Ideas sought - most efficient way to produce consistent length boards

[scsmith42]

So a local business has reached out to me with a request to provide an ongoing supply of 2x4's for their shipping needs.  

These will be a one time use, southern yellow pine, and the numbers are very good.  They go through them so quickly that they don't need to be dried or even stickered.  Initial estimate is 300 pcs / week.

I'm excited for the opportunity to have a strong, weekly revenue source, and am trying to figure out the most efficient way to produce them.

Here is the rub - they have to be 99-3/4" - plus or minus no more than 1/2".  Some bow / crook is acceptable.

I have jump saws set up in the shop, and can set up a stop, etc, but that means that I'm having to trim every single board - adding a lot of time and labor cost to the operation.  I could rig something on the outfeed roller tables from the sawmill to do the same thing, but would still have the problem of having to trim each board one at a time.

What I'd like to explore is to come up with a way to precisely cut logs to length before milling, so that every board coming off of the mill is the right length and can go straight into the stack for delivery with no additional handling.  Whatever I come up with has to be pretty precise though.

From a production standpoint, I'm hoping to use 16" - 24" diameter logs, or thereabouts, so that production volume is high.

I don't think that I can eyeball a chainsaw cut precisely enough, so I'm wondering about building a fixture to set a log into and then have some guide arms that a chainsaw bar would clamp into for making the cuts.  I would mark the log position in the fixture so that it could be aligned on the mill to make my opening face and second cuts perpendicular to the end cuts.  I'd want to design it so that I could use a loader to place and retrieve the logs, and take no more than a few minutes to do the end trims and R&R the log.  Ideally I'd trim enough logs in advance so that they could cycle through the mill quickly.

Another option would be to square the log into a cant on the mill, and then use some type of guide off of the mill rails to guide a chainsaw, but this seems to me that it would be slower and more risky in terms of a metal strike with the chainsaw.

What I'm looking for are ideas of how y'all would precisely cut a log to 99-3/4" length before milling, so that your boards were all within 3/4" or so of being the exact same length.

Thanks in advance.

Scott

[Magicman]

I could visualize a trough located on the log deck for the log to roll into and a chainsaw arrangement similar to what those firewood guys use.  The trough could pivot at the V so that the log could roll into and out of the other side.   

[Bert]

I feel the answer is to trim the lumber packs to exact length, not the log. A Holtec saw is designed for exactly that purpose.

[Resonator]

One suggestion would be to contract a logger with a CTL processor, to cut some logs exactly to length.
Do the cut 2x4 ends have to be square? That be the disadvantage chainsaw cut log ends, would be less likely to give consistent square ends on all the boards. 

Depending how much tooling/set up you'd want to do, you could automate the cutoff process. I know in window and door factories, they will have 2 miter saws set up a set distance apart. A piece of stock will slide on the table between them, be clamped in the center, and the 2 saws will come up from underneath, and cut the piece exactly to length. 

[TreefarmerNN]

I'd be tempted to set up a frame for the 2 x 4's to go onto in a single wide layer.  Have a stop at one end and two moveable guides to run a saw down.  Lay 8-10 boards down, cut the end next to the stop trimming only the barest amount necessary to square the ends.  Clear the cut ends (or have a trough so they would drop through, push boards back against the stop and cut the other end to length.  Use pallet forks to move the layer to your bundle.

If you have an off bearer, set up two frames so one is being cut while the other is being filled from the sawmill.

[Ron Wenrich]

I've seen carts that they use to stack lumber on that have a metal plate at the end to even end the bundle.  As long as your log is fairly square you can build a bundle like that.  Trim a layer or two at a time.  Use a jig or a guide to cut with a a saw like they use to cut beams.  10 wide will give you a 40" bundle if cut full.  15 layers high gives you a bundle of 150.  Build the bundle at the mill to reduce handling. 

I know of guys that cut bundles with chain saws.  I don't think it is a good option with that tight of a tolerance. 

[rusticretreater]

Logs are not straight so pre-cutting then ends wouldn't yield the results you expect IMO.  As you roll them to make the cant, it will end up off kilter.  

The main problem with this is that without high(er) dollar equipment, you are stuck with 1. pretty much working from one side 2. repetitive motions 3. long pieces that require handling

The most difficult problem is getting the first end cut even so that you can cut the second end to length.  This is solved by cutting the cant itself before you make the 2x4's. Not optimal, but necessary.  The boards need to be stacked with all the finished end to one side.

My initial thoughts are a radial arm saw, a table and your tractor.  The table is the same height as the cutting surface of the radial arm saw. You screw/bolt/clamp a fence to the table and position it so that the blade is at the proper length for the cut when you put a board on it.

Depending on whether you are right handed or left, put the stack to be processed on your left side with the pre-cut end to the left end(right handed) or the right side with the pre-cut end to the left-end.  You place the boards on the table with the pre-cut end already towards the fence, get them squared up and cut as many boards at once as the radial saw can handle.  Then take the boards and stack them to the other side on your transport tractor.

So its turn left, get the boards; turn center, get the boards on the table; cut; turn right, stack the boards.  The opposite motions for a lefty.  Handling 2 boards at a time will cut the repetitions in half.