Mesa choice for 6 axis CNC and servo spindle

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11 Oct 2020 20:12 #185748 by Archidea
Hi,

I started to build my first CNC project and I need some help with choosing the right driver board for my application.
My plan is to build the machine in phases, adding additional axis control and spindle options later. I don't know everything right now
and that's the problem. I'm not sure how it will go and what aspects of the design I will need to change.

I would apprecite your suggestion of MESA card that will give me the biggest flexibility and 6 axis capability based on the below assumptions.
- ethernet connectivity
- Initial design is for 3 axis (xyyz) + cheap VFD 24k spindle and I want to upgrade to 5 axis (xyyzab - 6 motors) and servo spindle in the second phase (potentially dmm DYN4 ac servo).
- at the moment I only have open loop drivers but might decide to change to close loop
- havn't yet desided what type of pendant to use, something like XHC-HB04 over USB or maybe wireless relay box wired into the control box

Reading forum I found some suggestion of using the below combinations:
- 7i76E + 7i85/7i78
- 7i96 + 7i78
- 7i96 + Ebay BOB
- 7i95 + ??

Would 7i76E be a good starting point? Or should I maybe get 7i96 and add 7i78 later.

It is a steep lerning curve for me so I appreciate any help given.
Thank you in advance.

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11 Oct 2020 22:04 #185765 by tommylight
7i95 seems like the closest choice for what you want to achieve, but leave the VFD to be controlled by an USB to RS485 adapter, and that has many benefits like having only two wires to control everything regarding the spindle and maybe have also some feedback from it (depends on the VFD).
Then again adding a servo spindle means that you would most probably need another step/dir and encoder channel, or have an analogue card added for it.
So the 7i76E with encoder add on looks more complete and leaves you the choice for analogue, RS485 or step/dir spindle control.
I would also wait for PCW to chime in as he knows Mesa best.

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12 Oct 2020 08:45 #185810 by Archidea
I might be wrong but comparing manuals of 7i95 and 7i76 I see that:
- 7i95 provides 6 axis step&dir motor or servo + 6 encoder feedback
for the first phase of the project, I will need something to connect VFD as tommylight suggested
for the second phase, I will need an additional board for step/dir spindle control + encoder

-7i76 provides 5 step&dir motor + 1 encoder interface + analog spindle control
for the first phase, I believe it is all I would need
for the second phase, I will need an additional encoder board for 6 channels + 2x step/dir (1x for the spindle, 1x for the axis)

How it can be achieved with expansion cards?
something like 7i85 provides 4 encoder channels, not enough, still will need something for 2 axis step/dir control
7i78 provides interfacing for up to 4 Axis of step/dir motor/servo, will I need an additional card for 2 encoders?

To be honest, I'm a bit lost with all the variants and expansion options for MESA cards

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12 Oct 2020 13:53 #185838 by PCW
I would probably chose a 7I76E + 7I85S initially, then add another 7I85S if You choose to add encoders later

7I76E+ 7I85S gives you
9 step/dir channels
5 encoder channels
32 digital inputs
16 digital outputs
2 SSerial expansion ports for additional I/O if needed

A second 7I85S gets you to 9 encoders.

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06 Mar 2021 12:36 #201179 by TobiE
Hi Archidea,

I have a similar setup with the 7i76e and a 7i85. I am trying to get the VFD running with the 0-10V Spindle Output at TB4. Did you got that working for you? If so, which Bitfile did you use?

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28 Jul 2021 11:18 #216119 by Archidea
Hi TobiE,
Sorry to respond so late. I used RS232 connection (usb receiver).
I tried also analog, as you have mentioned but it is VFD specific, yours can be completely different.
You can download the PDF from the link below. On page 11 you will see the diagram which helped me.
forum.linuxcnc.org/media/kunena/attachme...hluss_2016-12-03.pdf

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