CNC router occasionally makes jarring noise and home jumps when it does this. Help!!

[itsmillertime]

Ok guys,

I spent a few hours this afternoon stripping down bits and taking the bed off and removing the stepper motors from the router trying to look for any mechanical binding etc along the Y - the gantry driving axis.

It doesn't sound particularly smooth but I dont have much to compare it to. The gantry moves quite freely by turning the leadscrew by hand. I can freely push the gantry across the length of the machine and back with a gentle concerted push by hand. It's definitely less resistive in the middle section and approx the last 4" at either end the resistance increases by about an extra 15% and the noise from the ballscrew is slightly more pronounced and it's just a little more 'jerky' towards the last 4-6 inches of travel.

I checked the travel and the resistance of the x axis and this is noticeably smoother to push but I think thats because it's lighter and better supported on the 2 bars and less to travel. It does make a similar noise to the Y axis it's just less 'clanky' and smoother.

I moved the gantry right up to the ends and looked for gaps/ being square with the frame. At one end of travel (near the stepper motor) it's pretty much bang on. But at the other end of of the router I measured the gap at approx 2mm in one corner with the other corner at 0mm flush with the gantry. 2mm is quite a noticeable gap across the end. I have attached a photo.

So what's the best way to work out if its true? Could this be causing some resistance? I guess measure across rails at one end and do the same at the other? I haven't removed the lead screw or anything yet as I didn't want to really disturb anything else until I asked here!!

Is there any easy way of doing this, maybe loosen up the rails and run the gantry from the one end to the other? Then tighten up the rails? I checked all the allen screws and all are tight.

I may have found a possible cause of the motor stalling. One of the grub screws on the Y axis coupler didnt feel very tight (possibly loose) and maybe causing the coupler to slip when the load got too much? Not 100% certain that is it. But it's the very same axis that has had the problems.

I guess what I'm asking is, is the noise my machine makes when moved by hand (pushed) normal? Should I expect any resistance at extremes of travel. And whats the best way of making sure its square/ true and not a bent ballscrew.

Where should I go from here please guys?

While I have the bed up and I'm looking for biding/mechanical issues I want to rule them out I guess. Also should there be any oil of grease on the ballscrew? No nipple or any obvious lube in place.



Sorry that the video is 3 mins long but it shows the freedom of movement and sound of my y and x axis being moved by hand.

Below is a photo of the gantry with the gap approx 0mm/ flush at one side and 2mm at the other. I took measurements to show the difference in the gap.



Thanks again for all your advice. Just hoping to rule out any big mechanical issues before going for drivers etc..!

andy