Let’s talk about a plant built around a single lineal saw. Is it practical for some kinds of plants, but not others? To answer this, we’ll attempt to estimate how many truss assembly work stations a lineal saw can support, recognizing that different plants have different mixes of residential, commercial and agricultural work.
This will be highly simplistic, but may shed some light nevertheless.
Creating Cut Pieces on Lineal Saws
How many pieces an hour can a lineal saw cut? Clearly, having an automated infeed system and a full time person catching the lumber on the back end of the saw will make a considerable difference. Some of the literature from manufacturers claim the saws can cut 450 pieces per hour (7.5 per minute.) Certain sales reps, those practical fellows that have a reputation to consider, have been quoted as saying about
300 pieces per hour (5 per minute.) To be safe, let’s also consider we might only get half that number (2.5 per minute.) We’ll look at all three numbers (best, most likely, and worst case) in creating estimates.
Consuming Cut Pieces on Tables
Since production figures vary so greatly I want to start with an extreme case. Imagine a plant that never has to set up a truss, it simply builds 28’ fink trusses all day, every day. If that crew, working on one workstation, can build one truss (10 pieces) a minute, then it is pretty easy to calculate that there is no way, even in the best case scenario, that the saw (7.5 pieces per minute) can keep up with the table (10 pieces per minute.) But one truss a minute is p
retty fast. What if it takes five minutes for each truss? Now the table is consuming 120 pieces (12 trusses x 10 pcs/trs) per hour and a lineal saw would have no trouble keeping up – it probably would even be able to support two workstations building these 28’ finks.
Conclusion: In this ultra-simplistic scenario, if your workstation can build one truss a minute, a lineal saw cannot keep up. If that workstation takes five minutes a truss, the saw can keep up – no problem.
Let’s look at the same idea, but with a more complex truss, a cathedral truss with 14 pieces. In this case, if the table can produce a truss in less than three minutes, the saw will have a hard time keeping up.
In these charts, the red boxes indicate “the saw cannot keep up,” even in the ‘best case’ scenario. Orange or lighter means the saw will keep up – if our ‘best guess’ for lineal saw output is correct. To create metrics using units that may be more familiar, note that our fink has 65.33 BF; the cathedral 71.33. The BF/MH column indicates what a plant, with a three man crew, would produce per man hour producing nothing but finks or cathedrals with no setup time.
So much for “theoretical” truss plants. I know of a plant in the Far West described as “highly efficient” that produces pretty chopped up work at a rate of 110 BF/MH. These man-hours include only the three guys working the tables. If this is a “highly efficient” plant, let’s speculate that a plant that is merely “efficient” can produce 100 BF/MH. To keep things simple, let’s borrow the ‘number of pieces’ and ‘board footage’ from the cathedral truss above and assume that those represent a typical truss at this plant. This would mean that each workstation at this ‘efficient plant’ produces 300 BF or 4.2 trusses per hour, or one truss every 14 ¼ minutes. Going a step further, we can arrive at these numbers:
If our assumptions (3 men per table, average truss is 71.33 BF and has 14 pieces) are correct, then a lineal saw at a 100 BF/MH plant can support at least two workstations and perhaps as many as four.
Summary:
·Lineal saws can cut between 1200 and 3600 pieces per shift. This roughly equates to 6,000 – 18,000 BF depending on saw efficiency and mix of 2x4, 2x6, etc.
·A lineal saw can almost certainly keep up with two assembly workstations in all but the most efficient lines
·For custom residential work, a single lineal saw may be able to supply as many as four workstations
If you want a copy of the spreadsheet I used for his analysis, just drop me a line.