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mach appears to send odd signals
« on: February 26, 2014, 02:15:39 PM »
Hi,
I'm hoping someone can help me here with a, what appears to be, spurious signals for the software. I've been running Mach3 mill for a few years and getting good results. However, I'm starting to have problems.
The milling machine runs fine, then out of the blue, the x-axis stepper occassionally momentarily stalls and looses approx 5mm in travel on a fast jog mid program - it is like the machine has recieved a spurious signal that has put the stepper into stall.
I have changed steppers and drivers and checked everything out on the machine and all is OK. Today, when doing a test aircut I noticed that, part the way into the programme, the spindle was suddenly running at 4400rpm yet checking the G-code line it was set at 4000rpm. I stopped the machine and reset - re ran the programme and it ran the spindle at the correct speed. However, part way through the programme the X-axis did it's momentary stall again loosing approx 5mm.
I shut everything down to and came back to machine later - doing a test aircut from the same programme as previously run and found that the spindle was screaming it's head off (the readout on the actual mill was giving 5300! - this is more than the max that the motor can handle - usually max out at 4500) - checked the DRO and forund that Mach had set the spindle at 8400! I noticed that the spindle factor(?) - appeared alongside the spindle speed - was at 2.2. The G-code line was 4000rpm. I have checked the G-code and everything is as it should be. What is happening? Is this wrong signal for the spindle also what is happening with the X-axis too? Can anyone help?
GeoffB

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Re: mach appears to send odd signals
« Reply #1 on: February 26, 2014, 03:49:12 PM »
Can you attach your xml, also what version of Mach are you using?
What is the Time in Int and the the Frequency on Diagnostcs page?

Hood
Re: mach appears to send odd signals
« Reply #2 on: February 27, 2014, 06:14:12 AM »
Hi Hood,
The version is Mach3-043-022.
Time in Int - varies between +3.2 to +6.5.
Pulse frequency is what you are requiring? Varies from 58629 - 42
Attached is the xml file.
GeoffB
GeoffB

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Re: mach appears to send odd signals
« Reply #3 on: February 27, 2014, 07:58:48 AM »
If the Frequency is varying that much then you have issues with the pulsng of the driver, the frequency needs to be steady and very close to the kernel you have set.
I am not sure if you are meaning 42Hz or 42KHz but in any case varing even between 42KHz and 58KHz is not good.


Hood

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Re: mach appears to send odd signals
« Reply #4 on: February 27, 2014, 08:02:59 AM »
I just looked at your kernel in your XML and you have it set to 60KHz yet the most you need for your motor tuning is just over 10KHz. I suggest you set the kernel to 25KHz and restart Mach and see if that helps, it needs a stable computer to be happy at over 45KHz and there is normally no point in having the kernel higher than you require. 25KHz would still be more than double your requirements but it is the lowest so set to that.
Hood
Re: mach appears to send odd signals
« Reply #5 on: February 27, 2014, 03:07:01 PM »
Hi Hood,

Thanks for the info - to be honest, I'm not that clued up on the settings side, just what the guy who set it up and advice from Mach themselves (Scot I think it was - it's a couple or more years since I emailed him) so I've really no idea what anything should be. Does it make any difference what size steppers I'm using? They are 4.2amp 300Ncm and the drivers are M442 - X&Y / DM542 on the Z with voltage of 37VDC.
Where do I find the kernel to alter? And what does this do/mean?

Regards,

GeoffB
GeoffB

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Re: mach appears to send odd signals
« Reply #6 on: February 27, 2014, 03:48:13 PM »
The kernel is the max frequency of the pulse per axis that Mach will output, the higher you set the kernel the more chance you have of the pulse being of poor quality and thus it is usually best to set to the minimum that you require. Your steps per unit for the highest set axis (Z) are 640 and the Velocity is 1000.2 so that means that the pulse at max velocity required by your system is 640 pulses per unit x 1000.2 units per min = 640128 pulses per minute, divide that by 60 = 10668.8 pulses per second or Hz so 10.6688KHz. That means the lowest setting for the kernel in Mach, 25KHz would be more than twice what you require.

To set the kernel go to config menu then Ports and Pins and set to 25KHz, you will need to restart Mach after you do that. First thing once you have restarted is look at the pulse frequency on the Diagnostics page and see if it is steady and close to 25,000.

Hood
Re: mach appears to send odd signals
« Reply #7 on: February 28, 2014, 06:47:44 AM »
Hood,

Many thanks for the explanation - that makes things a lot clearer. As I said, as a mechanical engineer, if I can see it working then I understand, but where electronics are concerned I'm a complete neanderthal!  :) I wonder why it was set so high? I'll haved a look at this - perhaps be a few days as I'm away a bit and have other jobs that need doing - so I'll get back to you soon as I've tried it and let you know what the answer is - Fingers crossed you've hit on the answer!! :) I was thinking that there was something that had corrupted a file in the PC and was about to re-format and re-install everything. I'll give this a go before I do anything so drastic!
Many thanks,

GeoffB
GeoffB

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Re: mach appears to send odd signals
« Reply #8 on: February 28, 2014, 01:23:16 PM »
I wonder why it was set so high?


Human nature, more  always looks like its better :)

Hood
Re: mach appears to send odd signals
« Reply #9 on: March 07, 2014, 01:39:04 PM »
Hi Hood,

I've reset the kernel as you suggested and the frequency is now steady at 24994 - occassionally reads 92 or 95 but mainly steady - the spindle problem hasn't reoccured. However, I still have a problem on the X axis - and every time at one point in the programme. I've checked out the line code and can find nothing wrong here - just has a G0 for the X & Y positioning at this particular line - all the rest of the programe runs fine. Ideas? I've attached the .nc programme for you to look at if you will. the line of code is at - pocket 8 - G0 X20.7665 Y2.0

GeoffB
GeoffB