Enable limits during homing UC300eth/UB1

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Enable limits during homing UC300eth/UB1

Postby torch » Fri May 07, 2021 5:42 pm

When homing the signals from the limit switches are not considered.

Is there a way to enable this?

Reason is I'm doing a upgrade of an old mill which has +/- limits separate from home switches (located some 1/3rd between limits). If the machine is on "wrong" side of home at start up, it can crash during homing procedure.

Ideally hitting a lim during homing should make the direction change to reach home signal.

I could solve this by using the lim sw as home sw, but thought I might ask for other solution first. Having home 1/3rd between limits makes homing faster with less transport.

Im using UCCNC with a UC300eth + UB1.
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Re: Enable limits during homing UC300eth/UB1

Postby MikeM » Sun Jun 06, 2021 12:01 pm

I have the same question.

My machine is setup similarly with limits on the end of the axis and homing sensors in the middle of the axis travel.
I only have one input available for all the limits and one input for all the home sensors on the AXBBE.

When homing, the limits are ignored.
That is no problem when the machine is on the right side of the homing sensor.

The problem is when the machine is on the wrong side of the homing sensors it can continue moving up to the end of travel of the axis while the limit sensors are ignored, which will cause mechanical damage.

How do I configure UCCNC not to ignore the limit sensors during homing?

UCCNC version 1.2111
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Re: Enable limits during homing UC300eth/UB1

Postby beefy » Sun Jun 06, 2021 10:38 pm

Guys, this is just a question out of curiosity. I understand what you are asking for.

However, I'm a bit confused as to why you need it. Just wondering if I'm missing something I could learn.

Example whenever I need to home (plasma table) the gantry could be anywhere. So I basically jog at rapid speed to about 20-30mm from the home switch, then do homing.

The homing speed is normally not at rapid speed, so it makes sense to jog at rapid speed to get me near the home switch first.
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Re: Enable limits during homing UC300eth/UB1

Postby Greolt » Sun Jun 06, 2021 11:10 pm

Not much help but I used Mach3 on a mill for years which had a mid mounted home switch on the long X axis.

There is a setting in Mach3 called "Home Sw. Safety" which when set correctly the axis would
seek the home switch in the direction dictated by whether the home switch was already active or not.

I do not know of a similar setting in UCCNC
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Re: Enable limits during homing UC300eth/UB1

Postby MikeM » Mon Jun 07, 2021 8:00 am

beefy wrote:Example whenever I need to home (plasma table) the gantry could be anywhere. So I basically jog at rapid speed to about 20-30mm from the home switch, then do homing.

The homing speed is normally not at rapid speed, so it makes sense to jog at rapid speed to get me near the home switch first.


I agree with that operation to home the machine.

The problem I can see is after the machine has been homed and a axis is close to its end of travel and accidentally hitting the home button.
The issue is that I only have 1 input for all XYZ axis home switches, if I had an input available for each axis this would not be a problem.
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Re: Enable limits during homing UC300eth/UB1

Postby MikeM » Mon Jun 07, 2021 8:04 am

Greolt wrote:There is a setting in Mach3 called "Home Sw. Safety" which when set correctly the axis would
seek the home switch in the direction dictated by whether the home switch was already active or not.

I do not know of a similar setting in UCCNC


UCCNC operates similarly.

The issue arises when you have more than one axis on the same input, as in my case.
There is no way for the machine to know which axis is on the correct side and which is not.
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Re: Enable limits during homing UC300eth/UB1

Postby Battwell » Mon Jun 07, 2021 11:58 am

on my axyz router the home switch for y is outside the tool changer.
it can cause a problem if the head is inside the changer zone when homing.
my solution was to lengthen the home switch activation "stud" to the full length inside that zone (uses a prox switch)
then it knows the switch is already active and so goes directly to the home down procedure, backing off the switch. taking the head back out of that zone.
i also set my park position 100mm off the switch- into the good for homing position.
Uc300eth on router and mill
If they say it can't be done- I find a way!
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Re: Enable limits during homing UC300eth/UB1

Postby torch » Sun Aug 01, 2021 9:35 pm

As time went by and summer started, calling for other activities I did not realise further replies in this thread until now. Thank you all and interesting to see others also have this issue,

I have plenty of inputs available on the UB1 Max, but to save some for future expansion and still have a fairly easy job troubleshooting limit sw issues I've put neg lim and pos limit in series for one input for each axis. Home sw are individual on separate inputs for each axis.

But still, if machine is on wrong side of home sw when homing is started, the lim sw will not stop the machine, which to me is a bit disturbing. A limit should always be a limit imo.

After the summer I will probably rewire and not use the original home switches, but instead configure limit as home, but still have pos an neg sw in series on one input, if no other better solution can be identified.
Then, as homing direction is always the same machine will stop when it's reached... even if an unknown fault causes wrong homing direction (perhaps driver fault).

Still, I'm a bit surprised of this behaviour of UCCNC.
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Re: Enable limits during homing UC300eth/UB1

Postby cncdrive » Mon Aug 02, 2021 1:24 am

Limit switch cannot be always enabled when homing.
If the home switch is the same as the limit switch or they are separate switches but connected to the same input pin then the limit must be disabled while homing, otherwise the limit would trigger and the homing could never finish.
Are you sure your home and limit switch inputs are connected to separate input pins?
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Re: Enable limits during homing UC300eth/UB1

Postby MikeM » Mon Aug 02, 2021 7:38 am

I configured my machine with all the axis limit switches on one input and all the home switches on another input.
UCCNC completely ignores the limit switch input.

I do understand that if your home and limit switch is the same switch that the limit function needs to be ignored, but when they are separate inputs a limit switch always needs to stop the machine in my opinion.
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