Lumber Size Lumber Size Control Control Studies Studies Lumber - - PowerPoint PPT Presentation

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Feb 03, 2024 508 likes •691 views

Lumber Size Lumber Size Control Control Studies Studies Lumber Size Control Lumber Size Control Troubleshoot machine center performance Locate & identify problems Stabilize & improve sawing accuracy Reduce

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Lumber Size Lumber Size Control Control Studies Studies

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Lumber Size Control Lumber Size Control

Troubleshoot machine center performance

– Locate & identify problems – Stabilize & improve sawing accuracy – Reduce oversizing

Objective is to improve

– Lumber recovery – Sawmill efficiency – Productivity

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Lumber Size Control

Purpose

Lumber Size Control

Purpose

Stabilize & improve sawing accuracy—reduce lumber size variation (thick & thin lumber) Troubleshooting—locate & identify problems in sawing machine centers Properly adjusting lumber target sizes—control

versizing/undersizing to improve lumber

recovery and grade yield

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Thick & Thin Lumber

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Study Procedures

Sampling

Study Procedures

Sampling

Requires 50-100 study boards per machine center (or saw to saw pocket on gang saws) Sample 25-50 subgroups of 2 consecutively produced boards (3 successive sawlines or two consecutive pieces on gang saws) Maintain order of production (i.e., order in which subgroups are manufactured)

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Study Procedures

Measuring & Recording Procedures

Study Procedures

Measuring & Recording Procedures

Use a calipers to take 4-5 measurements

n both edges on each board (8-10 total

measurements per board) Record measurement data (0.001 in.), time & comments Note what is going on in the mill during sampling (saw snaking, hit metal,

verfeeding the saw)

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Study Procedures

Study Sampling & Measurement Positions

Study Procedures

Study Sampling & Measurement Positions

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Study Procedures

Subgroups of 2 Consecutive Boards

Study Procedures

Subgroups of 2 Consecutive Boards

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Measuring Lumber Thickness Measuring Lumber Thickness

Take 8 measurements per board & record to the nearest 0.001 inch Take 8 measurements per board & record to the nearest 0.001 inch

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Study Procedures

Measurement Location on Study Boards

Study Procedures

Measurement Location on Study Boards

Top Edge -First End into Saw Trailing End Bottom Edge

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Lumber Size Analysis Lumber Size Analysis

Components of lumber size variation

– Average measured size – Within-, between-, and total-sawing variation

SPC-LSA computer routine—demonstration Interpretation & troubleshooting—causes of lumber size variation

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Components of Lumber Size Variation Components of Lumber Size Variation

Average Measured Size ( ) Components of Lumber Size Variation

– Total variation (st) – Within-board variation (sw) – Between-board variation (sb)

Calculated with SPC-LSA program

X

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Interpretation of Lumber Size Variation Interpretation of Lumber Size Variation

Between-board variation—setworks system Within–board variation—sawing system Patterns of lumber size variation

– End-to-end taper – Edge-to-edge wedging – Thick or thin ends – Snake

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SPC-LSA Computer Routine SPC-LSA Computer Routine

Compiled MS-DOS based PC software Calculates the components of lumber size variation & oversize/undersize Graphical analysis reports (histogram, variation range graph, specification chart) Lumber size control charts (average, within- & between-board variation)

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Class Exercise - Statistics Class Exercise - Statistics

Described a set of numbers

– Calculate average – Measures of variation – Shape of its distribution

Statistics uses simple arithmetic The hardest thing about “Statistics” is its pronunciation

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