Messages

6581

General Mach Discussion / Re: Servos progressing well, but question about index

« on: September 22, 2017, 08:26:52 PM »

Hi Roger,
yes the Allen Bradley servo has an incremental encoder of 2000ppr for a resolution of 8000 counts. The servo reads the position 8000 times a second and
does the control calculation and correction. If the command is to maintain a constant speed the servo/driver loop can close the loop with a far greater
bandwidth than an index pulse alone. The index pulse is only useful to the servo when it is referencing at start up. That Mach uses a single index
pulse to snychronise thread starts is a useful coincidence. The servo loop is trying to maintain constant speed and it capacity to do so is very good,  its
trying to reduce the error 8000 times a second when the servo is rotating at threading speeds, say 300 rpm or only 5 revs per second.

Craig

6582

General Mach Discussion / Re: Mach3 always hesitates in arcs and circles

« on: September 22, 2017, 07:36:25 PM »

Hi,
I don't hold Chinese made gear in high regard but I think in this case your concern is unfounded. Where Chinese made stuff falls down is that certain
features like backlash comp or probing don't work and the  companies don't seem to be bothered to upgrade their plugins. Also their
documentation is often execrable most probably due to language and they don't seem overly concerned that their customers are struggling.

They do work tho...and any well constructed pulse stream is just as good as any other well constructed pulse stream be it Chinese constructed or
otherwise.

Craig

6583

General Mach Discussion / Re: help whit signal step

« on: September 22, 2017, 07:23:01 PM »

Hi,
yes that is how I saw it as well. The step pulse stream is likely to be that fast that you will not see the indicator LED turn off, you'll need to
use a scope. But it did occur to me that in absence of any resistance to ground even modest circuit capacitance could hold the base conducting
and therefore the opto output would not change state and couldn't signal anything to the drive IC.

Craig

6584

General Mach Discussion / Re: Servos progressing well, but question about index

« on: September 22, 2017, 07:16:52 PM »

Hi Roger,
just as a matter of interest I'm making a servo drive for a large servo I plan to use as a lathe spindle motor. The servo looks new but is in fact
from the mid nineties and has a four pole resolver and the only applicable drives I can find are beyond my budget, hence I'm making one.

Its refresh rate is 20kHz for Nyquist rate of 10kHz and pretty fair discrimination at 1kHz. Has been a lot of fun working out how it all works, its
been many years since I've had to get serious about control....isn't Matlab just the bees knees!

Craig

6585

General Mach Discussion / Re: Servos progressing well, but question about index

« on: September 22, 2017, 07:05:44 PM »

Hi Roger,
I disagree, the refresh rate on my Allen Bradley servo also used as a spindle motor is 8kHz. The manufacturer claims a control bandwidth of over 500Hz.
At max speed my spindle is rotating at 58 rev/second, easily slow enuf that the control loop is trying to close the error within a revolution.

Craig

6586

General Mach Discussion / Re: Servos progressing well, but question about index

« on: September 22, 2017, 07:00:48 PM »

Hi Dave,
RTFM, you don't need it

PZOUT+ Encoder Z phase differential positive output
PZOUT- Encoder Z phase differential negative output

The built in index pulse form the encoder is already available as an output, pins 42 and 43 of CN1. You are just making work for yourself, the manufacturer is
way ahead of you.
Secondly note that the A and B channels of the encoder are 2500 pulses per rev, when they are combined as a quadrature signal they give four times that as
encoder count or resolution. 10,000 count encoders like this are pretty much the norm for incremental encoders on current production models.
10,000 count encoder will give you potentially 2.16 arc minute resolution, surely that enuf even for an Aussie.
Last thing is that Mach ASSUMES constant spindle speed when threading. Your spindle could conceivably provide variance information in between each
revolution buy Mach can't do anything with anyway.

Craig

6587

General Mach Discussion / Re: Servos progressing well, but question about index

« on: September 22, 2017, 06:24:42 PM »

Hi Dave,
most servo drives have programmable outputs, usually encoder outputs. They can and often are manipulated versions of the encoder fitted to the servo.
I haven't read the manual for your servo but would guess quadrature A and B channels and an Index channel. If some or all of that info is programmed
as an output of the servo drive than Mach can read it. The servo speed will be that close to its programmed speed it doesn't serve any useful purpose except
perhaps peace of mind. The Index however would be very valuable as Mach uses that for speed, which we've seen has little value, but very importantly the
index can synchronise the start of the thread.

As Rich has pointed out that half the battle with threading is to achieve a constant spindle speed in face of a varying load. Your servo and drive should
manage that with aplomb. Now all you need is an indexing pulse. You could add some extra external hardware or you may be able to use the index pulse
built into the servo encoder. Whether the duration of the included index pulse is suitable for Mach is a matter of investigation. The pulse may have to
be manipulated electronically for it to be useful for Mach. Either way is very achievable and you will end up with a very capable spindle that handles threading
with ease...be happy!

Craig

6588

Third party software and hardware support forums. / Re: Need help -only some signals output on longs breakout board

« on: September 22, 2017, 03:07:09 PM »

Hi,
can you post screen shots of the first four Ports and Pins pages?

Craig

6589

General Mach Discussion / Re: Interference with axis motors

« on: September 22, 2017, 11:16:24 AM »

Hi,
I have a little mSATA SSD in my Atom platform that runs my mill, I luv it, fast, tiny and reliable. Just to think only 5 years ago would have been to
pricey for home use now cheap as chips.

Craig

6590

General Mach Discussion / Re: Interference with axis motors

« on: September 22, 2017, 11:12:37 AM »

Hi Maverick,
that's interesting, I wonder if the plugin flashes the controller with some sort of firmware but can thereafter run in absence of the plugin.

Glad that you've got the info tho...the chances are your going to need it over the coming months. CNC is not plug and play as a rule and the better
your info/knowledge the better chance you have of advancing your hobby and very personally satisfying it is too.

Craig