Re: [Emc-users] Limit switches for my lathe

[Gene Heskett]

On Monday 26 October 2020 11:27:20 Alan Condit wrote:

> Hi all,
>
> I am trying to wrap my head around limit switches for my Grizzly G4000
> lathe that I have converted to CNC.
>
> The X limit switches are not a major problem. They always goes to the
> same spot. I have the X+ switch mounted. Figuring out where to mount
> the X- switch so it doesn’t interfere with anything else is a little
> tricky.
>
>  I am having trouble figuring out the placement of the Z limit switch
> or switches. I can mount the Z+ limit switch on an adjustable mount on
> the ways down by the tailstock or even on the tailstock itself. But
> having a limit switch that is moveable seems problematic for
> configuration. The Z- limit switch could be attached to a moveable
> mount on the ways down by the head but it seems that it might be
> desirable to have the limit set to keep the cross-feed from running
> into whatever chuck is mounted. I have a 3” 4-jaw, a 4” 3-jaw, a 5”
> 3-jaw and a 5” 4-jaw. So I might need a different config for every
> chuck. What do you guys think.

I have the x switch on the front of the apron. with its roller reaching 
up so the crossfeed backs into it at the front, a long ways from center.

I found a bolt hole in the bed about a foot away from the chuck, and have 
another identical switch mounted there which gets dinged by the gib 
strip which is full length of the carriage H pattern so the switch also 
tells the homeing function which way to the switch. 

Just to make sure there is work clearance, I remove the tool from the 
QCTP before homing.  But if it hits, the steppers are now 3 phase 
stepper/servos, and Z will trip off before wrecking the tool.

The rest is just .ini file vars.

HTH, Alan
>
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Re: [Emc-users] Limit switches for my lathe

[andy pugh]

On Mon, 26 Oct 2020 at 15:29, Alan Condit  wrote:

>  I am having trouble figuring out the placement of the Z limit switch or 
> switches

I was troubled by the same issue, and did some bodgery to make the
resolvers return an absolute position, so that now I can home without
moving.

This might be an argument in favour of fitting linear scales.

Otherwise, it's probably best to home towards the tailstock and accept
that it's your job to move it to the end of the bed before pressing
the button.

You can (I think) move the soft limits using the ini.* HAL pins to
allow for different chucks.

-- 
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Re: [Emc-users] Limit switches for my lathe

[Sam Sokolik]

If it is a small enough lathe - I would just take the tail stock off to
home..  (that is what I do on the emco)

Have a cam style follower.   So it home somewhere halfway down the travel.
(so most of the time the tailstock is out of the way.  (if it is past the
trip point - it will home the other direction)  Then have a switch on the
tail stock that acts as an overtravel.

On Mon, Oct 26, 2020 at 10:29 AM Alan Condit  wrote:

> Hi all,
>
> I am trying to wrap my head around limit switches for my Grizzly G4000
> lathe that I have converted to CNC.
>
> The X limit switches are not a major problem. They always goes to the same
> spot. I have the X+ switch mounted. Figuring out where to mount the X-
> switch so it doesn’t interfere with anything else is a little tricky.
>
>  I am having trouble figuring out the placement of the Z limit switch or
> switches. I can mount the Z+ limit switch on an adjustable mount on the
> ways down by the tailstock or even on the tailstock itself. But having a
> limit switch that is moveable seems problematic for configuration. The Z-
> limit switch could be attached to a moveable mount on the ways down by the
> head but it seems that it might be desirable to have the limit set to keep
> the cross-feed from running into whatever chuck is mounted. I have a 3”
> 4-jaw, a 4” 3-jaw, a 5” 3-jaw and a 5” 4-jaw. So I might need a different
> config for every chuck. What do you guys think.
>
> Alan
>
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[Emc-users] Limit switches for my lathe

[Alan Condit]

Hi all,

I am trying to wrap my head around limit switches for my Grizzly G4000 lathe 
that I have converted to CNC. 

The X limit switches are not a major problem. They always goes to the same 
spot. I have the X+ switch mounted. Figuring out where to mount the X- switch 
so it doesn’t interfere with anything else is a little tricky.

 I am having trouble figuring out the placement of the Z limit switch or 
switches. I can mount the Z+ limit switch on an adjustable mount on the ways 
down by the tailstock or even on the tailstock itself. But having a limit 
switch that is moveable seems problematic for configuration. The Z- limit 
switch could be attached to a moveable mount on the ways down by the head but 
it seems that it might be desirable to have the limit set to keep the 
cross-feed from running into whatever chuck is mounted. I have a 3” 4-jaw, a 4” 
3-jaw, a 5” 3-jaw and a 5” 4-jaw. So I might need a different config for every 
chuck. What do you guys think.

Alan

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Re: [Emc-users] Limit Switches - 7i76

[John Thornton]

The reason you use NC limit switches it because if a wire breaks or 
falls off your limits go off and the machine goes into an estop 
contition. So it is actually a "major" item because any failure to get 
the signal back to the input results in estop whereas a failure of a NO 
limit circuit will never be seen by the system. Obviously on hobby 
machines driven by small steppers it is not as important as damage might 
be minimal after a crash.

JT

On 11/23/2014 8:06 PM, John Alexander Stewart wrote:
> It's no problem, just tie them as the plans say (+field voltage, IIRC) and
> set the correct "level" so that they trigger as expected.
>
> I understand that the NC switches are "better" as they will open if there's
> a wiring issue, but that's a minor item.
>
> On Sun, Nov 23, 2014 at 7:46 PM, Jeremy Jones  wrote:
>
>> I have a BP Boss knee mill. The switches are NO. How should I go about
>> wiring this to the 7i76? Would it be better to get NC switches? Appreciate
>> any help.
>>
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Re: [Emc-users] Limit Switches - 7i76

[John Alexander Stewart]

Whoops - by "correct level" I mean, either use the signal as given, or use
the signal as "-not" to use it inverted. My hal files are not nearby, so I
can't tell you which version I used on my NC switches.

If you use pncconf, you'll be able to set whether the signal is inverted or
not. If you get it wrong, LinuxCNC will give you an error on startup,
saying that the limit switch on axis [0-n] is set.

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Re: [Emc-users] Limit Switches - 7i76

[John Alexander Stewart]

It's no problem, just tie them as the plans say (+field voltage, IIRC) and
set the correct "level" so that they trigger as expected.

I understand that the NC switches are "better" as they will open if there's
a wiring issue, but that's a minor item.

On Sun, Nov 23, 2014 at 7:46 PM, Jeremy Jones  wrote:

> I have a BP Boss knee mill. The switches are NO. How should I go about
> wiring this to the 7i76? Would it be better to get NC switches? Appreciate
> any help.
>
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[Emc-users] Limit Switches - 7i76

[Jeremy Jones]

I have a BP Boss knee mill. The switches are NO. How should I go about
wiring this to the 7i76? Would it be better to get NC switches? Appreciate
any help.
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Re: [Emc-users] limit switches

[Dave]

That is the way my big lathe is setup also.  When it hits a limit it 
disconnects the servo drives from the motors, disables them 
electronically,  and shorts the phases of the motor together with a 
separate contactor to brake the motors ASAP.
In order to get off a limit I have to over-ride the hardware limit with 
a momentary pushbutton, re-enable the drives and then jog off the limit. 

The feed drives are about 4 kw.

Dave


John Prentice wrote:
> Stuart, greetings
>
> - Original Message - 
> From: "Stuart Stevenson" 
> Sent: Monday, September 21, 2009 4:31 PM
>
>
>   
>> Gentlemen,
>>   The Cinci was set up to use home switches. I am now using the limit
>> switches for homing. I did this to better match the homing cycle to other
>> machines in the shop.
>> 
> 
>
> Pardon me coming out of "lurk mode" to offer a comment.
>
> While seeing the advantage of direction sensitive disable to allow easy 
> jogging off the limits, personally I would want to treat limit switches on a 
> big machine like your 5 axis Cinci in the same way as E-stop - i.e. not rely 
> on software (or indeed perhaps silicon) to stop motion (ISO 13850:2006).
>
> Best wishes
>
> John Prentice
>
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Re: [Emc-users] limit switches

[Stuart Stevenson]

On Mon, Sep 21, 2009 at 11:59 AM, Jon Elson  wrote:

> Stuart Stevenson wrote:
> >During this I learned something. I have been trying to "fix" the servo
> > amps so when I hit a hard limit they just disable the direction the table
> > was moving when the limit switch was contacted. I found the servo amps
> are
> > working correct. It is EMC2 that is shutting the servos off when I hit
> the
> > limit switches.
> Are you using the individual amp enables?  I think if you use the E-stop
> relay to enable the
> amps, they will stay on after a limit switch is hit.  A limit switch
> normally does the same as hitting
> F2, which goes from "Machine On" to "Machine Off", but it doesn't cause
> an E-stop.
> >  I much prefer the servos to remain on. This is not a problem
> > on the X, Y or Z axes. The problem is the A and B axes. Given the weight
> of
> > the head and the reality that there are no brakes on the motors:
> >if the head is tilted enough to hit the limit
> > switch
> >and
> >the servos turn off
> >then
> >the weight of the head will cause the head to
> > coast (fall) until the pinion gear disengages from the rack.
> >This is not a huge problem and should be almost nonexistent. I will
> know
> > and do not feel comfortable with this as a possibility.
> >I have disengaged the limit feedback for each axis. I am just using
> one
> > limit hooked to the home feedback. This allows homing.
> >My question is this (and maybe I have just overlooked it in the
> manual).
> >   Is there a pin out of EMC2 that will disable
> the
> > motion in the direction of motion instead of shutting down all the
> servos?
> >
> Well, EMC by default doesn't produce separate amp enables for + and -
> direction.  it depends on
> additional limit switches to control those direction enable inputs on
> the amps.  But, of course,
> you could rig the regular limit inputs in HAL directly to digital
> outputs to drive the amp's
> limit inputs.  Given enough digitial outputs, that would be no biggie,
> and you shouldn't even
> need any hal component for it.  Just use the invert parameter of the
> output pin to select the
> desired polarity.  Of course, on a 5-axis machine, this will eat up 10
> more digital outputs.
>
> I hope this helps.
>
> Jon
>
>
>   Yes, I have individual amp enables.
  The current as configured (prior to homing) action is as follows:
   motion toward axis end of travel
   cam on slide hits the limit switch
   axis following error  (the limit switch disable motion in
that direction of travel but EMC2 does not stop it's motion output).
  The desired action would be for EMC2 to stop motion output in that
direction of travel also.
thanks
Stuart

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Re: [Emc-users] limit switches

[John Prentice]

Stuart, greetings

- Original Message - 
From: "Stuart Stevenson" 
Sent: Monday, September 21, 2009 4:31 PM


> 
> Gentlemen,
>   The Cinci was set up to use home switches. I am now using the limit
> switches for homing. I did this to better match the homing cycle to other
> machines in the shop.


Pardon me coming out of "lurk mode" to offer a comment.

While seeing the advantage of direction sensitive disable to allow easy jogging 
off the limits, personally I would want to treat limit switches on a big 
machine like your 5 axis Cinci in the same way as E-stop - i.e. not rely on 
software (or indeed perhaps silicon) to stop motion (ISO 13850:2006).

Best wishes

John Prentice

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Re: [Emc-users] limit switches

[Jon Elson]

Stuart Stevenson wrote:
>During this I learned something. I have been trying to "fix" the servo
> amps so when I hit a hard limit they just disable the direction the table
> was moving when the limit switch was contacted. I found the servo amps are
> working correct. It is EMC2 that is shutting the servos off when I hit the
> limit switches.
Are you using the individual amp enables?  I think if you use the E-stop 
relay to enable the
amps, they will stay on after a limit switch is hit.  A limit switch 
normally does the same as hitting
F2, which goes from "Machine On" to "Machine Off", but it doesn't cause 
an E-stop.
>  I much prefer the servos to remain on. This is not a problem
> on the X, Y or Z axes. The problem is the A and B axes. Given the weight of
> the head and the reality that there are no brakes on the motors:
>if the head is tilted enough to hit the limit
> switch
>and
>the servos turn off
>then
>the weight of the head will cause the head to
> coast (fall) until the pinion gear disengages from the rack.
>This is not a huge problem and should be almost nonexistent. I will know
> and do not feel comfortable with this as a possibility.
>I have disengaged the limit feedback for each axis. I am just using one
> limit hooked to the home feedback. This allows homing.
>My question is this (and maybe I have just overlooked it in the manual).
>   Is there a pin out of EMC2 that will disable the
> motion in the direction of motion instead of shutting down all the servos?
>   
Well, EMC by default doesn't produce separate amp enables for + and - 
direction.  it depends on
additional limit switches to control those direction enable inputs on 
the amps.  But, of course,
you could rig the regular limit inputs in HAL directly to digital 
outputs to drive the amp's
limit inputs.  Given enough digitial outputs, that would be no biggie, 
and you shouldn't even
need any hal component for it.  Just use the invert parameter of the 
output pin to select the
desired polarity.  Of course, on a 5-axis machine, this will eat up 10 
more digital outputs.

I hope this helps.

Jon


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[Emc-users] limit switches

[Stuart Stevenson]

Gentlemen,
   The Cinci was set up to use home switches. I am now using the limit
switches for homing. I did this to better match the homing cycle to other
machines in the shop.
   I have the soft limits set.
   During this I learned something. I have been trying to "fix" the servo
amps so when I hit a hard limit they just disable the direction the table
was moving when the limit switch was contacted. I found the servo amps are
working correct. It is EMC2 that is shutting the servos off when I hit the
limit switches. I much prefer the servos to remain on. This is not a problem
on the X, Y or Z axes. The problem is the A and B axes. Given the weight of
the head and the reality that there are no brakes on the motors:
   if the head is tilted enough to hit the limit
switch
   and
   the servos turn off
   then
   the weight of the head will cause the head to
coast (fall) until the pinion gear disengages from the rack.
   This is not a huge problem and should be almost nonexistent. I will know
and do not feel comfortable with this as a possibility.
   I have disengaged the limit feedback for each axis. I am just using one
limit hooked to the home feedback. This allows homing.
   My question is this (and maybe I have just overlooked it in the manual).
  Is there a pin out of EMC2 that will disable the
motion in the direction of motion instead of shutting down all the servos?
thanks
Stuart

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Re: [Emc-users] Limit switches

[Jon Elson]

John Stevenson wrote:
> New beginner here just getting my head round the capabilities of EMC2
> and would like to ask a few question on the operation.
>
> Just taking the limit switches on one axis, say X for arguments sake,
> we have two switched wired in series, done this way so as to only use
> 3 inputs per machine.
> If the table is traveling towards X+ switch and hits it - what ?
>
> [a] What does the screen / command line say.?
> [b] Will it deny you the opportunity to jog further onto the limit
> switch ?
>   
It says roughly "+/- limit exceeded on axis 0".  With only one input for 
both limits, it can't allow you to move one way and not the other.
If you had 2 inputs so it could tell + limit from - limit, it could 
allow you to only move the right way.  You have to hit a limit override 
button to allow you to back off the limit switch.

Jon

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Re: [Emc-users] Limit switches

[Kirk Wallace]

On Thu, 2009-04-02 at 13:20 +0100, John Stevenson wrote:
> New beginner here just getting my head round the capabilities of EMC2
> and would like to ask a few question on the operation.
> 
> Just taking the limit switches on one axis, say X for arguments sake,
> we have two switched wired in series, done this way so as to only use
> 3 inputs per machine.
> If the table is traveling towards X+ switch and hits it - what ?

EMC2 will stop all movement and indicate an axis limit error.
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Homing_And_Limit_Switch


> [a] What does the screen / command line say.?

I don't recall off hand, I am not at an EMC2 machine right now, but I
can check.

> [b] Will it deny you the opportunity to jog further onto the limit
> switch ?

There is a check box in AXIS that can over-ride the limit error in order
to get the axis off of the switch.

> John S.
> Regards,
> 
> John Stevenson
> L Stevenson [ Engineers ]

I personally, would try to install the inputs needed for a full
complement of limit and home switches. You can use cheap PCI dual
parallel port cards:
http://www.newegg.com/Product/Product.aspx?Item=N82E16815166007
(for other applications, one caveat is this card may not be compatible
with Pluto cards)

that will give you more than enough I/O. In my opinion, this will make
the machine much easier to use. Also consider using two "switches" for
the homes, one on the slide and another on the screw (or configure as
index on encoder setups). This will allow a much more accurate home, so
that you can conveniently reuse setups between power downs.

If you could post a description and pictures of your setup, this would
help draw more opinions (if that is what you want ;).

Kirk
http://www.wallacecompany.com/machine_shop/



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[Emc-users] Limit switches

[John Stevenson]

New beginner here just getting my head round the capabilities of EMC2
and would like to ask a few question on the operation.

Just taking the limit switches on one axis, say X for arguments sake,
we have two switched wired in series, done this way so as to only use
3 inputs per machine.
If the table is traveling towards X+ switch and hits it - what ?

[a] What does the screen / command line say.?
[b] Will it deny you the opportunity to jog further onto the limit
switch ?

John S.
Regards,

John Stevenson
L Stevenson [ Engineers ]

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Re: [Emc-users] Limit Switches

[Jon Elson]

Kenneth Lerman wrote:
> 
> Is that true? Since you always approach the home position in the same 
> direction, the width of the slot shouldn't matter at all. You should 
> just be looking at the leading edge.
Yes, that is exactly right.

Jon

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Re: [Emc-users] Limit Switches

[Leslie Newell]

I do this on my lathe. I use a LED/sensor out of an old ball mouse with 
a semicircular flag on the motor that is about 1.5" diameter. The output 
of the sensor is open collector(switches to ground). This is in parallel 
with the home switch. The home switch is normally closed.

Homing proceeds as follows:
While the axis approaches home, the home switch holds the input low.
When the axis is nearly at home the home switch releases but the flag is 
phased so that the sensor holds the input low.
Finally the edge of the flag interrupts the beam so the input goes high.

If I home slowly, I get repeatability within +/- 1 encoder count (this 
is a servo machine but the encoder does not have an index).

Les

Kirk Wallace wrote:
> I have thought about this, but I wonder how accurate these are. If you
> want to resolve .0002", I think you typically need angular accuracy
> to .16 degrees. I guess I could try it to find out.
>   


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Re: [Emc-users] Limit Switches

[John Kasunich]

Kenneth Lerman wrote:
> Well, for the same cost, you can use the material differently and 
> instead of having a half circle, have two quarter circles and get twice 
> the resolution. Or, you could have four 1/8 circles ...
> 
> :-)
> 

As soon as you do that, you lose the index pulse.

Regards,

John Kasunich

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Re: [Emc-users] Limit Switches

[Kenneth Lerman]

Well, for the same cost, you can use the material differently and 
instead of having a half circle, have two quarter circles and get twice 
the resolution. Or, you could have four 1/8 circles ...

:-)

Ken

John Kasunich wrote:
> Kenneth Lerman wrote:
>> Jon Elson wrote:
>>> Kirk Wallace wrote:
 On Mon, 2008-07-28 at 00:33 -0500, Jon Elson wrote:
 ... snip

> you might be 
> able to cobble up a substitute by making a disc with a narrow 
> slot and one of those U-shaped optical sensors from a floppy drive.
 I have thought about this, but I wonder how accurate these are. If you
 want to resolve .0002", I think you typically need angular accuracy
 to .16 degrees. I guess I could try it to find out.

>>> I came up with .36 degrees.  A good-sized disc with a 
>>> narrow-enough slot should work.  Basically, you are making a 
>>> 1000 line resolution encoder, but with only one line.
>> Is that true? Since you always approach the home position in the same 
>> direction, the width of the slot shouldn't matter at all. You should 
>> just be looking at the leading edge.
>>
>> Ken
>>
> 
> Exactly - which leads to another interesting possibility.  If you make a 
> disk that is as close as possible to 180 degrees "on" and 180 degrees 
> "off", you can mount two sensors at 90 degrees to each other.  The 
> result is a quadrature signal, with four counts per rev.  Since each 
> sensor still has only one rising edge per rotation, either sensor can be 
> used as the index.  (You would only need two hardware inputs, one of 
> which would be split in HAL to drive both phase A and the index of the 
> encoder, the other would drive phase B).
> 
> This would be a great candidate for a cheap lathe threading encoder. 
> The CVS version of EMC2 can use a single pulse per rev encoder for 
> threading, but this simple 4 count quadrature encoder would provide 
> about 16x better performance during load induced speed changes, for very 
> little extra cost.
> 
> Regards,
> 
> John Kasunich
> 
> 
> 
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Mark Kenny Products Company, LLC
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Re: [Emc-users] Limit Switches

[John Kasunich]

Kenneth Lerman wrote:
> 
> Jon Elson wrote:
>> Kirk Wallace wrote:
>>> On Mon, 2008-07-28 at 00:33 -0500, Jon Elson wrote:
>>> ... snip
>>>
 you might be 
 able to cobble up a substitute by making a disc with a narrow 
 slot and one of those U-shaped optical sensors from a floppy drive.
>>> I have thought about this, but I wonder how accurate these are. If you
>>> want to resolve .0002", I think you typically need angular accuracy
>>> to .16 degrees. I guess I could try it to find out.
>>>
>> I came up with .36 degrees.  A good-sized disc with a 
>> narrow-enough slot should work.  Basically, you are making a 
>> 1000 line resolution encoder, but with only one line.
> 
> Is that true? Since you always approach the home position in the same 
> direction, the width of the slot shouldn't matter at all. You should 
> just be looking at the leading edge.
> 
> Ken
> 

Exactly - which leads to another interesting possibility.  If you make a 
disk that is as close as possible to 180 degrees "on" and 180 degrees 
"off", you can mount two sensors at 90 degrees to each other.  The 
result is a quadrature signal, with four counts per rev.  Since each 
sensor still has only one rising edge per rotation, either sensor can be 
used as the index.  (You would only need two hardware inputs, one of 
which would be split in HAL to drive both phase A and the index of the 
encoder, the other would drive phase B).

This would be a great candidate for a cheap lathe threading encoder. 
The CVS version of EMC2 can use a single pulse per rev encoder for 
threading, but this simple 4 count quadrature encoder would provide 
about 16x better performance during load induced speed changes, for very 
little extra cost.

Regards,

John Kasunich



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Re: [Emc-users] Limit Switches

[Kenneth Lerman]

Jon Elson wrote:
> Kirk Wallace wrote:
>> On Mon, 2008-07-28 at 00:33 -0500, Jon Elson wrote:
>> ... snip
>>
>>> you might be 
>>> able to cobble up a substitute by making a disc with a narrow 
>>> slot and one of those U-shaped optical sensors from a floppy drive.
>>
>> I have thought about this, but I wonder how accurate these are. If you
>> want to resolve .0002", I think you typically need angular accuracy
>> to .16 degrees. I guess I could try it to find out.
>>
> I came up with .36 degrees.  A good-sized disc with a 
> narrow-enough slot should work.  Basically, you are making a 
> 1000 line resolution encoder, but with only one line.

Is that true? Since you always approach the home position in the same 
direction, the width of the slot shouldn't matter at all. You should 
just be looking at the leading edge.

Ken

> 
> Jon
> 
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Re: [Emc-users] Limit Switches

[Kirk Wallace]

On Mon, 2008-07-28 at 11:26 -0500, Jon Elson wrote:
> Kirk Wallace wrote:
> > On Mon, 2008-07-28 at 00:33 -0500, Jon Elson wrote:
> > ... snip
> > 
> >>you might be 
> >>able to cobble up a substitute by making a disc with a narrow 
> >>slot and one of those U-shaped optical sensors from a floppy drive.
> > 
> > 
> > I have thought about this, but I wonder how accurate these are. If you
> > want to resolve .0002", I think you typically need angular accuracy
> > to .16 degrees. I guess I could try it to find out.
> > 
> I came up with .36 degrees.  A good-sized disc with a 
> narrow-enough slot should work.  Basically, you are making a 
> 1000 line resolution encoder, but with only one line.
> 
> Jon

Oops. I meant half of .36 which is .18, but really, the more I think
about it, the important bit is how consistent sensing one edge is.

-- 
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)


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Re: [Emc-users] Limit Switches

[Jon Elson]

Kirk Wallace wrote:
> On Mon, 2008-07-28 at 00:33 -0500, Jon Elson wrote:
> ... snip
> 
>>you might be 
>>able to cobble up a substitute by making a disc with a narrow 
>>slot and one of those U-shaped optical sensors from a floppy drive.
> 
> 
> I have thought about this, but I wonder how accurate these are. If you
> want to resolve .0002", I think you typically need angular accuracy
> to .16 degrees. I guess I could try it to find out.
> 
I came up with .36 degrees.  A good-sized disc with a 
narrow-enough slot should work.  Basically, you are making a 
1000 line resolution encoder, but with only one line.

Jon

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Re: [Emc-users] Limit Switches

[Kirk Wallace]

On Mon, 2008-07-28 at 00:33 -0500, Jon Elson wrote:
... snip
> you might be 
> able to cobble up a substitute by making a disc with a narrow 
> slot and one of those U-shaped optical sensors from a floppy drive.

I have thought about this, but I wonder how accurate these are. If you
want to resolve .0002", I think you typically need angular accuracy
to .16 degrees. I guess I could try it to find out.

> I have used encoders with index pulses, and the machine will 
> home to far greater repeatability than I can produce with an 
> edge finder.  Presumably, it is homing to a precisely repeatable 
> encoder count, which on my Bridgeport is .5"  (50 u-inch).
> I can barely attempt to measure that with a Federal Maxxum 
> electronic indicator, but the various flexes and stictions in 
> the machone's ways produce more un-repeatability than that.

My Hall home sensors and encoder index (like Jons, I think) work very
well.

> So, presumably, I could re-index to a fixture on the machine the 
> next day, but I never trusted it enough to do it without at 
> least checking with an edge finder or coax indicator.
> 
> Jon

On my Shizuoka mill with steppers, I have a piece of tape on the ways
that I align, then very slowly jog to zero the dials and click Home. My
steps are .0005" each, so my home will be anywhere within .0005", which
is okay for most of my work. But it's kind of a bother, considering EMC
could home automatically with a click, if I had an encoder index.

-- 
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)


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Re: [Emc-users] Limit Switches

[Kirk Wallace]

On Sun, 2008-07-27 at 23:23 -0400, John Kasunich wrote:
> Len Shelton wrote:
... snip
> EMC has been able to do this just about forever - in fact you don't even
> need limit switches, all you need is a home switch.
> 
> It's called "soft limits".

Dooh, I don't know why I don't catch on to this. Soft limits got in the
way during my initial setups and I guess I got into the habit of not
having them. Homing is covered well. It might be helpful to have
something in the wiki covering limit behavior. I know it should sound
like I am volunteering, but I would not be qualified, until I get my
soft limits set up and get some experience.

-- 
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)


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Re: [Emc-users] Limit Switches

[Kirk Wallace]

On Sun, 2008-07-27 at 22:09 -0500, Len Shelton wrote:
> >> You are try to save pressing the "Override Limits" button?
> 
> I don't even want an audible alert.

The audible bit was for Emory.

>  I want it to pause and wait for the
> direction to change. Then it could indicate on the screen that for instance,
> ax X+ limit occurred, but then continue moving once the direction has
> changed.
> 
> BTW - Thank you for the step conf wizard! Everyone I've talked to loves it!

Jeff Epler (correct me if I am wrong), take a bow.

> EMC2 is on the verge of becoming widely acceptable. I wish I had time to
> help you program. 
> 
> Thanks.
> 
> >Len



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Re: [Emc-users] Limit Switches

[Jon Elson]

Len Shelton wrote:
> Anyone care to describe their experiences on the accuracy of their home
> switches, and the type, and relate that to the jigs they were using?
For best repeatability, you want to use the index pulse from an 
optical encoder to refine the home position.  Some people claim 
to get .0002" repeatability just from a mechanical switch, but a 
speck of swarf on the switch actuator will mess that up.  If you 
are not using servos with an index channel, then you might be 
able to cobble up a substitute by making a disc with a narrow 
slot and one of those U-shaped optical sensors from a floppy drive.

I have used encoders with index pulses, and the machine will 
home to far greater repeatability than I can produce with an 
edge finder.  Presumably, it is homing to a precisely repeatable 
encoder count, which on my Bridgeport is .5"  (50 u-inch).
I can barely attempt to measure that with a Federal Maxxum 
electronic indicator, but the various flexes and stictions in 
the machone's ways produce more un-repeatability than that.

So, presumably, I could re-index to a fixture on the machine the 
next day, but I never trusted it enough to do it without at 
least checking with an edge finder or coax indicator.

Jon

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Re: [Emc-users] Limit Switches

[Jon Elson]

Len Shelton wrote:
> I use a small desktop CNC router and axis.
> 
>  
> 
> Limit switches would be helpful in jog mode if they didn't pause EMC2 
> completely, but rather just stopped you from moving in that one 
> direction - with maybe an on-screen notification that you had reached 
> the maximum travel.
> 
>  
> 
> I would like to retain homing capabilities.
Use a home switch, and then program in the machine limits to 
prevent you exceeding the machine's travel.  You enter the + and 
- travel from the home position in the ini file, and EMC will 
stop jogging at that point.  If you program a move past the 
limit, the program won't even start to run, you'll get a message 
machine limit in (*) axis exceeded in line (x).

Jon

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Re: [Emc-users] Limit Switches

[Terry]

Len

I am going to assume that you have a stepper machine or you
would use the index pulse on the motor.
I have a Bridgeport with stepers and limit switches and
the method of "hitting" the limit switch is important.
Mine has a ramp with about a 30 deg angle that contacts
the switch.This with a fairly slow 5ipm movement to home
gets me about +/-.005 from day to day.If I need more consistancy I
dont shut off the computer I just kill the power to the drives.
I also put a milled circular pocket on a fixture at a known location
and MDI to that location and sweep it in.It wont take long when
you get close.

Terry
  

On Sun Jul 27 23:10 , 'Len Shelton' [EMAIL PROTECTED]> sent:

>Anyone care to describe their experiences on the accuracy of their home
>switches, and the type, and relate that to the jigs they were using?
>
>>Len
>
>
>
>
>-Original Message-
>From: [EMAIL PROTECTED]
>[EMAIL PROTECTED]','','','')">[EMAIL PROTECTED]
On Behalf Of Len Shelton
>Sent: Sunday, July 27, 2008 11:01 PM
>To: 'Enhanced Machine Controller (EMC)'
>Subject: Re: [Emc-users] Limit Switches
>
>>> EMC has been able to do this just about forever
>
>Thank you, John. I have witnessed this on my EMC2 powered pick n place, but
>somehow didn't connect it to my router.
>
>>Len
>
>
>
>
>-
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>
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Re: [Emc-users] Limit Switches

[Len Shelton]

Anyone care to describe their experiences on the accuracy of their home
switches, and the type, and relate that to the jigs they were using?

>Len




-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Len Shelton
Sent: Sunday, July 27, 2008 11:01 PM
To: 'Enhanced Machine Controller (EMC)'
Subject: Re: [Emc-users] Limit Switches

>> EMC has been able to do this just about forever

Thank you, John. I have witnessed this on my EMC2 powered pick n place, but
somehow didn't connect it to my router.

>Len




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Re: [Emc-users] Limit Switches

[Len Shelton]

>> EMC has been able to do this just about forever

Thank you, John. I have witnessed this on my EMC2 powered pick n place, but
somehow didn't connect it to my router.

>Len




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Re: [Emc-users] Limit Switches

[John Kasunich]

Len Shelton wrote:
> I use a small desktop CNC router and axis.
> 
>  
> 
> Limit switches would be helpful in jog mode if they didn't pause EMC2
> completely, but rather just stopped you from moving in that one direction -
> with maybe an on-screen notification that you had reached the maximum
> travel. 
> 
>  
> 
> I would like to retain homing capabilities.
> 
>  
> 
> Anyone have any idea how to pull this off?
> 

EMC has been able to do this just about forever - in fact you don't even
need limit switches, all you need is a home switch.

It's called "soft limits".

If your machine has hard limits (either switches or hard stops) at say
-0.100 and +12.000 inches from the home switch, you should set your soft
limits in the ini file at something like -0.090 and +11.090.  Then, once
you are homed, EMC will NOT ALLOW you to run past those limits.

Of course, before you home, you can run into the hard limits - that is
why you should train yourself to home all axes as the very first step
after turning the machine on.

If you _don't_ have a home switch, then of course this approach won't
work.  If you have limit switches but no home switch, then home to a
limit (EMC can do that).  If you don't have _any_ switches, then you are
out of luck - but that's not what the original question was about.

Regards,

John Kasunich




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Re: [Emc-users] Limit Switches

[Len Shelton]

>> You are try to save pressing the "Override Limits" button?

I don't even want an audible alert. I want it to pause and wait for the
direction to change. Then it could indicate on the screen that for instance,
ax X+ limit occurred, but then continue moving once the direction has
changed.

BTW - Thank you for the step conf wizard! Everyone I've talked to loves it!
EMC2 is on the verge of becoming widely acceptable. I wish I had time to
help you program. 

Thanks.

>Len

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Kirk Wallace
Sent: Sunday, July 27, 2008 9:20 PM
To: Enhanced Machine Controller (EMC)
Subject: Re: [Emc-users] Limit Switches

I vaguely recall, that an option to have the axis just stop and not turn
off motion was added recently. I can't seem to find anything to that
effect though. You are try to save pressing the "Override Limits"
button?

OR'ing all axis.N.neg-lim-sw-in and axis.N.pos-lim-sw-in to a parallel
port pin connected to a sonalert might work for an audible alarm.
~
On Sun, 2008-07-27 at 20:45 -0500, Emory Smith wrote:
> Hate to be a "me-too-er" but I'll be watching this thread. 
> What I'd like would be to assert a pin om the parport for a Sonalert.
> 
> On Sun, Jul 27, 2008 at 8:05 PM, Len Shelton <[EMAIL PROTECTED]> wrote:
> I use a small desktop CNC router and axis.
> Limit switches would be helpful in jog mode if they didn't
> pause EMC2 completely, but rather just stopped you from moving
> in that one direction - with maybe an on-screen notification
> that you had reached the maximum travel. 
> I would like to retain homing capabilities.
> Anyone have any idea how to pull this off?
> >Len
~
-- 
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)


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Re: [Emc-users] Limit Switches

[Kirk Wallace]

I vaguely recall, that an option to have the axis just stop and not turn
off motion was added recently. I can't seem to find anything to that
effect though. You are try to save pressing the "Override Limits"
button?

OR'ing all axis.N.neg-lim-sw-in and axis.N.pos-lim-sw-in to a parallel
port pin connected to a sonalert might work for an audible alarm.
~
On Sun, 2008-07-27 at 20:45 -0500, Emory Smith wrote:
> Hate to be a "me-too-er" but I'll be watching this thread. 
> What I'd like would be to assert a pin om the parport for a Sonalert.
> 
> On Sun, Jul 27, 2008 at 8:05 PM, Len Shelton <[EMAIL PROTECTED]> wrote:
> I use a small desktop CNC router and axis.
> Limit switches would be helpful in jog mode if they didn't
> pause EMC2 completely, but rather just stopped you from moving
> in that one direction - with maybe an on-screen notification
> that you had reached the maximum travel. 
> I would like to retain homing capabilities.
> Anyone have any idea how to pull this off?
> >Len
~
-- 
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)


-
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
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Re: [Emc-users] Limit Switches

[Emory Smith]

Hate to be a "me-too-er" but I'll be watching this thread.
What I'd like would be to assert a pin om the parport for a Sonalert.

On Sun, Jul 27, 2008 at 8:05 PM, Len Shelton <[EMAIL PROTECTED]> wrote:

>  I use a small desktop CNC router and axis.
>
>
>
> Limit switches would be helpful in jog mode if they didn't pause EMC2
> completely, but rather just stopped you from moving in that one direction -
> with maybe an on-screen notification that you had reached the maximum
> travel.
>
>
>
> I would like to retain homing capabilities.
>
>
>
> Anyone have any idea how to pull this off?
>
>
>
> >Len
>
>
>
>
>
>
>
>
>
>
> -
> This SF.Net email is sponsored by the Moblin Your Move Developer's
> challenge
> Build the coolest Linux based applications with Moblin SDK & win great
> prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>
>


-- 
Emory
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[Emc-users] Limit Switches

[Len Shelton]

I use a small desktop CNC router and axis.

 

Limit switches would be helpful in jog mode if they didn't pause EMC2
completely, but rather just stopped you from moving in that one direction -
with maybe an on-screen notification that you had reached the maximum
travel. 

 

I would like to retain homing capabilities.

 

Anyone have any idea how to pull this off?

 

>Len

 

 

 

 

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Build the coolest Linux based applications with Moblin SDK & win great prizes
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