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 sp01jjo...@gmail.com 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 - 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 sp01jjo...@gmail.com 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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[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]

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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Re: [Emc-users] limit switches

[John Prentice]

Stuart, greetings

- Original Message - 
From: Stuart Stevenson stus...@gmail.com
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.
snip

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 el...@pico-systems.com 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

[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 stus...@gmail.com
 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.
 
 snip

 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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[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

[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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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

[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

[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

[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










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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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