Re: Sanity check for homebrew CNC milling machine

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "bitnick78"
<arvidpublic@h...> wrote:

> This is a fixed bridge, moving table construction - not a
> moving gantry machine. So the weight of the bridge will be
> not be a problem - on the contrary, as it will help reduce
> vibrations.
>
> Also, since I can make the length of the table longer than
> the travel of the table, I can support the bars at the middle.
> I could get even more travel without this extra support, but
> I think it will be needed.

Of course the design is up to you, but there are some
significant advantages to a moving gantry machine compared
to a moving table machine.

For one, a moving table machine will use nearly twice the floor
space compared to a moving gantry machine with the same work
envelope.

Also, you will _still_ have an unsupported rod rod length
slightly longer than your travel distance. (The total
rod length will be more than twice the travel distance.)

With a moving table machine, rod length = travel length +
distance between table bearings (table length). With a
moving gantry machine, rod length = travel length + distance
between gantry bearings (usually much less than table length).

And finally, depending on the design and work materials,
the table + workpiece may be much heavier than the gantry +
cutterhead, which will require stronger motors or slower
movement.

Regards,

John Kasunich