Re: [CAD_CAM_EDM_DRO] re:Crashing CNCs: what gives ?

Hi Don;


While I truely believe that your brother had a good idea, I personally
don't want anything electronic down there!!!!!!! Its just one of
those things we never do and dread thinking about.

In my youth I happened to have the good pleasure of taking one of my
first jobs in a Zinc Die casting plant. One of the dies was having a
bit of trouble, so upon my arrival the engineer in charge assigned me to
monitor the machine. I was suppose to hit a rigged up E-stop at the
first sign of trouble. It is a bit amazing to realize that the body
and mind do not work in real time no matter what one thinks. Sure
enough I watched the machine crash and hit the E-Stop well after the
damage was done. While not a CNC machine it was a lesson well learned.

The biggest problems with CNC machines is that there are some modes of
failure that just won't be caught in time no matter what you do. Which
means that at some point, if the machine needs it, a mechanical shear or
clutch must be implemented someplace. This is where gluing the tool
post on helped with the diamond turning machines. While it may not
have saved the cutting tool, such break away did lessen the need to
rebuild the axis. All in all though life turned alot better with the
advent of better electronics.

I think this is one aspect of machining technology that is ceratinly
true. That is either go with manual machines or state of the art in
electronics, because some of that old stuff was flaky the day it came
off the factory floor.

Thanks
Dave



Don Rogers wrote:

>>Though I've seen it attempted many times I've never seen an operator
>>actuated E-stop that really saves tooling. Generally things happen to
>>fast especially with machines running production code, so man in the
>>loop protection is not a good idea.
>>
>>
>
>My late, younger brother, used to teach CNC machining for GM Tool and Die
>plants. He had this idea of a pucker switch. It was a switch that would
>fit in the chair of the operator. When the operator sensed an imminent
>crash, the switch could detect the contractions of the muscles in the upper
>legs, lower back and all in between. He figured that the switch could
>give up to a full 1 second advantage to the time required for the operator
>to sense a problem, his lungs develop the air to scream "Oh S#@t, and then
>leap for the EPO switch.
>
>I have now gone into CNC machining and my track record for needing the
>pucker switch is about 60 percent. Having seen what can go wrong with a
>1/4" end mill, the thought of the same going wrong with a 6" fly cutter
>leads me to believe there is a real need for the DPS ( Dennis Pucker
>Switch). Any of you electronic gurus up to the challenge??
>
>Don
>
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