Motion Control SureStep Stepping System - Control System Overview (1 of 5) from AutomationDirect

Hi, Tom with AutomationDirect here. The following video is a continuation on the subject of Motion Control. In this video I will cover using a SureStep Stepper System that is controlled with ASCII commands from a Do-more programmable logic controller. The Stepper Motor I use in this video will be applied to the Rotary Index Table Station. This is the Second Stage in an application that utilizes the various Motion Control solutions offered by AutomationDirect. Let's get started. When we started these series of videos on Motion Control, the object was to cover all of the various methods that we had at our disposal to control a SureStep stepper system. If you have read the Automation Notebook two part article titled ?Starting with Steppers?, it covered three various ways to command the stepper system from various PLCs. To recap, the stepper system can be controlled by either high speed outputs for step and direction from certain PLCs, or by using a CTRIO module with certain PLCs, and the last method that was mentioned was to communicate ASCII commands with the Serial Command Language from the PLCs serial port to the SureStep advanced microstepping drives that are offered. It might be helpful to also take a look at the Part Feeder Station Learn video. The link is shown here. Keep in mind this handout covering this video series can be useful as a refresher to the steps needed to create a working Motion Control System. And of course, there is much information contained in the eight part video series on Motion Control that can answer most questions that may come up. Links to both resources are shown here. Now that I have the Part Feeder Station that can take the various colored marbles, along with steel and brass balls, I can next feed the Part Feeders output into the next stage. This stage is a Rotary Index Table. A SureStep stepper system with an advanced microstepping drive, part number STP-DRV-80100, commanded by the Serial Command Language, more on this in a moment, indexes a rotary disk. The disk has eight pockets, which can also be described as stations, which allow different operations to occur at each of the stations. The marbles enter the first station in the circular disk that has eight pockets, spaced 45 degrees apart. The eight stations are defined as shown here on the slide: Position 1 is the entrance for the part and is due South when facing the unit. A laser distance sensor with analog output is used to detect when the part is present. Position 2 uses a proximity to detect the steel parts. Position 3 which is due East includes the Pneumatic slide cylinder used to reject the steel parts. Position 4 is Idle at this time. Position 5 is due North and is where the homemade sensor is used to detect the color of the marbles. It is not sold or supported by ADC. Position 6 uses a proximity to detect the brass parts. Position 7 which is due West includes the Pneumatic slide cylinder used to reject the brass parts. Position 8 is the exit from the Rotary Index Table. Direction of rotation for the rotary disk is counter clockwise. The Rotary Index Table can be thought of as a rotary assembly machine. Various sensors are used to provide information to the PLC during the operation of the Rotary Index Table. An absolute encoder is coupled to the backside of the stepper motor?s dual shaft. The output from the absolute encoder is Gray Code, 9-bit 360 pulses/revolution. The encoder is wired into a DC Input module, and within the Do-more ladder logic, a value of 1 to 360 degrees of rotation is converted/produced. The value is used to verify the position of the eight different pockets that are around the outer edge of the rotary disk. Please note that the absolute encoder is not used to automatically correct for positioning. It is used to initially set the starting position of the rotary disk to make sure the exit tube from the Part Feeder Station is aligned with one of the eight pockets. This is done by having a one degree jog push button function on the C-more Touch Panel for either a clockwise or a counter clockwise direction. The C-more has a numeric readout that is used to monitor the rotary disks position. A Laser Distance Sensor is used to determine that a part has been loaded into the first position of the rotary disk. The laser distance sensor has been setup to show a sensing range of 1.18 to 3.15 inches. The output of the laser distance sensor is wired into a 4-20 mA analog input module. A value of 0 to 4095 is produced in the Do-more PLC and is scaled to read 1.18 to 3.15 inches. Compare contacts used in the ladder logic determine if the distance reading indicates a part is loaded, or if the pocket is empty. Two inductive proximities are used to sort the steel and brass balls from the marbles. Although normally used to sense ferrous metals, can also detect non-ferrous metals, such as brass, just not as sensitive. It is this property that was used to sort the steel balls from the brass balls. So at rotary disk position 2, the first proximity is adjusted so that it can detect the steel balls, but the brass balls go by undetected. At position 6, the second proximity is adjusted closer to the rotary disk so that it will detect the brass balls. There are pneumatic slide cylinders at the next position after the two proximities that are used to reject the steel and brass balls into a tube that takes them to a sorting bin. The two reject slide cylinders used for the steel and brass balls are equipped with magnetic sensors that are actuated form the cylinders magnetic piston. These sensors are used to determine the position of the slide cylinder. The cylinder fully extended sensor is used to make sure the reject gates are fully closed before allowing an index to occur. The cylinder fully retracted sensor is used to make sure the reject gate has made a full stroke. A homemade color sensor, not sold or supported by AutomationDirect.com, is used on the Rotary Index Table to detect the color of the different colored marbles that have been loaded into the Rotary Index Table Station. Using the color sensor gives us the opportunity to show how to take a device that operates on 5 Volt TTL logic level signals and interface it to PLC 24 VDC input modules. We chose an AutomationDirect Signal Conditioner and Optical Isolator, p/n FC-ISO-C, for this task. Three digital signals programmed from the color sensor produce a three bit code that represents the marble?s color plus some additional information. See the truth table here. The SureStep advanced microstepping drive has the ability to be set up using the SureStep Pro Configuration Software. In our example we select the SCL Configuration as our Motion Control Mode, use the Step & Direction Command Mode, set our Steps/Revolution to 36, 000, and chose an output function of Closed when motor moving. We will use this signal, wired to a DC input, to know when our index cycle is completed, and allow us in the ladder logic to sequence other events to take place. One of the nice features of the software is we can save the configuration as a file so it can be used later. As with the other projects, drawings and reference materials that can be downloaded from the video site as ?Take Aways?, we have included the SureStep Pro Configuration Software file. As mentioned earlier, the stepper motor is driven with a SureStep advanced microstepping drive, which is controlled by commands communicated by a serial connection between the Do-more PLC, routed to the serial port on the drive. The commands are a combination of ASCII abbreviations that are part of the Serial Command Language. An example using the commands is shown here: AC25 is used to set the acceleration rate to 25 rev/sec/sec. DE25 sets the deceleration rate to 25 rev/sec/sec. VE5 sets velocity to 5 rev/sec/sec. FL20000 is feed to length and will move the motor 20,000 steps in the CW direction. All of the SCL commands are described in the SCL User Manual. The SCL User Manual can be found at the link shown here. Look for the other videos in this series. Thank you for watching.