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  1. #31
    Quote Originally Posted by Tom J View Post
    I think this is your option#3 " uses 2 inputs and 2 types of switch. NC wired in series for limits on one input. NO wired in parallel for Homes on other input"


    Well kind of but your way is a bit mixed up because the (+) Limit is NC but the (-) limit along with Home are NO so doesn't have the safety on the (-) limit side if wire breaks.!

    If you used all limits with NC wired in series on one input and homes with NO wired in parallel then you'll be safer.

    Quote Originally Posted by Tom J View Post
    I was wonder how you get away with having only one sensor, must use soft limits in Mach for safety. I've seen 3 sensors solution: limit+ limit- and home in one axis, but I think is not needed.
    Correct me pls. if we I am wrong.
    No Softlimits are optional and not required you still have Limit switch safety.
    Maybe what your not realising is that Mach only Watches Limit Inputs when working and ONLY watches Home Inputs When Homing and Ignores Limits while doing so. It also by default Moves one axis at a time so only looking for one Input to change state. If all set to same Pin # then any will do for mach.

    This is why you can share one input for ALL axis homes & limits provided they use NO switches. Mach doesn't know or care which Switch triggered it just responds to the trip.
    So if cutting it see's this trip and knows it's a Limit so E-stops.
    If it's homing then it knows the Axis it's moving and when see's Home Input change state it sets the Home position for that Axis. Then moves onto next Axis and does the same. It doesn't care which switch tripped so in practice you can actually set say the X axis Home by triggering the Z or Y axis switch.!

    The ONLY time it won't work is if you have changed the HOMING sequence so 2 or more Axis home at same time. In this case you need separate Home inputs for each axis.
    Last edited by JAZZCNC; 24-11-2015 at 06:50 PM.

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  3. #32
    Tom J's Avatar
    Lives in Melksham, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 3-4 years. Has a total post count of 148. Received thanks 7 times, giving thanks to others 18 times.
    Quote Originally Posted by JAZZCNC View Post
    This is why you can share one input for ALL axis homes & limits provided they use NO switches. Mach doesn't know or care which Switch triggered it just responds to the trip.
    Got it, but not quite to the end. How than having NO switch will provide safety on the limit side if wire breaks?

  4. #33
    Quote Originally Posted by Tom J View Post
    Got it, but not quite to the end. How than having NO switch will provide safety on the limit side if wire breaks?
    You can't have continuity safety with NO switches which I did say this in other post.

  5. #34
    Tom J's Avatar
    Lives in Melksham, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 3-4 years. Has a total post count of 148. Received thanks 7 times, giving thanks to others 18 times.
    Summarize, if I use TB6550 or similar BOB which has only 5 inputs: 1-X, 2-Y,3-Z,4-Limit/E-stop,5-GND than 3 switches used as home/limits detect the ground signal (NC-active low). Mach knows that this axis is in home position.
    How should I wire if I use the same switch as Limit? Can not wire the same switch to pin 4 (limit/E-stop)
    Using pin 4 will collide with homing (all switches will be in parallel - remaining two will have NC contact therefore no homing)
    Jazz, could you please send the wiring - loosing plot.

  6. #35
    Quote Originally Posted by Tom J View Post
    Summarize, if I use TB6550 or similar BOB which has only 5 inputs: 1-X, 2-Y,3-Z,4-Limit/E-stop,5-GND than 3 switches used as home/limits detect the ground signal (NC-active low). Mach knows that this axis is in home position.
    How should I wire if I use the same switch as Limit? Can not wire the same switch to pin 4 (limit/E-stop)
    Using pin 4 will collide with homing (all switches will be in parallel - remaining two will have NC contact therefore no homing)
    Jazz, could you please send the wiring - loosing plot.
    You got me bambozzled now and Not quite sure what your asking for but here's quick diagram showing 2 options. Option #2 is probably your best option.


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  7. #36
    Hi Jazz,

    Here's a question for you - If you are using one switch for home and limit does Mach ignore the limit function while homing?

    That leads on to another - If you have slaved motors on an axis does mach wind both motors until a home trips and then keeps winding the untripped screw until the other trips, thus squaring the gantry and then do the backing off the home switch to complete the homing and aligning process ? In which case I presume you would need to have separate inputs for each side of the machine.

    I see the point of having 2 targets and one switch, I only recently realised that Mach took into account which axis was travelling and the direction of travel when homing. It makes sense of commoning inputs.

    Cheers,

    Rob

  8. #37
    Quote Originally Posted by cropwell View Post
    Here's a question for you - If you are using one switch for home and limit does Mach ignore the limit function while homing?
    Yes if you turn off HomeSW Safety in General Config.

    Quote Originally Posted by cropwell View Post
    That leads on to another - If you have slaved motors on an axis does mach wind both motors until a home trips and then keeps winding the untripped screw until the other trips, thus squaring the gantry and then do the backing off the home switch to complete the homing and aligning process ? In which case I presume you would need to have separate inputs for each side of the machine.
    When using slaved motors Mach De-couples each motor turning back into two separate axis while homing happens which means the motors work independantly but move together in sync towards the home switches. When first switch is tripped that axis motor stops and backs off the switch while the other keeps going then does the same.
    In practise provided your Gantry is square and the switches positioned correctly this appears to happen has one action. If your gantry is really out of square then you can position the switches to force it square.
    When Both Motors have homed then Mach Couples the Axis again back into one slaved axis.

    This does mean that the Slaved Motor needs it's own Home switch on a Separate Input.
    Last edited by JAZZCNC; 25-11-2015 at 02:54 AM.

  9. #38
    Tom J's Avatar
    Lives in Melksham, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 3-4 years. Has a total post count of 148. Received thanks 7 times, giving thanks to others 18 times.
    Machining base for X -rails

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    Had to bend frame in the places to be perfectly straight - left those Irwin for overnight to see if 0.8 mm sag is dissapering
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  10. #39
    Tom J's Avatar
    Lives in Melksham, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 3-4 years. Has a total post count of 148. Received thanks 7 times, giving thanks to others 18 times.
    I managed to get 0.4mm off the sag, better than nothing, will use the technique like those who do not machine the profile or base. Simply will use filler gauge - industrial sheet in the middle to compensate - do not want to have tension on the bearing block while is sliding from middle towards end.
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    After welding so many frames came up with solution - there is not substitute for slow welding with min heat. Mean the welding bed have to be short and fully cooled before we weld again near by.
    I put all theory to the bin with current setting to metal thickness and speed wire on MIG.
    I use Clarke MIG TEC230 Turbo which is capable to weld up to 7 mm on max setting (switch pos.6)
    My profile is 2-2.5mm with plates 5mm and I use pos.3 - current/power and wire speed min as possible to stop splatter but fast enough to get good constant sound (not like a shooting gun)

  11. #40
    Tom J's Avatar
    Lives in Melksham, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 3-4 years. Has a total post count of 148. Received thanks 7 times, giving thanks to others 18 times.
    Here is where design doesn't match reality - X drive motor bracket doesn't make the belt tight, I made all the parts in Solid Works myself - using vernier rather than dimensions data and with belt 295mm long error was like 5mm.
    No big deal - 1hr+ lost for fabrication.
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    Here is the gantry. X motor bracket I will made longer and than will cut slots for adjustments. Lesson learnt
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