Standard Format for A-grader Data Inputs and Outputs – Type W
To function correctly the A-grader requires a number of dimensions from the mill. These dimensions are received by the A-grader through the serial port, via a RS232 link (RS422 available as an option).
A-grader Serial Inputs (ASCII String)
1)Timber Length - in whole mm.
Measured using an end point laser with a 4-20mA output connected to the mill PLC.
We can supply a suitable Serial (RS232) laser if required.
Accuracy requirement +/- 5% of Dimension
2)Timber Thickness - in whole mm.
Accuracy Requirement +/- 2% of Dimension
3)Timber Width - in whole mm.
Accuracy Requirement +/- 2% of Dimension
4)Timber Grade - 00 = Skip Board, 01 = Grade Board.
Required to tell the A-grader if it should grade a particular board.
The data must be collected and stored in the mill PLC, before the board reaches the first A-grader Sensor. At this point A-grader will indicate via one of its relay outputs, that the data is required to be sent from the mill PLC.
Serial Communication Details
Protocol - RS232, Baud Rate – 9600, Stopbits – 1, Parity – none, Flow control – Off or none
DataBits - 8
Cable - Normally Belden-M-9503 3pr 024 cable is recommended.
For short distances (<20m) a single pair screened instrument cable may suffice.
Regardless of the cable type the screen must be suitably earthed at one end only (Earth to computer).
The A-grader has a 9 pin male serial connector fitted to the rear of it.
For distances in excess of 80m or in high electrical noise areas, we recommend the use of a RS485 converter at each end of the serial cable to ensure reliable communications.
Serial Timing Details
Timing of the transmission of data is critical; The A-grader will activate a dry contact relay output when the serial string is required. The A-grader then polls the serial port for a set amount of time, before retrieving the data from the serial port.
Both these times are adjustable in the A-grader.ini file, we try to keep these times as short as possible.
Typical settings are
- A relay pulse of 40mS duration to indicate data required.
- A wait time of 60mS after the above pulse before reading in the serial data.
- The PLC needs to be able to reliably send the correct data every time to prevent missed boards and unnecessary rejection of good boards.
ASCII String details
20-digit string communicated as one word in the format 0000000000000000 with no CR or LF at the end of the transmission.
Any unused parts of the string must default to the correct number of zeros
00000000 0000000000 00
Length, mmThickness, mmWidth, mmDensity kg/m3not usedGrade/No Grade
Serial Hook-up Details (3 cores required)
The 2 data cores (i.e. 2 and 3 connections) must be a twisted pair to prevent data corruption.
9 pin to 9 pin25 pin to 9 pin
2323
3232
2323
5575
Serial Comms Testing Tools
Our Website contains some VB.Net based serial comms testing tools.
The SerialTestReader is designed to simulate A-grader and can be used to check the comms are working, and that the boards are being dimensioned correctly. It is important to use this tool at the location where A-grader will be physically located for a true test. A simple test writer is also available to test cable connections etc.
The VB.Net runtime is also required, follow the link on the web page to download the runtime from Microsoft.
Visit - follow the instructions as detailed on the web page.
Using the Serial Communications Tester
This tester is able to test the data format, but cannot test the actual timing of the data. To use this program correctly you need to install a temporary beam sensor in your line and use this to simulate the A-grader send serial relay to the PLC.
We recommend that you spend some time ensuring that the serial comms is set up correctly, as this seems to cause the largest number of problems with A-grader not grading the correct board.
A-grader Outputs (10 dry contact relays)
6 relay outputs representing grades, to run dye guns or to mill.
2 relay outputs representing high and low density thresholds.
1 relay output representing reject to run tipple gate or similar.
1 relay output representing a call to send the serial data string now.
Tally System
A Web Based Tally System is also available; this allows the A-grader to act as a web server on any suitable network. Current and historical information of board dimensions and grades can be retrieved for analysis.
The Tally System is individually tailored to suit the user’s business requirements.
Set-up and testing requirements
Prior to installing an A-grader we would like to see the following carried out.
1)Serial Data Requirements - Using the serial reader supplied, you will need to create a file containing at least 100 boards that have been run through the mill.
To carry this out you need to install a beam sensor at the point A-grader will be installed, this beam is then used to simulate the send serial message trigger to the PLC. With a Laptop running the serial test reader program, all the data will be saved to a file automatically. This file can then be emailed to us for analysis.
It is important that this test is as real as possible. The laptop must be set-up at the planned A-grader install point, and the serial cable must be the one that will be used for the A-grader install. This proves to you and us that the correct data is available, and is available at the right time.
2)Length requirements – If you require the addition of laser for measuring length this will need to be installed and working before the above test is carried out.
We can supply a high-speed serial laser if required. The laser is very fast and uses RS232 serial comms to communicate with your existing PLC. We can supply install instructions and give technical advice. A beam sensor or encoder can be used to tell the PLC, when it should read the current laser length.
3)Presentation of Boards – In order for A-grader to function properly the following must occur:
- The ends of the timber must be squared off smoothly.
- The square end needs to sit snugly against the fence before the A-grader.
- The lug chain needs to feed timber consistently to the point where A-grader is installed.
- The lug chain must present the timber squarely to the A-grader.
4)Upstream accuracy requirements – A-grader itself is very accurate, but is totally dependent on being supplied the correct information at the correct time. It is up to the client to satisfy themselves and us, that the information supplied is accurate and timely. We will not supply or install A-grader, until we are happy that the supply of information to A-grader is as per these requirements.
5)Post install testing - Once the A-grader is installed we will perform some trials to ensure both parties are happy with the install. This trial will consist of 25 boards of each grade; these will be manually marked at grading, separated from the line and individually graded on your QA tester.
Due to timber variances and the values of the default A-grader Grading Schedule, the grades may not be exactly right at this stage. We are not worried about this as the customers’ validation and testing will be required to match the exact grade to the local timber supply. At this stage we are interested in proving to the customer and ourselves, that the A-grader is performing linearly and sorts timber of a similar stiffness into the correct pile.
Once this is complete A-grader is considered installed and full payment will be required.
6)Grading Threshold Adjustment and Validation – It is the responsibility of the customer to run suitable trials in-house to set the A-grader grading schedule thresholds, to suit the species and local requirements.
This will require the customer to grade and QA timber in such a quantity to suit local legislation and validation requirements.
Falcon Engineering has no responsibility for this stage of the A-grader set-up, although we will supply an initial grading schedule based on our best knowledge of the type of timber being graded. We can also assist with any questions regarding the results obtained.
We have a number of companies available for validation set-up, and through our partner Forest Research can offer help in writing and setting up a appropriate schedules. (This would be at an additional cost).
Contact Details for Communication Problems or Questions.
Kris Zhu
Falcon Engineering Limited
Mobile 027 2435812
Email:
29-01-2005 C:\A-Grader\A-GraderSpecifications\Standard format for A graderv28W.docrev 2.8