Which servo config for a Mesa 7i77 seetup

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15 Dec 2017 22:59 #103147 by DeckelHead
I'm not sure this is the correct form or not, but if I'm not placing this in the right place just let me know and I'll repost elsewhere...

I have a Mesa 7i77 that I'm using in a conversion of a Hurco KMB1 CNC mill. For the X, Y, and Z axis I have Granite Devices VSD-E boards. I started work on this conversion years ago and then it sat for about 4 years while I was occupied with other "stuff." Anyhow, I'm back at it again. I've just validated my schematics, tested the I/O I had wired up previously, installed the latest 2.7 stack (my OS was old), etc.

Now I am at the point where I need to tune my servos. My belief (please correct me if I'm wrong) is that this is a two step process. First I must tune the Granite devices directly using the tools provided by the manufacturer. This means that LinuxCNC won't even be "on" as I'll be directly hooking up to the VSD USB port. After this is done on all the axis, I will need to complete my HAL setup and then tune the drives within LinuxCNC. Is all of that an accurate summation of what I have to do?

Assuming I have this right, the first question I have is what "mode" should I be placing the VSD drives in? Like many amps, they support position, velocity, and torque. I can see where some of those modes would be advantageous for different applications but I have never been able to figure out which is best for something like LinuxCNC. So, that is the topic du jour.

I welcome any comments, suggestions or thoughts.

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15 Dec 2017 23:36 #103149 by PCW
The most common LinuxCNC setups for servos are for velocity mode drives
Unless you need torque monitoring velocity mode is easier to deal with

Position mode with analog commands is not useful at all for CNC
The following user(s) said Thank You: DeckelHead

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15 Dec 2017 23:58 #103150 by DeckelHead
Thank you... That makes sense.

I guess I'm down for the weekend. I have a 60VDC servo power bus and two large filter caps. The 200VDC cap apparently failed with a short. The 35A fuse burned so I have to find a new cap and fuse. :( Oh well, that is, after all, what fuses are for so I'm not complaining. :)

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