Hello, I have project on my 1100MX where I am milling 18"x5"x.5" pieces of 6061 and I am getting all sorts of material thicknesses after the job is done. I was hoping for a +/- .005" tolerance but instead it is looking more like +/- .01" which is a lot considering that I get (target thickness is .315") anywhere from .308" to .320". It would be one thing if the part more or less be uniformly off by that amount but instead I am getting one extreme on one end and another on the other with gradients in between that are not consistent.
I have an SMW plate on top of my table that I have trammed to within .001" in the X and Y direction.
On top of the SMW plate, I have 3 SMW vices lined up to hold the part. I have trammed the vices, all 6 pieces to within .001" of each other by using shims.
I have probed Z from the top of the plate being machined at first, but now I am just going from the mating surface of the vice which made things a bit more consistent.
My biggest problem right now is that I am getting a .005" gradient (.320" on the near side) in the Y direction even though tramming the SMW plate in the Y gives me .000" gradient and vices maybe .001" not in favor of the gradient. This side that ends up thicker, has the moveable SMW vices that get tightened. I also use a rubber mallet and ensure that the plate is touching all the vices flat.
If anyone has any idea where these extra thousandths may be coming from, then I would greatly appreciate any advice. I suppose it could be the metal warping. Perhaps I need to be more methodical with how much torque I put on the vices with a torque wrench. That’s all I can figure. But how could extra torque on the part lead to extra thickness?