Window Manufacturing

AIE was contracted by Pentland Furniture to automate their entire process for manufacturing wooden double and triple glazed windows.

The complete project was broken down into the following steps-

• Replace the controller on the Wadkin Tenoning machine and re-commission
• Re-commission the Cattinair painting machine
• Develop a production server with an interface to the “Windowmaker” software package
• Add product and lot tracking using ink and bar code printing technologies
• Connect all machine centers to the production server

Wadkin Tenoning Machine

AIE replaced the existing redundant controller with a Beckhoff 6209 series PLC/HMI and Ethercat I/O

The principal functions of the controller were as follows-

• Accurately position the Docking Saw, 1st Tenon, and Profiling Spindle based on a window frame recipe prior to batch running to within 0.1mm.
• Provide a HMI interface for operator recipe setup, and frame selection prior to each machining cycles
• Use the HMI for alarms and machine mimic
• Provide high speed machine timing and sequence control
• Be network ready for future production scheduling

IEC61131-3 Programming Languages

AIE took full advantage of the various language subsets within IEC61131-3 when writing the application program. The Beckhoff Twin Cat2 PLC fully supports IEC61131-3, however programmers need to be aware that many PLC’s still only support parts of the standard. ST (structured text) was used to develop function blocks for – encoder based position control, alarm queuing across tasks, and overall order of code execution for each task. SFC’s (sequential function charts) were used for conveyor table and machine sequence control, whilst FBD’s (function block diagrams) were used for general control and logic functions.

Generating Alarms

The example below demonstrates the usage of the defined function block Alarm and its instance fwAlarm1. The rising edge trigger (R_TRIG) and the register (SR) are responsible for holding the alarm active until acknowledged by the Alarm.Ack output. The Alarm function block (FB) will queue the Message on the message queue pointed to by the Alarm.Qaddress input, and when successfully queued the Alarm.Ack output will reset the holding register.

The Alarm FB is written to work in a multitasking system where multiple tasks accessing the alarm queue asynchronously will not cause alarms to be lost, and the de-queuing task can run significantly slower. The de-queuing task is normally running the HMI so scan time only need to be in the order of 250 to 500 msec, whilst the task generating the alarm could be typically running at 10 to 50 msec.

Using data structures (shown below) makes your programs more readable, and easier to commission and maintain. They are especially powerful when used with pointers. New alarms are added to the Alarms array using the Next pointer, whilst alarms to be read out are removed by using the First pointer.

The instance of the Alarm_read FB shown below is executed by the HMI task and removes an alarm from the queue to be displayed on the HMI panel. Activation of “Alarm Clear” will cause the next pending alarm to be displayed.

State or Sequential control using SFC

The self documenting nature of SFC programs makes them essential for use for all process control functions which are by nature sequential or state based. Programmers are able to execute specific programs on entry, exit and continually within each step. Defined conditions between steps determine when step changes occur.

Shown below is an example of the program executed by the Clamp step of the SFC program. Note the use of the exception logic to reset the SFC back to the Home step.

HMI

The integrated HMI/TwinCat PLC was inserted into the existing control panel with the cat5 cable running back to the electrical cubicle housing the Ethercat I/O. The Operator selects the recipe to run that can consist of up to 10 steps, with each step holding the setup for the multiple cutting axis. The PLC program will move each servo axis to its desired position before automatically starting the machining process.

Helping Australian manufactures remain competitive

The automated rapid manufacture of wooden window frames for double and triple glazed windows made possible by the upgraded Wadkin machine will give Pentland Furniture a significant competitive advantage. Having each machine center connected to a factory wide product and lot tracking system will ensure that production runs efficiently with no part mismatch errors. AIE is pleased to be able to assist an Australian manufacturer remain competitive by implementation of advanced automation techniques.