Posted By: Bill  Anderson

In the world of electromechanical automation, the Cartesian machine using linear actuators is a common way to get things moving in a precise manner. I created a demo machine using a variety of components to give some examples of what is possible. The machine consists of three stations – a path following example that traces our Axis logo with a stylus, a pick and place example that uses a suction cup and vacuum sensor to move vials, and a rotary fourth axis that utilizes electronic camming to flip a switch back and forth as it spins.

The machine utilizes an Omron Delta Tau CK3 controller and communicates to the Copley drives over an EtherCat network. Using a Zimmer pneumatic gripper and an SMC pneumatic slide the machine picks up the different samples. Three Parker XE actuators with P-series servo motors handle the XYZ motion. A Lin stepper motor with encoder spins the fourth axis station. Three Copley XEL servo drives are in the cabinet to move the P-series motors, and a Copley SEM stepper drive module is mounted to the fourth axis station to control the stepper. Finally the machine is operated using a Parker XT HMI which communicates to the controller over Modbus.

On startup the machine uses sensors to make sure the stations are all in the correct place. The stepper motor then homes using a sensor mounted on the end of the Z axis. This same sensor is used to make sure the path following station is in the correct place and to confirm that no vials are on the right side of the pick and place station. If anything is out of place a message is displayed on the HMI to correct the setup.

For the first station – path following – a DXF file of the Axis logo was used to 3D print the station and create a G-code file that the CK3 uses to trace the logo. Real-life examples of this functionality would be a glue dispensing or coating process. The CK3 with G-code capability is also regularly used to control professional CNC machines.

The second station is a pick and place example. A Schmalz suction cup with a spring mount picks up the vials and moves them to the right side and back. The controller receives a signal from a Schmalz vacuum sensor with each successful pick. This type of process is common in the biomedical industry with samples being put into a machine and then moved around for various testing. The suction cup material is generally selected for the specific application and can be food grade and anti-static as necessary.

The third station brings a fourth axis into the machine. It is a completely self-contained axis of motion with the drive and motor mounted together. This is the fourth axis on the EtherCat network. Although a stepper motor is used, the Copley drive is able to run it as a servo due to the encoder feedback. The stepper spins around back and forth and the stylus on the Z axis flips the switch on and off. For this routine three cam tables were generated for the X, Y, and Z axes. Using trigonometry, the path of each axis follows the rotation of the stepper motor as it spins. Electronic camming and gearing like this is very common in electromechanical automation. It can also simplify programming as only one axis has to be coded to move after the cam tables are loaded. In this machine the cam tables are generated by the controller on startup, filling in a table much like using a formula in Excel. I also wanted to use the Copley SEM drive to show off something a little different than a cabinet mounted drive. This drive is perfect for integration into OEM control circuits. Our customers are able to design around these drives and incorporate them directly onto the PCP boards.

You can see this demo machine and dozens of others at our Spring Forward Automation Expos next Tuesday (Danvers, MA) and Thursday (Hartford, CT). If you have a path following, pick and place, or any other kind of process that you need automated, give us a call and we'll be happy to help.

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