VCP Feedrate override problem (stepmotor lossing steps) <don't run jobs above 100% override>

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ShawnM
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by ShawnM »

The feed rate override + button is there to increase the feed rate after you decrease it. Like Gary stated this is machining 101, if you understand feeds and speeds for your machine, bits and materials you never need to touch the feed rate override button. If you post a job and your machine can’t handle the book feeds and speeds numbers for what you are cutting you decrease the feed rate to find what works. Losing steps means you don’t have the machine setup or configured for optimal performance. If you overdrive a stepper, open or closed loop, it’ll miss steps. If your machine is not designed, setup or configured properly and you try to run it at 150% guess what happens?

Please share the model number of your motors and power supply(s) so we can see the specs of the motor and how much power you are feeding them. Your drives can handle 50 volts and supply 4.2 amps according to the Chinese manuals. I’m betting that’s PEAK power and not continuous.

I looked at your videos and in the video of the fault that machine is clearly being over driven.
helicop
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by helicop »

ShawnM wrote: Sat Jan 14, 2023 9:51 am The feed rate override + button is there to increase the feed rate after you decrease it. Like Gary stated this is machining 101, if you understand feeds and speeds for your machine, bits and materials you never need to touch the feed rate override button. If you post a job and your machine can’t handle the book feeds and speeds numbers for what you are cutting you decrease the feed rate to find what works. Losing steps means you don’t have the machine setup or configured for optimal performance. If you overdrive a stepper, open or closed loop, it’ll miss steps. If your machine is not designed, setup or configured properly and you try to run it at 150% guess what happens?

Please share the model number of your motors and power supply(s) so we can see the specs of the motor and how much power you are feeding them. Your drives can handle 50 volts and supply 4.2 amps according to the Chinese manuals. I’m betting that’s PEAK power and not continuous.

I looked at your videos and in the video of the fault that machine is clearly being over driven.
Hi ShawnM,
Did you run my test file on your machine? When the + button is only for increasing feedrate after you decrease it, why will it go over 100% feedrate when cnc12 not designed is for that?
My machine is working for many year on Mach4 with pocket57cnc board. This software not very stabil but feed override without any problem. I switch to Centroids Acorn with CNC12, and this software is very stabil. The only thing is that feedrate override didn't work. And this has nothing to do with the stepmotor voltage and amps. Please look at my findings and tests. And try it on your own machine. There are a lot more users with the same problem, and it is very easy te say it's a problem with my machine. With no acceleration every machine will fail, because the torc force is to high.
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by Nigelo »

... When the + button is only for increasing feedrate after you decrease it, why will it go over 100% feedrate when cnc12 not designed is for that?
The max feedrate AND the max override are set within the Wizard by you. If you did not apply a feedrate margin and left it just under the stall speed, of course the override will stall the motors when going over 100%. Keith has previously stated he calibrates each machine by increasing feedrate until each motor starts to stall, and then backs off feedrate by about 20% to arrive at the maximum. I also use this technique by back off about 30%. This calibration is the only time I ever need to go over 100%
The only thing is that feedrate override didn't work. And this has nothing to do with the stepmotor voltage and amps.
I think you mean that the override did not work with YOUR SETTINGS and yes, it has everything to do with the stepper motor capabilities i.e. voltage and amps.
With no acceleration every machine will fail, because the torc force is to high.
If you consider your problem to be inadequate acceleration whilst insisting on using current feedrates and 200% override then your configuration is incorrect. Go back to the wizard and reset the acceleration time for each axis - Double the current value would seem appropriate as a starting point.

You posted because you want help but don't seem to want to listen to Keith, Gary or Shawn - That's your biggest mistake

hope this helps
"You can lead a horse to water but you cannot force it to drink"
Hope this helps
Nigel
helicop
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by helicop »

Nigelo wrote: Sat Jan 14, 2023 3:28 pm
... When the + button is only for increasing feedrate after you decrease it, why will it go over 100% feedrate when cnc12 not designed is for that?
The max feedrate AND the max override are set within the Wizard by you. If you did not apply a feedrate margin and left it just under the stall speed, of course the override will stall the motors when going over 100%. Keith has previously stated he calibrates each machine by increasing feedrate until each motor starts to stall, and then backs off feedrate by about 20% to arrive at the maximum. I also use this technique by back off about 30%. This calibration is the only time I ever need to go over 100%
The only thing is that feedrate override didn't work. And this has nothing to do with the stepmotor voltage and amps.
I think you mean that the override did not work with YOUR SETTINGS and yes, it has everything to do with the stepper motor capabilities i.e. voltage and amps.
With no acceleration every machine will fail, because the torc force is to high.
If you consider your problem to be inadequate acceleration whilst insisting on using current feedrates and 200% override then your configuration is incorrect. Go back to the wizard and reset the acceleration time for each axis - Double the current value would seem appropriate as a starting point.

You posted because you want help but don't seem to want to listen to Keith, Gary or Shawn - That's your biggest mistake

hope this helps
Hi Nigelo,
Did you test my test file with you CNC machine on 150% feedrate override? Did you do the same tests as I described?
My machine can easy run a 3000mm/m. I test it on 1000mm/m with 150% override. Effectively 1500mm/m. Motors running at 50% off there max speed. This works perfect for G1 commands, but G2/G3 commands are bumping.
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by tblough »

Do your circular interpolation moves have any direction reversals in them? Are they only in a single quadrant? G1 and G0 linear moves are easy because they accelerate at the beginning and decelerate at the end.

Circular moves often require an axis to stop and reverse direction as well as account for backlash. These things can cause "banging" on systems that are not properly tuned.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
helicop
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by helicop »

Hi all,

I made a video from the CNC12 console, when running the CNC_Clamp_test4.nc test file. There are two things that I discovered.

1) The stepmotor bumps are on a strange feedrate spike when starting the G2 command (G2 X98.5 Y92.2 I-0.75 J0.313). In the slowmotion video you can see this.
Excel_graph_feedrate_spike.jpg
2) The max machine feedrate, which I am decrease from 3000 to 1500 mm/m is exceeded by CNC12. You can see this on the end of the video. The speedrate was 1800mm/m, when the machine max is 1500mm/m.
Axis_configuration.jpg
Attachments
CNC_Clamp test4.nc
(1.13 KiB) Not downloaded yet
CNC_Contro_preferences.jpg
CNC12_Feedrate_problem.mp4
(11.47 MiB) Downloaded 1 time
helicop
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by helicop »

New discovery, when I running my CNC_Clamp_test4.nc file on 100% feedrate override, also the max machine speed is exceeded.
when I set the max machine speed on 3000mm/m, the G0 X0. Y0. command has an feedrate of 3600mm/m.
When I set the max machine speed on 1500mm/m, the G0 X0. Y0. command has an feedrate of 1800mm/m.
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by ShawnM »

helicop wrote: Sun Jan 15, 2023 10:08 am
2) The max machine feedrate, which I am decrease from 3000 to 1500 mm/m is exceeded by CNC12. You can see this on the end of the video. The speedrate was 1800mm/m, when the machine max is 1500mm/m.
This is not a new discovery, what you set in the wizard is the max feedrate for each axis. What you see on the screen when the machine is running is the combined feedrate. So on some moves where two axis are moving at the same time you will see a higher number than your max rate. This is the “combined feedrate” of both axis moving at the same time but neither axis exceeded the max feedrate set in the wizard.

Do you get the “bumping” when the feedrate override is set to 100%?
helicop
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by helicop »

ShawnM wrote: Sun Jan 15, 2023 10:54 am
helicop wrote: Sun Jan 15, 2023 10:08 am
2) The max machine feedrate, which I am decrease from 3000 to 1500 mm/m is exceeded by CNC12. You can see this on the end of the video. The speedrate was 1800mm/m, when the machine max is 1500mm/m.
This is not a new discovery, what you set in the wizard is the max feedrate for each axis. What you see on the screen when the machine is running is the combined feedrate. So on some moves where two axis are moving at the same time you will see a higher number than your max rate. This is the “combined feedrate” of both axis moving at the same time but neither axis exceeded the max feedrate set in the wizard.

Do you get the “bumping” when the feedrate override is set to 100%?
Ok, that's good the know.
When the feedrate override is set tot 100% I get no "Bumping". With a feedrate about 110% or more the bumping will start.
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Re: VCP Feedrate override problem (stepmotor lossing steps)

Post by Scott Pancheau »

This is part of why I am leaning toward going back to Mach on my next build. They have real easy to use wizards for fast programming and the run from here feature that I use all the time. Langmuir Systems also has run from here feature.
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