Hi all.. this one has me completely stumped and I could use some help from those with far more knowledge of all things CNC.
Background.... I build displays for Honey Stinger and recently switched over to UCCNC/2017Screenset with a UC100 to replace mach3/PP setup. I have also changed over from sheetcam to fusion 360 for all my programs. Nothing else changed on the hardware side of the router which is a highly modified ShopDroid (nema23s, R&P) that is working well enough to get me by until I build a new one. I've made over 500 of these displays and I'm working on an order of another 90. So after all the changeover and outputting new gcode with Fusion 360 I set up and cut 30 sets of sides, changed programs and cut 60 sets of shelves, then back to 30 sets of sides. I'm loving the new UNCNC control and it has shaved a few minutes off of each run besides just feeling like everything is running smoother. 30 sheets of plywood cut, sanded and ready to ship in a little over 3 days so Life is good until.......
Problem.... I was finishing up the edge sanding on the second batch of sides and noticed that one of the angled slots looked a bit off. My router has some flex and I'm pushing it pretty hard so corners aren't exactly "square" and have a little overshoot but nothing too bad. This one though looked a lot worse and sure enough the shelf was more of a press fit than the normal loose fit. Measured and the slot was around .04" narrow but the corners were in the same place so it is the i-j movement that is off. So I start looking into what is going on and the first set of 30 were all perfect mirror images of each other which is what you would expect since it is the same part in fusion only flipped 180 degrees. Looking at the second set of sides I realized that every other one was off and one was exactly like the first set. Turns out the top side is the one that is off and I'm running the exact same g code that I did for the first set.
Trouble shooting so far..... Given nothing changed between the first set of sides and the second I verified the g code was indeed the same I had used for the first ones I assume it is a hardware issue with the Y axis since the bottom side is good and the top one is bad. Assume the X and Z are good because if the error was coming from them it would be the same for each side.
So I cut the feed rate down 50%, single stepped through the code, rebooted everything, turned off CV mode, checked all of the set screws, and gave the cnc a general look over for any issues but it still cuts the same way each time. I also added in a y axis offset so it is cutting in the same general area as the good slot and one is good and one bad so I'm thinking less of a hardware issue than when I first started looking at it.
At this point I'm at a loss as to what is going on since it worked great on Monday and Wednesday it cuts different with no changes to setup. The slots are the same size and one is a / and the other a \ which shouldn't matter? It would be one thing if everything was off but it is just 2 slots that are different. Anyone have a suggestion as to what to try next since I have another 30 sets to cut. One other data point, the error is at the start of the cut as the router is traveling in a counter clockwise pattern. Only "good" thing is I could sand out the problem and not waste all of the material but I really need to figure out what is going on...
Thanks!