Hello,

I own a chinese CNC3040T-DJ that has suddenly started to do weird things, but in order to put you in pespective:

-It's a 4 year old machine bought because it was cheap. It has ACME leadscrew with delrin (or white plastic) nuts. No endstops, has hit ends several times and probably suffered.
-Has cut 1000+ fiberglass laminate (FR4, G10) pieces, some aluminium, some acrylic, wood, etc. I would say it has had moderate to high use these years.
-It has had exaclty ZERO maintenance in all these years. No piece has been changed, no extra grease has been added. That's mainly been because of laziness, because I had zero expextations for the machine so I haven't developed a relationship with it (I don't love it enough) and because it kept working well enough for my needs. I only had to change the motor driver mosfet because it got burnt once that the motor stalled due to a piece jumping and jamming it.
-Only mods it has are capacitors added to driver board to eliminate the X+ axis drift these machines have (done 1 year ago, before that it suffered from drift like all the same machines with the same parallel port controller) and the cutting table, which came twisted and bent (>1mm Z deviation accross it) , has been substituted by a sacrificial particle board.


So, I mainly use it to cut intrincate fiberglass laminate pieces to make drones and other stuff, something that requires tolerances in the order of 0.2mm or less to work well, as I like to design frames that interlock together without screws and such.After all these years of abuse, the router has I'd say about 0.5-ish mm of mechanical play on each axis, pretty significant tool TIR that mainly comes from the Z axis and not from the spindle and collet and it screams while moving fast due to lack of lubrication in the linear bearing's rubber guards. Apart from those issues, I'm not sure how but until about two weeks ago it kept producing repeatable cuttings and my pieces turned out accurate enough to be assebled without problem (all checked dimensions within 0.2mm and less). Then suddently it has started having a problem,as the cuts produced are made like the tool were thinner than it is, with a random and geometry and toolpath dependant radius error, so my pieces don't come out accurate. If I cut a circle, it turns out as a pretty round circle with less diameter than it should, for example, but on some geometries it overshoots or does weird stuff. I've tried to compensate for this but I can't as this is toolpath dependant. It seems to be an issue balanced in both X and Y axis.

I think this is due to mechanical play, but I haven't noticed any extra increase on it since the last weeks, and this happened suddenly. I've tried old toolpaths and to reconfigure mach3 but the stuff persist. I think I'm going to give it an oportunity and try to repair it, so I'm asking for advice on how to do it. I was planning to replace the linear bearings and the leadscrew nuts but I can't find any source of spares, I only find spare brass nuts for ACME leadscrew but mines are delrin I think.. I was also thinking about replacing the spindle collet holdeing axle (the spindle is a 300W brushed air cooled model).

Do you know of any source of spares for these machines? Anything extra you would change/repair? is my problem consistent with a mechanical play issue?
Thanks in advance