement, switching over to USB serial, he found his machine could drop 1200 parts per hour. To see a complete walkthrough of deGalvina's PNP machine, including an extensive BOM, head over to his project page.