Basics of Ripping Lumber

A simple overview of straight-line ripsaw technology. October 11, 2010

This article reprinted with permission of Mereen-Johnson Machine Company Inc.

By Dave Joslyn

Ripping of random width lumber to create part blanks and stave material for wood products has for many years been accomplished using straight line (single blade) rip saws. The straight line rip saw provides great versatility in choosing what parts can be ripped from a random width board, but it is labor intensive and has limited production capabilities.

When production demands outgrow the capabilities of the straight line rip saw, the choice is either adding more straight line rip saws with the additional labor required, or upgrading to a gang rip saw.

The typical first step is the use of a 12 width capacity gang rip with fixed blades on the arbor. A fixed blade gang rip saw has some advantages and some disadvantages.

Some of the disadvantages are: The gang rip saw might not have the width capacity to have all the required sizes on the arbor and the setup time required to change the arbor rip width configurations takes time away from producing parts. The rip width combinations on the arbor may not provide good yield from random width lumber, but sorting the lumber by width prior to ripping to best utilize the different arbor setups will help in attaining better yields.

Some advantages are: rip width accuracy and parallelism is better than a straight line rip saw and can allow ripping narrower moulding blanks having less moulder allowance. The higher production capability over the straight line rip saw is the primary advantage.

Using a gang rip with one moving blade will provide more rip widths from which to choose. Many boards will be ripped into two or more rip widths. The moving blade pocket allows many different widths to be ripped but the fixed pocket next to the moving blade pocket will provide a high volume of that size of part. This scenario has been good for the cabinet shop that requires a high volume of stile and rail parts of the same width. Also the cabinet shop can use the moving blade pocket to rip random width parts for panel glue up staves. Ripping random width parts will increase overall yield from the lumber.

A gang rip saw with two moving blades and one fixed blade (two variable pockets) provides solutions of great flexibility when a board provides only two net rips. Adding a second fixed blade provides a fixed pocket that can generate a third net rip. If many of the boards provide a three rip solution, there will be a high volume of the fixed pocket rip width.

Gang rip saws with all moving blades provide the versatility advantages of the straight line rip saw and the production capability of the gang rip saw. The ability to select the many pocket size combinations available from an all moving blade saw can overwhelm or slow down an operator. Gang rip saws with all moving blades will be best utilized when integrated to a rip optimizing system. Part widths and required quantities can be input into the optimizer, allowing the gang rip saw to rip those parts until the required quantities are met and the part is disabled. New parts can be added to the cut list or parts can be removed from the cut list in a matter of just a few seconds. The all moving blade gang rip saw will respond to the changes, without any setup down time.

Some optimizers will provide an initial solution but allow the operator to change the solution based on wane or defects in the board if desired. The all moving blade saw allows keeping the same combination of rips provided in the initial solution but change the rip width positions on the board by flipping or rotating the solution. This may allow segregating a defect in a specific rip width.

There are many rip saw choices when it comes to ripping lumber. Each come with trade offs in production and/or flexibility, but the all moving blade gang rip saw integrated with an optimizing system will provide the best of both worlds.

For more information on gang rip saws and rip optimizing systems call Mereen-Johnson Machine Company at 612-529-7791.

This article reprinted with permission of Mereen-Johnson Machine Company Inc.