Make sure your dewalt is 90 from the surface in both directions, maybe you are off at a slight angle and that is causing your problem. You can shim the top with a few wraps of tape.
Bingo! I investigated a little more this morning and this was it. Unfortunately, it’s a function of the weight of the tool. With the tool in its mount and a carpenter’s square lined up with the z-axis tubes, there is about 1/8″ deflection over about a 9″ span. With no tool in the mount, everything is perfectly square. This easily accounts for the problems that I’m having where shallow cuts start out fine, but I run into issues as they get deeper. I could shim it and fudge things, but I would rather solve the root problem.
Have you milled wood successfully yet?
Yes, tons of MDF, plywood, hardwood, and acrylic. They really are that much more forgiving.
Can you snug up any of the center assembly a bit more?
Just tried this. I tightened everything that I could get my wrenches on. Everything was perfectly snug, but each bolt got about another 1/4 turn. This had no effect on the deflection, which appears to be coming from the plastic pieces of the middle section itself.
How big is your build in the x and Y direction?
Usable area is about 18″ x 20″
Can you cut more towards one corner instead of the center?
None of my cuts have been in the dead-center. If I move the toolhead all the way into a corner, there is seemingly no effect on rigidity which, again, points to the plastic parts of the middle section.
How long is the part of your bit that sticks out when fully inserted?
Just about 3/4″
As for camar0’s part. He took it down and removed all his accounts for some reason. Another user put it back on thingiverse, I can’t imagine he would be okay with that. The part itself, I have not tried it. It does increase the contact area with the rails, but it adds more rolling resistance and mass, and I’m not convinced of the geometery. I’m sure someone else will chime in on this but I really want to hear from someone that didn’t start with his parts and added them later. When it first came out I asked him and a few of the first people how much better it made the machine. None of them had tried it stock first, even Camar0, yet they all said it made it better. How could they know? I guess this one is a sore spot with me.
I agree that he took them down for a reason. I certainly would never be the one to re-post his work, but I may take advantage of it and give it a try. My machine may be a perfect candidate for this upgrade and, with the exception of a few bolts, I have all of the hardware and plenty of filament. It may do nothing for me, but I don’t think it will hurt to give it a try.
If that doesn’t do it (I too am a bit skeptical), I have considered a couple of alternatives. A counterweight might square things up a bit, but it would certainly be another detriment to rigidity and the added mass would probably just multiply any issues. The other thing that I was considering was installing a whole other set of cross-members with it’s own middle joiner and z-axis to box in the tool-head. I would either opt for the traditional dual-z motor setup like most 3d printers, or possibly slave the second z-axis threaded rod to the first using a belt and pulleys to maintain synchronicity. Thoughts anyone?