Quality Production of MSR Lumber
MSR lumber can be produced by several types of grading machines under various grading agency rules. As long as the grading rules are followed and the quality control tests indicate the process is in control, the grade stamp may be applied and the lumber sold as an MSR grade.
To reach into the real potential of MSR, there are many additional details which should be examined. The purpose of this paper is to raise the awareness of these details, provide a method of assessment of the current operating quality level, and provide a guide for improvement.
Categories of machine rated lumber include Machine Evaluated Lumber (MEL), and E-rated Lumber as well as Machine Stress Rated (MSR) lumber. The techniques describe here are appropriate for production of all machine rated lumber categories. For simplicity, the term MSR is used in the remainder of this paper.
This is a checklist and guide for MSR lumber production, explaining the importance of each item and how to evaluate it. Many of the topics came from a 1997 presentation(1) to the Interior Lumber Manufacturers Association in Kelowna BC. When using the evaluation questions, you should circle the answer which best represents your situation. If you score high in all categories, congratulations, you are doing an excellent job. If you score low in a number of these categories, you have an excellent opportunity to be a hero in your company. A significant improvement in revenues may be available.
This document should be used in conjunction with your "plant standard" document, grading rules, your equipment manuals and service bulletins. This presentation is based on Metriguard equipment and typical North American lumber grading rules. If a plant is using other equipment or is operating under different rules, many of the same principles apply, but the details may vary from that presented here.
THE MAGIC BULLET
To the very best of our collective knowledge, there is no computer program or piece of hardware that will produce an optimum, or highest profit result by itself. There are many tools available. The most effective tool is an organized process of continuous improvement. This is accomplished by studying an operation, producing a list of problems which can be turned into opportunities, prioritizing them and then making changes one at a time. As changes are made it is necessary to have in place a method of determining the effect of the changes. This can be as simple as a daily grade yield report, combined with lumber prices to determine MSR revenue. The score on this evaluation can also be useful.
So, the first order of business after doing this evaluation is to identify which items can be turned into opportunities. Then compile a list including the top five to ten opportunities. Then prioritize the items by considering the cost, the time to implement and the potential cash return. The item with the best combination should be approached first, and completed before going on to the second. The evaluation process should be repeated before tackling the third or fourth items in the final list to see if these are is still the most appropriate choices for attention.
The score from this evaluation is a rough indication of opportunity for MSR improvement. The potential can be studied by examining each of the items and determining the opportunity for each. As an example, the operator may be doing everything right except for using the process in the grading rules to optimize the grade threshold settings, or attempting to make an inappropriate set of grades. Under these circumstances profit from machine grading can be well below its real potential. If any significant problem can be identified and corrective action planned, it can be turned into an opportunity for improvement.(2) It is impossible to predict which items in this checklist are most important for any given operation. Except for the first item (Safety), there is no particular significance to either the order in which they are presented or the number of questions devoted to each topic.
I. SAFETY
It is not possible to list all the potential safety hazards which exist around a planer mill where MSR equipment is used. Safety should always be the first consideration, so it is placed first here. The reader should review the equipment operating manuals and other resources, and is encouraged to consider safety matters with care before entering a plant or working on equipment.
LOCK OUT electrical supply before removing covers from equipment. Close or re-install covers on the equipment before removing lock-outs.
MAKE SURE all operators and maintenance people who may attempt to start equipment know you are working on the equipment.
COMMUNICATE your intentions to start equipment to all personnel in the area before taking action.
REVIEW appropriate safety procedures with plant personnel before working on equipment.
WEAR appropriate clothing, including head, eye and hearing protection.
DE-ENERGIZE all pneumatic and hydraulic systems to establish zero energy levels.
The following safety-related questions cover only a few very basic issues:
GUARDS AND COVERS (SAFETY)
Do you have all of the guards and covers installed whenever you run your machine?
Rating
4 - Yes
0 - No
Infeed covers / protection
Is the planer outfeed conveyor equipped with a cover suitable for preventing lumber from escaping in case of an interruption in flow?
4 - Yes
0 - No
Passage ways ahead of and behind the MSR equipment:
Is there a guard, railing or chain in place to prevent anyone from entering the lumber path ahead of and behind the lumber testing machine?
4 - Yes
0 - No
Ear protection:
Do all operators wear ear protection while working around an operating machine?
4 - Yes
0 - No
Lockout procedures:
Does each operator have a lock with which he can lock out the equipment?
4 - Yes
0 - No
Do the operators and maintenance people use these locks every time they remove a cover or guard to work on the machine?
4 - Yes
0 - No
Communication:
Do all operators communicate their intentions to start the equipment before they activate motors and pneumatic systems?
4 - Yes
0 - No
VIII. MSR EQUIPMENT PERFORMANCE
Is the MSR equipment performing as well as it could be performing? If the CUSUM quality control tests indicate an in-control process, the equipment is working at the required level of performance. However, there is a desired level of performance which requires more attention to detail but has potential for increased benefits. Two of the main concerns are repeatability and accuracy. Many details of equipment adjustment and maintenance affect repeatability and accuracy. Consider the following details:
REPEATABILITY
Repeatability can be measured in a number of ways. One efficient method is to use the Metriguard Repeatability Measurement Program(3), in which 32 pieces are passed twice through the machine while recording Low-Point E and Average E for each pass. These results are then sent to Metriguard for analysis. Scoring is as follows:
Repeatability Score
4 - 90-100 (A)
3 - 80-89 (B)
2 - 70-79 (C)
1 - below 70 (D)
Metriguard recommends checking repeatability error (a) once per month, and (b) whenever a change in performance is noted, and (c) after any maintenance which may affect performance.
How often do I check the repeatability error?
5 - Every month and after any maintenance or equipment changes.
4 - Every month.
3 - Once every two months.
2 - Once every 6 months.
1 - Never.
CALIBRATION
How well do off-line test results compare with the production machine, and how much does the calibration vary from shift-to-shift and from month-to-month?
We are concerned about the quality control equipment function, repeatability and calibration as much as the production line equipment. Records are required to be kept of all calibration changes, and one method of assessment is to examine these records.
4 - All records are complete, well organized, legible and up to date.
3 - Some records are missing or not complete.
2 - Many records are missing, not complete or difficult to read.
1 - Most records are missing, not complete or difficult to read.
Examination of records
Information is created when a reading taken and recorded. Before that information can be useful it must be turned into knowledge. This requires a reading of the record and an understanding of the significance and how it applies to the corporate goal of making a profit.
4 - Records are scanned at least once every week by the shift manager looking for changes and clues to performance trends. Graphs are prepared showing these trends.
3 - Calibration records are reviewed once every month and graphs brought up to date.
2 - Records are reviewed only if there is a problem. No graphs are used
1 - Calibration records are reviewed only by the grading agency.
Accuracy of calibration
How much does the machine calibration vary? Plot the changes in calibration over the past month as shown in the calibration records. We are concerned with the range of these changes. We want to look at this range as a percentage of the value shown. To get the percentage range, use the following formula:
Range (%) = (maximum - minimum)(200)/(maximum + minimum)
5 - Less than 2%
4 - 2% to 5%
3 - 5% to 10%
2 - 10% to 15%
1 - More than 15%
0 - I don't know
Variations in calibration
If calibration varies by more than 2-3%, one should search for an assignable cause.
4 - Calibration does not vary more than 3%
3 - Calibration varies more than 3%, we know why and are working on it
2 - Calibration varies more than 3%, but we don't know why
1 - I don't know how much variation we have
Calibration technique
Is proper technique being used? To get a consistent result, it is necessary for every operator on every shift to use the same process.
4 - A written checklist is followed by every operator on every shift, following every item on the list as prescribed. Reviews are held with all operators on a regular basis to correct any misunderstanding and answer questions
3 - A written checklist is followed most of the time. Every operator has had a review within the last six months
2 - There is no written checklist, but operators appear to be following the same procedures
1 - Operators don't always use the same technique, and calibrations vary from shift to shift
ADDITIONAL QUESTIONS
Some additional questions which may lead to finding assignable causes for variations in calibration are as follows:
Is the bar value consistent when the carriages are raised and lowered 7-10 times? Look for changing values that may allow an operator to pick and choose one for convenience.
With the test bar in place and clamped, roll the bar back and forth a couple of inches by turning the rollers by hand while watching the readout. Large variations indicate either surface roughness on the rollers or on the bar.
Does calibration vary from shift to shift? If the calibration varies between shifts, or there is a significant systematic difference in yields between shifts, assuming the same type and species of lumber is being graded, it may be possible to find an assignable cause in either the operator technique or environmental conditions which are different at different hours of the day.
Does calibration vary more in one shift than in another? If so, why? Could this arise from operator effects or environmental effects?
Do the yields vary from shift to shift without a reasonable explanation?
Is there a correlation between grade yields and the calibration values recorded in the records? If there is such a correlation with yields, it confirms that the calibration is changing. Also any significant variation in yields may be caused by variations in calibration of which the operator may be unaware, so this is one place to look when assigning cause.
TEST BARS
The test bar is a calibration device the company depends on for accuracy in setting up the grading equipment. Test bars should be handled and stored with care.
Storage and handling
4 - Test bars have their own special storage location with a sign indicating they are not to be used for any purpose other than calibration of the equipment
3 - Bars are examined on a regular basis. They are stored in a secure location and handled to prevent damage
1 - Test bars are kept on the floor near the machine
Backup Test bars
5 - A set of back-up test bars(4) has been calibrated and is kept in a safe place. These are used for cross-checking whenever a problem is suspected. Records are kept in a safe and accessible place which include calibration values for both sets of test bars
0 - There are no backup test bars available at the mill
Condition of test bars
Are the test bars damaged in any way?
4 - Test bars are clean, straight and free of burrs
3 - Some wear and tear is evident
2 - Bars are dirty, wear and tear evident, but are straight
1 - Test bars are seldom examined
0 - Bars are not straight, or have gouges from starting the machine with the bars in place in the machine
SETUP - STOP BOLTS(5)
Stop bolt settings on Metriguard CLT and 7200 machines are critical to proper operation, long equipment life and low repeatability error. The stop bolt settings required depend upon planer performance (see above), and the presence of scant material in the lumber flow which may fail to feed. With good planer performance and thickness control, Metriguard recommends the stop bolts be set for about zero motion at the thinnest cross section in the lumber. This can be done by means of the Lane Ladder(6) device, which provides a constant thickness reference from which adjustments may be made. After the equipment is started, the operator should look(7) to determine if the stop bolts are set as required. This is very important, because it can catch mistakes and bad assumptions about the actual thickness of the lumber.
How often do the operators check the stop bolt settings?
4 - Four times each shift and after every planer adjustment
3 - After every planer adjustment
2 - Once every shift
1 - Once every week or so
How do the operators set the stop bolts?
4 - By means of a Lane Ladder, and by visual means as described above
3 - By means of observations from the last run-time
2 - By means of a stick of wood clamped in the machine
1 - By guess
0 - We don't pay much attention to the stop bolts
Are the operators getting the stop bolt settings they think they are getting?(8)
4 - Visual observation, feeler gauges and machine performance all say "yes"
3 - Visual observations indicate a good solid "probable"
2 - Visual observations indicate a "maybe"
1 - Visual observations or machine performance say there is reason to question the accuracy of the settings
KICK PLATES (Lumber feeding guides)
Are the kick plates positioned as required? How can I tell?
With a straight piece of lumber clamped in the machine, [MACHINE OFF AND LOCKED OUT] the minimum distance between the lumber and the kick plate is:
4 - 0.125" [3.175 mm] to 0.1875" [4.75 mm]
3 - 0.1875" [4.75 mm] to 0.25" [6.35 mm]
2 - More than 0.25" [6.35 mm]
0 - Less than 0.125" [3.175 mm]
SPEED
Is the machine running at the best speed? What is the testing machine speed relative to the planer speed?
4 - 50 to 100 fpm faster than the planer
3 - 100 to 200 fpm faster than the planer
2 - More than 200 fpm faster than the planer
1 - Less than 50 fpm faster than the planer
0 - Slower than the planer
AIR PRESSURE
Do I keep the air pressure set as required for each size?
4 - Yes
0 - No
XXIII. MAINTENANCE
Many of the activities described in this section require covers and guards to be removed from the machine. MAKE SURE POWER IS LOCKED OUT BEFORE BEGINNING ANY OF THESE PROCEDURES.
FUNCTIONALITY
Is everything functioning?
4 - Yes, and I know this is correct because I have checked it myself
3 - Yes I think this is correct because someone told me
2 - I think so
1 - I doubt it
CLEANING AND LUBRICATION
Rollers should be cleaned(9) before every calibration and at any time there is a significant build-up of resin and sawdust on them. A significant build-up is an amount which changes the calibration of the equipment or increases the stop bolt motion more than 20% or so. Lubrication should be performed per manufacturers' recommendations.
How often do I clean the rollers?
4 - Before every calibration and if significant buildup occurs
3 - Every day
2 - Once a week
1 - Less than once a week
How often do I lubricate the machine?
4 - Per manufacturers' recommendations
1 - Seldom
BEARING CONDITION
The accuracy and repeatability of these machines depends upon maintaining correct roller position, which in turn depends upon the bearings which support the rotating components. The condition of the bearings may be evaluated by placing a dial indicator gauge against the top or bottom roller surface then lifting the roller by hand or by means of a prying device. The maximum free movement should be 0.002" or less.
4 - All rollers have 0.002" or less movement
2 - All rollers have 0.004" or less movement
0 - One or more rollers has more than 0.004" movement
CLT MECHANICAL EVALUATION
The following equipment components should be examined:
Slide blocks (lower carriages, behind pinion). Check for looseness between the sliding surfaces and the casting and between the shaft and the slide block. Sliding clearance should be 0.015 to 0.020". Shaft/block clearance should be 0.002 to 0.005"
4 - OK
2 - 50% over
0 - More than 50% over
Flexure condition. This component replaces a flange bearing which supports the load roller single-tree mount. All flexure springs should be intact, bolts tight and adjusted for sufficient torque on #1 load roller to apply pressure to the load cell, zero torque on the #2 load roller flexure mounts.
4 - OK
0 - Not ok
Bridge hanger wear. The bridge hangers are found in four places at the ends of the #2 load roller mounting bridge. Over time these bridge hangers and the lower carriage castings wear, the effect of which is that the bridge moves to a lower position requiring adjustment of the deflection adjustment screw on the #2 load roller assembly. The wear rate depends upon the stop bolt settings and speed of operation. If stop bolts are maintained at 0.015" or less clearance these parts will last nearly indefinitely, but with looser stop bolt settings and operating speeds in excess of 1,000 ft/min, these parts can wear out in 6-7 years requiring major repairs. This can be evaluated by means of a feeler gauge placed between the hanger ring and the carriage casting on the lower side, or by placing a dial indicator gauge on the bridge (indicating the carriage casting elevation) and lifting upward on the bridge. If this clearance is in excess of 0.120" the machine is approaching the time for major repairs.
4 - Less than 0.050" wear
3 - 0.050 to 0.075" wear
2 - 0.750" to 0.100" wear
0 - More than 0.100" wear
Load roller pivot bearing clearance. These bearings allow the load roller to rock about an axis parallel with the length of the machine. This clearance should be zero with a significant preload on the bearings. Adjust by means of an adjustment screw on the single-tree end of the bearing assembly. If your machine does not have this adjustment, Metriguard can supply the required parts.
4 - Zero clearance
0 - More than 0.002" clearance
Load roller bearing clearance. The load rollers must be tight on the shaft and the bearings adjusted for zero clearance with a light pre-load. Adjustment in older machines is difficult, requiring that the assembly be removed from the machine. Metriguard can provide an upgrade kit in which the bearing adjustment is made at the ends of the shaft and rollers attached to the shaft by means of a shrink disk assembly.
Infeed alignment. The requirement is that the lumber generally run down the centerline of the machine and with the odd exception, not touch the fences after entering the machine.
4 - Zero clearance
0 - More than 0.002" clearance
Rollers all turn free. All the rollers in the machine should rotate without binding. This should be checked when the machine is calibrated (off and locked out). If one or more of the idler rollers binds or turns with difficulty, the problem should be corrected.
All idlers turn when lumber is present. It is most desirable that all the idlers run in contact with the wood with the exception of the #2 top idler roller. This is not always the case because the rollers are sized to present the highest loads on the large rollers at the ends of the bending spans, and the wood will contact the idler rollers only if there is sufficient compression of the wood under the large rollers.
4 - OK
0 - One or more rollers bind
Variable frequency drive (VFD) RF noise. Variable frequency motor drives have become a very popular addition to the mill environment. These devices emit powerful radio frequency energy from the wiring and must be installed so that this RF energy is properly contained. This requires that all wiring from the controller to the motor be run in shielded conduit with good grounding and bonding. Some types of flexible conduit provide only very poor shielding, and internal shielding may be required. Do not run these motor leads through an electronics cabinet. It will drive the electronics (and you) crazy.
4 - All variable frequency drives properly installed. No evidence of RF interference.
0 - Evidence of RF interference. Equipment does not operate properly when VFD is operated.
ROLLER CONDITION
When did I last check the machine for roller runout?(10)
4 - 3 months
3 - 6 months
2 - 1 year
0 - Never
What is the maximum runout (T.I.R.) at mid position on each roller?
4 - 0.002"
3 - 0.002" to 0.004"
2 - 0.004" to 0.006"
1 - More than 0.006"
BEARING WEAR AND LOOSENESS
When did I last check the machine for bearing wear and looseness?(11) Bearings in the Metriguard CLT and 7200 model machines are critical components which affect accuracy and repeatability.
I checked my equipment for bearing wear and looseness within the past:
4 - One month
3 - One to 3 months
2 - 3 to 6 months
1 - More than six months
SPARE PARTS
Do I have all the spare parts I might need? The correct answer to this question depends upon how long you can afford to wait for replacement parts. If a piece of equipment is used on a daily basis, and the production schedule does not allow for unscheduled maintenance, it is important to keep on hand everything one might need to make repairs. It is also important to know if all the spares on hand are functional.
I last checked my spares inventory within the past:
4 - One month
3 - One to 3 months
2 - 3 to 6 months
1 - More than six months
PNEUMATIC SYSTEM
How often do we check the equipment for air leaks? Air leaks are a preventable energy loss and can affect accuracy of the machine if sufficient air pressure is lost at critical components.
I checked my equipment for air leaks within the past:
4 - One month
3 - One to 3 months
2 - 3 to 6 months
1 - More than six months
IMPROVEMENTS
Do I have all the latest equipment improvements installed?
Some of the CLT machines are 30 years old, or older. Many improvements have been made in the CLT equipment design to improve its repeatability and accuracy. These improvements include:
CLT:
A flexure coupling device(12) which replaces load roller mounting bearings(13).
Inertial compensation system
Improved kick plates
Lock-ring mounted rollers (large)
Radius-machined rollers (small)
Machine-generated clock signal & improved kink compensator card
Single-point inking head and stainless steel tanks
Load roller assembly with external clearance adjustment
Timing belt drive (Motor to roller)
PC digital data system
Model 7200 High Capacity Lumber Tester (HCLT)
PC digital data system
Model 312 Bending Proof Tester:
Roller-bearing load heads
Has the equipment been kept up to date?
4 - All relevant items have been installed
3 - Some of these items have been installed
1 - None of these items have been installed
MANUALS & LITERATURE
Are the equipment manuals located where I can find them?
4 - Yes
0 - No
Has everybody read the manuals who needs to know the information contained in them?
4 - Yes
0 - No
Do you have available all of the service bulletins(14) that have been issued for your equipment?
4 - Yes
0 - No
XXXIV. GRADING THRESHOLDS
From an operations point of view, setting grading thresholds is similar to setting target sizes in the sawmill. If you set the target sizes (or the grade threshold) too low, you produce a product that does not meet the grade requirements. Any grade threshold (or target size) larger than necessary results in loss of potential revenue. The difference here is that for the same percentage increase in grade threshold, revenues can drop off faster than that percentage increase in target size. Setting of grade thresholds deserves at least as much attention as setting target sizes in the sawmill.
ADJUSTMENTS
When was the last time I reduced my grading thresholds?
4 - Less than 4 months ago
3 - 4-8 months ago
2 - 8-12 months ago
1 - More than one year ago
0 - Never(15)
CUSUM RESULTS
When was the last time I went out of control?
4 - Less than 4 months ago
3 - 4-8 months ago
2 - 8-12 months ago
1 - More than one year ago
0 - Never
Last time I went out of control, which CUSUM went out? ________________
4 - I now watch this one by plotting test results
3 - I made a note of it, we corrected the problem, and went on
2 - I had that information but lost it
1 - I don't know
Why did I go out of control last time?
4 - The cause was identified and corrected, and afterward we re-optimized the grade thresholds
3 - We searched for a cause, were unsuccessful, so we assumed it was a statistical situation
2 - We assumed it was a statistical thing, increased our grade thresholds and got back on line
0 - We don't know, and we're still down
What were the yields before and after the last time I went out of control?
4 - Yields increased
2 - Yields decreased
0 - I don't know
How do I feel about going out of control?
4 - I accept it as part of the challenge to make more profits for my company
3 - I keep a small comfort zone so I don't have to go through the out-of-control exercise any more than necessary
2 - I avoid going out of control due to statistical effects by using a large comfort zone
1 - I am more concerned about going out of control than about mill profits, so I avoid it at all cost(16)
Do I know what to do if I go out of control?
4 - Yes, it is a well-understood procedure. I don't have to look it up
3 - We have been through it, and we could get through it again if necessary
2 - I guess we could find the procedure if we had to
1 - I don't know where to begin looking
Do I plan on going out of control? How often?
4 - Yes, 2 to 4 months
3 - 4 to 8 months
2 - 8 to 12 months
1 - No, Never
GRADE RECOVERIES (YIELDS)
The main reason for installing MSR equipment in a plant is to obtain better profits through improved grade recovery, so it would seem reasonable to monitor this result.
Do I know how much my grade recoveries are: (Mark all that apply)
4 - for each season in each species mix?
4 - For each shift?
4 - for each species mix?
0 - No
Have I ever investigated the cause of declining recovery?
4 - Yes, we watch the yields and attempt to learn the cause of every change
3 - Yes, we attempt to trace down the major shifts
1 - No.
Have I ever taken action to change a declining yield trend?
4 - Yes
1 - No
Have I ever blamed the wood resource for declining grade recovery?
4 - No, every decline in grade recovery was traced to other causes
4 - Yes, and test results prove that the resource had declined in quality
1 - Yes, but this was just an assumption
0 - No, we never gave it a thought
THE "COMFORT ZONE"(17)
First, how do we define the "comfort zone"? A comfort zone results when an adjustment is placed on the conservative side to prevent an unpleasant event. You have a comfort zone when you drive at a speed less than the posted limit. In this case, the unpleasant event is going out of control in the MSR quality testing process. To prevent this, grade thresholds are increased. For the operator, everything is fine as long as he doesn't have to do any extra work to correct the problem of going out of control. For the owners and managers who have a responsibility to the bottom line, having the luxury of never going out of control can produce a significant loss of profit. If, for example, MSR grade yields are 10% less as a result of these adjustments, it can result in failure to put $1,000,000 on the profit line(18) which could be there just by setting in a lower grading threshold. We can get the same effect by increasing sawmill target sizes by 10% or so. One valid measure of the comfort zone is its cost in bottom-line profit.
A large (and expensive) comfort zone will protect the operators from going out of control due to statistical variations. This will not, however, provide any protection from going out of control from other causes such as equipment failure, operator mistakes or loss of structural value in the wood because of improper kiln operation.
The following questions are designed to encourage the operators to think about the logic in establishing a reasonable comfort zone.
Do I know how much comfort zone I have in my grading thresholds?
2 - Yes
0 - No
How much does my comfort zone cost?(19)
10 - Less than $10,000/yr
8 - $10,000 to $50,000/yr
4 - $50,000 to $100,000/yr
-8 - $100,000 to 1,000,000/yr
-10 - More than $1,000,000/yr(20)
Did I make a conscious decision about how much "comfort zone" to use in setting the grading thresholds?
4 - Yes
0 - No
Was this decision based upon: (check all that apply)
4 - Grade yield
4 - Meeting minimum grade requirements
0 - Convenience
Do I know how much comfort zone I need to take care of variations I cannot control?
Many variations can be controlled if an assignable cause can be identified. Some variability results from statistical sampling, and this cannot be improved without increasing the sample size. Some can be assigned to the differences which result from edgewise quality control testing and testing flatwise in the production equipment. Much of this variability can be avoided by using a flatwise E measurement(21) for process control, while continuing to use the edgewise quality control test. When the edgewise quality control test results are used to determine if there was a calibration shift in the machine, there is an approximate 10% variability introduced. This can be reduced to less than 2% by using a flatwise test for process control.
To determine how much comfort zone you need, you need to know how much variability there is in the quality control test results.(22)
4 - I graph the QC test results and plot them on wall charts daily so I can see the variability and where we are with respect to control limits
3 - I bring the charts up to date once a month or so
2 - I put some charts together more than a year ago but haven't looked at them since
1 - I would like to make some charts, but I don't know how
0 - I assume that if I stay in control, everything is fine
Bonus points:
4 - I use flatwise E testing for process control to determine if my equipment calibration has changed
0 - I don't do any extra testing
Do I put the control graphs on the wall where everybody can see them?
4 - Yes
2 - No
0 - I don't make graphs
Have I ever increased the grading thresholds when I went out of control so I could keep operating? If yes, what did I do next?
4 - I found the cause, fixed the problem AND returned the grading thresholds to their original settings
3 - I fixed the problem and plan to improve the grade thresholds as soon as possible
2 - I fixed the problem but don't see any point in going through the grade optimization process
0 - I'm still out of control
XXXIX. PLANER
Correct planer setup and performance are essential to delivering an accurate-sized piece to the MSR equipment and to the customer. It is important to the MSR machine because its performance is reduced if large variations in thickness are present. Perhaps even more significantly, it is important to the truss customer because to obtain proper plate embedment, the pieces being joined must match in thickness. Correct plate embedment requires no more than 1/32" (0.031" [0.79 mm]) difference in thickness between the two pieces being joined. This requires that the thickness depart no more than (+/-) 1/64" (0.016" [0.4 mm]) from the target thickness to assure proper plate embedment in all cases. If plates are installed on the edges of the piece, then a small width tolerance is also essential. Laminators require tight thickness tolerance to maintain a uniform glue-line and to reduce residual bending stress in the final product. Some of the tolerance range must be assigned to changes in thickness after manufacture, so it is easy to understand that the desired planer thickness tolerance is very small indeed.
One method for assessing planer thickness range is to select 10 fresh-manufactured pieces of lumber and measure the thickness at three points along each edge of each piece by means of a dial caliper with a precision of 0.001" [0.02 mm]. A go/no-go check gauge will not suffice. To get a good assessment, these measurements should be taken at any obvious thin or thick areas because plates can be placed at any position along the length of the piece. Specimens should be drawn at intervals during a shift to assess the planer variability during a shift. These readings are then ordered from smallest to largest, and the range of values is evaluated by answering the following questions.
PERFORMANCE
Thickness range
4 - 0" - 0.010" [0-0.254 mm]
3 - 0.010" - 0.015" [0.254 - 0.381 mm]
2 - 0.015" - 0.020" [0.381 - 0.508 mm]
1 - More than 0.020" [0.508 mm]
Difference from nominal target thickness
4 - 0" - 0.010" [0-0.254 mm]
3 - 0.010" - 0.015" [0.254 - 0.381 mm]
2 - 0.015" - 0.020" [0.381 - 0.508 mm]
1 - More than 0.020" [0.508 mm]
PLANER SETUP & MAINTENANCE
Some additional questions:
Who makes the decisions about planer setup?
Is this person aware that there is a tradeoff in the back plate settings between reduced thickness tolerance and reduced number of planer stalls?
Are they considering the value lost with loose thickness tolerance?
Is the material on size from the sawmill/kiln process?
XLVI. MANUFACTURING DEFECTS
EXAMINATION OF VISUAL DOWN-GRADED PIECES(23)
First, separate growth features from manufacturing defects, and then look at the manufacturing defects. Trace them to their sources and determine which can be eliminated. Estimate the dollar value in grade yield loss resulting from each type of manufacturing defect so that progress can be measured as improvements are made.
We want to identify the defect in each piece which resulted in the down grade, then find the mill operation which produced the defect. Then we examine that operation and attempt to correct the problem. If a machine is not properly adjusted or operated, then by making adjustments the mill profits can be improved.
Manufacturing defect categories:
Dry kiln defects, Planer snipe, Saw cuts -- including chain-saw & mill saw cuts, scant sawn pieces, odd length, etc.
Growth feature categories:
Knots, splits, checks, shake, wane, compression wood, timber break, etc.
Method:
For a measured time period, place all pieces in one sort bin which have MSR ink spray marks and visual grade stamps. Continue this process until one unit of lumber is collected. Record the time required to do this.
Remove the unit to a location where it can be broken down by hand. First separate out the pieces downgraded because of growth features and tally them. Then sort the remaining pieces according to type of manufacturing defect. For each group determine the value as graded and the value it would have had without the manufacturing defect. Total the differences, divide by hours required to collect the sample and multiply by 2,000 to get the annual value lost per shift.
Time _______ (minutes) Divide by 60 to get hours(24) ___________
No. of Pieces in sample ___________
Number of pieces with manufacturing defects ___________
Value as graded (manufacturing defects only) ___________
Value if defects were not present ___________
Value lost (difference) ___________
Divide by hours required to collect sample ___________
Multiply by 2,000 to get annual value lost per shift(25)
___________
MARKETING
XLVIII. MARKETING GOALS
Marketing, as opposed to sales activity, attempts to identify current and future market opportunities and also those which may slip away in the future so proper accommodations can be made in planning.
MARKETING ACTIVITY
Is someone in your company watching market trends? Trading rules, duties, quotas, interest rates, changes in commerce such as highways, bridges, railroads, freight rates, and other commercial events which may change the way you do business.
4 - We have someone assigned full time to this task and reporting to the management about these matters so they may be incorporated into our planning
3 - We have a person assigned part time to look after marketing issues
2 - We have our sales staff take care of this for us
1 - We tend to take life as it comes, and we don't plan to get involved with this.
What does this person do?
4 - We have an experienced individual assigned to this task who spends at least 30% of the work-month visiting with customers at the customer's plant, and attending industry meetings
3 - We have a marketing person who spends at least 10% of an average work month in contact with customers
2 - We have a marketing person who seldom gets out of the office
1 - We don't have a marketing person
0 - We don't see any value in this kind of effort
OTHER MARKETING QUESTIONS
These questions may help you identify areas for potential improvement in your marketing activities.
Trends
Is there a change coming in the future that I can predict?
Do I know how it will affect my life?
Did this change improve the business environment or did it make things worse?
Is there a new opportunity that wasn't there under the old rules?
What is the opportunity?
How can I take advantage of it?
If I am presented with a new adversity, can I get around it? How?
Is there anything I can do now to help my company deal with this change?
Do we have a system in place in the company that will pass news of coming changes to me as soon as possible?
If not, how can I keep myself informed?
Customers
Who buys my MSR lumber? Why?
What mix of sizes, lengths, grades & moisture content do the customers want?
When do they want it? Can I predict the demand on a seasonal or some other basis?
Machine grading categories
What are the MEL grades doing for the other producers?
How do the MEL grades work for the customers?
Should I be making MEL grades?
Is there an opportunity for making E-Rated Lumber grades for laminators?
Resource
What is the profile of my resource material today?
What will the resource profile look like over the next ten years?
Miscellaneous market-related decisions
How much more valuable is my MSR if the thickness tolerance is right on the money?
How much less valuable is my MSR lumber if I don't hold thickness tolerance?
What happens to the mill's operating result if I could increase the volume going into MSR by 5%?
What happens to my MSR value if I add tensile values to the grade stamp?
Would I open any new doors for the Sales Department if I added tensile design values?
How many customers prefer MSR lumber that is quality controlled in tension? What volume does this represent?(26)
Am I meeting my customer's delivery needs?
What do the customers want in the way of wrapping and marking? Is there anything else that would make my lumber more valuable to them?
Is there anything beyond price, time of deliver and certified grade stamp that would
affect the value of our service to our customers?
OPERATIONS PLANNING
LXXVIII. GRADING STRATEGY
For each lot of wood there is an optimum combination of sizes, lengths and grades that will produce the largest profit. Constraints include length and size limitations in the mill, sorter capacity, market acceptance and the time and money required to learn the facts, analyze them and make changes. The optimum grading strategy will be different for each mill because each mill has a different set of constraints from all the others unless they are identical mills working from identical wood resources and selling into the same or identical markets.
PLANNING
How can I tell if I am making the right grades?
4 - We use computer spreadsheets to play various "what-if" games based on yield estimates from a number of strategies, and we change strategies based on this information combined with marketing input which tells us which grades, sizes and lengths will sell and at what price
3 - We optimize grade yields for each species group we make, but we don't do much market analysis
2 - We started making our grades based on a customer we had back in the beginning, but haven't looked at it for more than a year
1 - We just try to make the grades others are making
ADJUSTMENTS
When did we last change our grading strategy by adding or deleting a grade?
4 - Within the last six months
3 - Six months to 1 year ago
2 - One to three years ago
1 - More than three years ago
LOGS - THE RESOURCE
Have we discussed log purchases and considered yields associated with each kind of log mix that is available to us?
Do we have a choice in the type of log we run through this mill?
If we have a choice of logs, what type should we run here for best profit?
TARGET SIZES
Have we discussed sawmill target sizes?
Do we know how much grade loss we can expect if we reduce target sizes further?
Do we know how much grade loss we have now from sawmill target size & cutting tolerance? (27)
DRYING
Kiln maintenance and operation represents a very large cost for a sawmill operation, and one in which the value of products can be increased or decreased depending on how well it is done. We refer the reader to the very complete evaluation checklist shown in the reference below.(28)
Do we operate an optimum kiln schedule?
How do we know it is optimum?
What would happen if we changed the kiln schedule?
Do we know all the right questions to ask about the kiln schedule?
SAWMILL PRACTICES
Have we discussed our primary log breakdown practices?
Can we reduce spike knots by making more flat-sawn cuts?
Can we increase the volume of square-edged product?
Can we better utilize the material in the outer part of the log where the structural properties are higher?
Can we improve our MSR product by curve sawing?
OPERATIONS
Are we separating species and optimizing operation for each species?
Do we adjust our operating strategy to market conditions?
How does information about market conditions come to us?
Do we react to new market opportunities when the happen, or do we go out and find them?
Do we keep information about yields from each log type? How could this be useful?
Are the log buyers aware of the yield information?
Can we determine the mill profit for each market item?
Can we determine mill profit for each log purchase? Would this be useful?
Do we have someone assigned to keep an eye on these issues? What is this person doing?
FORESTRY
Are we making our planting decisions on the basis of higher volume or higher grade recovery?
OTHER QUESTIONS:
These questions are provided to help identify opportunities in grading strategy. Some of these may be more appropriate for your operation than others.
Do I know what would happen if I added another MSR or MEL grade?
Do I have enough sorter capacity to do this?
If I don't have enough sorter capacity, is there a way around this problem?
Could I improve my average selling price if I added, deleted or replaced a grade?
Are the other mills in the area making the same grades I am making?
What would happen if I produced grades typical of some other region?
Do I use the same grading strategy for all species? - Is that appropriate?
What strategy should I use for each species?
Can I separate species?
If I can separate species, can I improve my drying as well?
Could I improve my profits if I used a different strategy for different species groups?
Am I developing an economic volume in all my grades?
What happens to the grades I make now? Are they mixed with other grades for marketing? Do my sales people ever throw in a load of MSR when the customer ordered visual grade lumber? Is this a good idea?
What would happen to the volume in the other grades if I deleted a low-volume grade?
What would happen to my yields in a grade if I deleted the next higher grade? Would
this improve my profits?
COPYRIGHT NOTICE
Copyright 1998 by Metriguard Inc.
Permission is granted to make copies for use in mill evaluation without fee. All copies
and/or derivative works must include this Copyright Notice. Writers referencing this
document are requested to acknowledge the source, e.g., "Logan, J.D., Quality
Production of MSR Lumber and Grade Yield Optimization, Release 1.0, Metriguard Inc.,
Pullman WA"
THIS DOCUMENT IS PROVIDED "AS IS", INCLUDING FAULTS AND WITHOUT EXPRESS OR
IMPLIED WARRANTY. ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE AND OF
MERCHANTABILITY ARE HEREBY DISCLAIMED.
DOCUMENT INFORMATION
This is a "first release" document. The next step in this process is to have
some MSR producers apply the material in this document to their operations and provide
feedback. If significant changes result from this feedback we will modify the document for
a later release.
SCORING
Total the points for each section of this evaluation. Then add up the points for all the sections.
I. SAFETY
Score ____ Total Possible 28 Percentage ____
II. MSR EQUIPMENT PERFORMANCE
Score ____ Total Possible 67 Percentage ____
III. MAINTENANCE
Score ____ Total Possible 80 Percentage ____
IV. GRADING THRESHOLDS
Score ____ Total Possible 96 Percentage ____
V. PLANER
Score ____ Total Possible 8 Percentage ____
VI. MANUFACTURING DEFECTS
(Not scored) Annual dollar value _____________
VII. MARKETING GOALS
Score ____ Total Possible 8 Percentage ____
VIII. GRADING STRATEGY
Score ____ Total Possible 8 Percentage ____
Total
score _____ out of a possible 295 Percentage _____
ACTION PLAN
Compute a percentage for each section of the evaluation to help identify the more broad areas of concern. Compute the overall score to provide a baseline for future evaluations.
Examine each of the questions to help find items for the improvement priority list. Identify items for consideration.
Evaluate the potential for improvement of those major items which appear to need attention. It will not be necessary to compute the potential for all of the items in this evaluation.
Identify the items which may be improved with minimum expenditure of time and effort, and assign them to someone.
Identify and prioritize five to ten major items with the best potential for improvement. Begin work on the highest priority item.
Re-evaluate the operation before going past about the fourth or fifth item. Endnotes
1. Logan, James D. (1997) "156 Questions you should ask yourself from time to time". ILMA workshop 3 Dec 1997, Kelowna BC
2. Logan, James D., (1996) Improving MSR Profits, Workshop Paper, MSR Lumber Producers Council Workshop, 25 April 1996, Seattle WA (Copy available from Metriguard Inc., Pullman WA)
3. . Logan, J.D., (1991) Introduction: Repeatability Measurements in the CLT Continuous Lumber Tester, Metriguard Inc., Pullman WA
4. . A plant can go along for years depending upon a set of test bars for calibration. Then one day a millwright will use one of these to pry a sprocket off a shaft (because it is handy). Suddenly you are out of the MSR business until a new set of test bars can be obtained. Then because the new bars have an unknown relationship with the old bars, there may be another week of down-time before operations can resume. I'm not making this up. It has happened on a number of occasions over the years.
5. . Staff,(1995) CLT -- Stop Bolts, Service Bulletin, Metriguard Inc., 5 May 1995
6. Staff,(1994) CLT -- Lane Ladder, Service Bulletin, 7 July 1994, Metriguard Inc., Pullman WA
7. With some experience an operator can tell from observation if the stop bolts are moving by the correct amount.
8. . It is important to remember to check ALL of the stop bolts. In one case we were trying to trouble-shoot over the telephone, the operators were only adjusting the stop bolts on one side of the machine, and we didn't discover the real problem until about a year later when they finally had one of our service people in the plant. I'm not making this up either.
9. Staff,(1988) CLT Load Cells / Pitch Removal from Rolls, Service Bulletin, 11 Feb 1988, Metriguard Inc., Pullman WA
10. Staff,(1994) CLT-- Rollers and Bearings, Service Bulletin, Metriguard Inc., Pullman WA, 7 July 1994
11. Bechtel, F. K., (1987) Installation of McGill Bearings in CLT, Service Bulletin, 23 June 1987, Metriguard Inc., Pullman WA
12. Staff,(1990) Flexure Coupling, Service Bulletin, 13 Dec 90, Metriguard Inc., Pullman WA
13. These bearings do not rotate, and tend to develop a "sticky" action after a few years of use which leads to hysteresis in the measurement and drift in the load cell zero.
14. Most of the Service Bulletins for the Metriguard equipment are cited in other footnotes.
15. If you have never adjusted your grade thresholds, we suggest you pay particular attention to the section below discussing the comfort zone.
16. If you have serious fear of making these adjustments and you have never gone out of control, we suggest you experiment by first determining what your grade yields were for the past month. Then reduce all your grade thresholds by 1%. Then for the next month look at your grade yields, and of course watch your quality control test results to make sure you don't go out of control. If the results were positive for your plant, you may wish to consider a more aggressive program of optimizing grade thresholds.
17. These questions may put you outside of your comfort zone.
18. Based on 1997 lumber prices.
19. To determine the "opportunity costs" it is necessary to run an experiment. First record the grade yields, then following the grade rules and the plant standard, reduce the grade thresholds by decrements of not more than 3% until CUSUM indicates an out of control condition. Then increase the thresholds by enough to cancel the last decrease. At this point an intensive sample is required to assure that the process is "in control" again. The purpose of this is to find the minimum setting required to stay in control. Then resume operation and record yield results. Combine the new yield results with the old yield results and combine current (or year average) mill prices with the yield changes to get the dollar value of the comfort zone.
20. For a real thrill, take this information to the person in the company who is responsible for profits and attempt to get approval for keeping your grade thresholds at their old settings. Don't forget to wear your hard hat and ear protection!
21. i.e., Metriguard Model 340 Transverse Vibration E-Computer or Metriguard Model 440 Static Bending Tester
22. CUSUM is designed as a go/no-go test and it tells you only if you are in control or out of control. Additional information is needed. CUSUM operates a bit like a speedometer with duct tape covering everything below the speed limit. We need to tear the duct tape off to see the reading and how much the needle is bouncing around.
23. The design of this test includes some assumptions. The accuracy of this estimation depends upon the rate at which the defects are generated, which we assume to be constant. For some types of defects this may not be a good assumption. The sample is large enough to contain material from a number of logs in a small to medium log size mix, but may not contain material from all types of logs. Some types of logs present more manufacturing challenges than others. If this study is repeated a number of times with a large variation in results, it may be advisable to increase the sample size.
24. . Example: If it takes 87 minutes to collect the sample, divide 87 by 60 to get the time in hours, i.e., 87/60 = 1.45 hours
25. You may wish to perform this test on lumber produced in each operating shift to determine if one shift is producing better (or worse) results. This assumes you operate 2,000 hours per shift. You may wish to use a different multiplier if your shifts operate for a different number of hours.
26. Answers to these questions help Metriguard sell tensile testers!
27. Almost all MSR producers understand that the grading rules allow more wane in the product than the customers will tolerate. The best MSR yields come from the outer part of the log where mature wood is found. Flat-sawn cuts in this part of the log tend to have more wane, but it is desirable to avoid spike knots also, so there is a definite need to plan the log breakdown with care.
28. Milota, Michael R., R. Sidney Boone, Jeanne D. Danielson, and Dean W. Huber (1991) Quality Drying of Softwood Lumber: Guidebook, General Technical Report FPL-IMP-GTR-1, USDA Forest Products Laboratory, Madison WI
Boone, Sidney R., Michael R. Milota, Jeanne D. Danielson, and Dean W. Huber (1992)
"Quality Drying of Hardwood Lumber", General Technical Report FPL-IMP-GTR-2,
USDA Forest Products Laboratory, Madison WI
(These publications are available on the internet at http://www.fpl.fs.fed.us/)
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