Gene,
Your limit switch over run issue is quite easy to solve. Rather than have your
stops run into the switch, have the stops run across the switch. The typical
switches used in industry has a roller on the end and the stops designed with a
'V'. Thereby allow virtually unlimited ability to over run other than physical
limits.
Regards
Paul
On 31/03/2019 18:19, emc-users-requ...@lists.sourceforge.net wrote:
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Today's Topics:
1. Re: Home-limit switch measuring (Jon Elson)
2. Re: Home-limit switch measuring (Gene Heskett)
3. Re: Home-limit switch measuring (Gene Heskett)
4. Re: Home-limit switch measuring (jrmitchellj)
5. Re: Home-limit switch measuring (Chris Albertson)
----------------------------------------------------------------------
Message: 1
Date: Sun, 31 Mar 2019 12:07:50 -0500
From: Jon Elson <el...@pico-systems.com>
To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] Home-limit switch measuring
Message-ID: <5ca0f3e6.5010...@pico-systems.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 03/31/2019 08:59 AM, Gene Heskett wrote:
Greetings everybody;
I think I've got the coolant pump starting problem fixed. Ignore that
faint knocking sound.
Now I would like to use a teeny little pushbutton (6x6x2.5mm tall)
between two solid parts of this machine for home and potentially as
limit switches.
However the amount of available overtravel after the switch has clicked
is quite limited unless this switch is mounted on something crushable so
that the getting stopped overtravel does not crush the switch like a
Coors can.
Is there a way to determine how much overtravel vs approach speeds is
occuring?
Yes, use Halscope, and watch the limit switch and the axis
position, have the scope trigger on the switch. Then, set
it up to home at the desired velocity, and hold a metal rod
or something that will trip the switch but not hurt anything
when it overtravels. That should give you a trace of travel
vs time. Then, select the position trace and use the cursor
in the scope window and it shows you the actual numerical
reading at the bottom.
Jon
------------------------------
Message: 2
Date: Sun, 31 Mar 2019 13:14:58 -0400
From: Gene Heskett <ghesk...@shentel.net>
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Home-limit switch measuring
Message-ID: <201903311314.58424.ghesk...@shentel.net>
Content-Type: Text/Plain; charset="iso-8859-1"
On Sunday 31 March 2019 11:07:51 TJoseph Powderly wrote:
hi gene
maybe redesign to drive past the switch
like you can brush a wall mounted light switch by swiping your hand
over the wall surface
rather than punching it :-)
( try mounting so the direction of switch activation is 90 degress to
the joint motion )
tomp
I hadn't thought of that idea, mainly because that would put the
mechanism out in the breeze and subject to damage, or maybe snagging a
hose etc as it moves. Mounted so as to detect the touch of the two parts
as it comes to the end of travel is quite appetizing in addition to
being "in out of the weather" so to speak. Mounting a 90 degree angled
and flexible lever for z would either project forward or sideways, and
sideways would cost me x travel too. I'll have to go stand and stare at
it some more & see what I can imagine AND make. I've already done some
of that, and keep throwing it away for one reason or another. The best
idea seems to be to make a spring loaded button pusher with 1/4" of give
in the spring, but that sticks out. On both moving and stationary parts.
Sliding a ramp over the top of the button equals wear on the plastic
button. And complicated by the inability to get at it to drill & tap
screw holes without a huge teardown. So whatever is going to have to be
set in position and superglued to the epoxy paint on everything.
Imagination will be made to work overtime for sure. Changing switch
style to roller lever is looking like a possibility. Put a short tab of
sheet alu to stick out of the gap and hit the roller might work, and
that would put the switch body flat on the stationary part. They can
stand some overtravel by flexing the lever. I have enough of those for
homes, but not for limits too. And with no Radio Shacks left, China is
the nearest vendor. 6 weeks. Humm, for x home at left, peel my cable
back out of the gantry cable chain early. Y home never gets to the
gantry cable, only thru the new cambric coming down from the electronics
shelf. Like I said, stand and stare at it. And let my imagination out
without a chaperone...
Thanks TomP.
On Sun, Mar 31, 2019 at 9:03 PM Gene Heskett <ghesk...@shentel.net>
wrote:
Greetings everybody;
I think I've got the coolant pump starting problem fixed. Ignore
that faint knocking sound.
Now I would like to use a teeny little pushbutton (6x6x2.5mm tall)
between two solid parts of this machine for home and potentially as
limit switches.
However the amount of available overtravel after the switch has
clicked is quite limited unless this switch is mounted on something
crushable so that the getting stopped overtravel does not crush the
switch like a Coors can.
Is there a way to determine how much overtravel vs approach speeds
is occuring?
I ask because a wide open x or y move can do around 220 ipm on this
machine, and that stopping distance is not an ignoreable distance
when the switch only has maybe .010" of overtravel after its
clicked.
So I first would like to determine the maximum safe SEARCH_VEL I can
use for homeing, then from that, be able to set MAX and MIN LIMITS
far enough away from the crash stop to provide crash protection in
the space between the LIMIT set in the ini file, or how much crush
room I have to build into the switch mount?
Also, in attempting to minimize this stopping distance, what or how
can one detect a motor step slip if the ACCEL's are stopping the
motor faster than it can stop? Hopefully without pounding a $90 dial
into junk.
Thanks all;
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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Cheers, Gene Heskett
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