MESA boards recommendation
09 Oct 2014 21:07 #51918
by llrjt100
MESA boards recommendation was created by llrjt100
I'd be very grateful for any guidance in terms of which MESA boards I need for the following setup:
1. High resolution Renishaw lathe spindle encoder (1-2 MHz)
2. High resolution lathe cross-slide encoder + stepper motor
3. High resolution rotary table Renishaw encoder with direct drive servo motor (Granite VSD)
4. Possible spindle servo motor control in the future
It's basically a hobbing machine, the rotary table follows the spindle encoder. Whilst hobbing, the x-slide steadily feeds the hob into the gear.
I'm using a PC with PCI slots and parallel port running LCNC under Ubuntu.
Richard
1. High resolution Renishaw lathe spindle encoder (1-2 MHz)
2. High resolution lathe cross-slide encoder + stepper motor
3. High resolution rotary table Renishaw encoder with direct drive servo motor (Granite VSD)
4. Possible spindle servo motor control in the future
It's basically a hobbing machine, the rotary table follows the spindle encoder. Whilst hobbing, the x-slide steadily feeds the hob into the gear.
I'm using a PC with PCI slots and parallel port running LCNC under Ubuntu.
Richard
Please Log in or Create an account to join the conversation.
10 Oct 2014 02:59 #51929
by emcPT
Replied by emcPT on topic MESA boards recommendation
The most common setup for analog control is the combination of 5i25 + 7i77 + extras if you need more IO.
Also for step direction set up the 5i25 + 7i76 + extras for the same reason as the 7i77, is a very usual combination.
If you currently use only the parallel port, you will not need any more IO card.
Also for step direction set up the 5i25 + 7i76 + extras for the same reason as the 7i77, is a very usual combination.
If you currently use only the parallel port, you will not need any more IO card.
The following user(s) said Thank You: llrjt100
Please Log in or Create an account to join the conversation.
10 Oct 2014 18:29 #51941
by andypugh
Replied by andypugh on topic MESA boards recommendation
This looks basically like a Servo system with an extra channel of stepper.
So maybe a 5i25 with the 7i76/7i77 firmware, then a 7i77 for the encoders and servos and the 7i78 for the step/dir channels connected to the secondary header of the 5i25.
store.mesanet.com/index.php?route=produc...83_84&product_id=214
store.mesanet.com/index.php?route=produc...83_87&product_id=121
store.mesanet.com/index.php?route=produc...74_79&product_id=235 (to bring out the internal header)
So maybe a 5i25 with the 7i76/7i77 firmware, then a 7i77 for the encoders and servos and the 7i78 for the step/dir channels connected to the secondary header of the 5i25.
store.mesanet.com/index.php?route=produc...83_84&product_id=214
store.mesanet.com/index.php?route=produc...83_87&product_id=121
store.mesanet.com/index.php?route=produc...74_79&product_id=235 (to bring out the internal header)
The following user(s) said Thank You: llrjt100
Please Log in or Create an account to join the conversation.
10 Oct 2014 20:19 #51946
by llrjt100
Replied by llrjt100 on topic MESA boards recommendation
Thank you very much guys - your help is much appreciated - there are a lot of MESA boards, and it can be difficult to work out what's required.
Quick question - will MESA boards drive VSD-E servo drive with a step/dir signal, or in some other way?
Quick question - will MESA boards drive VSD-E servo drive with a step/dir signal, or in some other way?
The following user(s) said Thank You: emcPT
Please Log in or Create an account to join the conversation.
10 Oct 2014 20:36 - 10 Oct 2014 20:39 #51947
by emcPT
Replied by emcPT on topic MESA boards recommendation
You can use the VSD in both ways: Step/Direction and analog.
Normally you would use a 7i77 with VSD in analog; or 7i76 with VSD in step direction.
If you want the best direct setup go for 7i77 in analog with the VSD. I have several systems like this (for professional machines - long working hours) and the results are very good.
I forgot to mention that using the 7i77 you will have the encoder feedback directly to linuxCNC, this means that the DRO on LinuxCNC corresponds to the actual position of the motor encoder rather than the expected position of the system.
Normally you would use a 7i77 with VSD in analog; or 7i76 with VSD in step direction.
If you want the best direct setup go for 7i77 in analog with the VSD. I have several systems like this (for professional machines - long working hours) and the results are very good.
I forgot to mention that using the 7i77 you will have the encoder feedback directly to linuxCNC, this means that the DRO on LinuxCNC corresponds to the actual position of the motor encoder rather than the expected position of the system.
Last edit: 10 Oct 2014 20:39 by emcPT.
The following user(s) said Thank You: llrjt100
Please Log in or Create an account to join the conversation.
13 Oct 2014 17:20 #52007
by llrjt100
Replied by llrjt100 on topic MESA boards recommendation
Thanks again for the advice - interesting to note that an analog interface (is this 0-10 V?) is better than step/dir.
The spindle motor can run open loop, and the rotary table follow the spindle encoder, so I guess I only need one VSD servo drive for the rotary table. Would it be best to run the rotary table in velocity or position mode with the 7i77 and analog interface? The rotary table is simply following the spindle as an electronic gearbox (approx. 200:1).
I can't find any documentation about the MESA boards maximum encoder input frequency - I'm using a high resolution Renishaw encoder on the spindle, and don't want it to saturate the MESA board at 450 rpm.
The spindle motor can run open loop, and the rotary table follow the spindle encoder, so I guess I only need one VSD servo drive for the rotary table. Would it be best to run the rotary table in velocity or position mode with the 7i77 and analog interface? The rotary table is simply following the spindle as an electronic gearbox (approx. 200:1).
I can't find any documentation about the MESA boards maximum encoder input frequency - I'm using a high resolution Renishaw encoder on the spindle, and don't want it to saturate the MESA board at 450 rpm.
Please Log in or Create an account to join the conversation.
13 Oct 2014 17:29 #52010
by andypugh
"(bit r/w) filter
If set to True (the default), the quadrature counter needs 15 clocks to register a change on any of the three input lines (any pulse shorter than this is rejected as noise). If set to False, the quadrature counter needs only 3 clocks to register a change. The encoder sample clock runs at 33 MHz on the PCI AnyIO cards and 50 MHz on the 7i43."
So this looks to be 2Mhz with the filter enabled and 10Mhz with the filter off.
Replied by andypugh on topic MESA boards recommendation
It would be interesting to see if it is actually better. Step/dir to a servo drive from LinuxCNC basically involves running the drive in position mode and using the feedback to LinuxCNC to convet this to velocity mode. At very low speeds I can see this leading to dithering problems, where LinuxCNC would be sending very slow step pulses and the drive will attempt to respond immediately to each one. In practice an experiment might be needed to see which works better, but Analogue mode (actually +/-10V) places more of the control loop inside LinuxCNC where you can analyse it and adjust it.Thanks again for the advice - interesting to note that an analog interface (is this 0-10 V?) is better than step/dir.
The hostmot2 manpage includes this informationI can't find any documentation about the MESA boards maximum encoder input frequency - I'm using a high resolution Renishaw encoder on the spindle, and don't want it to saturate the MESA board at 450 rpm.
"(bit r/w) filter
If set to True (the default), the quadrature counter needs 15 clocks to register a change on any of the three input lines (any pulse shorter than this is rejected as noise). If set to False, the quadrature counter needs only 3 clocks to register a change. The encoder sample clock runs at 33 MHz on the PCI AnyIO cards and 50 MHz on the 7i43."
So this looks to be 2Mhz with the filter enabled and 10Mhz with the filter off.
The following user(s) said Thank You: llrjt100
Please Log in or Create an account to join the conversation.
13 Oct 2014 17:35 #52012
by llrjt100
Replied by llrjt100 on topic MESA boards recommendation
Thank you for your fast reply Andy.
The main requirement for good tooth to tooth spacing whilst hobbing is for the rotary table to accurately follow the hob/spindle. The hob infeed, controlled by the closed loop stepper on the cross slide is less critical.
In terms of the rotary table servo mode, I guess I can try both and measure the result when I look at the transmission error in the gear.
2 - 10 MHz is plenty - thanks for this!
I guess I can go ahead and order up the 5i25, 7i77 & 7i78 as you suggested now
The main requirement for good tooth to tooth spacing whilst hobbing is for the rotary table to accurately follow the hob/spindle. The hob infeed, controlled by the closed loop stepper on the cross slide is less critical.
In terms of the rotary table servo mode, I guess I can try both and measure the result when I look at the transmission error in the gear.
2 - 10 MHz is plenty - thanks for this!
I guess I can go ahead and order up the 5i25, 7i77 & 7i78 as you suggested now
Please Log in or Create an account to join the conversation.
13 Oct 2014 18:08 #52015
by andypugh
I have a hobbing setup on my milling machine much like you describe, but I have not tried helical gear cutting yet.
Replied by andypugh on topic MESA boards recommendation
I would imagine that it is important when cutting helical gears? You would need to increment the gear angle relative to the hob position by a factor of the infeed distance.The main requirement for good tooth to tooth spacing whilst hobbing is for the rotary table to accurately follow the hob/spindle. The hob infeed, controlled by the closed loop stepper on the cross slide is less critical.
I have a hobbing setup on my milling machine much like you describe, but I have not tried helical gear cutting yet.
Please Log in or Create an account to join the conversation.
13 Oct 2014 18:27 #52016
by llrjt100
Replied by llrjt100 on topic MESA boards recommendation
I'm hobbing worm gears, so I simply run the hob against the wheel at the required gear ratio and gradually infeed the hob into the wheel.
Please Log in or Create an account to join the conversation.
Time to create page: 0.075 seconds