Updated FPInnovations Saw Design Software Tool

Sawmills are pushing the limits of sawing systems to maximize production and recovery while trying to maintain acceptable sawing accuracy and uptime.  There are a set of calculations based on bite per tooth, the sawdust carrying capacity of the gullets and cutting power that have been used for decades to ensure the tooth design is within a range that results in good sawing performance.  However, these calculations are too simple to account for several known factors, such as:

1. Double-arbor circular saws, particularly canter saws, are a challenge because the depth of cut needs to be determined for both saws. Also, fully buried saws require more power.
2. Cutting power increases as the bite per tooth decreases because more energy is required to reduce solid wood to sawdust. In the traditional formula, the power factor assumes a bite per tooth of about 0.035 inches.
3. Wood strength, which determines cutting power, is significantly affected by wood temperature and moisture content.
4. The traditional design calculations only apply for a single saw, but with gang saws the feed speed may be limited by motor power or the holding capacity of the feed system, not the saw design. The feed tables on most machines allow for reducing the feed speed as the number of saws increases, but the feed values are usually determined by trial-and-error, which may be too conservative, leaving opportunities, or too aggressive, creating production problems.

To address the above shortcomings, the FPI Saw Design program has been updated to:

1. Include bite per tooth, wood moisture content and temperature in power calculations
2. Estimate the holding forces that the feed system can provide and the cutting forces on the wood. If the cutting forces exceed the holding capacity the feed speed is reduced.  From this, a feed table based on the number of saws is produced.

A common finding in many saw design reviews is that feed speeds are too fast for large depths of cut but could be faster for small depths of cut.  Since there are typically few deep cuts, adjusting the feed table can result in more production while avoiding saw reliability problems.  The new program provides more realistic calculations to allow mills to maximize saw performance.

Feed speed chart for depth of cut and number of saws for a double arbor gang saw.