I’m moving on to a new project with my MPCNC, and it involves cutting out multiple sections of wood from a larger piece.
So lets say I have a 12" x 12" flat piece of wood and I want to cut out of it a couple 5" x 10" rectangles.
What is the best way to do that? Do I generate tool paths to fully cut all the way through the large piece of wood all the way down to the base table (spoilboard)? I assume that is the point of the spoilboard is to take the extra cut-through distance of the endmill when cutting parts out.
I’ve only had experience with carving stuff into wood and not actually cutting full parts out.
Yes, your generated tool paths will cut all the way through, and yes, that’s what the spoil board is there for.
You’ll also want to be sure that the workpiece and the waste are securely held in place as the cut is completed, as a shift in either has the potential for damaging the workpiece and causing injury if the part is thrown off the table.
Some strategies include using double-sided adhesive tape (or the masking tape/crazy glue trick), leaving small tabs that keep the workpiece connected in a few places (which are then trimmed by some other process) or clamping/screwing through each piece to ensure they don’t move as the cut is completed.
6 Likes
I’ve got bad luck with table saws throwing parts I’m cutting… maybe I need to build an enclosure for this thing!
I think this is the concept I was thinking of. I have no issues trimming the tabs once the cutting is complete.
1 Like
I will also add that I have found it best to cut one piece at a time. Meaning secure your wood and have the program ready to cut out just one of your boxes. Set the starting point and let it go. If it works well the. Set a new starting point and let it run the same program again to cut the next piece. That way if one cut goes wonky you don’t lose the entire piece of wood.
2 Likes
Yikes! There are ways to prevent that from happening too. I learned them really quick the first time I saw a friend have a backfire cutting 1/4x1 strips for a breadbox on an industrial table saw… shattered into 100 tiny pieces after hitting the wall 20ft behind him. In his case, it was not letting the part come off the fence… his push stick got cut in the wrong spot and he did not notice.
Table saw kickback is almost always caused by the back of the blade (where the teeth are travelling up) grabbing the work piece, often because it has gotten pinched between the blade and fence. This can happen if the workpiece twists, or if stresses released by cutting the wood cause it to bend, twist, or bind on the blade.
To avoid, keep the rip fence parallel to blade, and don’t let parts get pinched at the back of the blade. A riving knife or old-style splitter which rises behind the blade and carries the blade guard are common protective pieces, that are also commonly removed in demonstration videos.
2 Likes
Yeah tbh I removed the splitter, blade cover, and one way shoes from my saw after a few cuts with them installed. I feel better being able to see the blade and kerf as I go, as well as any warping behind the blade. I work in construction though, so swinging saw blades around safely is a long hardened habit for me. I was intrigued by those new electronic safetied that instantly stop the blade when it senses flesh… but things can fail to work so fundamental safety is always a requirement.
2 OT… gotta make up for that.
Ttraband mentioned the tape superglue method, which I think is one of the best methods available for this. I use double sided carpet tape to hold manual router templates for carpentry work… doesn’t work so well with a robot behind the wheel and a bit yanking on up on the tape. The carpet tape has enough flex to ruin a part… plus if you use blue tape with superglue it won’t damage the part surface during removal like carpet tape often does. This all said… don’t try and do a Cnc drag race with tape… you need solid fixturing with clamps or codes when the loads get high.
And… The non-obvious danger isn’t just the workpiece flying at your gut. It is also any hands or fingers on the board behind the blade getting pulled into the blade.
Never grab the workpiece behind the blade with any part of you that you’d like to keep.
Thanks for the replies everyone, I think I have the information that I need.
I don’t have issues with my MPCNC throwing things (hopefully it stays that way). I’ve just managed to have really bad luck with tablesaws. Even while under the supervision of professional woodworkers, its happened and even they are clueless of how it happened.
The worst and LAST time I used a table saw was well over a decade ago. I was cutting some large sheets of wood (I think they were about 4’x4’) to make some speaker cabinets. First few cuts went well, but about a third of the way into cutting a full size sheet, the saw snatched up the wood and flung it BACK AT ME. It nailed me at my waist line, knocked me down, and the entire impact area was numb.
Got rushed to the hospital right down the road and I was perfectly fine thankfully. I don’t think I even had a bruise from it strangely.
The piece of wood that went rouge ended up having a large arc cut into it from when the saw grabbed on. The blade physically warped as it was cutting because of how tight the arc was. No one had even seen that before.
So I stick to my hand-held circular saw for larger cuts. Never had a problem with it.