Re: Need help to decide what rack and pinion to use in a 6'x10' table

Jarrett, Im located in Monterrey, Mexico, but I have a address in
the States in Mcallen Texas, so I always try to order online and
pickup the stuff my self, Mcallen is a 2:30 drive from here, so is
not far away.
Regards,
Hector

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jarrett & Heidi Johnson
<hjjohnson@...> wrote:

>
> Hector, Make sure you use a strong spring. There
> is more force there than you'd think. For my
> system. I'm using a 640 oz-in stepper, it goes
> through a 10:1 gearhead and the out through a 2"
> pinion gear to my rack. This gear will put about
> 400 lb's of force to move my gantry. It will also
> put about 146lb's force, trying to push the gear
> out of the rack, so that's enough to need a fairly
> strong spring.. or a pretty long arm on your
> spring.. or both.
>
> Can I ask you where your located [city/state/town]
> I'll find you a couple suppliers for rack/pinion
> stuff nearby. [feel free to send it to me directly
> instead of on here if you wish.]
>
> Jarrett
>
>
> ----- Original Message -----
> From: "Hector" <hector_a_quintanilla@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Tuesday, April 25, 2006 5:12 PM
> Subject: [CAD_CAM_EDM_DRO] Re: Need help to decide
> what rack and pinion to use in a 6'x10' table
>
>
> > Hi Jarrett,
> > In some posts from cnczone ive seen some mods of
> > pre-laods, I think
> > a plain good selected spring will do the trick,
> > I seem different
> > ways of acomplishing this, some also recomended
> > by 'Al the Man' I
> > tend to go for the 20 PA but it seems I can get
> > it anywhere online.
> > 14.5PA is available from lots of source, ex.
> > mcmaster but 20PA not,
> > if you know where i can get it from, please send
> > the link...
> > Regards,
> > Hector
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jarrett
> > & Heidi Johnson
> > <hjjohnson@> wrote:
> >>
> >> Hector, just a side note. If your running rack
> >> and
> >> pinion. I'd recommend using some type of
> >> pre-load,
> >> to push the pinion into positive contact w/ the
> >> gear. I'm using rack and pinion [ well not
> >> using
> >> yet as its still getting built] but I'm going
> >> to
> >> use two gas shock's per each pinion/drive
> >> assembly. This will cover for any variation on
> >> the
> >> rack mounting, by allowing the pinon to 'float'
> >> in
> >> contact w/ the rack. There are forces that are
> >> trying to push the gear back out of the rack
> >> when
> >> its being used and they can be calculated and
> >> then
> >> you base your pre-load force on this number.
> >> I
> >> still think you should go w/ 20PA. It's been
> >> recommended to my by others who have 'been
> >> there
> >> done that'. Do some Rack/pinion searching on
> >> cnczone.com and watch for 'Al the Man' as he's
> >> one
> >> of those guy's who know's what he's talking
> >> about
> >> .. [and no.. thats not me :-). Mind you.. I
> >> did
> >> reply to your post on there..]
> >>
> >> Jarrett Johnson
> >>
> >> ----- Original Message -----
> >> From: "Hector" <hector_a_quintanilla@>
> >> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> >> Sent: Sunday, April 23, 2006 5:34 PM
> >> Subject: [CAD_CAM_EDM_DRO] Re: Need help to
> >> decide
> >> what rack and pinion to use in a 6'x10' table
> >>
> >>
> >> > Hi, folks, thanks for the replyes,
> >> > Ballendo,
> >> > I see you mention you are using steppers, in
> >> > my
> >> > case i want to use
> >> > servos.I dont realize if you have to take
> >> > different aspects into
> >> > account in the decision of what rack and
> >> > pinion
> >> > if your are using
> >> > seros or steppers. To make it clear does it
> >> > matter what kind of
> >> > motors are you using in the rack & pinion
> >> > decision?
> >> >
> >> > --- In CAD_CAM_EDM_DRO@yahoogroups.com,
> >> > "ballendo" <ballendo@>
> >> > wrote:
> >> >>
> >> >> Hello,
> >> >>
> >> >> Snips, inserts below...
> >> >>
> >> >> >In CCED, "Hector" <hector_a_quintanilla@>
> >> >> >wrote:
> >> >> >Hello,
> >> >> >Im confused on which combination of rack
> >> >> >and
> >> >> >pinion to use for a
> >> >> >6'x10' table.
> >> >> >1.- which presure angle (PA) to choose,
> >> >> >14.5
> >> >> >PA or 20 PA?
> >> >>
> >> >> I have long used and suggested--look in this
> >> >> group archive for my
> >> >> many previous posts-- 14.5 Pressure angle,
> >> >> as
> >> >> it will minimise
> >> >> backlash caused by changes in pinion to rack
> >> >> distance.
> >> >>
> >> >> Others have replied that the undercutting of
> >> >> teeth on small
> >> > pinions
> >> >> using this PA is not a good thing, and
> >> >> mention
> >> >> that certain
> >> > machines-
> >> >> -including Bystronic CNC laser cutters--use
> >> >> 20PA.
> >> >>
> >> >> I still prefer and suggest 14.5 PA. (But
> >> >> would
> >> >> use 20PA for
> >> >> a "lightly loaded" machine, where I might
> >> >> want
> >> >> to economise by
> >> > going
> >> >> with a smaller rack and DP.)
> >> >>
> >> >> >2.- after knowing what pressure angle will
> >> >> >be
> >> >> >used, the next step
> >> >> >is to decide the diametral pitch to use.
> >> >>
> >> >> The DP (Diametral Pitch, which is the number
> >> >> of
> >> >> teeth in a one
> >> > inch
> >> >> gear) affects cogging, strength, and cost. I
> >> >> use 16DP. Coarser
> >> > gears
> >> >> can carry more load, but also are more
> >> >> susceptible to backlash
> >> >> (especially is 20PA is used.) Smaller
> >> >> teeth--larger DP--will have
> >> >> less ability to endure shop swarf and dust,
> >> >> and
> >> >> a lower strength.
> >> >> They may even cost more. 16DP seems to be a
> >> >> good compromise for a
> >> >> 4'x8' or thereabouts size machine...
> >> >>
> >> >> >3.- In this step we already know the PA and
> >> >> >DP
> >> >> >we are going to
> >> > use,
> >> >> >now comes to decide how many teeth on the
> >> >> >pinion, so what governs
> >> >> >this decision?
> >> >>
> >> >> I nearly always use a 1" pinion. This gives
> >> >> about 3" of travel per
> >> >> rev, and is large enough to have reasonable
> >> >> undercutting of the
> >> >> teeth in my preferred 16DP.
> >> >>
> >> >> What governs this decision is your speed and
> >> >> resolution
> >> >> requirements. Larger pinion equals faster
> >> >> speed, but a lower
> >> >> resolution, all else being equal.
> >> >>
> >> >> I use a 4:1 reduction from motor to pinion,
> >> >> so
> >> >> in the old days<G>
> >> > of
> >> >> halfstepping, I would get 240IPM at only 300
> >> >> RPM at the stepper.
> >> >> This kept the drive cheap, and was plenty
> >> >> fast.
> >> >> The resolution was
> >> >> traded to get speed, as it was only about
> >> >> .002". (500SPI)
> >> >>
> >> >> Using modern drives and motors, you can
> >> >> easily
> >> >> exceed these
> >> > results.
> >> >>
> >> >> >I think is better if someone could really
> >> >> >make
> >> >> >clear this for me
> >> >> >and others, i guess other have the same
> >> >> >doubts.
> >> >>
> >> >> Hope I've donethat!<G>
> >> >>
> >> >> Ballendo
> >> >>
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > Addresses:
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> >
> >
> >
> >
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> > 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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