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Mach Discussion => Mach4 General Discussion => Topic started by: Azalin on December 12, 2021, 02:49:25 PM

Title: Mill: General question about limit switches
Post by: Azalin on December 12, 2021, 02:49:25 PM
I currently have 2 switches on X, 2 switches on Y and 1 switch on Z.

Is it best to have 2 for X and 2 for Y or single for each with soft limit enabled?
Title: Re: Mill: General question about limit switches
Post by: Graham Waterworth on December 12, 2021, 02:52:26 PM
Physical switches are always better, if the machine looses position for some reason softlimits are useless.
Title: Re: Mill: General question about limit switches
Post by: joeaverage on December 12, 2021, 05:33:26 PM
Hi,
I have six limit switches, a '++' and a '--' for each axis, and three Home switches, one for each axis.....all on their own inputs.
I have soft limits set up to trigger just inside (about 1mm) the physical limit switches. This is because if you hit the physical limits the machine
Estops and therefore loses reference whereas SoftLimits do not cause an Estop and therefore no loss of reference.

Losing reference part way through a job is a PITA

Craig
Title: Re: Mill: General question about limit switches
Post by: Azalin on December 22, 2021, 02:10:50 PM
I have a question. As I said I have 2 inductive switches on X, 2 on Y and 1 one the Z. They work well. Homing and soft limits works OK.

When soft limit is disabled, while jogging the axis does not stop when any of its switches gets triggered. It just hits the switch (crashes).

Is there a way for this?
Title: Re: Mill: General question about limit switches
Post by: joeaverage on December 22, 2021, 02:23:25 PM
Hi,

Quote
When soft limit is disabled,

Yes, enable Soft Limits, that's exactly what they are supposed to do. If you turn them off then the only over-travel protection the machine has is the Limit switches.
As you say having a Limit switch event happen is a PITA it that the machine loses Reference with an Estop, that's why Soft Limits are much preferred.

Craig
Title: Re: Mill: General question about limit switches
Post by: Azalin on December 22, 2021, 02:32:24 PM
Thanks Craig but, I'm a little lost. If soft limit is the way then what is the point having 2 individual switches on each axis?

By the way, to use soft limits do I need to hit the "On\Off Soft Limits" button then home every time I open Mach4? Because Mach4 looses machine coordinates whenever I start it.
Title: Re: Mill: General question about limit switches
Post by: Azalin on December 22, 2021, 02:57:16 PM
aahh OK sorry, it appears that the PoKeys plugin does support shared switches as home and limit.

First try the Mach4 went into E-Stop condition when the switch is triggered (weird). This is what I need to solve now.

Again, sorry.
Title: Re: Mill: General question about limit switches
Post by: joeaverage on December 22, 2021, 02:59:25 PM
Hi,

Quote
If soft limit is the way then what is the point having 2 individual switches on each axis?

Because Soft Limits should prevent you or the Gcode from going out of bounds, and Mach will not execute any instruction which attempts to do so.
If however Soft Limits fail or get confused, or are not enabled....That's when the Limit switches are the last line of defence.

I have my limit switches set up to be 2mm inside the physical stop of the ballscrew, ie when the damage occurs. The Soft Limits are set up 2mm inside the Limit switches,
which means 4mm inside the physical/damaging limits.

Quote
do I need to hit the "On\Off Soft Limits" button then home every time I open Mach4?

Yes you do. Mach by default when it powers up does not have Soft Limits enabled. ONCE you have Referenced/Homed your machine THEN enable Soft Limits.
This is the critical point, the machine MUST, ABSOLUTELY MUST be Referenced/Homed before Soft Limits are enabled. Soft Limits only make sense once
the machine coordinates for the Home loaction are established.

You can program Mach to operate that way automatically at start up if you wish. At one time I had mach such that I could not jog, run Gcode (all the buttons were disabled) or do ANYTIHNG UNTIL
I had Referenced/Homed the machine. You could easily include <Enable Soft Limits>  at the end of your Homing procedure. If you don't Home your machine properly then what's the point of Soft Limits....
they will never work anyway.

Craig
Title: Re: Mill: General question about limit switches
Post by: joeaverage on December 22, 2021, 03:04:32 PM
Hi,
you've got swags of inputs why do you not have separate Home switches?

The PoKeys, much like my ESS, allows a switch to do double duty, ie a Limit and a Home switch.....but why?? To save an extra
switch per axis....a little bit of wiring....don't be so lazy. Why have Mach be potentially confused as to whether it should
reference an axis or cause an Estop?

Craig