Deciding on boards for a knee mill retrofit
Posted: Fri Dec 13, 2019 6:26 pm
I've got a Matchmaker knee mill that's reached the top of the retrofit list, but am still umming and arring over what boards to use.
Requirements are -
XYZ running servos.
Option to add an A axis (might be stepper, might be servo..).
Spindle powered by VFD, but it is also varispeed currently fitted with a stepper (it's a 3 phase stepper, so it will probably get replaced, as a 3 phase driver is as expensive as 2 phase stepper and driver), along with a hi/lo gearbox. I'd like to keep the varispeed working for the rough speed adjustment, then use the VFD for fine tuning and keeping the spindle motor speed up for cooling purposes.
Eventually motorise the knee. I'm thinking suitably geared servo, but feedback done by glass scale (the ones with the coded index strip, so it doesn't need fully homed every time - I've forgotten who does them, so if anybody can prompt me, I'd be very grateful!)
SSO, and FRO.
So with that list in mind, I think I've got the following needs.
4 Servos, that could be Analog or Step/Dir.
A axis is probably best left as step/dir to keep options open.
One analogue output for the VFD.
One step/dir for the varispeed.
Encoder feedback for 5 possibly 6 motors (XYZ, Knee, & Spindle, with possibly the A)
Two analogue inputs for SSO and FRO.
So the potential totals are-
4 +/-10V and 2 step/dir outputs OR 6 step/dir outputs
1 Analogue output (only 0-10V)
5 or 6 encoder inputs (every axis will have a differential index as well)
2 Analogue inputs
All that is ignoring the required digital outputs, which I'd like to handle via a Konnect or two.
If I go the Kanalog option, that would give me all the DACs and ADCs I'd need, but would need encoder indexes connected to conventional inputs via suitable buffers (not a big issue, but something to consider), as I'll need to use one of my adapter boards to utilise two off the encoder channels for step/dir outputs.
If I go KNozz, that could take care of the 0-10V and ADC requirements. Then have step/dirs and encoders split between JP7/JP5 on the KFlop, but then if my understanding/counting is correct, I'm going to run out of high speed digital inputs for all the index pulses (I'm assuming that any reasonable homing speed will be too fast to be reliably caught by a Konnect input, especially if two boards are in use?)
Any body got any thoughts?
I had been hoping to go closed loop step/dir for a bit off simplicity, but I'm now swaying back towards analogue, so as not to limit myself.
Requirements are -
XYZ running servos.
Option to add an A axis (might be stepper, might be servo..).
Spindle powered by VFD, but it is also varispeed currently fitted with a stepper (it's a 3 phase stepper, so it will probably get replaced, as a 3 phase driver is as expensive as 2 phase stepper and driver), along with a hi/lo gearbox. I'd like to keep the varispeed working for the rough speed adjustment, then use the VFD for fine tuning and keeping the spindle motor speed up for cooling purposes.
Eventually motorise the knee. I'm thinking suitably geared servo, but feedback done by glass scale (the ones with the coded index strip, so it doesn't need fully homed every time - I've forgotten who does them, so if anybody can prompt me, I'd be very grateful!)
SSO, and FRO.
So with that list in mind, I think I've got the following needs.
4 Servos, that could be Analog or Step/Dir.
A axis is probably best left as step/dir to keep options open.
One analogue output for the VFD.
One step/dir for the varispeed.
Encoder feedback for 5 possibly 6 motors (XYZ, Knee, & Spindle, with possibly the A)
Two analogue inputs for SSO and FRO.
So the potential totals are-
4 +/-10V and 2 step/dir outputs OR 6 step/dir outputs
1 Analogue output (only 0-10V)
5 or 6 encoder inputs (every axis will have a differential index as well)
2 Analogue inputs
All that is ignoring the required digital outputs, which I'd like to handle via a Konnect or two.
If I go the Kanalog option, that would give me all the DACs and ADCs I'd need, but would need encoder indexes connected to conventional inputs via suitable buffers (not a big issue, but something to consider), as I'll need to use one of my adapter boards to utilise two off the encoder channels for step/dir outputs.
If I go KNozz, that could take care of the 0-10V and ADC requirements. Then have step/dirs and encoders split between JP7/JP5 on the KFlop, but then if my understanding/counting is correct, I'm going to run out of high speed digital inputs for all the index pulses (I'm assuming that any reasonable homing speed will be too fast to be reliably caught by a Konnect input, especially if two boards are in use?)
Any body got any thoughts?
I had been hoping to go closed loop step/dir for a bit off simplicity, but I'm now swaying back towards analogue, so as not to limit myself.