Fangzheng Liu (MIT)

Semi-Automatic-PnP

My main goal is combing the advantage of human and machine during the PCB assembly process. Human can easily localize where the components are, and machine can easily pick the specific components.

Currently, there are two ideas I have for the Semi-PnP machine system. The first is using a manual PnP as a base, and carries a machine controlled PnP. For the components that don't need to be strictly aligned, we can do the manual PnP. For the components that need to be strictly aligned, we can do the manual Pick first, move the components close to the corresponding pads, and then let the machine do the rest: human do the rough localization, machine do the final fine localization.

Another idea is using one set of machine to realize both, when the actuators are disabled, the machine can be freely moved manually. When the fine localization is needed, the actuators can be enabled and the machine can do the fine components placings automatically. For this idea, I will choose BLDC for the actuators. Both needs a smooth linear guide since when controlling the machine manually, we need to move things smoothly. The linear guide I designed:

The Machine actually will be comprimised of three parts:

The base CNC part that can be easily moved by hand.
A small CNC machine that is carried on the gantry of the base CNC.
A pick and place end effector.

I designed a configurable motion block for the linear motion guide. There are three SG20 ball bearings on the guide. To adjust the position of the bearing to fit tight to the guide, I designed a simple adjustable jig to adjust the position of the third bearing. You can change the position of the bearing by screwing/unscrewing the two screws from both sides. It works smoothly!

This is the whole system:

I designed the electronics control the machine and the pump:

The machine control board is the main control board I designed for the CircuitScout PCB probing machine. The pump control board is the spindle driver board I designed for the Clank machine.

The machine can work in two different modes:

Manual mode: the machine can be moved freely by hand.
Machine-control mode: the machine can be controlled by the small CNC machine on top to do fine components placings.