Lead screw/travel problems, Circles aren’t circles, and I’m a noob

Hey everyone. This forum has helped me a great deal in getting my machine set up. I have zero experience in programming/machining/etc but am teaching myself along the way based on great information provided from people on forums like this. Anyway, onto the questions

My machine is physically put together, laptop connected, stuff hooked up, I’m moving the torch around, making stuff in Fusion 360 and getting it over to the FireControl. Very exciting.

My first cut was a square with a fillet at one corner and a circle in the middle. Corners on the square were perfect 90’s, but the circle looked like a lemon. Found my couplers on the X and Y axis lead screws were loose, so those got tightened and I thought I’d be golden…. not so much…

Trying to cut 16ga steel this morning and I’m encountering the following issues:

  1. When moving the gantry in the Y-axis, if speed is 200-300ips, I’m getting some significant vibration/wobbling in the lead screw and audibly it just doesn’t sound very nice. This occurs in the middle but not so much out toward the ends of the travel. Meanwhile on the X-Axis, I’ve got perfectly smooth-looking travel when going away from the Y-axis, but when coming back toward “0”, if traveling 200-300ips, I get a very sudden binding and stop in the travel prior to actually reaching the end of the tube. If I lower the speed down to about 100ips and below, then I don’t notice these things visually/audibly, but I’m suspect as to whether there are still issues from what seems like lead screws that are not straight perhaps? If not the lead screws being warped or something, what else should I check?

  2. I made a drawing with a series of shapes to be cut out all at once on Fusion 360. The shapes were separate and pretty simple (Basically some rectangles) and the tool paths all looked sense all before wrapping it all up to send over to Fire Control. It was early so I forgot to ground the piece, so the torch didn’t pierce through, but I could still see exactly where it had passed on the metal afterwards. All of the spots it tried to cut were overlapping… I had the machine set to 100ips for cutting to avoid the problems I’d seen with the lead screws and travel at 200+ips, but I was cutting metal over in the area of the travel (Both x and y) where I had noticed the issues at higher speeds before and I’m wondering if there was still binding happening that wasn’t as noticeable, but causing the machine to think it was moving the proper distances, when in reality it wasn’t due to binding? I then went over to the opposite side of the table where travel of the torch and gantry was smooth at all speeds and made some more cuts and all the shapes were properly spaced seemingly (I had to jet and couldn’t grab measurements to check). At least they weren’t overlapping.

  3. Despite going in and finding some loose couplers between the motors and the lead screws and also the bearings and the lead screws and then tightening those all up with a dab of some blue loc-tite, I’m still getting crappy looking circles. Straight lines and angles look fine, but circles not so much. I came in expecting perfect circles, but I’m getting circles that look like someone drew them with a pencil they were holding in their mouth… What else do I need to check? Or is this all an issue that leads back to the lead screw and travel oddities?

Thanks in advance.

go to 0,0 and mark it, move 30" in Y and measure and see if it’s true 30"… do same with X but in 48"… lead screws might be a bit tight … start there first… and use grease on the rods

you lead screw mount might also be off axis with the rod hence why you are getting binding in the middle. loosen up the mount a little and jog it a few times and see if it will reset itself… then tighten back up…

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Ah good input I wondered if there was something like that going on but I don’t recall seeing any sort of torque specs or recommendations on “how tight” so I just sort of tightened it all to German spec.

Will try the test and some tweaking with things and report back

Thank you

@Jcham1157 Do not use grease use 3 in 1 oil.

OK Thanks guys - couple updates here:

  1. I loosened the x and y-axis lead nuts (The four socket cap screws and nyloc nuts around them) and right away could see a difference in how the X-axis travels. No binding even up to 300ips. After loosening the y-axis, though, I’m getting a significant amount of wobble in the lead screw still…

  2. Looking closer at the y-axis lead screw, I’m thinking it’s something with the coupler on the motor side actually. Possibly the bearing side, too. I believe that since there is no flat on the lead screw for the set screw in the couple to tighten down onto, it’s just finding its way into the threads somewhere and causing stress on the lead screw perhaps? Thing is - When I tighten and loosen the set screw going into the lead screw on that coupler, I can visibly see the lead screw rise and fall in the middle as though its being warped by the set screw being tightened. When that set screw is tight and the motor is coupled to the lead screw, I have wobble. I did a little experiment and loosened that set screw, decoupling the motor from the lead screw, and then used a drill with a 5/32 bit on the end over on the bearing side and just used the drill as a sort of motor on the socket-cap fastener holding the bearing-side coupler. Basically - the drill was making the lead screw spin and the lead screw was not connected to the motor. When I did that, I had significantly better travel and nearly zero wobble. The litle wobble that was present I believe was simply coming from the drill. I took a video of all this and I’ll try to upload it later on today if it’s helpful. Or if anyone can spot exactly what I’m doing wrong please do let me know. Is my motor off axis somehow that when coupled to the lead screw, it’s causing stress on the lead screw? Something else? The x-axis now seems to be fine and it’s set up basically the same obviously.

  3. I’ve got 3 in 1 lubricating the lead screws. Luckily had some laying around the shop.

Thanks again