- Hardware & Machines
- CNC Machines
- Need Help! - X/Y motors all of a sudden chattering/struggling under no load
Need Help! - X/Y motors all of a sudden chattering/struggling under no load
- Sray69
- Offline
- Elite Member
- Posts: 255
- Thank you received: 13
I have been running my CNC now for quite some time with no issues at all. The other day I started it up and when Homing it I noticed some high pitch whining sound coming from one/some of the motors. I was not sure what it was. I proceeded to manually move the machine around the table in all directions and at slow to rapid speeds and it seemed to work fine with no strange noises. So I setup my job and started cutting. Instantly the machine started chattering/vibrating quite violently. I immediately turned the speed all the way down to like 10% of the job speed (80 in/min). Even at 8 in/min it was chattering/vibrating, just not violently. I decided to mess around with feeds and speeds but nothing helped. At the time I was just cutting out a test piece from a 1/4 piece of plywood at a depth of .1 inches with the router at 16000 rpm and using a 1/8" straight bit (new). I have ran many jobs at much deeper depths and higher speeds with amazing success. This boggled me. While it was running I was feeling/observing/checking every single part/connection on the machine to see if I could find where it was coming from, but I couldn't.
Because I was able to move the machine manually all around the table at any speed/direction with no sign of vibration or noise I starting to think it may be a bit/collet issue. I checked the runout on the first bit I used and it came to .007". This seemed a little high. So I chucked up another new bit and that one came to .006". Then I started to think that maybe it was the Dewalt collet. I was thinking that maybe I need to upgrade to a precision grade collet but wanted to be sure it was a collet issue. Today I decided to see if the machine would vibrate even with no load. So I ran a job with no wood or bit chucked. I was going to put slight pressure on the router as it was running to see if that caused the vibration. Well as soon as I started the job it started vibrating throughout the entire movement. There does not seem to be any direction that it does not vibrate. So that tells it is not the router at all.
Next I disconnected the X/Y ballscrews from the gantry and Z axis assembly to see if maybe one/both are binding somehow. Once I disconnected I was able to easily slide the gantry and Z axis assembly back and forth. So that tells me it was not that, but I decided to run the job with them disconnected anyway just to see what is up. Well as expected the vibration started immediately. I can visibly see the ballscrews struggling/chattering (X/Y axes, not sure about Z though) accompanied by a whine that fluctuates. You can hear them struggling.
This ONLY happens while running jobs, not while manually moving around. I have done nothing what-so-ever to the machine. It literally just happened overnight. I am not sure if there is something in my g-code that could be causing this? I am using the same software (Carbide Create Pro) I always use. I do not see anything visibly wrong/going on in my cabinet.
Here is a link to a video I took. You cannot really see much in the video. I was mainly trying to capture the sound it was making. At times it almost sounds like grinding. This was taken under no load at all and disconnected from the gantry and Z axis assembly.
VIDEO
I have no idea even where to start. I am really hoping you guys can help and that there is a simple fix here.
Thanks
Please Log in or Create an account to join the conversation.
- tommylight
- Away
- Moderator
- Posts: 19375
- Thank you received: 6485
Please Log in or Create an account to join the conversation.
- Sray69
- Offline
- Elite Member
- Posts: 255
- Thank you received: 13
Question though. Why would it only cause this issue when running a job and not when manually moving the machine around?
Thanks for the suggestion! Fingers crossed that is it.
Please Log in or Create an account to join the conversation.
- tommylight
- Away
- Moderator
- Posts: 19375
- Thank you received: 6485
Check grounding and shielding first.
Then check power supplies for noise/ripple.
I had a bad batch of power supplies, had to change all 3, they would cause so much noise the machine would shake and rattle sometimes, not always, just some times.
If you do not have an oscilloscope to check ripple, use a DVM set for AC voltage, anything above 0.2V = new power supply. Also, beware that some cheap DVM are not good for this.
Please Log in or Create an account to join the conversation.
- Sray69
- Offline
- Elite Member
- Posts: 255
- Thank you received: 13
Same thing happens whether the spindle is on or off.Spindle on, makes electrical noise, messes with signals.
I will check the ground connections. Nothing has changed with shielding.Check grounding and shielding first.
Please excuse my ignorance here. What exactly do I check? The output power of the PS's? At the PS or the input at the drivers?use a DVM set for AC voltage, anything above 0.2V = new power supply.
Thanks
Attachments:
Please Log in or Create an account to join the conversation.
- tommylight
- Away
- Moderator
- Posts: 19375
- Thank you received: 6485
Both, if the power supply is ok but at the stepper there is above 0.2V, means the noise is not from the supply but from the cabling.What exactly do I check? The output power of the PS's? At the PS or the input at the drivers?
Also measure between neutral and ground, should be under 2-3V AC. Probably even a bit more is OK, but that depends on other equipment in the shop/house/office.
Please Log in or Create an account to join the conversation.
- tommylight
- Away
- Moderator
- Posts: 19375
- Thank you received: 6485
Please Log in or Create an account to join the conversation.
- smc.collins
- Offline
- Platinum Member
- Posts: 688
- Thank you received: 123
Please Log in or Create an account to join the conversation.
- Sray69
- Offline
- Elite Member
- Posts: 255
- Thank you received: 13
Thanks. That is helpful.Both, if the power supply is ok but at the stepper there is above 0.2V, means the noise is not from the supply but from the cabling.
Where exactly should I be measuring this? And using the same settings on the DVM?Also measure between neutral and ground, should be under 2-3V AC. Probably even a bit more is OK, but that depends on other equipment in the shop/house/office.
I assume the blinking LEDs would be on the drivers? Or on the PS? If the power supply is good then it should have enough power. I feel like I made sure of that when I purchased it. I am not sure what the motor current is set at currently. I thought I set it on the lower end when I set them up just to be safe. I will check that in the morning.check the power supply when the machine is running, if the LED blinks = not enough current for the drives motors, so a bigger power supply or lower the motor current on motors that can handle it.
Thanks for your assistance!
Please Log in or Create an account to join the conversation.
- Sray69
- Offline
- Elite Member
- Posts: 255
- Thank you received: 13
Yes. Nema 24s for X/Y and Nema 23 for Z.I assume this machine uses stepper motors ? like a typical router setup. just X and Y or X Y and Z ?
Not real sure I understand what backdriving the steppers means. I can say that I ran a successful job one day. Shut everything down as normal. I do recall shutting off the 30 amp breaker in my shop electrical sub-panel (which I had never done before). The next day flipped the breaker on and started the CNC up and when I tried to run a job that is when I noticed this issue. So I don't think I backdrove the steppers.is it possible that someone backdrove the steppers while the machine was off ? usually when I have seen steppers misbehave in other non cnc applications, it is becuase the output driver has a problem and the motor gets stuck in 1 phase and then jitters violently. Backdriving a stepper could depending on the motor and drive output topography a induce a very high voltage and current that if improperly clamped COULD MAYBE burn the gate or short it to where it no longer cycles properly. That would cause jerking and other strang motion issues.
Just so I understand correctly. I would first check A+/A- and then B+/B- and compare? I assume this would be done while the machine is running a job?Try this, put your multi meter on the motor pairs, usually A and B, put the meter in RMS mode and then check and see if the RMS voltages are significantly different, if they are, put the meter in duty cycle " probobly kiloherz range, and see if the frequency and duty cycle are different. Typically a stepper has a 50% duty cycle and that produces a relatively constant AVG voltage RMS. Just something to peek into
Thanks for your suggestions.
Attachments:
Please Log in or Create an account to join the conversation.
- Hardware & Machines
- CNC Machines
- Need Help! - X/Y motors all of a sudden chattering/struggling under no load