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Limit switches and home switches
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bob_quale
I'm not sure the difference between limit and home switches. I have
a bridgeport with limit switches, they are in series with a mushroom switch. If one is off, it kills the power to the power supply for the motors, via a contactor, stopping all motion. I then have a over ride to jog off the switch. Where do the home switches come into play and how do they work? Bob |
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Peter Homann
The simple answer is, in normal operation home switches are meant to be
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activated. Limit switches are not. When the machined is commanded to reference (or "home") the machine, the software moves the machine towards the home switches until they are activated. The software now knows where the machine is. The limit switches should only be activated if something is wrong and the machine has travelled too far. This is how your machine is wired. Mach1/2 allows the home and limit functions to use the same switches. If you tell the machine to "Reference" then the software is expecting the switches to e activated. It therefore treats the switches as home switches and nudges the machine off the switch. During normal operation the switches are treated as limit switches. If activated, the software stops the machine in an ESTOP operation. So, if you want to use the referencing feature of Mach1/2 you have two options. 1 - Install a 2nd set of switches for the home switches. 2 - Rewire your machine so that the limit switches are not in series with the big red button. Cheers, Peter Homann mailto:Peter.Homann@... Adacel Technologies Limited, 250 Bay St, BRIGHTON, 3186, AUSTRALIA <> Telephone +61 (3) 8530 7777, Facsimile +61 (3) 9596 2960 Mobile 0421-601 665 -----Original Message----- |
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Bob Campbell
Bob,
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I sent you a long private note, but Comcast does not like you. It returned the note. Bob Campbell ----- Original Message -----
From: "bob_quale" <Robert.Quale@...> To: <mach1mach2cnc@...> Sent: Tuesday, August 12, 2003 5:37 PM Subject: [mach1mach2cnc] Limit switches and home switches |
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bob_quale
I thought when you homed, it was based on where you told mach2 home
was originaly, Perhaps x0, y0, z0? so what do you need the switches for? also would the switches have to trigger precisley? --- In mach1mach2cnc@..., "Peter Homann" <peter.homann@a...> wrote: The simple answer is, in normal operation home switches are meantto be activated. Limit switches are not.machine, the software moves the machine towards the home switches until they areand the machine has travelled too far. This is how your machine is wired.switches. expecting the switches to e activated. It therefore treats the switches as homeswitches and nudges the machine off the switch.If activated, the software stops the machine in an ESTOP operation.two options.series with the big red button.have mushrooma bridgeport with limit switches, they are in series with a overswitch. If one is off, it kills the power to the power supply for ride to jog off the switch. Where do the home switches come into |
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Art
Bob:
Imagine turning on a machine which has a tool sitting in the middle of the bed. If you have home switches, you can say "ref axis" and the axis will move to home and then zero the DRO's. Or it can put any amount in the DRO's. So if the switch is 2 inches away from limit, the DRO's can then be programmed to read 2". Its a handy way to make sure that 0,0,0 today is the same as every other day. The switches do not need to be great, once hit, the axis moves off the switch before zeroing. You can share the limits with this on some systems. Hope this helps, Art www.artofcnc.ca |
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Peter Homann
Bob,
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There were 2 terms I used Home and Reference. The Mach1/2 "Home" switches are used for referencing. When you reference the machine, The machine moves in the direction configured in the software. The machine keeps moving until it activates the home switch for each axis. These switches can be at any position you like. i.e. X=2, Y= -4.3, Z=6. When the machine activates these switches it knows where it is. i.e. 2,-4.3,6. Without the reference switches the software doesn't now where the machine is when it powers up. With the switches, you 'Ref all" as the first operation when you power up. the machine moves until the switches are activated, and the software now knows where the machine is. Then, when you instruct the machine to home it goes to 0,0,0 relative to the reference position, 2,-4.3,6 A lot of machines have the reference position at x=0,y=0. I guess that's why the reference switches are called home switches in the mach1/2 set-up screens. Without the switches, you need to manually jog the machine to a position, say 0,0,0. type 0,0,0 into the DROs, then press "REF All" The software now knows where the machine is. Yes, the accuracy of your reference switches will determine how accurate your reference positioning is, Cheers, Peter Homann mailto:Peter.Homann@... Adacel Technologies Limited, 250 Bay St, BRIGHTON, 3186, AUSTRALIA <> Telephone +61 (3) 8530 7777, Facsimile +61 (3) 9596 2960 Mobile 0421-601 665 -----Original Message----- |
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Daniel Maioli Padua
--- In mach1mach2cnc@..., "Peter Homann"
<peter.homann@a...> wrote: If you tell the machine to "Reference" then the software isexpecting the switches to e activated. It therefore treats the switches as homeswitches and nudges the machine off the switch.switches. If activated, the software stops the machine in an ESTOP operation. What do I do if I hit the limit switch while jogging? I can?t get out of the e-stop condition. I thought that if I hit the low switch, the machine stops movent to this direction and should let me move the machine off the switch. Does it performs this way? If yes, how can I get it work? I am using Lim--X, HomeX (same pin); lim--Y, HomeY (same pin) and at end of the positive way, I put the e-stop switch. Reference works fine here. Daniel. |
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