How do you cut all boards to the same thickness?

[scottbot]

Hi All,
I want to machine a bunch of rough lumber to all the same thickness. My programming skills in the ShopBot control software aren't that strong so I would like to use PartWorks to get the job done.

I thought I could zero the Z axis to the table top and then, using a pocketing tool path, get the Bot to make my cut to a desired finished thickness rather than a cut depth. I haven't been able to figure it out.

As I mentioned, I will be using rough cut lumber so the boards will all be slightly different thicknesses so measuring each board and then setting a cutting depth won't likely give me the precise results I need.

Thanks in advance.

Scott

[sawdust535]

Scott,
If you set the Z to the table top, and set the material thickness to be 1 inch, and set the depth of cut to be 1/2", the depth of cut will be 1/2" above the table top. You can adjust those numbers to suit your desired thickness.

[sawdust535]

Make sure you click on "Set Up Materials" under "Tool Path Operations" and click the Z Zero radio button at the bottom of the material (for top of table). Then use the Z Zero routine to zero the table top.

[jsfrost]

Scott,


"I thought I could zero the Z axis to the table top and then, using a pocketing tool path, get the Bot to make my cut to a desired finished thickness rather than a cut depth."

For final thickness this is the right idea, however, unless you have vacume available, hold down details need to be considered.

Is your stock rough on both sides? If so, consider first taking a light cut on side A, zeroed from the top, and just deep enough to leave a clean surface.

One approach for the B side is this:
After clearing the A side, measure the typical thickness of the partly machiined stock. Lets say it measures .795 on the thickest sample. And assume the desired finished thickness is .5. Lie to PW, and enter material thickness as say .75 and select zero at bottom, but think ahead, so your selected cutter will not need to take a bigger bite than it can handle.

Next place a rectangle around the area you wish to surface. Toolpath a pocket inside the rectangle, giving start depth as 0 and finish depth as .250. The tool path will cut .250 from the .750 level plus the excess. In this case, .045.

Others will have other methods. Pick what makes sense to you.

[jsfrost]

I type to slow or too much. Sorry for the repeated info.

[scottbot]

Thanks George and Jim.
I'm going to try those suggestions tonight.

Scott

[Gary Campbell]

Scott...
We do this often with large pieces of rough lumber. Using David Buchsbaum's surfacer (which you can find on this forum) we plane down our pieces in steps and write down the cut depths for each pass. When we put in another piece, we simply use a negative cut depth that is the total of all the steps used on the prior piece. That starts over at the top and we simply copy the steps from the first.
Gary

[myxpykalix]

Scott,
Do you have a jointer or thickness planer?
I deal with a lot of rough cut lumber from a sawmill myself. I usually have wood cut at 1.25" that i am going to use for 1. or .75" final thickness.
My sawmill guy uses a bandsaw so consequently my cuts usually are not that rough, however, a log on a conveyor and a bandsaw blade are not that precise so i build in enough waste factor.

I have used my jointer or thickness planer to get one flat edge, then i use a pocketing toolpath on the opposite side to get that flat.

You are now at a point where you have one side that you know is flat relative to the bot. Then turn your piece over and run your pocketing toolpath on the jointed side and you should be uniformly thick and both sides flat and relative to the cutter on the bot.

[scottbot]

Thanks everyone.
I never got to try the earlier suggestions tonight because I ended up watching the American Election results. That was just too interesting to miss.

Gary, I downloaded David Buchsbaum's surfacer from Paco's site. Thanks for telling me about it. I was getting a lot of tear out today on my practice pieces that the surfacer will probably help reduce.

Jack, No planer or jointer. I've been using the Bot for the whole process. I flatten side A and then flip it over and do side B. I was having trouble getting the boards to a uniform thickness but with all the help I've been given here I think I'll be able to be able to manage it tomorrow.

Thanks again everyone.

Scott