Re: [CAD_CAM_EDM_DRO] Twin motor axis

IDA wrote:

>Over on the Geckodrive group, a chap who seems to know what he is talking about said it is a seriously bad idea to use two motors on a single axis of a router or plasma table because of the risk of serious damage to the machine if one motor fails when the other continues. I am planning a large 2.5m x 3.5m router using 2 motors on the x axis, and that post reawakened worries. The idea seems fairly common, so what safeguards can be put in place to alleviate this risk?
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All the large machines (gantry bed mills, vertical boring mills, etc.)
that use tandem axes have bearings on
the beam that joins the gantry pillars. This allows the paired slides
to get out of sync with no harm to the
machine. One bearing is a conventional bearing, the other is a sliding
fit, so it allows the beam to tilt without
pulling the pillars together. (They probably have estop switches to
kill motion if it gets seriously out
of sync.) This allows the two axis halves to move independently toward
the home location, and get sync'ed
at home. Then, the CNC control is responsible for keeping them synced.

There are thousands of large machines in industry made this way.

Jon