Pete, Usually on larger, stronger machines, the limits are not used as home switches, since the limits are the "OMG" last ditch effort to keep you from breaking expensive parts.
You really want to wire your limits into the Estop system. One possible Estop control scenario: You push a button when you start the machine that pulls in a sealed-in relay circuit - oftentimes labeled the "Power On" button or similar. If you hit the Estop button (usually a latched switch), or your machine hits a limit on any axis, the sealed in relay drops out which results in a machine Estop. The same relay circuit can hold in contactors that feed your Teco servo drives. A side benefit of this is that if you have a power outage, your machine will power down and not power back up when the power returns - until after the "Power On" button is depressed. If you need to jog off a limit, you can install another button or switch which bypasses your hard limits... I've seen these buttons or switches mounted inside the control cabinet so they are not inadvertently switched on by some unknowing operator. I have also seen key switches used for the same purpose. BTW, the Teco servo drives are set from the factory for a 300% torque limit before they trip out. You might want to back that down a bit while you start up your machine. :-) Dave On 2/12/2013 11:50 AM, Pete Matos wrote: > Okay another point I am missing, if you have your limits tied into the > estop to depower the entire system how the hell do you home the machine? > Do you have seperate home switches. I intend to use to the limits as homes > for the purposes of homing the machine. > > On Tue, Feb 12, 2013 at 11:44 AM, Pete Matos<petefro...@gmail.com> wrote: > > >> Sam, >> okay now we are getting somewhere, you bring up a valid point here. I >> have been in that situation before with a runaway servo and buddy it is no >> fun. I can see what you mean about getting the drive depowered in the event >> of a runaway. I guess I was more thinking about a limit trip during a >> program run accidentally when I screwed up the program placement or >> overestimated the size of my travels ( I NEVER DO THAT REALLY!! LOL) so >> yeah I can see your point and I wonder if there is a happy medium somehow >> with a limit setup tied to the estop circuit and still being able to power >> up and jog off the damn switch so I can get back to work without major >> machine disassembly... You would think that would be kinda the way things >> are done really. I am right now talking with Machmotion about my servo >> drives and amps and should be draining my paypal account momentarily LOL... >> we shall see how that goes. Peace >> >> Pete >> >> >> >> On Tue, Feb 12, 2013 at 11:31 AM, sam sokolik<sa...@empirescreen.com>wrote: >> >> >>> Ok - I will say a couple more things and then shut up about it. :) >>> >>> - On conventional machines (not robot arms or such) the linuxcnc soft >>> limits are rock solid. After the machine is homed - they work 100%. >>> (again - I have never hit the limit switch when the machine was homed) >>> If you may be used to another machine control software which shall be >>> unnamed which may not be as consistent - you don't have to worry about it. >>> >>> - It really is a safety thing. what happens if the servo drive runs >>> away towards the limit switch? (encoder failure or some such failure >>> mode) Do you really want the servo drives enabled still when it hits >>> the physical limit switch? (I know I want the estop to trigger and kill >>> power) Your Cincinnati isn't a hobby machine run with small steppers. >>> You probably have tons of force that would slam into the hard limits - >>> then maybe smoke other things.. >>> >>> - You could setup a button that then allows you to enable the drives to >>> jog off the limit switches. (again - it should happen never) >>> >>> sam >>> >>> >>> >>> >>> On 2/12/2013 10:03 AM, Pete Matos wrote: >>> >>>> Well that may work fine for you and honestly I love soft limits as much >>>> >>> as >>> >>>> the next Guy but I honestly prefer to have the drives enabled in a limit >>>> switch trip situation so I can just backoff,backup and punt my way back >>>> into the program. It worked fine that way on my RF45. If I have my >>>> >>> way I >>> >>>> will have both hard and soft limits working continually and the estop >>>> shutting down the show in an emergency situation. So I appreciate all >>>> >>> the >>> >>>> ideas here but can we kinda keep the ideas pointing in that direction >>>> >>> so my >>> >>>> already befuddled mind does not get any more befuddled than it has to >>>> >>> be. >>> >>>> LOL thanks guys....peace >>>> >>>> Pete >>>> >>>> >>>> >>>> On Tuesday, February 12, 2013, sam sokolik<sa...@empirescreen.com> >>>> >>> wrote: >>> >>>>> We have a brake on the y axis also. Yes it is a pain. :) I should >>>>> disable the jog until after the machine is homed. Problem fixed. :) >>>>> >>>>> sam >>>>> >>>>> On 2/12/2013 9:43 AM, Pete Matos wrote: >>>>> >>>>>> That would be a real bitch to have to back off a millhead on a VMC >>>>>> >>> off a >>> >>>>>> limit with a motor brake installed... >>>>>> >>>>>> Also as per the complete power down issue, having been ringside >>>>>> >>> when >>> >>>> my >>>> >>>>>> Y axis drive blew and watching the bright white light coming from >>>>>> >>> behind >>> >>>>>> the machine I was VERY glad the estop circuit cut all power to the >>>>>> >>> drives >>> >>>>>> LOL....yeah I am good with watching the spindle coast to a stop any >>>>>> day....peace >>>>>> >>>>>> Pete >>>>>> >>>>>> On Tuesday, February 12, 2013, sam sokolik<sa...@empirescreen.com> >>>>>> >>>> wrote: >>>> >>>>>>> My axis limit switches are hooked directly into the estop loop. I >>>>>>> >>> have >>> >>>>>>> soft limits setup. The only time I have ever run into the >>>>>>> >>> over-travel >>> >>>>>>> limits was when I was jogging before homing (not paying attention... >>>>>>> >>> ) >>> >>>>>>> (and yes - I have to back off the limit manually) >>>>>>> >>>>>>> sam >>>>>>> On 2/12/2013 9:07 AM, andy pugh wrote: >>>>>>> >>>>>>>> On 12 February 2013 14:53, Pete Matos<petefro...@gmail.com> wrote: >>>>>>>> >>>>>>>>> Thanks for the info...can you explain that last part 7i77 GPIO? >>>>>>>>> >>>>>>>> The 7i77 has 32 inputs and 16 outputs for general-purpose IO. (on >>>>>>>> >>> TB7 >>> >>>>>>>> and TB8 I think). >>>>>>>> >>>>>>>> >>>>>>>>> Did I hear you correctly when you said you wired your limits >>>>>>>>> >>> and >>> >>>>>>>>> homes in series and in with the estop circuit? >>>>>>>>> >>>>>>>> No, as you say that would cause problems with backing off of a limit >>>>>>>> >>>>>> switch. >>>>>> >>>>>>>> In actual fact the machine I am describing doesn't yet have limit >>>>>>>> switches, it is a bit of a slow-burning project. They are likely to >>>>>>>> >>> be >>> >>>>>>>> added fairly soon, though. >>>>>>>> However, my intention is to keep them entirely software-controlled. >>>>>>>> >>> I >>> >>>>>>>> would be interested to hear opinions on the advisability of this. >>>>>>>> >>>>>>>> >>>>>>> >>>> >>> ------------------------------------------------------------------------------ >>> >>>>>>> Free Next-Gen Firewall Hardware Offer >>>>>>> Buy your Sophos next-gen firewall before the end March 2013 >>>>>>> and get the hardware for free! 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Learn more. > http://p.sf.net/sfu/sophos-d2d-feb > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
