Looking for advice on a machining strategy for difficult plywood parts...

[Grunblau]

I am making a custom cabinet for myself and I have been held up on a machining strategy that I may be over thinking. I figure many people on this board may have run into something similar and have likely found a creative solution which is currently eluding me...

The setup is multiple consecutive layers of baltic birch that will be laminated together to form door fronts. I have everything nested on (8) sheets of 3/4" Baltic Birch. I have maintained a gap of at least 3/8" between all of the parts. As you can see, there is occasion where there is a thin tapered piece between the parts that I suspect would be all too happy to snap my bit the second it is cut loose.




The machine cutting this will be a Shopbot Alpha with a 5HP spindle with a 10HP vacuum hold down table. I am planning on using a 1/4" compression bit cutting a 3/8" deep clearing pass and then all of the way through to the bottom of the cut. The vacuum table is great until the pieces are small or more cuts are made in the stock.

There are 100's of parts so onion skinning the profile cut is not really a great option. I'd like the profile cut to be all of the way through except for tabs that are easily removed. These tabs are located at the tips and at the mid points of the long parts.

My current approach would be to pocket these interstitial slivers of stock, leaving 1/8" on the parts and then run the profile cut... My concern is that these pieces are too delicate to machine if they are fully relieved from the sheets and that they will move away (or toward) the cutter. This is why I added a tab at the mid span of the part that attaches to a continuous block.

Then a bunch of options started swirling in my mind like cutting every other profile, or onion skinning the pockets, etc... Am I over thinking this? Is there a simple solution I am not seeing? I would be grateful for any advice!

Thank you very much!

Brian

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[ger21]

I think they might move with a 3/8" final pass.
I don't think you need to pocket the waste. I occasionally cut stuff like this without breaking any bits.

I conventional cut everything, so that any waste material is pushed away from the part when it's cut loose, so the bit won't grab it.

On the small parts on the upper right, I'd cut them from right to left, with the start of the cut on the left side near the bottom. You want the parts to be attached to the sheet as long as possible, so they can't move. By working from right to left, each part is fully attached to the sheet along the left side, until the end of the cut. The scrap material will just fall to the side when it's cut loose.

I'd do the same with the longer parts, with the start of the cut on the left side near the bottom.

I've never used a 1/4" compression bit, so I'm not sure what the best strategy would be. If time is not an issue, maybe two passes leaving about .02" for a finish pass, and leaving a thin onion skin, than a final finish pass all the way through, at a lower feedrate.