On a few occasions now I have had an issue when engraving my c02 mantech laser at speeds of say 300m/s on very small details such as numbers or letters (it does them individually) I will hear a bump/nudge like the belt has slipped and then the engraving is slightly off. When it homes it also gives an error because it thinks it is a few mm to the side.
It sounds like it is skipping the teeth, I have just tightened up the top rail belt on the x-axis but it didn’t seem too loose.
Could there be anything software wise i could do to stop the issue occuring?
It seems like if put all the cluster of text into a group it will engrave all this at the same time and this issue wont occur.
Is it a simple case of too much speed in such a small area or is there a bigger issue at hand?
The sound you hear is called “cogging” and is produced by the stepper motor, not the belts slipping. Mechanically, it hurts nothing. However as you discovered, you lose positioning accuracy because the motor could not keep up with the commanded move.
Yes, you can slow it down, or use a raster scan pattern to reduce the possibility of it happening. Kind of like fast speeds on the interstate but slow speeds in the neighborhood.
If the machine is more than a few years old or has been used heavily in production, the belt teeth may be worn down enough to skip over the pulleys
If the motor pulley has a setscrew holding it to the shaft, that screw can work loose and let the pulley slip back and forth. Some motor pulleys are press-fit without a screw, but the screw may be recessed into the teeth rather than sitting in an obvious place.
While you have your head in there, mark the pulley and the motor shaft so you can tell if they move relative to each other:
The idler pulley on the other end of the gantry may have a loose screw on its mount letting it move, so check all those bits & pieces, too.
Until ruling out any hardware issues, don’t change the settings.
The X-axis speed and acceleration may be too high, but if the machine has suddenly begun misbehaving, it’s unlikely to have a software or settings problem.
On a side note should I be able to move the laser head left and right when it’s off? I saw a video of Russ on YouTube saying it shouldn’t be able to. And mine moves quite freely.
The stepper motors are permanent magnet motors, so you can move it, but it will generate power and likely light up the controller leds, maybe other things. You can feel the magnetic fields rotating when you move it.
Assuming you eliminate the items @ednisley advised, it is usually the magnet field of the stepper motor moving too fast for the mechanical motor parts to follow… results are as you and everyone else advised.
I have seen similar issues when the power supply isn’t producing the current the motor drivers need.
In theory, you shouldn’t be able to program this. The controller should handle the acceleration values and prevent this from happening, that is their main purpose.
A few things can cause this, such as the acceleration being near it’s limits and/or you are trying to engrave vectors at a speed that can’t be attained within that short of an area, which the controller should have handled.
Mine was set near it’s limits when I was changing things and it took me a while to figure it out the root cause. The acceleration was fine, unless I got all the mass moving in a certain direction and made a quick directional change.
Look in your Ruida and let us know what your current acceleration values are for X and Y axes. Edit → Machine Settings → Vendor settings → X axes – slide down and get Y axes… Or multiple screenshots of all of them, if that’s easier.
Ensure it’s not mechanical, then we can look elsewhere. Might want to post a link to your vendor so we know what machine you’re using… Did a quick google and didn’t find anything specifying a V2 type..
Ok so on the right side there’s no screw as shown but there is an Allen key inside the motor pulley. This was tight already.
I did tighten up the belt which was a little slack but not enough for me to worry about.
The belt teeth are a bit worn, bits of metal in the belt as I cleaned it but it’s only about 2 years old. It is a mantech vector V2 ruida control 80w c02 and I use it 5 days a week for an average of 4 hours a day. It’s a workhorse!
The idler pulley side I tighten it up fully. Booted up the machine and belt flapped all over the shop and it wouldn’t home. Must have been too tight so I loosed it until it could successfully home.
That is where I am at. It doesn’t happen all the time just at fast speeds (250+ m/s) doing individual letters at 250dpi.
Nothing else is loose or unstable.
Should I now look at the software side as per jack’s message?
The tiny bits of metal were only visible on the X belt I haven’t cleaned it for 2 years, so assume its just little bits of wear and tear over time. It doesn’t look particularly worn or bad and it isn’t slipping all the time its only on rare occasions.
Only when going at 300mm/s on very small objects of text which are like 1cm wide for example the number ‘1’ as the setting is engraving each item individually. To counteract this I am grouping sections together now instead.
There may be other issues in play, but if you haven’t changed anything and the machine has suddenly stopped working properly, then something physical has changed. Fiddling with various settings will only dig the hole deeper.
Fix the obvious physical problem first, then look for secondary physical problems.
You have to let us know, if you know, that this is new. Meaning, if you have done this before, using the same data or similar with no issues, then it’s likely a hardware issue, as @ednisley has mentioned. I noted that if everything @ednisley has mentioned is OK then we can move to maybe a software issue. I’m just looking at your settings, not advising you change anything.. This means we must eliminate any chance of it being hardware.
I have to note that the settings in your controller don’t randomly change. You must go there and change them, so there’s increased suspicion that this is a hardware issue.
Hardware issues can be exacerbated by settings that are on the edge and the operator attempting to push the machine beyond it’s limits or expecting too much. Especially with vector graphics.
It takes, using your numbers from the controller, 4.5mm to reach 300mm/s and you have to start slowing down at 5.5mm to be able to stop.
I kind of doubt you want to speed of 300mm/s for 1mm of the 10mm length?
This is on the verge of it’s limits and any setting within the controller that is near it’s limits can cause this.
I think you might be trying to get too much out of this… If you can determine that this is new or that you just don’t know if it’s a new failure or not, it might help us.
Most controllers have the information setup with a large amount of leeway to allow for variations in setup without impacting stated performance, so an incorrect setting is unlikely.
I’d suspect @ednisley is correct about this being a hardware issue… these can be tough to locate.
If i think about it, I think I have only recently been trying to increase the speeds to meet the demand naturally. Without thinking about the design. So if i was to group text it of course can travel much faster, but it physically can’t do that on small little letters. I am not very technical, but that calculator seems to resonate with my feelings. I think it is just probably going a bit too fast. I do think the teeth are OK, sure they probably will need replacing in the future, but I don’t think it is necessary unless it starts doing it all the time. As stated, it only happens on some occasions in those very specific situations I have mentioned where I am pushing it too much. I’d say we’re done here - thank you guys for your help!
When this happens with individual letter/numbers (that you are presumably filling), does the slip ever happen in the middle of the fill where the evidence of the slip would be very obvious?
Or does the slipping happen between individual shapes - so much harder to visually identify exactly where in the job it first happened?
The reason I ask is that it’s unlikely that changing fill strategy and reducing the speed will completely solve your problem, which is more likely to be triggered by how quickly the speed is changing (acceleration), rather than by the top speed itself — which only affects how long the acceleration stress is applied, not the intensity of that stress.
300 m/s ? that’s fast, a bullet muzzle velocity is 120-370 m/s
300 mm/sec
in one of my old config files
my acceleration is 30 mm/sec
max rate 2500 mm/min
I don’t race and break things
I also have a large capacitor at the power supply pins of the motor driver to supply surge current.
Cogging can be caused by badly configured current/micro-stepping
