Gang rip yields

      Determining the factors which influence optimal yields. June 13, 2001

Q.
We operate a Mereen Johnson 424 gang rip saw. We mostly run #2ac red oak random widths and lengths. The rips set up in the machine range from 1.75" to 2.875" in width, with an average of 2.5".

By my calculations, we recover approximately 83% (before going to the chop saw). What is a GOOD yield recovery?

Forum Responses
How are you determining how the board is aligned with the saws? Fixed fence? Barr-Mullin, DYSYS, Taylor or some other optimizing system? Are you cross cutting crook? How are you building your saw arbors? In other words, how do you determine how many 1.75's or 2.25 widths and where they are located on the arbor?

We have customers that get only in the middle 50% range stacked behind the optimizing chop saws, and we have some that get day in and day out 65% to 70%.

Rip yield is important, but it is important to realize that one can have very good rip yield and a terrible yield at the chop saw, not only because the cut bills are not properly set up for the chop saw, but because the rips are not what the chop saw needs.

For instance, to make a wild example to make the point: one can edge an 8" wide by 12' long board and have as near 100% rip yield as it is possible to get, but it is not worth anything to the chop sawyer who needs 2.25" wide pieces.

Defects in a board will effect yield at the chop saw even though the rip yield is good. We can demonstrate that vision systems improve yield by positioning defects in different rips, thereby increasing yield at the chop saws even though the rip yield might be and frequently is lower.

In other words, the best rip pattern may not be the best rip pattern for the chop or optimizing saws.

Each case has to be investigated and treated individually.



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