Re: [CAD_CAM_EDM_DRO] Re: Limit Switches ???

I don't really see the use of limits switches unless you're using it to find
home. I have two on my lathe, one is right down the headstock end of the
machine and the other is on the X axis. On the X axis there is a tapered rod
inside that is connected to the cross-slide. If it move too far in or if it
moves too far out it cuts the power. On the Z however the switch is at the
headstock only.

Right, but now the limit on the headstock end is so far up towards the
headstock I can crash the carridge into the chuck while it's spinning. The
switch only prevents a non-toolposterised cross-slide from passing under it.
When it reaches the switch nothing much happens (It may be bust but it's
barely been used). With a toolpost on though the carridge will travel into
the headstock no trouble. What's seriously annoying though is that the X
axis [towards and away from you] does genuinely turn it's motor off before
the slide reaches it's extremes.

I mentioned this before. It's not annoying because it does what it does but
because it's so damm hard to undo what it does. If I accidently bump this
limit the entire lathe, but for the controller, turns off. Bear in mind that
there are no hand wheels to manually move the slide about. What this means
is that to start the lathe again I must remove the protective covers and
manually crank the pulley with my digits (Which always scares the crap out
of me when the machine's braker cluncks back on). Surely this machine hasn't
been designed to do this? It's meant for use by kids who aren't meant to
have their fingers in with the pulleys.

What's stranger is there is no limit at the other end. The Z axis will
readily bang into the tailstock and sit there making a stalling sound until
the machine is stopped. I'd quite happily just remove them, they do nothing
but get in the way at the moment. Maybe when I get a proper controller I
could use them for homing. Otherwise they're just an accesory I don't use.
I'd rather they'd put a coolant pump on it for me.

I'm thinking of taking to the hegna saw, making a centrifugal fan shape in
MDF and casting it for a DIY pump. To be honest, I am having sleepless
nights thinking about using that furnace. But I must face it some time.

Regards,
John

> Guys:
>
> I doubt that you really need excellent repeatability for limit switches,
> unless those switches are also being used to determine the home positon of
> the tool. A limit switch is set to trigger somewhere between a soft limit
> (essentially a count of the number of steps travelled from some "home"
> position) and between the hard limits of the machine. It's function is to

be

> benign while the carriage is within a "legal" envelope and to change state
> whenever the carriage moves out of that envelope towards the hard limit so
> the motor can be stopped before the carriage literally crashes into the

hard

> stop at the end of the travel.
>
> I'd stay away from automotive points since they might be difficult to

mount,

> are uninsulated from the chassis, and require a relatively strong force to
> open. I'd be more apt to use a microswitch (these are also cheap) in a
> normally closed circuit. Thus, if either the carriage opens the switch, or
> something causes a wire to break, you're protected.
>
> -- Jerry
>
>
> |-----Original Message-----
> |From: mart_wid [mailto:vwa1244302@...]
> |Sent: Thursday, May 30, 2002 2:12 PM
> |To: CAD_CAM_EDM_DRO@yahoogroups.com
> |Subject: [CAD_CAM_EDM_DRO] Re: Limit Switches ???
> |
> |
> |--- In CAD_CAM_EDM_DRO@y..., "reed_irion" <Reed_Irion@h...> wrote:
> |> Any suggestions on who and how much for some limit switches with
> |> decent repeatablity? Since my first XY table is mainly
> |experimental
> |> Im looking for some cheap.
> |>
> |> Any good website discussions on limit switches ?
> |>
> |> Thanks in advance for any suggestions.
> |>
> |> Reed
> |
> |Well I haven't tried this myself, but I can't see why Contact
> |Breakers (Points) from a car ignition system wouldn't work if
> |carefully setup. They're cheap, readily available, come in many
> |configurations and can be safely overun by 1 or 2 mm. They are also
> |designed to activate instantly (for consistant ignition timing) and
> |so should have good repeat.
> |
> |Hope this helps, Martin.
> |
> |
> |Addresses:
> |FAQ: http://www.ktmarketing.com/faq.html
> |FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> |
> |OFF Topic POSTS: General Machining
> |If you wish to post on unlimited OT subjects goto:
> |aol://5863:126/rec.crafts.metalworking or go thru Google.com to
> |reach it if you have trouble.
> |http://www.metalworking.com/news_servers.html
> |
> |http://groups.yahoo.com/group/jobshophomeshop I consider this as
> |a sister site to the CCED group, as many of the same members are
> |there, for OT subjects, that are not allowed on the CCED list.
> |
> |
> |
> |Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> |Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> |Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> |List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> |Moderator: jmelson@... timg@... [Moderator]
> |URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> |bill,
> |List Mom
> |List Owner
> |
> |
> |
> |Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
> |
> |
> |
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:

aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.

> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this as a

sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.

>
>
>
> Post messages: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>