Messages

3611

General Mach Discussion / Re: Mach3 MDI line issue

« on: September 26, 2018, 10:15:17 AM »

Hi,
sounds like your in incremental mode.

Confirm that you are in absolute distance mode and IJ Incremental mode.

Next read up on G90 and G91 modes. MDI a G90 to be sure.

Craig

3612

HiCON Motion Controller / Re: Liener scale Feedback

« on: September 26, 2018, 03:51:01 AM »

Hi,
I do not have a Hicon so what follows is my best guess, there would need to be several confirmations of various features
before this could be considered practical.

In the diagram attached note that the Hicon unit (which includes the add-on boards) receives Step/Direction input from Mach and compares
that to the Linear Encoder feedback. The Hicon would be required to process that via its PID processor and output an analogue voltage
to your servo/drive. The servo/Drive would have to be in Velocity mode. The rotary encoder of the servo would still be hooked up to the drive
per normal, its just that it is not used as a positional measure but rather velocity measurement. The output shaft is connected to the axis and finally
the linear encoder is connected to the axis and measures the table position.

This arrangement is shown with the Hicon but could equally describe a Galill controller..

Lets take a few components and look at the requirements to make it work.

The first is the Linear Encoder. It will be hooked to the Hicon so it will require an output that the Hicon can decode, namely A and B quadrature
channels and probably an Index signal. This could be a problem, I have seen linear scales with quadrature output but don't recall seeing one with an Index
signal and yet I suspect that the Hicon requires it. This would best be discussed with Vital Systems.

The second issue, still related to the Linear Encoder is the quality of the encoder itself. Have a look at Hidenhan and Reinshaw websites to see what they
offer, and make sure you are sitting comfortably when you read the price. What sort of corners have to be cut by Chinese (and others) manufacturers
to sell linear scales at the prices they do?

I'm of the opinion that to get decent linear scales, not Heidenhan or Reinshaw, just decent ones is likely to be quite expensive, I'm guessing $200 per axis.

The Hicon itself is not cheap, the basic board is $600 and the addon board and activation cost another $600.

I assume you already have analogue input servos and drives?

What is not certain is that the Hicon can do the PID part without additional on-board programming. The Hicon does offer that low level programming
but could require some very clever programming on your part. There again I would rely on Vital Systems advice as to what is possible 'out of the
box' and what extra may be required to get this setup to work.

Note that this general arrangement is not uncommon, it is uncommon in CNC lathes and mills, but is used in semiconductor wafer processing.
Semiconductor machines require extreme precision. The absolute best (Heidenhan or Reinshaw) linear scales are probably only just good enough.
Some use LVDT (Linear Voltage Differential Transformer) transducers and all the high precision (and tricky) stuff use laser interferometry. Zeeman splitting/stabilization
will get you to about 10nm and iodine cells are required to get you to a few nm.

I make the point that in those situations where linear position feedback is employed the feedback components (scales/LVDTs/interferometers) are very
VERY expensive. While you may not require the sort of precision these technologies seek to achieve I think you can rely of the fact that you will spend
significant money trying to do linear feedback. I suspect rather more than it would cost to fit C5 or better ballscrews.

Craig

3613

General Mach Discussion / Re: Slow Zones not working using soft limits (no homing switches fitted)

« on: September 25, 2018, 02:56:48 PM »

Hi,
I suspect the RnR USB card does not support that feature.

The only people who would know are those who make it but good luck trying to find and contact them.

Craig

3614

HiCON Motion Controller / Re: Liener scale Feedback

« on: September 25, 2018, 02:51:01 PM »

Hi,
yes it is possible and it is done for exactly the reasons you have mentioned. It does complicate the issue in a big way.
The Hicon when the feedback part is enabled will probably do it.

Galill controllers are known for their applicability to these situations, they are expensive.

I use C5 grade ground ballscrews which are accurate to less than 18um over 300mm and a cyclic accuracy of less than 8um.
As a consequence if I know the rotational position (encoder) of the screw I have a fairly accurate notion of where the table is. Most industrial
CNC machinery operates that way with C5 or C3 ballscrews.

Craig

3615

HiCON Motion Controller / Re: Liener scale Feedback

« on: September 25, 2018, 08:06:37 AM »

Hi,
why? Are the servos not equipped with encoders?

Craig

3616

Third party software and hardware support forums. / Re: Xhc HB04 MPG Pendent with Mach4

« on: September 25, 2018, 08:03:56 AM »

Hi,
I use a VistaCNC P1A USB pendant. I seem to recall having a bit of of a battle to get it installed and working correctly buts
its been fine ever since.

Craig

3617

Mach4 General Discussion / Re: Mach 4 Probing issue - "Can't transition from MDI running to stop."

« on: September 23, 2018, 11:47:23 AM »

Hi,
I use Autoleveller AE. I had a problem initially that sometimes there would be recorded more data points in the probe log file than
there were G31 calls. I tried all sorts of ways to find out why without success. In the end I wrote a Lua script that could deduce the correct
number of probe points and correct, if necessary, the probe log file.

The full discussion of it is on the Autoleveller forum.

May I suggest that you double check that Mach has not inadvertently put more data points in the file than you expected.

Craig

3618

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: September 23, 2018, 04:06:43 AM »

Hi,
if you set Machs velocity and/or acceleration higher than the servo/drive then when Mach issues a max velocity positional move,
ie a G0 then the servo cant keep up and will fault out 'following error'.

At all times the servo/drive must be at least as capable as Mach expects. In fact the higher the acceleration of the servo/drive
the better it can follow the commanded input.

It is for this reason that I advocate the servo/dive be programmed for its maximum practical velocity and acceleration.

Note that as the forward gain (velocity/acceleration) is increased if there is a fixed phase lag in the drive chain, the encoder for instance,
then the phase margin reduces and may become unstable. Hood has already described that situation. Even if the velocity/acceleration
commanded by Mach is less than the servo/drive and that the servo/drive loop has an instability (low or vanishing phase margin) the
instability will be excited. It is not because Mach has commanded an impossible move but rather the servo/drive has an instability.
It is for this reason that much is made of self tuning notch filters...they can restore phase margin without undue reduction in forward gain.

By reducing the maximum velocity (or acceleration) of the servo you are in effect throwing away forward gain......ie you bought a servo that has 'sports car'
performance but you throttle it back so it performs like a 'Morris 1000'.

Craig

3619

Mach4 General Discussion / Re: Need help with M6 Macro, translating from Mach3 to Mach4

« on: September 23, 2018, 03:25:49 AM »

Hi,
now open the script editor and put this code in it:

Code: [Select]

[mc.ISIG_INPUT3]=function(state)
if state==1 then
toolindex=1
else
toolindex=0
end
end
Save it as 'siglib' or some other unique name.

Note that I have declared a variable 'toolindex', and I have not put 'local' in front of it. It is therefore a global variable and as it is declared,
or least will be when its finished and put in its permanent location, in the screen load script and is therefore visible throughout the GUI.
We may have to get a bit creative if we wish to pass it to a macro because a macro is not technically in the GUI. Anyway that's for the future.

You might ask why I chose input #3? If you look in the screen load script and the signal library table in particular you will see that Mach is already
using, or at least has table entries for inputs #1 and #2. I didn't want to confuse you, or me come to that so I left those out.

If you look on the machine diagnostic page, if the lathe screen set even has such a page you will see that there are LEDs for the first six inputs.
It is convenient to use those to start with because if you reach over and flick the index switch by hand you should see the LED on the diagnostic screen
light up. At a later date you might chose to reassign the switch to input #19 say, of course you wont have an onscreen LED to tell you whether Mach
has seen the switch or not, but by then you have already experimented with it enough to know it works.

If you can tell me how the tool position encoder works we can make a start on that code as well.

Craig

3620

Mach4 General Discussion / Re: Need help with M6 Macro, translating from Mach3 to Mach4

« on: September 23, 2018, 02:45:15 AM »

Hi,
having probably confused you....you can now start to use what you have learnt.

You have at least one input, the index switch. You have at least one other, tool position encoder, can you tell us about how that works.

For the one input that we are sure of, we can make an entry in the signal library table for it.

When writing Lua code you will often find that you will write some parts in the form of macros which will end up in the macro folder
but there will be code fragments that end up in the screen load script and other places, this little addition to the signal library table is an example.
Its a good idea to set aside a temporary folder where you can write and maybe test these little fragments of code. Once you are happy with them
THEN you put them in their final location.

May I suggest that you open the main Mach4 folder and make a new folder within your current profile called 'tempfolder' or similar.

Now open the Script Editor under the Operator tab and you will have an untitled script page that you can save in the tempfolder you have created.
This tempfolder will hold all the little bits of code that you will put together.

Craig