Controll rebuild
- kmeld
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12 Oct 2023 09:16 - 12 Oct 2023 09:17 #282802
by kmeld
Controll rebuild was created by kmeld
Hi,
Admittedly I do not have neither experience in electronics nor specific knowledge of the subject, so I would very much use straightforward advice in simple words.
I need to rebuild control for my 4 axis CNC mill (Damaged in fire). And most likely I will have it ordered for someone to assemble.
But I need at least to know basics.I read about mesa boards and it seems like a solution to go for to connect to PC.
My PC will be only used to control the CNC and it will be stationed max few meters from the machine.What kind of card and connection you think will be best for me. PCI, PCIe, external, LPT, Ethernet …..
Also I do not fully understand how this cards work. I read that they are running some software that takes over generation of step signals.So what is PC communicating to the card?
Is it basically the case that PC sets signal rate that card generates and only sends commands to the card to change this rate.If this is the case how does this work for arcs.
Cris.
Admittedly I do not have neither experience in electronics nor specific knowledge of the subject, so I would very much use straightforward advice in simple words.
I need to rebuild control for my 4 axis CNC mill (Damaged in fire). And most likely I will have it ordered for someone to assemble.
But I need at least to know basics.I read about mesa boards and it seems like a solution to go for to connect to PC.
My PC will be only used to control the CNC and it will be stationed max few meters from the machine.What kind of card and connection you think will be best for me. PCI, PCIe, external, LPT, Ethernet …..
Also I do not fully understand how this cards work. I read that they are running some software that takes over generation of step signals.So what is PC communicating to the card?
Is it basically the case that PC sets signal rate that card generates and only sends commands to the card to change this rate.If this is the case how does this work for arcs.
Cris.
Last edit: 12 Oct 2023 09:17 by kmeld.
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- rodw
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12 Oct 2023 09:47 #282804
by rodw
Replied by rodw on topic Controll rebuild
Linuxcnc on the PC remains the motion controller.
The step generation is offloaded to the stepgens on the mesa card
Linuxcnc tells the stepgens to generate steps at a given frequency.
It will continue to generate that frequency forever or until it is told to stop or change frequency.
Which linuxcnc can do 1000 times a second.
Sounds like you need an ethernet Mesa Card. The 7i96s might work for you. The ethernet cable can be up to 100 metres long.
There is a tool called pncconf that will create a Mesa configuation that is included with linuxcnc.
The step generation is offloaded to the stepgens on the mesa card
Linuxcnc tells the stepgens to generate steps at a given frequency.
It will continue to generate that frequency forever or until it is told to stop or change frequency.
Which linuxcnc can do 1000 times a second.
Sounds like you need an ethernet Mesa Card. The 7i96s might work for you. The ethernet cable can be up to 100 metres long.
There is a tool called pncconf that will create a Mesa configuation that is included with linuxcnc.
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- kmeld
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12 Oct 2023 11:17 #282809
by kmeld
Replied by kmeld on topic Controll rebuild
Thanks,
So Linux is setting frequency and mese is executing it.
So to have high acuracy in corners or areas where there are accelerations key is still latency of the PC on Linux side.
When CNC software executes arc move is it actually linearised in the motion controller or actually steps are generated based on required acceleration functions?
Why do you think Ethernet card is will be better than PCI or PCIe?
Cris.
Cris
So Linux is setting frequency and mese is executing it.
So to have high acuracy in corners or areas where there are accelerations key is still latency of the PC on Linux side.
When CNC software executes arc move is it actually linearised in the motion controller or actually steps are generated based on required acceleration functions?
Why do you think Ethernet card is will be better than PCI or PCIe?
Cris.
Cris
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- PCW
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12 Oct 2023 13:38 #282822
by PCW
The stepgen does linear interpolation between waypoints
but the chord error (difference between arc and polygon) at a 1 KHz
update rate and typical machine tool accelerations is much smaller
than mechanical errors so nothing is really gained by adding parabolic
interpolation between waypoints.
For example say your machine is fairly fast and can cut a 10 mm circle
in 0.1 second, the 100 side polygon created (1000 waypoint/second *0.1 second)
would differ by no more than ~1.6 u from a perfect circle.
For faster devices (for example laser galvanometers) Mesa firmware does
incorporate acceleration (as the effective acceleration of a galvanometer
steered laser spot can be 100s of Gs)
Replied by PCW on topic Controll rebuild
LinuxCNC depends on low latency as it _is_ the motion controller.So to have high acuracy in corners or areas where there are accelerations key is still latency of the PC on Linux side.
The stepgen does linear interpolation between waypoints
but the chord error (difference between arc and polygon) at a 1 KHz
update rate and typical machine tool accelerations is much smaller
than mechanical errors so nothing is really gained by adding parabolic
interpolation between waypoints.
For example say your machine is fairly fast and can cut a 10 mm circle
in 0.1 second, the 100 side polygon created (1000 waypoint/second *0.1 second)
would differ by no more than ~1.6 u from a perfect circle.
For faster devices (for example laser galvanometers) Mesa firmware does
incorporate acceleration (as the effective acceleration of a galvanometer
steered laser spot can be 100s of Gs)
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- tommylight
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12 Oct 2023 22:27 #282837
by tommylight
I use some on plasma cutting machine that do a lot of interference, had one connected over a 30M long LAN cable, never ever had issues, for over 2 years.
Replied by tommylight on topic Controll rebuild
From my experience, easier to set up and less prone to interference when the PC is 3 or more meters away from the machine control box.Why do you think Ethernet card is will be better than PCI or PCIe?
I use some on plasma cutting machine that do a lot of interference, had one connected over a 30M long LAN cable, never ever had issues, for over 2 years.
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- kmeld
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31 Oct 2023 08:49 #284159
by kmeld
Replied by kmeld on topic Controll rebuild
OK,
I have deciced to go with ethernet card as you suggested.
Now I am not sure what I need to make spindle control.
It will be powered by 3 phase inverter that accepts 0-10V control signal.
It is 7,5 kW 18000 rpm, 300 Hz, 400V spindle.
Does mesa board directly supports this function or I need to buy some extension. Was trying to figure this out from description on mesa site but not conclusively.
Can you please advice. Or perhaps there is some better option to go for.
I have deciced to go with ethernet card as you suggested.
Now I am not sure what I need to make spindle control.
It will be powered by 3 phase inverter that accepts 0-10V control signal.
It is 7,5 kW 18000 rpm, 300 Hz, 400V spindle.
Does mesa board directly supports this function or I need to buy some extension. Was trying to figure this out from description on mesa site but not conclusively.
Can you please advice. Or perhaps there is some better option to go for.
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- tommylight
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31 Oct 2023 09:58 #284164
by tommylight
Replied by tommylight on topic Controll rebuild
Mesa 7i96S has also the spindle control for 0-10V VFD.
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- kmeld
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16 Dec 2023 19:08 #288355
by kmeld
Replied by kmeld on topic Controll rebuild
Hi again,
So I have managed to get MESA board and control is being built.
Now I need to source the PC.
I was looking threw hardware specs, but did not figure out what I should look for in terms of computer to control my machine.
Could someone give me a hint here. Any verified spec that works well.
I can go with used ore new computer. Used will most likely be cheaper, but affordable new computer also has benefits (I do not have to build it and do not have to deal wit things that might not work).
As a minimum I would like to narrow down CPU brand and type and motherboard.
Any suggestions please.
Cris.
So I have managed to get MESA board and control is being built.
Now I need to source the PC.
I was looking threw hardware specs, but did not figure out what I should look for in terms of computer to control my machine.
Could someone give me a hint here. Any verified spec that works well.
I can go with used ore new computer. Used will most likely be cheaper, but affordable new computer also has benefits (I do not have to build it and do not have to deal wit things that might not work).
As a minimum I would like to narrow down CPU brand and type and motherboard.
Any suggestions please.
Cris.
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16 Dec 2023 19:40 #288359
by tommylight
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