Messages

4241

Mach4 General Discussion / Re: Vista CNC P1A-S with Mach4 - Problem

« on: June 23, 2018, 07:32:43 PM »

Hi Mauri,
kool.

I think Lee is the only manufacturer who has an OEM Mach4 plugin. Kudos to VistaCNC.

I note there are a couple of users who have written plugins for XHC pendants and having some success. It seems strange that the manufacturer is not participating
in the plugin development, although if I read between the lines the manufacturer has supported at least one of the people involved in writing said plugin.

Our very own Daz-the-Gaz has spent a lot of time on the Xbox 360 plugin and is working well.

That makes three styles of pendants/remotes.

My belief is that the rate of uptake of Mach4 is increasing and so we might expect the momentum to have Mach4 ready controllers/pendants and other accessories to grow apace.

Craig

4242

General Mach Discussion / Re: Reboot whenever I open Mach3

« on: June 23, 2018, 03:48:10 PM »

Hi,
this is a Mach4 Discussion board whereas your enquiry is about Mach3  and you will get greater assistance if you post on the Mach3 Discussion board.

Bryanna has indentified three updates that have caused issues with people running a parallel port with Windows 7 as OS. There are three alternatives:
1) Find and un-install the three updates and keep your PC off the net to avoid future updates.
2) Buy an external motion controller like a UC300 or Ethernet SmoothStepper, the update issue affects  the parallel port only, external controllers are unaffected.
3) Upgrade to Mach4....its a much more modern program and is unaffected by the updates and is additionally still is active development and gets updated itself regularly
    unlike Mach3 which ceased development five years ago.

Craig

4243

General Mach Discussion / Re: Mach3 for Large CNC Router Table - or Not?

« on: June 23, 2018, 03:34:35 PM »

Hi,
Mach3 is fully capable of controlling a router. It is true that you will have to write some custom code for your particular machine for ATC.
Note that all development ceased on Mach3 five years ago and while it remains popular and used by many Mach4 is recommended for new projects.
Mach4 is fully capable but will likewise require some coding to enact your specific ATC requirements.

Craig

4244

General Mach Discussion / Re: Lathe Spindle Synchronisation

« on: June 23, 2018, 03:26:49 PM »

Hi,
yes, that is how the majority of Mach users synchronise their spindle for threading.

Craig

4245

HiCON Motion Controller / Re: Following Error

« on: June 23, 2018, 01:56:39 AM »

Hi,
kool.

From the point of view of simplicity you could try the current drives but the 7766 open loop, after all that's only keystrokes.
If you have plain drives you could try those for the sake of wiring them in.

Two reasonably straight forward experiments you can try.

I suspect that if you take the time to learn to use the software scope you will learn a lot about your system and what an 'optimum' solution looks like
rather than 'by guess and by God' approach.

Craig

4246

General Mach Discussion / Re: Calibrating for A axis

« on: June 23, 2018, 01:39:16 AM »

Hi,
glad you got the licence drama sorted, it sort of makes you feel like a mug... and that's on top of being just plain confused about Mach!

So you have had reasonable success with making things with the machine as three axis? If that's the case then you must have the steps per unit values in the respective axis
tuning pages correct or all your parts would turn out misshapen or the wrong size.

Now that you have started to use the 4th axis things are going crazy? May I suggest open the motor tuning pages and have a look at the steps per unit value in each of your
three linear axes. Have they changed? They should not have, if they have then the xml file is corrupt and you will have to try one of your backups, you do have one I hope, or
redo your profile.

My guess is that the steps per unit values have NOT changed. What has happened is that you have enabled another axis an put an appropriate number in its steps per unit value.
What is the steps per unit value for your new A axis? If I made a guess and said 55 steps per unit, we can carry on.

Remember that that value is the number of steps Mach issues to get the A axis to move 1 degree, so it would have to issue 55 x 360 = 19800 steps per revolution.

Lets say you want the X axis to move 450mm and the A axis to rotate once and you issued a move like:

G1 X450 A360 F360
The A axis would take 1 minute to rotate 360 degrees and so the X axis will slow down so it arrives at its endpoint at the same time, ie 450mm per min. You can see that adding an A axis
may well have a significant effect on the speed of your remaining axes.

Have a look at the steps per unit values of all your axes a post them.
Confirm that they are good by issuing and MDI for each axis in turn and confirm that its moving the right distance:
G0 X100....did the X axis move 100 mm?
G0 Y100....did the Y axis move 100mm?
G0 Z100....did the Z axis move 100mm
G0 A90....did the A axis move 90 degrees?

Craig

4247

HiCON Motion Controller / Re: Following Error

« on: June 23, 2018, 01:02:58 AM »

Hi,
OK that explains the origin of the different styles of loop closure.

I bought a big servo a while back for a spindle motor, 2.8kW and 14Nm. Its fitted with a resolver rather than an encoder so drives are a rare as rocking horse s*********t.
I decided to make one of my own, electronics is my thing and studied control engineering at University. I have had to learn and in many cases relearn stuff to do it.
I always maintain that the value of a hobby is best measured by the things you learn in pursuit of it. In which case my decision to make my own drive has been very valuable.

Amogst the things that you need to know about Field Oriented Control is control loops. There are some very good YouTube clips by Texas Instruments of Field Oriented Control, really well
done and a fascinating insight as to how AC servos work.....highly recommended.

The upshot is that for an AC servo to work you need three control loops. The innermost one is the acceleration (an expression of torque which is proportional to current) loop, then the next outer loop is the velocity control loop
and then the outer most one is the position loop. The advice is that if you are going to combine loops you have one loop per differential time. Thus the torque (or acceleration)loop is 'integrated'
(mathematically) to the velocity loop, which is in turn integrated (again in the mathematical sense) to the position loop.

Your drives AND the 7766 have three levels as well but you now have two acceleration loops, two velocity loops and two position loops. I suspect that the multiplicity of loops of the same
time 'dimension' will interact in a way that may be very hard to sort out.

I would certainly in the first instance reduce the complexity of your Z axis by having the one feedback control. Two different ways:
1) As I've already suggested use the 7766 as an open loop command generator and have the drive/stepper as the one feedback control element OR
2)Replace your drives with non-smart drives, ie just plain step/direction stepper drives like the AM882 from Leadshine and then have the 7766 close the loop.

If you already have plain ordinary drives 2) is perfectly doable but having to buy new drives just to avoid the complication of your current ones seems a real pain.
I am not aware that there is any advantage of one or the other. Having said that I would be tempted to guess that the manufacturer of your stepper and drive has made a combination
that works well together and would be easiest to achieve a good result. I do not mean any disparagement to the 7766 but it does lack the software driven scope and also its by
necessity more generalized in nature resulting in a more difficult tuning task.

I think this is the least confusing way forward. No matter how you work it out a good result is determined by the overall PID dynamics. Lets say you choose one of the above strategies
and find that the best performance of your machine is had with a P(roportional) gain of 1400, an I(ntegral) gain of 200 and a D(ifferential) gain of 175. If you now decide that you want
both the drive AND the 7766 to participate in the PID dynamics you at leat know the approximate distribution of gains required....so if you had the P gain of the 7766 at 14 then the
P gain of the driver would have to be about 100. (14 X 100 = 1400, our previously discovered sweet spot for Proportional gain) Alternatley you may decide the differential component
of the driver is numerically very noisy, a common problem with differentiators so you might set the drive D gain to 1 but have the 7766 D gain set to 175 and take advantage of the less noisy
differentiator Vital Systems built in.

Is your head spinning yet?.....mine sure as hell is!!!!

Craig

4248

HiCON Motion Controller / Re: Following Error

« on: June 22, 2018, 11:06:28 PM »

Hi,
kool, That was my concern that if you did not have the encoders hooked to the stepper drives everything else tips over.

The next question is why bother? You have two ways to close the loop, namely the drive and stepper  AND the 7766. Why have both? My question is that one
loop could be counteracting the other.

May I make a suggestion...just have the drive/stepper close the loop and have the 7766 as open loop command generator and use the scope facility built into the drive
software to watch the error. In order to do this you would have to increase the accel in Mach4 to an effective infinite and widen the following error window in the drive
to as wide as possible or even turn it off. Note that all of that can be done by programming, shouldn't have to rewire or buy extra bits.

Then you could issue a G0 Z100 say, an effective Step move. Initially the error would be 100 units and as the axis accelerated it would diminish and end when the stepper assumed position 100.
You could display this with the scope. Now try reducing the acceleration in Machs tuning and try again. Eventually you will reduce the acceleration so that the maximum error is some small
value, say 0.05mm say. You will then have found the maximum acceleration that your Z axis can attain AND remain within a given tolerance. The scope will allow you to view the results of changing
the PID parameters also. What the scope would not show you is if the 7766 changes the input command in response to its own feedback dynamics. Thus if the 7766 were not just an open loop
command generator then you tuning effort would be masked by the 7766 dynamics.

As far as the following window is concerned my only experience is my servo. It has a 2000 line encoder or 8000 count per revolution. The default following error is 20 counts or 0.9 degree and its zero window,
that is when its so close that it doesn't bother trying to reduce the error any more is 4 counts or 0.18 degree.

If your drive follows the same idea then your 1000 line, 4000 count encoder with a 500 wide following error would be 1/8 a revolution or 45 degrees, which seems awfully high to me. With a 5mm pitch ball screw
that would equate to 0.625mm, quite substantial.

Craig

4249

HiCON Motion Controller / Re: Following Error

« on: June 22, 2018, 09:55:52 PM »

Hi,

The 7766 cannot arbitrarily decide to add or subtract a step, that is done by the stepper driver. The wiring diagram of the 2HSS86H clearly shows the
encoder hooked to the driver.  You are trying to insert the HiCon in the loop and yet the HiCon CANNOT control the stepper....servos yes....steppers no.

I have the HiCon manual open in front of me and my previous statement may be wrong, maybe the HiCon can introduce extra steps as required.

However even if that is the case the 2HSS86H REQUIRES the encoder be plugged in, if you don't the drive has no way of knowing that the stepper is trying to follow the commanded
input and will produce a 'following error'.

You have steppers and drivers that form a closed loop AND a HiCon which can also close the loop. While you might possibly arrange to have both operating if you don't have the encoder
feedback to 2HSS86H it will fault no matter what the HiCon does.

Craig

4250

HiCON Motion Controller / Re: Following Error

« on: June 22, 2018, 09:35:44 PM »

Hi,
closed loop steppers REQUIRE that the encoder be connected to the matching drives. Having the 7766 included in the loop is redundant.
The 7766 cannot arbitrarily decide to add or subtract a step, that is done by the stepper driver. The wiring diagram of the 2HSS86H clearly shows the
encoder hooked to the driver.  You are trying to insert the HiCon in the loop and yet the HiCon CANNOT control the stepper....servos yes....steppers no.

Additionally the manufacturer of the stepper also designed the driver. I rather think a manufacturer has the resources to do a much much better job than you or
even Vital Systems.

I use an ESS from Warp9 and it has never made any claim to being able to close a servo loop. I bought a second hand Allen Bradley AC servo of 1.8kW for a spindle motor.
Its the first time I've had a chance to play with an AC servo, very very impressed.  It beats the hell out of the servos we experimented with at University all those years ago.
The ESS provides the commanded position in the form of step/direction pulses just like the HiCon. Those pulses are feed to the Allen Bradley servo drive and the encoder
is hooked to the servo drive. Thus its the servo drive that closes the loop, not the ESS. This is the same arrangement you'll have to use because the HiCon cannot control the stepper
drive directly, that requires the programming and circuitry built into the drive and its not available for you to fiddle with. Both my ESS and your HiCon are being utilized as open loop
command generators and the driver/servo in my case or the driver/stepper in your case are closed loop. If the closed loop fails to accurately follow the commanded input it will signal
the ESS/HiCon with a 'following error' fault.

Craig