Re: plasma cutting table

Hi Chris,
I was out of town over the holiday weekend so I'm a bit slow
responding.
As I stated at the beginning of my previos post, I am still
Designing/accumulating my table. This makes me less qualified than
you guys who are burning up the steel allready. Thats why I read this
list each night, to keep learning. My observation for the possible
need for dual racks came from the studying of sucessfull units such
as the torchmate. They offer their unit with a single rack, but also
recomend thair dual drive upgrade. I see one other user is driving a
13' gantry from one side so it must work out pretty good. Maybe
torchmate does it because they are sometimes adding a router for
light work. Supertech uses a dual drive with dual moters as you
suggest, but it seems to me that this just complicates the
electronics, trying to syncronise two moters on the x axis. I will
be using cog timing belts as you suggest, but I'm not sure Im ready
to concede to needing tall sides in order to position the rack up
side down for self cleaning. Im still working it out in my head, but,
I think if I run the sides of the gantry down beside the table, like
many commercial routers do, I can mount the rack low on the bottom of
my framework rail and have the shaft that goes between the pinion
gears run under the water tray.
Another objection My inexperienced mind has to the "T square" design
is that it adds to the "footprint" of the machine without adding
additional capacity. The longer your T top is, the more your linear
rail loses in travel. With dual racks, You can have a pretty thin
gantry, and more travel in less shop space.(and less linear rail cost)
If I'm thinking out in left field, I always appreciate you guys
bringing me back to center.
Thanks
Dale


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In CAD_CAM_EDM_DRO@y..., Chris L <datac@l...> wrote:

>
>
> aspaguy wrote: (snip)
>
>
> > I wouldn't drive a unit the size of yours from one side only as

if the lower end

> > of your "T square" lags behind you will get square cuts that are
> > paralellograms.
>
> If something is "lagging" in this regard on a non-contact machine,

Something was NOT built right !!!

>
> > I like Chris's suggestion of turning the rack
> > vertical to allow the swarf to fall away, but it won't allow

joining

> > the opposite pinion gears together with a shaft to feep them
> > syncronized unless you add a right angle gear box on each side of

the

> > shaft. Perhaps a better thought would be to mount the rack with

the

> > teeth horizontal, but pointing down, with the pinion gears under

them

> > so the swarf can still fall away, but you can join the pinions

easily.

>
> You could do your method of rack mounting very easily, but maybe

instead of the cross shaft, you'd be better off running two motors,
one on each side. This way you could drive your pinions with

> toothed belt and mount your motors up higher on each side. Running

a cross shaft will require you to put the rack high enough so the
shaft can cross along with the gantry. Keeping enough space for

> material under the gantry then almost makes the "sides" of the

machine stand up pretty high. Then you have to drop steel down into
this "hole" over the top of your sides with the rack, or put your

> steel in from the ends. Kind of like the old digital tool CNC

Routers.

>
> I don't know about others, but my stuff generally gets welded to

something else, so the accuracy is nothing critical compared to stuff
you'd do on a router or mill. Straight non welded edges just have

> to be straight... thats about it !
>
> I feel pretty strongly about designing right away with toothed belt

for any hobbiest "piecing" such a machine together. It is the only
way you can adjust the machine to run the most effectively with

> any kiddywumpas mix of components you end up with.
>
> Chris L