Re: [CAD_CAM_EDM_DRO] Handwheels on a retrofit? Why!? was Re: software questions DRO

The most important reason to not use a CNC machine manually is a safety issue. A mill with ballscrews is unlike a mill with acme threads in that: when force is applied to the table it will "feed" the ballscrew. Acme threads have an inherent binding effect. Think of a scissor jack. Try it, unhook one of your drive motors and push on the table. Now turn the handwheel in the direction you are pushing it will keep spinning. Push hard enough and it will gain speed. So, if you are manual milling with ballscrews and a large rougher and it grabs the work piece. The table will not hold position on its own resulting in a very dangerous scenario. It's best to operate as outlined below.

Ron



ballendo <ballendo@...> wrote:
Kim,

I completely agree...

I just posted this on the turbocnc list; seems appropriate to this
thread:

Hello,

How about these reasons:

1)"Jogging" is just power feed on all axes. Work all day without your
hand/arm getting tired, and feed more evenly than most can turn a
wheel... AND "GO" faster than you can turn the handle.

2)Using incremental jog values you can easily stop on a dime... or
a "tenth" if you will EVERY TIME... Need to drill a series of
holes? set the distance as a jog increment, and a single keypress
replaces precision turning of the handwheel...(especially valuable
when the distance is something like .3794;or do you wanna do that
addition in yer head?) of course with the CNC powered up, you have
DROS, so you can reset zero instead... When you get where you're
going, another keypress (Z minus) drills the hole...

3)With some controls, you can save each jog move to a file, so
whatever you've done can be repeated...

Hope this helps,

Ballendo

P.S. These things are why I don't understand the desire to keep
handwheels in place on a CNC retrofit... This type of 3 axis,
distance precise, powerfeed is what most MANUAL machinists WISH FOR!!!

I hear people saying, "I'll keep the handwheels for those jobs where
it's just not "worth" turning the computer on." Just what type of
part is that?!? In windows, maybe;with its long boot time. But in
DOS, I'll betcha I have the part more accurately made faster than a
person turning the wheels... The second argument is "feel", but one
learns quickly to replace this feel with other senses; much like a
blind person relies on senses other than sight. I can smell, hear,
see, and yes, even FEEL(place my free hand on the ways, and feel
vibration, etc.), what the machine is doing...

--- In turbocnc@yahoogroups.com, " T . Ackland" wrote:
> I was of the impression that the jog is just used to touch the work
> piece with the cutter and then Zero'd or whatever figure you want
> to entered through the jog screen.
> I cannot see the advantage of machining with the jog over turning a
> handle?






--- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux wrote:
>
> We just put electronic handwheels on our CNC equipment. By
electronic,
> I mean that the feedwheel is attached to an encoder and the signal
from
> the encoder is fed to the CNC software, TurboCNC in this case.
>
> I think this is much more practical and powerful than retaining the
> mechanical handwheels. For example, one can operate in MDI mode,
using
> the electronic feedwheels to position the tool and then issue a
manual
> feed like drilling (G78) or straight feed (G77). With mechanical
> handwheels, one would be stuck drilling or feeding manually. With
> TurboCNC, one has feedrate override as well. The time this saves
when
> drilling and milling is incredible, to say nothing of being able to
> manually position and then do some arcs ie G02 and G03.
>
> Kim
>
>
> On Mon, 2003-09-29 at 10:56, Jon Elson wrote:
> > vlocci wrote:
> >
> > >I'm just getting started on a conversion and have a few
software
> > >questions that I haven't found answered in the archives. I'm
inclined
> > >to keep the handwheels on my mill, since I plan on the
occasional job
> > >done by hand.
> > >
> > >1) Assuming I use servo's with encoders, can I use the encoders
as a
> > >source for positiong info that can be displayed within a
software
> > >package as a DRO? Which software packages allow this? Is EMC
my
> > >only choice?
> > >
> > >
> > I think Mach 1 and 2 may support this.
> >
> > >2) Is the above possible with steppers instead of servo's? Can
it be
> > >done without encoders? Which software allows this?
> > >
> > >
> > How can you measure position without encoders?
> >
> > >I realize I'm limited by the accuracy of the axis ACME threads,
I.e.
> > >backlash induced errors (a ballscrew conversion is in the
future, but
> > >I want to get things running first)
> > >
> > >Realize that I dont necessarily need CNC capabilities and the
option
> > >of manual DRO read out at the same time. (real time jumping back
and
> > >forth) I'm only after the ability to either cnc a part
automatically
> > >(hands off), or elect to manually do things with a computer
driven
> > >DRO arrangement. Can this be done?
> > >
> > >
> > Yes.
> >
> > >If it matters, I'm considering Gecko drives (either servo or
stepper)
> > >but am open to a change if it offers me DRO capability.
> > >
> > >
> > You don't say what size machine you are planning on converting.
But,
> > for the
> > larger machines, it may be cheaper to go with servos, if you plan
on
> > using encoders
> > for DRO readout anyway. Also, sevo motors won't drag as much
when you
> > move the machine manually.
> >
> > Jon
> >
> >
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
> > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> > Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
> >
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> > List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com,
wanliker@a..., timg@k...
> > Moderator: pentam@c... indigo_red@q... [Moderators]
> > URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> >
> > 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
to be 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.
> >
> > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO
EXCEPTIONS........
> > bill
> > List Mom
> > List Owner
> >
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> --
> Kim Lux


Addresses:
FAQ: http://www.ktmarketing.com/faq.html
FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com

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Moderator: pentam@... indigo_red@... [Moderators]
URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO

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 to be 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.

NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
bill
List Mom
List Owner



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