Hi everyone! I'm new here, hope I'm posting this thread in the right section I've built a LEAD 1515 with a Rat Rig Kit, and I'm currently trying to make the first cuts. I'm having a remarkable lack of precision when making curves and circles, while rectangles and squares seems to be fine. I'm attaching a picture to be more clear of what the problem looks like. So far I've tried checking the tension of the lead screws, the correct distance of the Y sides, changing end mills and the feed rates to very low values. Nothing really made a difference. I'm quite frustrated and I'd really appreciate any help! The controller is a CNC xPRO v5, the software I'm using is cncjs. Thank you! Max
This is called backlash and is much easier to diagnose if you also tell us which way you were cutting, clockwise or anticlockwise, and indicate in the picture which is X and Y. The summary is 'something is loose' and this allows the tool pressure to affect the cut. The tool is spinning clockwise so when it is moving 'up' (Y+) it will try to push itself left.
Before reading this I've tried tightening all setscrews on shaft couplers, and run a test with a marker to see a more accurate result of the problem. So, no spinning involved in this last test. Still I'm getting this odd shape when trying to make a circle. Any idea of what might be? Thanks again!
Still looks like backlash in the X axis - are you sure the setscrew is on the flat of the motor shaft? And tight on both motor and leadscrew side - from what I can see its got backlash during direction changes in X (pending David's more in depth analysis that may prove me wrong later) Make sure there's no axial play in the leadscrew (tensioned properly as per the assembly video)? - can you move the screw by hand [<--axially-->] - it should be tightly constrained by the endplates
The setscrew was positioned on the flat of the motor shaft, but I tried repositioning it and tightening everything more. I've tensioned the leadscrew by tightening the bolt just enough that there is tension before it moves again. I'm going to check the axial play but I'm pretty sure it is well constrained and doesn't move at all. Thanks for the help so far!
So I've checked also the axial play and there was no movement at all. Tried tensioning everything again, did the same marker test and came out exactly with the same odd shape. I'm out of ideas and getting really frustrated Any other suggestion or test I can try to figure out the problem? Thanks
Grab the endmill and give it a firm wiggle - if it moves on you, use your hands to follow the unwanted movement until you locate whatever is loose. Wheel adjustment, fastners, router not seated right in router mount, etc
It doesn't move, it feels really firm. Could the wheels be too tight? To me they seems fine because when I freely move the XZ carriage it looks accurate and also there's no strange noise. I've tried a different test with the marker, a bunch of parallel lines at 45degrees. There's always a mistake in the beginning of the "routing" of every line: it goes straight in the Y direction and then "correct" his position going at 45degrees. The first and the last (signed in cyan and purple) lines aren't affected by this problem. I'm pretty confused!
Which looks exactly like a shaft coupler slipping (i know I know, it has me baffled too) So, it changes direction, slips to one extreme of the backlash. Starts moving, the shaft spins, inside the "backlash" space until it finally catches up and start moving. During the next direction change, again. The times we see this, it has almost always been either that something is so loose you can wiggle the endmill, or, the shaft coupler slipping on the motor shaft - as the grubscrew catches the edges of the D shape, in between it dead space where its neither here nor there - until the setscrews are tightened. This is one of those cases where you kind of have to see it move during the direction change to see whats standing still when you expect it to move - visual inspection is the only way to find what is causing the backlash in the X axis. And it has to be something loose
Thank you! I managed to find the problem, which obviously was the only thing I haven't checked: the screws on the nut blocks! They were pretty lose for some reason. So it's perfectly working now, thank you so much again!
