On 2010-06-26, Pete C. wrote:

Ignoramus31989 wrote:

On 2010-06-26, Dave B wrote:
Much that has been discussed is ok for "Hobby" or home type machines.

As someone that retrofits drives and controls fora living I yet to
hear much about the real world issues of safety and "Safety
Standards".

The attached link is a 5 axis digital drive I completed last week and
every possible safety issue has been adressed.

http://s32.photobucket.com/albums/d1...current=m5.jpg

In large gantry machines like this, all axes drive motors have brakes
to ensure a quick stop in an error condition.

Soft over travel limits are set and deal with normal overtravel
condition and extreme overtravel result in a complete drive shutdown.

E Stops are handled by relays designed for this purpose.
http://www.pilz.com.au/products/cont...y/index.en.jsp

Not being critical but none of this would work in any real world
manufacturing plant.

Looks very nice Dave. How *would* you do this in a real world
manufacturing situation? (without adding additional limit switches,
etc).

Particularly considering that the 5 limit switch and no brakes on the
servos *was* a "real world manufacturing plant" design, though from a
few decades ago.

The series2 Bridgeport knee mill certainly doesn't have enough mass or
weight to need servo brakes, or hydraulic counterbalance on the Z axis
as is common on the big iron.

Actually it has a pneumatic support for the knee. It is not absolutely
necessary, just a convenience.

I do not know about brakes, but the drives are four quadrant drives.

I used to work on some big gantry machines back when and they certainly
were a lot of fun. Not exactly home shop size though when they weigh
60,000#.