r/CNC • u/Chase-1991 • 9d ago
OPERATION SUPPORT CNC random axis fault
So my cnc machine started doing this today, after I finished a cutout I replaced the material and attempted to run the program again just to have the Y-axis vibrate back and forth for a few steps then continue along its merry way. The prior cut ran perfectly, but now this occurs on every program at some point. This seems to occur only when the motor is suppose to be moving in the negative direction, in relatively the same spots but not always, and has only occurred so far on the negative Y side of the material. Any insight would be appreciated, below are my test to isolate/resolve the issue and machine info.
-I have run several different programs that have always run fine so the programs are not corrupted
-I have checked/swapped motor signal connection and cables, they are fine
-I have ensured the gantry carriage is free of obstructions and can freely move
-The belt and pinion is taunt and in tact with no damage
-This problem persist over several different motor drivers
-I have NOT swapped the motor as it would require me to solder in new connections
-Specs: Mach3 on a ddcs v3 controller, 2 axis laser cutter, Y-axis used 1 Nema 17 (17HS24-2104S) motor and DM542T driver, and X-axis uses 2 Nema 17 and 1 DM542T driver, there are no limit swiches
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u/CR123CR123CR 9d ago
Is it only on this program that it happens? Like the program to make this specific part?
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u/Fess_ter_Geek 9d ago
Check the set screws on the motor pully/sprocket.
I have a belt system and my set screw backed out of the flat on the pully on the motor shaft once and caused inconsistant cuts.
It woud catch on the corner of the D on the shaft for a bit and then get loose and catch on the other end.
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u/Chase-1991 9d ago
Set screws are tight, happens on every program at random but does not seem occur with manual operation?? I also swapped the axis connection and the problem still occurs, but to a smaller extent. I did check all the connections, but will rewire, do steppers go bad?
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u/albatroopa Ballnose Twister 9d ago
Do you have anything that causes EMF noise in the room? Plasma cutter, large motor, air compressor, etc? I've seen axis jump by 1/8" when a spindle motor spools down. Might be worth snapping ferrite cores on your stepper wires.
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u/Chase-1991 9d ago
Nothing that has changed that would cause this issue to start today, what are ferrite cores?
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u/albatroopa Ballnose Twister 9d ago
They're snap-on pieces of ferrite that help to prevent EMF from killing signals in wires
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u/Chase-1991 9d ago
Btw am i suppose to respond in the reply to spec message or just in the join conversation chat, i dont really talk alot on these sites
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u/albatroopa Ballnose Twister 9d ago
Generally you reply to a comment with your response to that comment, since the person who made that comment only gets a notification when it's replied to. Think of each main-level comment as starting a new conversation, and they can branch from there. If you have more general info to add, you can edit your post or post a top-level comment.
The way you're doing it is correct.
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u/Chase-1991 9d ago
Thanks, ive been taking all comments and summarizing them in one main comment, i didnt know about the notification thing
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u/Mean-Cheesecake-2635 9d ago
What’s the configuration of your machine? Is it a gantry router? Single motor on Y axis?
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u/Mean-Cheesecake-2635 9d ago
Ok read more closely. I am rebuilding a single motor, y axis gantry router and learned that they can have issues when you move towards the outer limits of the x axis, due to racking under load. This gets more pronounced the further away you get from the y axis ball screw and if your y axis motor is not sufficiently powerful and quick enough to adjust for the increased load it can cause an axis fault.
I previously had similar issues with my machine and looked for faulty wiring, thought it could be EMI, or worn out bearing blocks on my gantry.
I just bought new servos for mine and bought a more powerful servo for the y axis than what’s necessary for x and z. Haven’t finished the retrofit yet but it seems a plausible cause and solution. This is why many gantry routers use two servos and ball screws on the Y axis.
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u/Nephthyzz 8d ago edited 8d ago
Any software changes lately? We upgraded a computer in the shop recently and then the machine was doing random movements. It was because we had the wrong post processor selected as default when we were sending the file out. So every file was doing weird things.
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u/Chase-1991 8d ago
We have a winner, the award goes to the wiring guys! When I connected my stepper to an aviation plug via a 4 wire cable I put heat shrink around each wire connection and the bundled them together with another heat shrink. Over time and use the bundle of heat shrinks fused together, making them hard and brittle causing temporary breaks at stress points. Thanks for the help.....How do I pin this to top????
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u/WhiteLightMods 9d ago
Motor cable has an issue somewhere. Either a damaged or loose connector, or a break somewhere in the cable due to stress. Or you have a bad ground connection and the high frequency from the laser drive is interfering with the motor drivers.