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Introduction:

BuildYourCNC's very own Pick and Place Machine offered to the public. This is the pick and place machine we use in-house to assemble our electronic products. The redFrog (our name for the pick and place machine) is a machine that picks-up very small components (SMD - Surface Mount Devices) and places them on the PCB (Printed Circuit Boards).

Description:

If you're still wondering what these machines do, please have a look at the video below showing the complete assembly process starting from applying the solder paste, pick and place and finally sintering (reflowing) the board to fuse the parts to the board. This machine is constantly in development and features will be updated as further development and revisions happen.

The features of the redFrog pick and place machine include the the suction responsible for the picking functionality, 3 axis motion and control, reel and tape holder, gravity pulled tape cover and internal computer. The suction for picking the components is created using a vacuum pump (3 CFM) and tank combination (vacuum shown may not be the one provided in the system). The computer being housed internally enables the user to locate the machine more conveniently (only a keyboard, mouse and monitor, not included, is plugged into the machine. The motion control is provided by stepping motors for all axes and the part rotation and is powered by drivers capable of 3.0 amps. A good base is still in development, so the current machines will need a base/table 21-1/2" x 20-1/2" (546.1mm x 520.7mm). The carcass shown in the video is not included as it really is not the most elegant solution for this system.

Specific details regarding the steps per inch and dimensions:

The steps per inch is relative to the microstepping that you set on the drivers. The Drive pulley used for the X and Y axes are .2" pitch with 14 teeth. Native motor steps per revolution is 200 steps. Microsteps per single step: 16 (1/16 microstepping set onthe driver). So, the steps per inch is as follows: = (200 * 16) / (.2 inches * 14) = 3200 / 2.8 = 1142.86 steps / inch. Expect 900 - 1000 effective steps per inch since there is minimal load at the end effector to influence much deviation. You can opt to increase the microstepping to 1/32 or 1/64 and your effective steps per inch will increase.

The area that is reserved for the PCB layout measures 5-3/4 x 15-1/4 inches (146.05 x 387.35 mm). The PCBs can be laid out in grid form and the g-code is designed to be able to place to each of the PCBs through looping and offsetting (automatically handled by the g-code). All you set are the parameters for the arrayed PCBs and measurements of the actual board. You can lay a panelized PCB in this area, or simply place the PCBs in a tight row and column grid.

The vacuum pump is controlled by a circuit that has a pressure sensor, not included, (similar circuits used in industrial applications carry a very high price due to their specialization. This circuit keeps a range of suction in the tank at all times so the picking can be at its best performance. The range of suction is controlled by two potentiometers (components that can be adjusted like a dial on a stereo) to maintain a high and low vacuum and only run the vacuum when the tank needs to be . This vacuum is shown in inches of mercury. The higher the inches of mercury (Hg), the higher the vacuum.

Instructions

This pick and place project is recommended for advanced users. The assembly requires understanding mechanical principles, connecting computer components and installing the operating system, solding connections, connecting pneumatic equipment and working with mains voltage (120/240v). If you have any reservations on your abilities to complete this project, take a look at the assembly videos, which will give you a good idea on the difficulty level of this project.

Full redFrog Playlist on Youtube (For assembling the redFrog Pick and Place Machine)

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The pneumatic schematic of the tube and tube fittins for the vacuum source for the redFrog pick and place machine.

Correct pneumatic configuration for the redFrog (or other) pick and place system. Tube Fittings are shown in a heavy line weight. Thin lines between the fitting are 1/8" ID silicone tube

All straight fittings have 1/8" barbed connection and a 1/4" Male NPT (Nation Pipe Thread) with the exception of the fittings for the solenoid valve. The solenoid valve ports have 1/8" female NPT thread, so 1/8" male NPT fittings are used.

The solenoid valve in engaged when the suction is needed, which is received from the tank's reservoir of pressure below the current atmospheric pressure. It is intended that the solenoid activate using the computer control.

The check valve is needed so that the pump can be off for the time that the tank is adequately pressurized. If a check valve is not used, there would be leakage from the vacuum pump when not in use.

It is highly recommended that a vacuum pressure sensor be used in conjunction with this system to provide automatic tank pressure regulation using a pressure sensor and relay to control the vacuum pump when the tank falls below a specific level of inches of Hg (Mercury). A vacuum pressure sensor switch can be found at http://www.buildyourcnc.com/item/

electronicsAndMotors-vacuum-pump-

controller-sensor

This schematic can also be used to setup a manual pick and place system using a foot pedal, or other type of controlling mechanism connected to the solenoid valve for suction control.

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