Re: Plasma cnc

I'm guessing your inaccuracy comes from the length of belts. The PnP
machines frequently run belts with better accuracy, however there
generally isn't more than 3 feet of belts (well between pullies).
The servos generally just have a pully on the shaft, but they are
beefy units. put your encoder on the highest RPM part for accuracy.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Chris Ramirez"
<Ironarbor@u...> wrote:

> les,
>
> Im converting my table to servos and was going to use 2 to 1 ratio

timing

> pulley. Do you have to worry about putting side load directly to

the output

> shaft of the motor or did you use some kind of bearing to help

support the

> shaft? How much tension would you guess it takes to keep the belt

tight?

>
> -----Original Message-----
> From: Les Newell [mailto:les@l...]
> Sent: Saturday, January 18, 2003 1:44 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Plasma cnc
>
>
> I used 30mm HTD toothed belt for my plasma. It stretched very

slightly over

> the first couple of months but seems to be pretty stable now. As

close as I

> can measure the error is within +/-0.5mm (20 thou) over the whole

travel of

> my 2.5m x 1.5m (8' x 5') machine. This is of course nowhere near as

accurate

> as ballscrews but plasma isn't exactly high precision anyway!
>
> the HTD belt appears to have very little give in it. If I push hard

on the

> gantry I can just see a small amount of deflection before I

overcome the

> steppers. I would have thought it would be good enough for light

routing,

> especially if you use two belts to move the gantry, one either side.
>
> I would be a little wary of chain, especially with all that

abrasive plasma

> dust hanging about. If my experience with motorcyles is anything to

go by,

> you would need to tension the chain on a regular basis. Also chain

is

> probably more expensive than toothed belts. You could buy all the

belts and

> pulleys for less than the cost of one ball nut!
>
> Les
>
>
> > Yeah, the Hypertherm Powermax 1250 is top of the line
> > for CNC plasma operations. It allready has the remote
> > torch on/off terminal installed for the G-Code to run
> > the torch. But at $3500 I say ouch. I am also drawing
> > up plans for a combo plasma/router cnc machine and am
> > looking at drive options. The ball screws for an
> > 5'X10' table run in the thousands of dollars. I was
> > wondering if anyone here has ever seen,used,heard of
> > chain and sprockets instead of screws? My parents have
> > a picture framing shop and they use a CNC mat cutter.
> > I was looking at the gantry rails to see what kind of
> > drive system was there and it's all small chain and
> > sprockets. a littls smaller than a bicycle chain would
> > be. seems like if the chain was tight enough there
> > would be no backlash. Since I want to use dual drive
> > on the long axis, I am going to need 20 feet of ball
> > screws, this is way out of budget at this point.
> > --- "Jens Swales <jipeess2000@y...>"
> > <jipeess2000@y...> wrote:
> > > hi
> > >
> > > i was recomended a plasma-rig from hypertherm, they
> > > dont produce
> > > those nasty ignition-sparks that knocks out the
> > > system
> > >
> > >
> > > js
> > >
> > >
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reach it if

> you have trouble.
> http://www.metalworking.com/news_servers.html
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> 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.

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