I'm not sure how to word this better, so forgive me if the issue isn't very clear. I will try to post a video soon. I am a student in a High School, and we have a gantry style ShopBot CNC in our wood shop, one of the large ones. I think it is a pretty old one. I have attached a picture of it. I am the only one in the school who knows how to operate the CNC, so I handle all the upkeep for it as well.
The CNC had been working perfectly until one day it started acting up, being jittery, skipping around, and losing its place while carving. The v-bearings on the right side of the x-axis were falling off the rails when the x-axis was moving at high speeds as well. I don't know how it happened, the teacher said that someone may have accidentally gotten something in the way of the x-axis while it was moving, but nobody knows for sure what happened.
Basically the issue is that when the x-axis is moving at high speeds, (unsure about the exact speed, I will get back on that. Maybe 50 inches per minute?) you can definitely see the x-axis getting stuck or jumping around. It makes a bad grinding sound sometimes too. This causes problems because the computer thinks the CNC is in a different place than it really is, and it screws up the entire carving when this happens. Things end up in the wrong spots, overlapping, etc. At first the v-bearings on the right side of the x-axis would fall off the track/rail they are on, but that part seems to have been pretty much solved. We had to re-square the entire machine multiple times, and the rail that the v-bearings ride on seemed bent, so we used clamps to pull on it while someone tightened the bolts underneath, and that seemed to straighten it out. We haven't had issues with the v-bearings falling off anymore, but it does still skip/jump/jitter/etc a lot. It happens a lot less when I lower the speed.
Currently we have the CNC moving very slow because that's the only way to get a consistent carve without jittering, but it is a bit annoying because we have a lot of students who want to carve and can only get through a couple per period because of the time it takes to carve.
Can anyone offer up some suggestions on what might be going on here? I don't know how much detail I need to provide, so if there is something you need, I will be happy to share more details. It may take time to give more details because I can only work on the CNC for a few hours a day since I have other classes. I can record videos, take pictures, etc. I know a lot about computers and electronics, so feel free to ask the more technical questions. I can get you guys any details you need in order to help me fix this. Thanks!