Process Control with Coordinate Part Position - Position Synchronized Output (PSO)

Table of Contents

Design Features
New Feature: Part-Speed PSO
Don’t Derive Part Quality–Control It
PSO and Laser Processing
PSO Is Versatile
PSO Set-Up
User-Specified PSO Output Pulse Trains
Fixed-Distance Firing
Array-Based, On/Off PSO Output Control
Array-Based Grayscale PSO Output Control
Window-Based PSO Output Control
Custom PSO Pulse Spacing
Control Any Tool and Improve Process
Applications

Design Features

  • Activate a process tool based on distance traveled, avoiding trigger faults based on deceleration, acceleration, or any other velocity instability
  • Combines well with fast-pulsed lasers, enabling next-generation display and medical device manufacturing
  • Includes versatile, process-improving features

Aerotech's Position Synchronized Output (PSO) feature coordinates motion with output that activates lasers or data acquisition devices for high-quality, high-speed, and unmatched process control.

New Feature: Part-Speed PSO

Programed analytical velocity can be used as the tracking input for activating the PSO output. With the new Part-Speed PSO, the ability to activate the PSO output based upon real encoder feedback is currently extended to the part-space vector velocity command.

Part-Speed PSO allows:

  • Control of the PSO output based on user’s process tool's part-processing velocity, even when kinematic mechanical set-ups are used
  • Control of the PSO output when using non-linear opto-mechanical axes, for example 3D galvo scanners
  • PSO control with reduced wiring complexity

Don’t Derive Part Quality – Control It

Why control a process based on velocity when you really care about position? Aerotech’s control solutions are designed to fire position-calculated PSO pulses at up to 12.5 MHz and with latencies as low as 80 nanoseconds. Users can use these pulses to activate a laser, camera, sensor, or other devices that accept IO. As processes become more reliant on throughput and accuracy, firing based on actual part position becomes more crucial. PSO pulses can be directed up to three axes of vector motion while monitoring the calibrated feedback at low latencies and high-speeds.

PSO and Laser Processing

Laser technology is continually evolving, and fast-pulsed lasers are facilitating new material processing capabilities. These processes often involve the use of short-pulse or fast-pulse lasers. The PSO is a differentiating controller feature for these processes since no other control technology enables the sub-micrometer accuracy of laser spot placement without compromising throughput. Thermal management is possible even at high accelerations. Furthermore, the PSO has long been appreciated by laser welding and laser cutting applications. These applications include the use of YAG, CO2, and excimer fiber lasers.

PSO Is Versatile

The PSO’s versatility is well-defined not only by its high frequency and low latency, but also by the several modes of operation that allow precise integration with a number of processes. The following sections describe more about the workings of PSO.

PSO Set-Up

The PSO arrangement is easy. A four-step process is executed in Aerotech’s AeroBasic conversational programming language.

  1. Specify which axes are involved in the vector-based distance calculation
  2. Specify the spacing of the PSO firing event
    1. This can be stated as: Fixed distances across a part
    2. Custom fire-to-fire event distances loaded to a data array
  3. Design the PSO output pulse train needed at each firing event
  4. Specify which PSO firing events generate PSO outputs from the drive hardware; PSO outputs can be specified such that:
    1. They take place at all PSO firing events
    2. PSO firing events become PSO outputs centered on binary data array values
    3. Only when the specified axes are within a specific position-based window
    4. The duty-cycle of the PSO output pulse train is altered based on a grayscale array value

Most techniques of specifying PSO firing events and PSO outputs can be mixed and matched to enhance application’s needs.

Aerotech’s Position Synchronized Output

Figure 1. Aerotech’s Position Synchronized Output can be implemented in four easy steps.

User-Specified PSO Output Pulse Trains

At each PSO firing event, denoted by the red dot in each image, a PSO output pulse train is produced but not essentially output by the drive hardware. When a PSO output pulse is activated, the drive will output the PSO output pulse train as indicated. Multiple cycles can be involved in a pulse train, based upon the application’s needs. The amplitude of the PSO output is reliant on the voltage level linked to the PSO circuit. The ability to alter the on/off behavior and amplitude of pulsing makes the PSO the most flexible position-based tool command available to high-end, precision processes.

User-Specified PSO Output Pulse Trains

Figure 2. A PSO pulse train specifies the on/off behavior of the PSO output. A PSO pulse train occurs every time the controller generates a PSO firing event and is specified by a total time, an “on” time, a number of cycles, and delay time (from the PSO firing event). The behavior of this PSO output pulse train can be thought of as a single “event”, represented by the darker blue bar on the right-hand-side of the image.

Fixed-Distance Firing

The Fixed-Distance PSO pulsing is the typical use case for PSO, because firing based on position feedback is the most accurate method to guarantee critical process control, such as data acquisition or laser firing, occurs where users intend. In this mode:

  • The fixed-distance spacing of firing events is indicated by the user
  • Up to three axes of encoder feedback can be used to calculate the actual distance traveled
  • At each PSO firing event, the user-indicated PSO output pulse train is created
  • The PSO output pulse train becomes the PSO output at every PSO firing event

Fixed-Distance Firing

Figure 3. The red dots represent PSO firing events generated at a fixed distance by the PSO distance counter. The blue bars represent a PSO output pulse train generated by the pulse generator. In this example, the user is generating a PSO output at each PSO firing event. Therefore, the specified PSO output pulse train is output at the drive hardware every time the distance counter creates a PSO firing event.

Fixed-Distance Firing

Figure 4. A highlight of fixed-distance firing is that changes in velocity (acceleration) do not affect your pulse-to-pulse laser spacing. This type of control increases part quality and throughput in high-dynamic precision processes.

Array-Based, On/Off PSO Output Control

Another typical mode for PSO is to stipulate which fixed-distance PSO firing events generate an actual PSO output via the use of data array values. In this mode:

  1. The fixed-distance spacing of firing events is indicated by the user
  2. An on/off sequence of preferred PSO outputs is produced and downloaded to the drive hardware
  3. Up to three axes of encoder feedback can be applied to calculate the real distance traveled
  4. At each PSO firing event, the user indicated PSO output pulse train is created
  5. The PSO output pulse train becomes the PSO output based on the on/off sequence on the drive hardware

Array-Based, On/Off PSO Output Control

Figure 5. Bitmap firing is represented in this image. In this PSO output mode, array values are indexed through as PSO firing events occur. The array values are used to specify which PSO firing events result in a PSO output at the drive. In this implementation, the distance counter still tracks the same spacing between events, but commands your process tool at specified locations.

Array-Based Grayscale PSO Output Control

Applied for applications such as grayscale laser marking, this PSO mode integrates the array-based technique above with control of the duty cycle of the PSO output pulse train. In this mode:

  1. The fixed-distance spacing of firing events is indicated by the user
  2. An on/off sequence of preferred PSO outputs is produced and downloaded to the drive hardware. Furthermore, each on/off value has a duty-cycle value related to it, which is also downloaded to the hardware.
  3. Up to three axes of encoder feedback can be used to calculate the real distance traveled
  4. At each PSO firing event, the user indicated PSO output pulse train is created. The PSO output pulse train becomes the PSO output according to the on/off sequence on the drive hardware.
  5. The PSO output pulse train is altered based upon the related duty-cycle value

Array-Based Grayscale PSO Output Control

Figure 6. Grayscale or “Bitmask” firing is represented in this image. In this PSO output mode, array values are indexed through as PSO firing events occur. The array values are used to specify which PSO firing events result in a PSO output at the drive. Additionally, analog or “grayscale” values are used to control the duty cycle of the specified PSO output pulse train. In this implementation, the distance counter still tracks the same spacing between events, but commands your process tool at specified locations.

Window-Based PSO Output Control

Besides on/off and grayscale output control, users can stipulate position-based windows. These windows can be used in applications that require only pulsing to take place in certain specified position ranges. The array-based on/off, fixed-distance, and array-based grayscale control are all available along with window control. To use window control:

  1. The user stipulates the window range and enables window operation
  2. PSO is used in accordance with the above modes

Window-Based PSO Output Control

Figure 7. In this example, windows are established that mask the PSO output unless the tool is in the specified window ranges. PSO firing events (represented by the red dots on the bottom graph) occur outside of the window ranges. However, PSO outputs (represented by the blue bars) do not occur unless within the specified position-based windows.

Custom PSO Pulse Spacing

When executing any of the above modes, users can use custom PSO firing event-to-event spacing. Users can stipulate custom spacing values for applications where constant spacing is not needed.

Control Any Tool and Improve Process

Customers of Aerotech use PSO to activate processes that include:

  • Nondestructive test triggering
  • Laser firing
  • Data acquisition
  • Camera capture

Applications

The PSO's versatility services offer many remarkable precision manufacturing processes, including:

  • Imaging
  • Wafer Dicing
  • Via Hole Drilling
  • Laser Processing
  • Additive Manufacturing
  • Fuel Injector Drilling
  • Flat-Panel Manufacturing
  • Printed Electronics/Dispensing
  • LED-Based Display Manufacturing
  • Processing of Turbine-Blade Holes
  • Laser Hermetic Seam Welding of Pacemakers
  • Laser Cutting Stents and Other Interventional Cardiac Devices

This information has been sourced, reviewed and adapted from materials provided by Aerotech, Inc.

For more information on this source, please visit Aerotech, Inc.

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