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Author Topic: Soft stop at limit switches  (Read 13853 times)

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Offline BR549

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Re: Soft stop at limit switches
« Reply #50 on: September 16, 2010, 10:41:08 AM »
1. Some machines stop faster when there is a controlled stop instead of killing the drive clock.
2. On stepper drives, hitting "stop" usually results in lost steps, causing the need to re-reference position. So operators usually ponder whether it's really necessary to hit "stop" but maybe "line feed" does as well. That's not the sense of a "stop" button to ponder before hitting it!
3. Sometimes, soft limits simply don't work.
  3a) Sometimes soft limits just are switched off by operator
  3b) Some machines do not have a rectangular working area!
  3c) Some machines have changing dimensions of working area.
  3d) If soft limits always worked, they would be useless.
4. At some machines (usually smaller ones), the impact on the machine by the abrupt stop when triggering the limit switch is even harder than that one caused by crushing into the elastic dead stop.


#1  WRONG, if you stop the pulses to the drive while it is enabled THAT is the fastest you can stop the axis period. You will have FULL dynamic braking

#2 IF you run a program that has NOT been tested for clearance SHAME on you. You need to fire the operator DON't blame the machine. The machine is basically dumb as a box of rocks. It can ONLY do as it has been told. The operator on the other hand is suppose to be intelligent.

#3 The only time i have seen Soft limits fail is IF they were not turned on OR they were turned off.   Operator error

#3a Retrain or fire the operator. The "second" time he turned OFF a "safety" he would be fired so fast he would think he had a stroke

#3b  It has nothing to do with the subject. Soft limits are there to protect your "part" in the event you really screw up and have not tested for proper clearances. Hard limits are there to protect the machine.

#3c (;-) I have never seen a machine that could GROW. They all have a physical limit to movement

#3d  Makes no sense(;-)

4.    WRONG again it won;t happen.  Worse case IF you hit the axis hardstop wide open you ARE going to tear up the machine. Best case it has to be inspected and retested  for accuraccy even for a light tap. AND IF the operator hid from me a light tap hardstop see #3a

Sport I have been around this industry a long long time. What you are asking for is something to REPLACE an incompenent OPERATOR.  In the old days yes there were slowdown switches on machines. they simply dropped the feedrate down. AND that was ONLY because there was NOT enought CPU power to do otherwise. Today you have very powerfull CPU and PLC to do the job. AND they do a much better job than the old mechanical machines ever did.

Full 6 axis control (;-). Mach can move on 6 axis BUT does not have any kenimatics as to KNOW where it is. It is just a GOOD low co$t  pulse generator. That is why you cannot JOG in full 6 axis mode.

Now what exactly are you expecting for $175 there are limitations.

NOW IF you need all those bells and whistles they can be had but BRING your checkbook full of $$$$$$$$ cause it is a little MORE than $175.

(;-) TP

Re: Soft stop at limit switches
« Reply #51 on: September 16, 2010, 01:04:37 PM »
Now what exactly are you expecting for $175 there are limitations.
NOW IF you need all those bells and whistles they can be had but BRING your checkbook full of $$$$$$$$ cause it is a little MORE than $175.
Mach is a good software for a good price. How much must a software be overpriced to give a reason for suggesting improvements?
Sorry, I'm not that expert in software development ethics.

Greetings
Nicolas