Leaving skin along edge during outline

[Ian Richardson]

Just a few facts first: 3/4" Melamine. 1/2" tool for outline.
No matter if its a large piece (cuts outline in one pass) or small pieces( 2 passes). The finished process leaves a 0.01" skin along the bottom edge. The length of the table. About 1/2" - 3/4" wide. I hope Im explaining this right. Example: If the bind dado was 96" long. I would have to physically break off this skin after cnc-ing. Just along the edge of the table??
Any ideas? The rest of the table is fine with cutting. just this long edge? All tools measured and wasteboard flycut first thing in morning.

Thanks
Ian

[Josh Rayburn]

Ian,
I don't know what type of cutter you're using for your surfacing operations but mine is an insert cutter. I notice that when the inserts get dull they don't cut right and I end up with exactly what you're seeing there. You could try fresh inserts (if your cutter is like mine) and see if that helps. The next step is to add .005" to the daylight value of the outline tool to compensate.
Melamine holds down a lot better than anything else - as a result it is possible that the melamine is sitting a few thousand's of an inch lower, and thus the problem only appears on these materials. I haven't really tested that theory, but it makes sense to me...
Not sure how helpful any of this is, but if you get it figured out let us know what did the trick for you.
All the best,
jnr

[Ian Richardson]

Thanks Josh, that makes sense but its just weird that it just happens when it travels along the edge. Cuts great everywhere else.
They say a picture is worth a thousand words. Heres one. As you can see the skin. Even after it has done the second "removing skin" pass.

Ian

[Daniel Odom]

I'd try and Increase your cut through depth. It's prob just not quite deep enough to cut through, but when you cut the adjacent part the tool paths overlap and overlapped areas get cut again, the skin left is being cut by the next parts path except on the edge where there are no adjacent parts. Could be your wasteboard isn't flat on that edge as well, check your dados and make sure they are all the right depth/ consistent across the table, that should tell you if it's a flatness issue, but I think if you increase cutting depth a bit it should fix your problem. If all of your dados aren't deep enough you need to adjust wasteboard value. You should be seeing slightly indented outlines of your parts after the sheet is run, but not too deep grooves. So increase your cut through depth or adjust wasteboard and see if that helps. Always try the easiest solution first. Look at the gcode too and verify that it's supposed to cut through.

[Rob Davis]

Ian, we see this from time to time. Biggest reason we can find is that the operator gets sawdust between the waste board and spoil board and then when we flycut, it makes the top board too thin, then we clean out the dust and now the sheet is low on the edge. Other cause can be if the table doesn't pull the spoil board down hard enough when we flycut so it cuts it too thin on edge for some number of passes and then the sheet is too low when we cut. Or the board is old and is curling up on edges and when we flycut it cuts edges thin. And either of these issues gets worse when we use melamine since you get a very good seal on melamine and it compresses the spoil board due to suction. This last reason is one factor why we believe thicker spoil boards are better.

[Daniel Vonderheide]

The laminate on the edges is being pushed down on the edge. It has nothing on the opposite side of it or under it to hold it so it is flexing downwards. This is due to the material and wasteboard slightly overhanging the actual table board allowing it to be pushed down. If you watch the machine when it cuts on that edges, you can see the bottom laminate flex downwards most likely.