I love my Domino DF 500. But I have trouble aligning boards when edge joining for, say, a table top. Typically the boards are off by about 1mm or so. For example, this morning I tried joining 6 boards together with dominoes, but in each case, the boards were off by 1mm. Each successive board is 1mm off from the closer one, so it is "consistent". I thought about re-drilling the hole on one side and raising (or lowering) the tool by 1mm to counter this, but then the domino would be very loose.
Is this typical, or is there something I might want to try in order to get better alignment in my edge joining?
You don't say clearly what direction the boards are misaligned
If you are getting a step in the face surface, the most likely explanation as already mentioned is that you are referencing the domino fence on opposite faces of adjacent boards when cutting the mortises. The best way to avoid this is to lay the boards out as you plan to join them and then marking all of the visible surfaces. As you mill the domino mortises, make sure you can always see the marks, i.e. the boards are kept same side up. It's also possible that the fence height is slipping, though the systematic difference of 1 mm makes that less likely.
If the ends of the boards form a stair step, you are having a problem with horizontal alignment. If you are referencing from pencil marks using the plastic gauge, your gauge is misaligned. If you are spacing by putting the fence pin into the previous hole, you need to adjust the movable pin. Rick Christopherson's manuals, cited above, have directions for making both of these adjustments, or you could send it back to Festool for tuning. I usually leave some extra length in boards for a table top and then trim them after assembly, so this direction of alignment isn't a problem for me.