Nelson Bros Engineering Scanner / Optimizers

Lineally Scanned and Snapshot Scanned Log Systems


The creative nature of mechanical designers is best exemplified by the variety of Log Breakdown machines used in sawmills.  Carriages, End-doggers, Chip-N-Saws, Sharp Chains, Double Length Infeeds and Small Log Processors...   When will it end?

NBE and associates have done lineally scanned optimizers on Sharp Chains, Chip-N-Saws and Small Log Processors.  We have done snapshot scanning on Sharp Chains, End Doggers and Carriages.  We like the simplicity of a lineally scanned sharp chain feeding twin bands and we like the challenges provided by the snapshot system.  Mainly we like scanner systems that get accurate data on as much of the log as possible and mechanical systems that can repeatedly place the cuts as commanded by the optimizer.  Log systems are the mechanical designers method of challenging scanner/optimizer designers.
 

Scanners

There are three basic methods of scanning logs:  Transverse, Lineal and Snapshot.

The log travels laterally thru a Transverse Scanner that spans the length of the log.  Most transverse scanners use light curtains to collect diameter data in one or two axes at each light curtain element.  Transverse log scanners are normally used in systems where the log is already held in the positioning system (i.e. dogged), such as carriages and end-doggers.  There may be transverse log scanners that collect profile data much like transverse cant and board scanners, but I have never seen one.  Generally transverse log scanning is referred to as the "old way".

The log travels lengthwise thru a Lineal Scanner.  The scan zone is much smaller (i.e. cheaper) since only 2, 3 or 4 heads are needed to collect data around the entire log's periphery.  NBE normally uses two or three JS-20 scan heads to collect log profile data.  We prefer the single scan zone, which requires the entire log to pass the scanner before the scan is complete and optimization can begin.  For a Chip-N-Saw upgrade we did not have the runway length requirement for one zone, so we cleverly tucked 3 zones in the Lift & Shift infeed section.  Lineal scanning is the least expensive, most accurate, easiest to maintain and most simple scanning method (see our Edger Description for more of NBE’s opinion on lineal scanning).

Snapshot scanning does not require log motion.  The two contending methods are the multizone line laser system and the rastering laser time-of-flight system.  NBE does not use the rastering system, so we obviously think it is inaccurate, expensive, unreliable and hard to calibrate.

NBE uses the JS-20 single or dual laser scan heads for snapshot scanning.  Multiple heads are positioned above the log, with one bank of heads on the left and one on the right.  Each head projects a laser line that drapes around the log, collecting data for 130 to 150 around the log. 

 

Optimization
 

Log Optimization is always time limited.  No optimizer attempts every possible offset, taper and curve path.  Therefore, the design of the system requires tradeoffs in computing hardware and software.  Computer hardware gets faster every year, so NBE tends to avoid exotic processors, multiple computers and other hardware configurations that sound good today, but quickly becomes expensive junk.  We have always used a single optimization computer from a common vendor (i.e. Dell, Compaq, HP, etc.).  NBE believes that effort spent improving the speed of the optimization algorithm, pays off forever, while the effort and money spent on exotic hardware only pays off until it's advantage is eclipsed by next year's standard computer.

NBE does provide all the software features needed to maximize recovery, obtain sufficient reporting and maintain the system.  Sadly, this does not include the Rendered, 3D log display with rotation controls, which is so popular with log systems.  This feature does help sell a lot of systems, but does nothing to improve recovery or maintain a system.

Like all systems, to select a log optimizer, you need to address the following:

  1. Does it do what I want?
  2. Can it be maintained?
  3. Does it have the best Return on Investment?

1.  Does it do what I want?  The NBE log optimizer has the following capabilities:


Like any vendor, we can do anything, but you should know what exists.  Our company's size and experience makes us a better choice for custom systems.


The following block diagram is for a lineal board edger, but the same diagram works for lineal cant optimizers and lineal log optimizers.  The system hardware is truly identical!  The optimizer computer is networked to the scan heads and to the supervisor's switching hub.  The switching hub allows multiple monitor computers to display the optimizer solutions or get reports without any burden on the optimizer's network.

The snapshot system uses the same configuration with more scan heads connected to the network hub and scanner cabinet.  An encoder is not used on a snapshot system.

The simplicity of the NBE systems is best illustrated in the number of parts.  To have 100% spares coverage, you need a scan head, encoder, power supply, network hub and a couple of solid-state modules.  The total cost of the spare parts is always less than $9,000.

Like all NBE systems, the Supervisor computer is identical to the Optimizer computer so it acts like a "hot spare".  When (not if) the Optimizer fails, the Supervisor already has the latest parameters, so you swap some cables, select the "Switch to Optimizer" icon and start the Supervisor as the Optimizer
 
 


Click for full image

 

The Optimizer Computer will be in the computer room. The Optimizer's monitor and keyboard will be mounted near the scanner or the operator to allow for scanner calibration and troubleshooting, plus give the operator a graphical view of the optimizer decisions.

The Supervisor Computer will initially be in the computer room, but can be moved into a maintenance or QC office if desired.  The Supervisor is linked to the Optimizer via an Ethernet network.

The Supervisor Computer normally follows the Optimizer, by reading the data from the 25 board archive, then displaying the solution on the Supervisor Monitor located in the computer room.  The Supervisor computer is not necessary for optimization, thus is can be used for offline functions, such as, reviewing previous boards, printing shift reports or replaying boards from recovery tests.

The SUPER program in the Supervisor Computer can be copied to other computers and be used for training or to monitor the optimizer.
 
 

NBE's Log Optimizer Solution Screen

The most important display is the solution screen shown above.  It gives a graphical display of the solution in real-time, some production and decision text and a list of the previous logs.   This screen is displayed on the optimizer, supervisor and any monitor computers.  The optimizer's monitor is normally positioned within the operator's view.
 

 

Now we are ready for the second major requirement

2. Can it be maintained?  This discussion is the same as in the NBE Board Edger Optimizer.
 

3.  Does it have the best Return on Investment?

Again, this discussion is the same as in the NBE Board Edger Optimizer.

 

LINKS TO ADDITIONAL INFORMATION

NBE Home Page

NBE article on Curved Sawing Gangs

Customer List

 

Email NBE

 



www.millsmart.com/log.html - (360)951-2737  19-Dec-05