By: Tyler Jones (Manufacturing)
The pick and place needs to have a way that it can easily access all the integrated circuits, and components that cannot fit in SMT part reels. This means that an IC tray must be created to house all the components for the nozzle to pick up. The IC tray must also be very accurate in dimension that way there is no room for error for the nozzle to pick and place the part in the center of the part. The IC tray must also stand up off the picking surface and be able to to have small wells, or housings were the parts can fit into. The IC tray is shown below in Figure 1 It shows the basic dimensions of the overall build of the IC tray.
The 3DoT tray contains 22 unique part wells, as well as 6 copies. The copies of the wells exist on the tray because there are sometimes multiple of the same components necessary to complete the 3DoT board. The 3DoT board also contains components that need to be flipped or oriented at 45,90, or 180 degrees from the well. The A axis stepper motor accomplishes the task of flipping the component while it is already on the nozzle. This is done by programming the A axis stepper motor to turn using the GCODE commands. The A axis stepper motor is the axis that handles rotation of the parts, it also is connected to the nozzle and vacuum pump tubing. For further information on how to control the A axis stepper motor, or the design of the motors please refer to INSTRUCTION MANUAL FOR PICK AND PLACE OPERATION blog post, or the CALIBRATION blog post.
There was a problem in creating the wells of the IC tray. The first issue was that the Lulzbot TAZ 5 3D printer has an error of printing thickness of about 0.1-0.2mm. This means that after taking into account all the sizes of components an oversizing of about + 0.1 -0.4mm needs to be used in order to have the wells a little bigger than the part. Every part that goes onto the 3DoT tray was measured using calipers, and also cross-referenced with the datasheets from the manufactures. The following tables below in Table 1 Table 2 shows the size, part, number, description, dimension, error margin calculation, and other information for each part. The table is contained in the INSTRUCTION MANUAL FOR PICK AND PLACE OPERATION in order to aid the user in knowing where to place the components into the IC tray.
The positions outlined in column 1 of Table 1 correspond to the positions used on the 3DoT board. They are organized from left to right and top to bottom, with the number of the part corresponding to the same number on the IC tray itself.
The 3DoT IC tray was designed so that the centerline of each part is consistent. This allows for much easier programming and calibration as the X coordinate does not move when the G CODE is running. Similarly, the height of the tray does not change which allows for the Z coordinate of the pick and place to not change. This also makes the machine much more time efficient. For information on troubleshooting the code corresponding to the 3DoT tray or how to calibrate the machine, please see the CALIBRATION blog post.