Re: [CAD_CAM_EDM_DRO] Re: Help a confused newbie out please

Catching on to this thread late in the day, I thought I'd toss out How FlashCut treats Limits.

For the Limit Switches on each end of an axis, well, that's what they are for.. *Limits*. They are to STOP dead, the controller from driving any motor once tripped. Why ?? It means something is
Wrong.

In FC's case, with a tripped limit switch, you LOSE position and I thought this to be the case with most of the controls. I am not sure why one would allow an axis to ramp down beyond a tripped switch,
forcing you to jog back out to continue operations. I mean, if you happen to have a "loose" ramp for some smooth swanky 3d work your doing, heck, that "over travel" distance could be very, very long on
a flatbed Router running at 200-300ipm... Many inches even !

Flashcut, relys heavily on "Software" limits. I though most controls did. These are in effect the "dimensions" you tell the software that your machine really is. So, no matter how fast you jog, or how
long you hold down a Jog key towards any end of the machine, the software itself >knows< it has to >apply< the ramp settings you placed in your setup, for it to come to a safe, controlled stop, and do
this prior to hitting anything. When you set up things correctly, it will stop before your limit switches, because typically, you would setup your home end to "step off" a short distance before setting
machine Zero, and, your "software limit" (machine dimensions) would dictate a safe stop before you'd reach the positive end of the machine. Also, with the software remembering machine size, most often
you do not apply a Z limit that would indicate a maximum down travel location. After all, tool length changes constantly, and you'd never really get it in the right location unless it was adjusted
manually every time you changed tooling.

What the above clearly points out, is that the ONLY way Flashcut will "trip" a limit switch, is if you *lose position*. And, seeing how that is the *only* way you can trip a limit switch,,, something
is wrong, and, you'd have to Re-home anyhow. If your system is setup correctly, Servo or Stepper, You can pretty much go thru life without "tripping your limits", "getting your limits tripped" or words
to that effect. ( I knew a guy once who had his tripped...ah, wrong NG )

Flashcut also uses a "Feedhold", which is a Software control, activated by a mouse click or tapping any keyboard key, that allows for controlled, decelerating stops. This would be used if you
temporarily had to reposition a clamp, Check a dimension or remove melted plastic from tooling. Flashcuts 16 bit version did not automatically kill the I/O lines with this event, so, you'd turn off the
spindle via software, unless you used special M-codes. (plasma, torch and waterjet guys have really enjoyed "pierce delay" adjustments right at the control instead of using G04's.)

You would benefit by using a manual means of switching off a spindle anyhow, in any controller where a TTL signal could threaten your life ! Upon restart, you'd turn it back on, and continue the
program. Unfortunately, the 16 bit version also does not have the ability to "hardwire" in a feed hold, but many have applied the use of a keyboard emulation type keypad like X-keys (sometimes called
Y-keys). This has served as an adequate "remote" feedhold.

Good thing a new Flashcut version is soon to be reality as the above issues have been addressed !
(btw, those generic keyboard emulator keypads can "pendantize" just about any PC based control Windows, DOS or Linux for under $100)

When it Comes to an Emergency Stop Switch, this is really outside the realm of the control. Not only does it need to send a signal to the control that somethig is amiss, But It also needs to address a
full cut off of power to your motor drivers AND Active Spindles, Cutters or Knives. Yep, this is a "seek yer home switches" scenario no matter what.

Many have already described how to accomplish this, and the hobbiest should realize that IF he gets himself in a compromising situation, like when he wears a necktie in the shop, That that big
"Mushroom Button" is Only going to be enjoyable...... if it Works !! Do not neglect this most important part of your project.

I was a bit suprised to hear that the Ah-Ha controls actually allowed a ramped, controlled stop after Limits were tripped. I had it on a machine that would not allow enough room to do that, so maybe
that is why I never realized it. One learns stuff everyday !

Chris L