I just got my machine put together and have my test file all ready to go. I started doing a dry run and noticed that my axis are not rolling very smooth at all. They’re binding quite a bit and causing the tool to be very jagged (just from looking at it while it does its dry run). It’s almost like when you slide a chair across a hardwood floor and it starts skipping and vibrating really hard against it. My build is larger than advised (about 3.5ft x 4ft) and was wondering if this was the cause. I ran out of propane for my garage heater tonight, but I started to loosen the middle gantry bolts to see if that would help. I haven’t gotten around to loosening all of the ones that I’d like, however I wanted to see if anyone has seen this issue before. I have a picture of my setup attached if anyone is interested.
My gut reaction is way too tight on all the tension bolts. All the rollers don’t need much, if any, tension on the tension bolts. If I were you I would loosen everything before something cracks.
I’ll be sure to do that as well. If one motor is flipped on the daisy chain cable, just that one motor will turn the opposite direction, right? I’m just wondering if the second motor is plugged in backwards on the daisy chain cable. I did line up the arrows. Thanks for the speedy replies, too!
Really good idea to check your stepper direction and strength before you put the belts on. Could be the issue. Snip the cable ties and double check that each one is moving in the right direction and has roughly equal strength. If you got the board from me the current is set for the drivers, if not that could be another problem. Hard to say, start there. Blind guesses are no fun.
I think it’s probably not the size of the machine, mine is almost as big and does not have the issues you describe.
When I assembled the machine, I noticed quite a big difference in how easily each roller would slide on the conduit. Some were so tight that they would hold the conduit against gravity. I really thought I had left all bolts loose, but I could get all rollers to slide freely by loosening the bolts even more. By the way, I had to loosen all bolts, not just the tension bolts that are meant for adjusting the tightness. My guess is that it’s possible to tighten the bearings just far enough off center to make it too tight even when the tension bolt is completely loose. My problem, I think, was that it is difficult to judge tightness with nylocs. My nylocs gripped so well that I could not hand tighten the bolts and with a wrench, it is hard or impossible to feel when you are starting to squeeze the plastic. I cannot feel an increase in torque when it’s just snug (backing off a quarter turn after hearing the crack did not work well either). Even with all rollers sliding freely, the machine did not move very easily by hand, but there were no issues moving under power aside from a bit of noise. The good news is that there is a break-in period where things magically align themselves. Everything slides much more easily and quietly now that I have used the machine for a while.
I do not think you have one of the cables flipped. I connected and disconnected my wires a few times during assembly and accidentally flipped one of the X axis steppers after I had installed the belts. This is immediately obvious even for a small motion if you try to move the machine with the LCD, and I don’t think you could move very far without something bad happening.
I also had a wire come out of a stepper connection because of the cheaply made connectors I was using. I would definitely solder the stepper extensions if I had to redo it and have done that for one of the axes. The symptoms for a missing stepper wire were pretty violent and I immediately turned the machine off. I think there might be a danger of frying the stepper driver if only one coil is connected as it is probably still trying to supply the set current to the disconnected coil. If you can move the machine by more than a few mm, I think it is likely not a wiring problem but something mechanical. Just to be safe, I would undo the belts and try it out and turn the machine off quickly if the steppers do not sound right.
Aside from how tight the rollers are, I would double check to make sure the rails are parallel. The only other thing I can think of is to make sure there is no skew by setting the rollers at the same distance from the corners before you enable the steppers. With a large machine, it is quite easy to get several mm of misalignment. I made some mechanical end stops that clip onto the rails so all I have to do is butt up the rollers against the stops before enabling the steppers. They work so well that I am not sure if I’ll even bother to wire the dual end stops.
Ryan has designed a flexible pen holder that survives being pushed 5mm into the board by people connecting their Z axis the wrong way. Wouldn’t know about that myself, of course, but I did use that pen holder for a while before mounting the router. I can only recommend it for working out the kinks before moving on to milling.
What a great community! I appreciate your reply, Hubert. After reading your post I think I do have the middle gantry bolts too tight. I’ve been known for cranking bolts too tight in the past (broken off a couple battery terminals, actually). I’ll start loosening the middle gantry bolts and go from there! Thanks!
Let the troubleshooting begin. Decided to disassemble tonight and see how things were sliding. The conduit seems to slide through the middle gantry fairly well. The conduit slides through it from gravity alone- not so much that it drops immediately, but with some light resistance. I decided to call it a night from here and will work on it more this weekend.
Got a lot of improvement out of tonight. Took the gantry apart and loosened every bolt, even the 7" long one that goes vertical. I found that two of the bearings weren’t spinning at all (see attached). Here is a quick video of things. They could still be a little better, however it’s a huge improvement.
So at this point I would say it has a lot to do with the size of your build. It even looks like when moving along the short axis it is worse meaning the long axis is acting like a spring.
Not the end of the world. While in use that should not actually happen in a bad amount as it will be pre-loaded a bit. You do seem to have pretty rough conduit but that can works itself out or you can sand it down a bit.
