Spindle Orientation Methods

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23 Mar 2021 22:28 #203449 by Xnke
Initially, I plan to run a 1.8kW servo spindle drive-this means that spindle orientation will be trivial with LCNC. I will probably gear it up 1.5 or 1.8:1 as the servo still has acceptable torque at 1.8:1 compared to an induction motor driven spindle, at low speeds.

The spindle itself will have its own encoder with index, so I'll know actual spindle position as well as speed and direction.

But, the servo I have maxes out at 4500RPM. I'd like to be able to run the full 8000RPM the spindle cartridge can handle, and preferably I'd rebuild it with bearings capable of 10,000RPM to take advantage of modern tools and machining methods. I have a huge pile of 3 phase induction motors, some are rated for safe operation at 6000RPM rotor speeds, and a 3HP motor with VFD is relatively inexpensive to achieve these speeds.

What are some ways I could manage this? Do I need to look for a specific VFD that has certain abilities for LCNC to be able to get spindle position control?

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23 Mar 2021 23:06 #203461 by andypugh
I know that it barely works with an old 1980s VFD that I once experimented with.

Some VFDs have homing built-in, but they home to the encoder on the motor, not the spindle. There is an other thread about one like that, but so far no conclusion.

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14 Aug 2021 03:01 #217730 by Becksvill
ideally you want a vfd with a encoder card then it works really good.

i have a altivar 71 drive with encoder card and the spindle is basically a servo. its awesome

otherwise you can use m codes and if the vfd has a low speed input pin you can use that to rotate the spindle at low speed and stop when it sees a proxy sensor

here is my mill doing spindle orientation

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