Re: plasma bridge

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ironarbor" <ironarbor@h...>
wrote:

> Has anyone built a plasma table driving a 5ft bridge or gantry from
> just one side? if so have you had any problems with it?
>
> Is there a formula to caculate how much force there will be on the
> side of the bridge that follows when it changes direction at max
> speed?
> I know my bridge ways about 40#s as it is curently designed, that I
> will be looking at speeds up to 400ipm in that axis and will be

using

> dualvee type bearings.
>
> Thanks for all the help from everyone Im finally getting close!!
>
> Chris

WOW! 400IPM with a 5ft gantry driven from one side. I did see one
design that looked like a giant T square and had a non-track roller
on the far end. I don't think they were moving at 400IPM. An
interesting calculation is to consider the total weight of the head
and slides and move it 5' from the pivot point. Since the worst case
would be during acceleration and deacceleration with the weight at
the far end of the gantry, the formula would have to contain mass
(weight), time and the length of the lever. You may have to dig out
the old physics books!

I have a dual screw 5' gantry and it weighs in at 100 + lbs. I was
concerned about racking. Since I use it for both routing and plasma
I had to consider the cutting forces when the router is at one end or
the other. I can't move my beast at over about 200IPM. I used 6'
long ballscrews and they start to whip at those kinds of RPM.

Currently I have it cranked back to 165 IPM on rapids and I cut at
about 100 IPM with the router...slower in dense hardwood. Snapped
two 1/4" router bits trying to cut to deep and move too fast :>(