Please take great care that...
1 Your machine doesn't really need an emergency OFF/STOP
switch
2 Place it where it is useful - near to the Operator and
near to bystanders.
Years ago, I remember seeing one of the most impressive
multi-ton presses for bending metal I had ever seen while
working at HP in Palo Alto. As rookie engineers we were
required to get an understanding of the sheet metal
processing to make us better designers. In a "dry run" I
activated the press. It moved a shear type of blade
downward. When I released the activation, the blade's
motion simply ceased, did not retreat. Activate, and the
blade continued down. The blade never retreated until the
cycle had been completed - down to something like 60 mils
clearance into a V notch holder. My first horror was that
the machine did not reverse action when the Operator
stopped pressure, simply halted where it was positioned.
OK, now picture your fingers are captured in this, so
where is the emergency STOP/RELEASE button. The machinist
pointed to a giant red button mounted on the wall about 15
feet from the machine! When I pointed out the two errors
in this scenario, the machinist agreed but said, "What are
you going to do? It's what we have to work with." Well
what I did was refused to use that equipment.
Based upon the vivid images and sensation of potentially
having my fingers crushed in a machine whose STOP button
couldn't even be reached with your free foot; I stress
point 1 & 2 mentioned earlier.
- Robert -
> To List Members;
>
> I would appreciate guidance on the subject of emergency
> stop switches
> (buttons).
>
> When (if every) is an emegency stop switch manditory?
>
> Must an emegency stop switch be a hardware only function,
> or can it operate
> through the machine's computer and software?
>
> Does the emergency stop switch have to turn off power to
> the machine, or
> can it just stop the offending action, while leaving
> power on?
>
> What sort of responce time should be expected for an
> emergency stop switch
> (2 part question):
> a) How long (realy how short a time) must the operator
> hold emergency stop
> switch in order for it to operate (i.e when I want to hit
> the button and
> run, how long to I need to stand there and hold the
> button before it
> functins)?
> b) How long can the machine continue to move/run/function
> after the switch
> is pressed?
>
> Thank you.
>
> J. Sandberg
>
-
This message is from the IEEE Product Safety Engineering Society
emc-pstc discussion list. Website: http://www.ieee-pses.org/
To post a message to the list, send your e-mail to [email protected]
Instructions: http://listserv.ieee.org/request/user-guide.html
List rules: http://www.ieee-pses.org/listrules.html
For help, send mail to the list administrators:
Scott Douglas [email protected]
Mike Cantwell [email protected]
For policy questions, send mail to:
Jim Bacher: [email protected]
David Heald: [email protected]
All emc-pstc postings are archived and searchable on the web at:
http://www.ieeecommunities.org/emc-pstc
