Re: [Emc-users] Home + Index home positioning problem.

[Yahnis Chris <yahnis21@gm...>]

"if you have proven its effectiveness and usefulness."

Accurate zero position is the key for many jobs. It is especially important
if you have a job, that spreads over several days and you want to turn off
your machine for night and continue next day.

Mechanical switches are unreliable.
Proximity switch has hysteresis problem, larger diameter switches are less
accurate (usually)
The only real candidate that is relatively inexpensive is the encoder with
index if you want to do precise work especially true for rotating axis.

Of course all this depends what is your target application - "el cheapo"
home made oxy cutters or plywood routers do not matter, metal milling or
lathes need accurate positioning especially for repetitive work. Steppers
can also do quality work for most jobs if they are properly sized.

Y.

Re: [Emc-users] Adlink PCI-8136 card

[Stephen Wille Padnos <spadnos@so...>]

Tomasz Brzozowski wrote:

>Hello.
>What do you think about using Adlink PCI-8136 card with EMC ?
>link to producer:
>  
>
It looks like a nice card to me.

>http://www.adlinktech.com/PD/web/PD_detail.php?cKind=&pid=134&seq=&id=&sid=
>
>There is no Linux driver, but this card has every things needed for 
>build real servo system.
>- DAC
>- ADC
>- Encoder input
>- I/O ports
>  
>
It's too bad they make you register to see the manual or the drivers.  
That's always annoying to me.

>The price of this card in Poland is about 700 $.
>  
>
I've asked my ADLink rep to get pricing in small quantities, and also to 
see if I can get a manual.

>I know that EMC doesn't  support this card, but I'm thinking about 
>writing driver for it.
>What do You think ?
>  
>
More hardware drivers == better, I think :)

Thanks
- Steve

[Emc-users] Adlink PCI-8136 card

[Tomasz Brzozowski <tomekbrzozowski@in...>]

Hello.
What do you think about using Adlink PCI-8136 card with EMC ?
link to producer:

http://www.adlinktech.com/PD/web/PD_detail.php?cKind=&pid=134&seq=&id=&sid=

There is no Linux driver, but this card has every things needed for 
build real servo system.
- DAC
- ADC
- Encoder input
- I/O ports

The price of this card in Poland is about 700 $.
I know that EMC doesn't  support this card, but I'm thinking about 
writing driver for it.
What do You think ?  

with regards Tomek

Re: [Emc-users] Home + Index home positioning problem.

[Jeff Epler <jepler@un...>]

On Tue, Aug 19, 2008 at 09:24:00PM +0200, Yahnis Chris wrote:
> [...]
> Checked the stepgen C code and see no reason why an additional flag
> check would not be feasible. When index-enable is not on just skip the
> "settozero" subroutine. Maybe a future feature?

Indeed, there's no reason you couldn't add this feature to stepgen.  We
would be happy to consider this modification for inclusion if you have
proven its effectiveness and usefulness.

Jeff

Re: [Emc-users] Home + Index home positioning problem.

[Yahnis Chris <yahnis21@gm...>]

First thanks for the fast answer.

"Everything you are doing looks correct. You don't show the HAL lines, but I
assume that you are connecting the A and B phases of the
encoder as well."

Of course. Just tried to keep the story in limits.

" Does it turn off again when the index pulse arrives?"

Yes clearly visible on the scope.

"Does it turn off again when the index pulse arrives?"

Yes both of them go to zero and they start to count again as the axis
travels to previous position.

" Does that mean you are running a stepper machine with encoders?"

Yes. The machine still have manual handles and the encoder/DRO is practical
for manual position checking.

"If so, are you taking the position feedback from the stepgen module or
from the encoder module? "

Stepgen only, never had luck with the encoder FB, regardless how big was the
following error always got FE message. In fact I get following error on the
first 0.005mm or so. (The ball screw is metric and has 0.03mm backlash
because of the timing belt.)

"I think that could give the result you are seeing."

It is clear now, however I see no reason, why stepgen can't check a flag/bit
for encoder Z status and zero the position target and FB, during homing.
Wasting only few processor cycles, when timing is not a real issue at low
search speed and this would have a lot of benefits in fact that is the way
it should work to meet with the documentation. Checked the stepgen C code
and see no reason why an additional flag check would not be feasible. When
index-enable is not on just skip the "settozero" subroutine. Maybe a future
feature?

" If you are sending the position command to a PID loop"

PID is what I wanted to avoid. Chapter 14 section 1  says stepgen has a
pre-tuned internal position loop when in fact this is not entirely correct
term (or maybe I do not use the "pre-tuned loop" term properly). Would be
better to say stepgen "makes itself  happy" ;-) regardless of the actual
position or say stepgen has a fixed preset position loop without any error
correction to make it very clear.


"EMC is happy, but it has no idea that you have an encoder and cannot use
the encoder data for homing."

Understand, but consider to put it into stepgen, otherwise the entire
documentation is misleading or not fully clear as it never states that
switch+index homing is only working in PID mode. Or someone should change
the docs or add a remark.(I am not complaining in fact I appreciate that you
guys are spending your free time here.)

Anyway I am going back and try to change the config to PID.

Thanks,
Y.

Re: [Emc-users] Lead screw

[Kirk Wallace <kwallace@wa...>]

On Mon, 2008-08-18 at 23:23 -0700, An Pham Duc wrote:
> I am finding some lead screw for my mini CNC. Please tell me what kind
> of lead screw I should use
> Thank you

With a manual machine, which usually has leadscrews, a bit of clearance
is needed between the nut and threads to keep friction and wear down.
With this clearance, the machinist needs to have a technique that
compensates for this clearance by always coming to a dimension from the
same direction and if necessary locking the non moving axes while
cutting. 

For CNC, these techniques are not available, so you need to have a low
friction, zero clearance ball screw as well as zero clearance ball
bearings to mount the ends of the ballscrews. For zero clearance, the
nuts and end bearings need to be preloaded some way. For nuts, I believe
the best way is with two ball nuts with adjustable clearance between
them. Some single ballnuts can be preloaded with slightly over-sized
balls which may need to be changed as the screw wears. There is a choice
between ground and rolled ballscrews. The ground ballscrews are
generally more accurate and last longer under heavier loads, but are
considerably more expensive.

What will work for your application, will depend on the details of your
machine, what you want to do with it, and your budget.

-- 
Kirk Wallace (California, USA
http://www.wallacecompany.com/machine_shop/ 
Hardinge HNC/EMC CNC lathe,
Bridgeport mill conversion, doing XY now,
Zubal lathe conversion pending
Craftsman AA 109 restoration
Shizuoka ST-N/EMC CNC)

Re: [Emc-users] I'M STUCKED, GIVE ME A HELP ON PYVCP

[Jeff Epler <jepler@un...>]

Oddly enough, I wrote a message about exactly this problem earlier
today.  Here it is:

> From: Jeff Epler <jepler@...>
> To: "Enhanced Machine Controller (EMC)" <emc-users@...>
> Subject: Re: [Emc-users] pyvcp on install from image
> 
> It looks like the extremely abbreviated way to run pyvcp shown in the
> manual works for the "sim" version of emc but not for the realtime
> version.
> 
> On a true realtime system, the shortest incantation seems to be
>     halrun -I loadusr pyvcp -c mypanel tiny.xml
> which will start the realtime system, load pyvcp, and then present you  
> with a 'halcmd' prompt so you can do things like 'halcmd show'.  When
> you exit the halcmd, the panel will disappear.
> 
> I'll see that this is included in the documentation.
> 
> Thanks,
> Jeff

Jeff

Re: [Emc-users] Home + Index home positioning problem.

[John Kasunich <jmkasunich@fa...>]

Yahnis Chris wrote:
> Hi All,
> 
> I experienced some homing problem on a home switch + encoder index
> configuration.
> The install was simple. After the initial timing issues and a subsequent
> motherboard change the machine runs fine and quite stable, timing is good,
> except emc does not reset the axis position at the index signal. After the
> home switch release the .index-enable goes on. When the encoder index "Z"
> signal is "on" instead of resetting the internal position counter to
> HOME_OFFSET (0.0) value and move to HOME (0.0) the axis travels back at
> rapid speed to the original axis "zero" position and the axis is "homed".
> This "zero" position is exactly the same position, where emc was first
> turned on. Homing is sequential XYZ all do the same way. Polarity and index
> is properly connected at least I think so. Phase-Z is traceable on the
> HALscope for encoder.n, axis.n, and parport.n.pin.
> 
> HAL config (only for X Index section)
> 
> net X-index encoder.0.index-enable axis.0.index-enable
> newsig X-phaseZ             bit
> linksp X-phaseZ <= parport.1.pin-08-in-not
> linksp X-phaseZ => encoder.0.phase-Z
> net Xhome parport.1.pin-13-in-not  axis.0.home-sw-in
> 
> Home switch is stable proximity switch and works fine.
> Encoder is counting  the same way as stepgen so all pins should be correct.
> 
> The homing section of the ini:
> HOME_USE_INDEX = YES
> HOME_OFFSET = 0.0
> HOME_SEARCH_VEL = -5.0
> HOME_LATCH_VEL = 1.50000
> #HOME_FINAL_VEL = 5.0
> HOME_SEQUENCE = 0
> HOME_IGNORE_LIMITS = NO
> 
> EMC2    2.2.2 and  2.2.5 versions were tested with same result on the 2.2.2
> the HOME_FINAL_VEL was commented.
> 

Thanks for providing good details.

Everything you are doing looks correct.  You don't show the HAL lines, 
but I assume that you are connecting the A and B phases of the encoder 
as well.  I'm away from my Linux computer, so I can't test anything 
right now.  However there are a couple of simple tests that you can run 
to try to isolate the problem.

You say that signal X-index (pin axis.0.index-enable) goes on when you 
come off the home switch - that is good.  Does it turn off again when 
the index pulse arrives?  If not, the software encoder counter is 
missing the index.

If X-index does turn off, what happens to encoder.0.counts and 
encoder.0.position?  Both should become zero on the falling edge of 
index-enable.

Hmmm - you say "encoder is counting the same way as stepgen".  Does that 
mean you are running a stepper machine with encoders?

If so, are you taking the position feedback from the stepgen module or 
from the encoder module?  Whatever is connected to axis.0.motor-pos-fb 
is the feedback source for that axis.  If you are talking feedback from 
stepgen, then the encoder data is being ignored.  I think that could 
give the result you are seeing.

This is a complex situation - EMC assumes that something (either a 
stepgen module or a PID loop) will drive the feedback to equal the command.

If you are sending the position command to a PID loop, and getting the 
position from an encoder, the PID loop will drive the feedback to equal 
the command.  This is the standard servo setup.  In that case, when you 
hit the index pulse during homing, the encoder position jumps from 
whatever it was to zero.  EMC expects this, and it makes a matching jump 
in the command, which keeps the PID loop happy.

If you are sending the command to a stepgen and taking the feedback from 
that stepgen, the stepgen drives the feedback to equal the command.  EMC 
is happy, but it has no idea that you have an encoder and cannot use the 
encoder data for homing.  I suspect that is what you are doing right now.

If you are sending the command to a stepgen and taking the feedback from 
   an encoder, there is nothing to drive the feedback to equal the 
command.  If the scales are right and both encoder and stepgen start at 
zero, it will work "open loop" like all stepper systems, and you won't 
get a following error unless you lose steps.  When you home and the 
index pulse arrives, the feedback from the encoder will jump to zero. 
But the stepgen will not know about that jump.  You will wind up with a 
difference between the stepgen position and the encoder position, and 
you will get a following error.  Even worse, I suspect the machine will 
start chasing its tail each time you enable it, trying to make that 
difference go away.

I don't have time right now to dig deeper.  Do the encoder test I 
suggested above - look for index-enable going false and counts and 
position resetting to zero.  Then see if my theory fits.  Are you taking 
feedback from the encoder or the stepgen?

If my theory of the problem is correct, I know of one definite but 
inconvenient fix.  You can switch the stepgen from position mode to 
velocity mode, add a PID loop, and treat the system as a true servo 
system.  Then homing and everything else will work as designed. 
However, you will have to tune the PID loop yourself, rather than using 
stepgen's convenient built-in position loop.

There is probably second solution - a way to use HAL to allow you to 
home to an index while still using the stepgen position loop and no PID. 
  But figuring that out will take more time than I can spend right now. 
  I'll think about it and reply later (maybe tomorrow).

Regards,

John Kasunich

Re: [Emc-users] pyvcp on install from image

[Jeff Epler <jepler@un...>]

It looks like the extremely abbreviated way to run pyvcp shown in the
manual works for the "sim" version of emc but not for the realtime
version.

On a true realtime system, the shortest incantation seems to be
    halrun -I loadusr pyvcp -c mypanel tiny.xml
which will start the realtime system, load pyvcp, and then present you
with a 'halcmd' prompt so you can do things like 'halcmd show'.  When
you exit the halcmd, the panel will disappear.

I'll see that this is included in the documentation.

Thanks,
Jeff

[Emc-users] pyvcp on install from image

[Stuart Stevenson <stustev@gm...>]

Gentlemen,
   I am requesting help for a man in Nigeria. He is learning EMC2. The
pyvcp example from the documentaion 'pyvcp -c mypanel tiny.xml ' does
not work from the terminal on his laptop. On my controls the command
works. My installs are cvs not from the image. He downloaded the
Ubuntu/EMC2 image, burned it to CD and intalled from that.

This is the error he gets -

abode@...:~$ pyvcp -c mypanel tiny.xml
RTAPI: ERROR: could not open shared memory (errno=2)
HAL: ERROR: rtapi init failed
Error: Multiple components with the same name.

   He has created the tiny.xml file and it is in the same directory (I
think) that he issues the command. We went through it step by step
with him on his computer and me on mine so I am pretty sure he didn't
type something wrong. Mine worked his didn't.
   Is there an obvious problem?
thanks
Stuart

Re: [Emc-users] Lead screw

[John Thornton <jet1024@se...>]

A ballscrew is best.

John

On 18 Aug 2008 at 23:23, An Pham Duc wrote:

> 
> I am finding some lead screw for my mini CNC. Please tell me what kind
> of lead screw I should use Thank you

[Emc-users] Home + Index home positioning problem.

[Yahnis Chris <yahnis21@gm...>]

Hi All,

I experienced some homing problem on a home switch + encoder index
configuration.
The install was simple. After the initial timing issues and a subsequent
motherboard change the machine runs fine and quite stable, timing is good,
except emc does not reset the axis position at the index signal. After the
home switch release the .index-enable goes on. When the encoder index "Z"
signal is "on" instead of resetting the internal position counter to
HOME_OFFSET (0.0) value and move to HOME (0.0) the axis travels back at
rapid speed to the original axis "zero" position and the axis is "homed".
This "zero" position is exactly the same position, where emc was first
turned on. Homing is sequential XYZ all do the same way. Polarity and index
is properly connected at least I think so. Phase-Z is traceable on the
HALscope for encoder.n, axis.n, and parport.n.pin.

HAL config (only for X Index section)

net X-index encoder.0.index-enable axis.0.index-enable
newsig X-phaseZ             bit
linksp X-phaseZ <= parport.1.pin-08-in-not
linksp X-phaseZ => encoder.0.phase-Z
net Xhome parport.1.pin-13-in-not  axis.0.home-sw-in

Home switch is stable proximity switch and works fine.
Encoder is counting  the same way as stepgen so all pins should be correct.

The homing section of the ini:
HOME_USE_INDEX = YES
HOME_OFFSET = 0.0
HOME_SEARCH_VEL = -5.0
HOME_LATCH_VEL = 1.50000
#HOME_FINAL_VEL = 5.0
HOME_SEQUENCE = 0
HOME_IGNORE_LIMITS = NO

EMC2    2.2.2 and  2.2.5 versions were tested with same result on the 2.2.2
the HOME_FINAL_VEL was commented.


Any idea?

Regards,

Yahnis

[Emc-users] Lead screw

[An Pham Duc <ducanpham@gm...>]

I am finding some lead screw for my mini CNC. Please tell me what kind of
lead screw I should use
Thank you

Re: [Emc-users] Spindle load meter

[Kirk Wallace <kwallace@wa...>]

On Mon, 2008-08-18 at 20:37 -0700, Terry wrote:
> Hi all,
> 
>    I would like to put a spindle load meter on my VMC.The VFD has
> a 0-10V output for such a purpose.How would be the easiest(I am not a
> electronics expert)way to use this analog signal? Do I need a analog
> to digital converter? I added a speed meter to the right hand side of
> my Axis GUI so that part I know how to get done,but I assume that is
> the easy part.
>   If this is too involved I could just add an old school volt meter
> to the panel I just think that a matching speed and load meter would
> be cooler.
> 
> Thanks
> 
> Terry

I don't know if this helps, but just in case:

http://www.wallacecompany.com/machine_shop/EMC2/serial_adc/

One of my VFD's has Modbus, which could provide even more information. I
just haven't gotroundtoit.

-- 
Kirk Wallace (California, USA
http://www.wallacecompany.com/machine_shop/ 
Hardinge HNC/EMC CNC lathe,
Bridgeport mill conversion, doing XY now,
Zubal lathe conversion pending
Craftsman AA 109 restoration
Shizuoka ST-N/EMC CNC)

[Emc-users] Spindle load meter

[Terry <tjmm01@ca...>]

Hi all,

   I would like to put a spindle load meter on my VMC.The VFD has
a 0-10V output for such a purpose.How would be the easiest(I am not a
electronics expert)way to use this analog signal? Do I need a analog
to digital converter? I added a speed meter to the right hand side of
my Axis GUI so that part I know how to get done,but I assume that is
the easy part.
  If this is too involved I could just add an old school volt meter
to the panel I just think that a matching speed and load meter would
be cooler.

Thanks

Terry


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