My rapid speed on x axis was randomly insanely fast. bug?

[86bg]

I turned on my machine to cut some parts yesterday. When I went to rapid to the tool change position the machine tried to F1 launch in the x axis and immediately started skipping steps after moving about 300mm. turned off machine and restarted uccnc. same thing. Went into the x axis settings and the rapid speed was set to 25,000mm/min, which is correct. I typed in 20,000 and hit save and apply. problem solved. typed 25000 back in and it went back to normal. No, it wasn't set to 250,000. If I encounter this problem I will surely check the profile file to see if it got corrupted somehow. Wondering if anyone else has encountered this problem?

[crjohnson]

I have seen some strange instances where my machine will be happily cutting away and then all of a sudden the feedrate jumps much higher, though the cutting program has not done anything different. I think the last time it happened was boring a hole at a constant rate, then it jumped. When this happens I have to click the feedrate overide down to say 90% and then back up to 100% and it goes back to the normal speed it was before jumping.

I posted this a while ago and got no where.. Good luck!

[cncdrive]

Usually this false conclusion in uers head comes from a misunderstanding of what rapid feedrate it.
For example you set the valocity to 10000 on X and 10000 on Y then the rapid feedrate on the XY plane is not 10000, but 14400 max. and that case is when the XY runs the same distance, in other words when there is a 45°diagonal movement then the rapid is 14400.
We having many users missunderstanding how this works and getting threatened by seeing higher feedrates as the max. they set for an individual axis, but this is not a bug, it is how the rapid feedrate works in CNC controllers.

[beefy]

Thanks for that info Balazs.

To be honest, for all the years I've been involved with this I never considered that. I was mistakenly under the impression that the rapid speed on a combined XY move would be interpolated to limit the max speed to whatever the rapid speed of the fastest axis is.

Better late than never to learn it doesn't work that way.

So users need to understand a bit of Pythagoras to be able to calculate their max rapid velocity LOL.

[cncdrive]

It's simple angular function, however it is a bit more complicated because the velocity of the axes can limit the other axes velocity.

[crjohnson]

Hi cncdrive,
Thank you for the explantion but I don't think that is what happened in my case (on multiple occasions). My machine seemed to return to the normal rate after pressing the overide and there was no change in how the g-code was operating/programmed.

I wouldn't be suprised if it had something to do with my laptop or windows or something else?

[86bg]

Usually this false conclusion in uers head comes from a misunderstanding of what rapid feedrate it.
For example you set the valocity to 10000 on X and 10000 on Y then the rapid feedrate on the XY plane is not 10000, but 14400 max. and that case is when the XY runs the same distance, in other words when there is a 45°diagonal movement then the rapid is 14400.
We having many users missunderstanding how this works and getting threatened by seeing higher feedrates as the max. they set for an individual axis, but this is not a bug, it is how the rapid feedrate works in CNC controllers.

I understand 1.414. My post didn't imply that was the issue, did it? The machine was trying to send my X axis at an insanely high rate. I restarted machine AND twice before changing the field for the X rapid speed to a lower value, testing to see that it worked, and then bumping that value back up to what it was previously and it went back to working as it had for the past few years. The text field was showing the correct value but it was as if the software was interpreting that value as a much higher value. Strange.

[cncdrive]

I don't know what "insanely fast" means, it could mean 1.414 times the axes feedrates if they are already close to "insanly fast"
And I don't think anything could cause the axes to run faster than the set velocity values.

[86bg]

No way to know what the speeds it was attempting. Stepper could never keep up but at the acceleration rate my gut tells me upwards of 100,000mm/min If anyone else has this issue, at least it's documented. Could very well have been a corrupted settings file? I'm just querying others and documenting the issue.

[Parkgrr]

I have the same issue, intermittent occurrence, probably 1/20 times.