Homing Y/A Axis Says Limit Switch Triggered

My new table cnc approx. cut area 20”x26” made all in aluminum with 7 limit mechanical switches, Mach3 register, ESS, C11G BOB, ASUS Laptop with Windows 8.1 was working very well and did my first 3 sample cuts until I decided to re arrange wiring for better looks

The attached snip shows at the top left of the screen the Homing of all axis is complete but there are two limit switches on the Y and A axis shown on the right of the screen which are triggered but at least I can back out my axis. Just wonder where to look for to solve this minor problem.

I reroute motors/limits wiring but when I connect the shielded ground to the star point ground and try to Home the Y axis it says “Limit switch is active, fix the wiring and try again”. Try again it says “Limit switch is triggered”. For now I left the ground wiring not connected,

I don’t know if the ESS has anything to do with it but reading on the web some suggest to install a capacitor to the limits wiring but I don’t know what size capacitor and where to connect the capacitor and besides I don’t know if it will help.

Thank you

If your switches are wired NC then you may have a bad connection or a break in the cable somewhere. Cable internally fractured seem to be the bane of my life. After homing and doing an eight hour print, my 3D printer would not home for the next print as the cable went OC in with the movement. Easily fixed but a PITA all the same. I advise that cables are routed to give the largest possible radius of curvature where they move and the cable ends are clamped where they meet the switch or motor so they don't move relative to the connection.

Hope this helps,

Rob

Thank you Rob for your time, I understand it’s a PITA to find this kind of a problem but have no choice except to give it a try again and check the cables for sharp turns. What’s strange is that all limit switches work fine when I press each one individually and homing the X and Z axis I have no problem, it’s only the Y and the slaved A. Eventually I will get it…..

May not be the problem, but I have suffered from this one...

When you home, it is possible that the axis barely moves away from the home/limit switch (and I am assuming that you have a single switch for home and limit). When homing, Mach3 treats the switch as a home switch so that it does not trip the "limit" function at this point. However, as soon as that axis has homed, it reverts to being a limit switch while Mach3 goes off to home the next axis. If the first axis is still just about at the switch trip point, it might actually trip the switch due to vibration, and Mach3 sees this as a "limit" event. The cure is to set the Mach3 parameters to move the first axis a couple of millimetres away from the point at which the switch tripped. I had this problem with proximity switches but I guess it might happen with mechanical switches as well. It's a quick thing to check - just a change of a few Mach3 parameters - so worth a try, perhaps.

Good point Neal, thank you sharing your experience, but we must remember that the cnc was working before very well and I have not touch the Mach3 configuration since. It’s true also that I have single switch for Home and Limit. In addition, when Homing if the axis moves even a millimeter I will see/hear it and this doesn’t happen, What happens as soon the Gantry touches the Home switch I hear it clicking the switch and then the Gantry stops moving then the DRO numbers start to move to zeros and when it does I get the message “Limit switch is triggered”.

First I will try to fix it without touching the Mach3 configuration which was good and I did 3 sample cuts with no problem at all

As Rob says, there's a high probability that moving the wiring has broken a core somewhere - I have also suffered my share of broken wires! A real pain in the posterior to track down although at least you generally know which cable is broken (it's the one that's most difficult to get to...)

However, I made my suggestion on the basis that even though it's not very likely, it is so easy to check that it might be worth doing. In my own case, I was getting these limit trips maybe 50% of the time - maybe it would fail once or twice at the beginning of a session and then work perfectly for the rest of the evening. There was no visible movement of the axis causing the trip when it happened. Still, the hysteresis in mechanical switches should mean that it can't happen. And that's what I thought with my proximity switches as well - that wasn't a very sound assumption!

Good luck with it anyway - these kinds of things are a bit of a nuisance but once you've got the thing fixed, you should have a decent machine.

You are right Neale but if you have a broken cable would the switch alone still function? I just don’t see that. Anyway if I want to check a cable how do you go about?

Just check the resistance from one end to the other?

If that’s so I can do it and hope for the best.

Just came back from my garage and no matter what I change I still get the same bloody message..

Many thanks

Quote:

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Originally Posted by Stevenson

Just check the resistance from one end to the other?

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If you have a buzzer type continuity indicator, clamp the test leads on and wiggle the wires about at the same time muttering the incantation "Sh*t, F**k, B*gger, *rseh*les". Also check all the wiring at the switch many times over. The correct word to say when doing this is B*stard, repeated constantly and vehemently.

Believe me, I have done it many times.:mad::mad:

Rob

No problem Rob, tomorrow I will do as you say and yes I do have a buzzer type continuity indicator

Almost finish checking the cables and will post results soon but I have a question which if I know the answer I may solve my problem

On the attached diagnostic screen where I have the two red arrows pointing what it means the M4++Limits and M4Home? Do they refer to a motor, axis or what?

When I try to Ref Y and the gantry starts to move, when the move stops this M4++Limits & M4Home is also lit but in a few seconds the 2 lights come OFF.

To check if the limits cables were broken or not I knew the problem was related to the Y and A axis limits because the problem happens only when I try to home these 2 axis. So I disconnected first the A axis limits cable at both ends and installed a temporary brand new cable. Then I try to home the Y axis and the same message comes up. Did the same for the Y axis and the results was the same. So the message “Limits switch triggered” is not related to broken cables.

If someone can answer my previous post about what the M4++Limits / M4Home message refers to I may understand more and perhaps be able to solve the problem

Thanks

Just checking:- have you made any alterations to Mach3 settings since 'tidying up' your wiring runs? It has been a couple of years now since I used Mach3. My current thought is that there is some fault between the C11G and the ESS, which is an area of zero expertise for me.

Cheers,

Rob

Have done no changes to Mach3 configuration so now I give up!!! I also have no experience with the ESS, this is my first cnc with ESS.

My thinking is that the limits/E-stop/Probe and Homing work as they should so why bother with this darn message?

Anyone has an idea what the M4++Limit etc. as I asked in my previous post referring to?

Cheers

Can you trigger each switch in turn and see which indicators light up on the diagnostics screen? I assume that these Mx indicators map to the notional 6 axes that Mach3 can handle but why they have not picked up the usual X/Y/Z etc labels I don't know.

I switched to UCCNC on both my CNC machines so I can't replicate this screen, unfortunately. I had been using Mach3 with an ESS but had problems with it so swapped to a UC300 and UCCNC - but not the same problems you are seeing.

It’s difficult to describe what you ask Neale because when I click a switch I can’t take a snip so I made the attached sketch. The black cells mark from the top down the lights ON in the indicated axis on the left of each bank.

But in my notes I found that M1=X, M2=Y, M3=Z and so I don’t understand why when I reference the Y I get on the diagnostic screen the M4 lights as shown but only for a few seconds and then I get the message “Limit switch triggered…”

I also switched to ESS because it’s difficult if not impossible to find a PC today with a parallel port and besides where can I find XP or Vista to run the PC?

Thank you

Quote:

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Originally Posted by Stevenson

T

If someone can answer my previous post about what the M4++Limits / M4Home message refers to I may understand more and perhaps be able to solve the problem

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M4 refers to the A limits. You can turn off the light by going into the Ports and Pins settings, but you are using slaved Y and A. Have a look at limits and home switches here https://www.machsupport.com/wp-conte...all_Config.pdf

Cheers,

Rob

Many thanks for your time Rob,

I printed the Mach3 Mill Installation & Config back in Nov-06-2008 and have read it many times but I didn’t see anything related to “turning OFF the light.. In any case before I turn the lights OFF I would like to know the reason why they come ON in the first place.

I’m retired and I build table cnc all in aluminum as a hobby, the last one I’m working now I think it’s my 9th and my first with ESS, before that one all were with printer port and never had any problems. It takes me about 1.5 years to build and sell one after to recover at least my cost. Yesterday I went thru the ESS config “Noise Filtering of Inputs” and changed the Limits number from 0.00 to 20.00. Then after a re boot I press the down arrow on my keyboard to move the Y (which is slaved to A) and suddenly to Y & A moved BUT the Y went much faster than the A and almost twisted the Gantry to the breaking point before I pressed the E-Stop, quite scary…

So now after 3 successful cuts on this cnc I’m losing confidence on the machine and thinking to remove the ESS and going with a printer port setup like I used to do before. The problem is I can get a desktop PC for $50 but where do I get the Windows OS like XP or Vista to run the desktop? I do have both XP-Pro and Vista DVD’s but I have to register them again with MS and it’s a hassle to do so, I’m thinking my options….Linux it’s an option but I’m not very good with it.

Today I have no time but tomorrow I will go thru all ESS settings carefully to see if I find anything I missed and then I will decide what my next step will be.

If the Y and A axes are moving at different speeds, that suggests that something like the "steps per" settings are different, or maybe the driver DIP switch settings are different - but neither explains your other symptoms! I almost suspect ESS hardware problems, but it's very difficult to diagnose remotely like this.

My CNC mill is based on German-built hardware, but the CNC electronics were installed by a US company. Hence it used Mach3, ESS, and Clearpath servos - all US-sourced, of course. However, Mach3 has been obsolete for years,and there have been issues about poor levels of support for the ESS. So when I started getting data buffer errors, there seemed to be little point in trying to diagnose them and I scrapped the lot and replaced them with a UC300ETH and UCCNC - both of which are current and fully supported (and European!). I haven't had a problem with that setup, although I do use Win10. Unfortunately my Mach3/ESS setup did not have a slave axis so I have no reference settings to compare with you.

One odd thought - you are using a fully-licensed copy of Mach3? There are known issues with some copies of Mach3 from less than scrupulous suppliers which manifest themselves in all sorts of strange ways. Maybe worth a re-install of Mach3 and if necessary using a trial licence, to ensure that you have "clean" software? Apologies if your copy comes from an impeccable source!

Thanks Rob for your ideas but if I go with a parallel port I will get a desktop with build in parallel port which will be easier to setup Mach3. I also know the eBay XP copies but that too I don’t trust, I will install mine and I have 30 days to activate the install with MS. But I have another option which I will describe later.

Thank you too Neale for your thoughts. I forgot to mention yesterday when the Y/A went out of alignment I revert the ESS settings to original, re aligned the Y/A axis as they should be and re booted and then all was fine. This mean my motor settings were good. In addition my Mach3 license which I bought from cnc4pc.com from USA in 200 is good since I use it in all my previous cnc and never had a problem. (when I sell a cnc I remove my license and the purchaser knows he only has a demo version of Mach3)

However this reminds me that when I started installing ESS, the instruction were saying to install an older more stable version of Mach3 and they had a link for that version and that is what now is install in my laptop. I think it may be worthwhile to re install the latest Mach3 version and see the results. I think that is what I should do before I scrap everything and start from scratch again. I know that Mach3 support is not as it used to be.

Another option I may take is to contact wap9td.com, the ESS support site. Before my current problem I had another major problem with my Probe to set the Auto Tool Zero. Then the probe had its own mind and did all kind of crazy moves and finally this guy at ESS support helped me despite he originally said “I don’t support Mach3” (I’m telling you this machine goes from one major problem to another, never experienced anything like that before).

Tomorrow first I will go line by line to assure ESS is set up as per instructions.

If no luck, then I will re install Mach3 with the latest download I have

If no luck, I will contact ESS support for further help.

If no luck will try to do another cut(s) with my finger on E-Stop button

Neale you say you are using UC300ETH and UCCNC , does this include the BOB (Breakout board)?

Hi,

I would not advise a PCI PP card. They work OK, but getting the drivers installed with XP is not easy (English use of understatement!!!).

I must admit, I am out of ideas. I have a suspicion it is the ESS setup or a fault in the ESS.

Hope you get it sorted soon.


Regards,

Rob

Quote:

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Originally Posted by Stevenson

On the attached diagnostic screen where I have the two red arrows pointing what it means the M4++Limits and M4Home? Do they refer to a motor, axis or what?

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Yes, they refer to the 4th axis or motor output. If you are slaving motors with the 4th axis then usually you would turn off the LIMIT++/-- in ports and pins but leave the HOME input so can home. In this case, the M4 will light up when homing and then go off after the axis as backed off the switch, which I think is probably what's happening in your case but you have the LIMIT turned on and using the same pin number so the M4++ lights up as well.
In which case this would be correct when homing if the Home SW. safety button is not set in the General config screen while homing. If the Home SW.safety was ticked you would get a Limit tripped error.

Edit: Ignore this I can see it's been answered. It's been several weeks since I've been on here and this showed as a current post on my system.?

That looks off topic.