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Mach Discussion => General Mach Discussion => Topic started by: mjzrpr on April 22, 2022, 12:41:32 PM

Title: Homing acceleration in mach3
Post by: mjzrpr on April 22, 2022, 12:41:32 PM

in homing process when home signal activated, the axis must stoped. whats is acceleration of this stop?
when I set axis acceleration  to low value for example 80 mm/s2  ,  jog moving is very smooth but when do homing the axis stopping hard...
in config>home/limit   can just speed of homing. what is acceleration homing?

Title: Re: Homing acceleration in mach3
Post by: JohnHaine on April 22, 2022, 04:47:41 PM

Since the point of homing is to find the limit switch and the machine doesn't know where that is, deceleration is not possible only a hard stop.  The homing speed is usually set to a few percent of the normal jog speed to minimise the overrun.

Title: Re: Homing acceleration in mach3
Post by: mjzrpr on April 23, 2022, 03:20:23 AM

Quote from: JohnHaine on April 22, 2022, 04:47:41 PM

Since the point of homing is to find the limit switch and the machine doesn't know where that is, deceleration is not possible only a hard stop.  The homing speed is usually set to a few percent of the normal jog speed to minimise the overrun.

Hi JohnHaine
You are right. hard stop Avoid crash axis and improve position error.
but beter is home stop acceleration should be selectable.
thanks and regards

Title: Re: Homing acceleration in mach3
Post by: JohnHaine on April 23, 2022, 03:34:20 AM

How would you know when to start decelerating?

Title: Re: Homing acceleration in mach3
Post by: mjzrpr on April 23, 2022, 04:43:59 AM

when I set axis acceleration  to low value for example 80 mm/s2  ,  jog moving is very smooth.  but when do homing the axis stopping hard...
Due to very low acceleration, it is visible to the eye!

Title: Re: Homing acceleration in mach3
Post by: JohnHaine on April 23, 2022, 05:20:50 AM

Go to config\homing/limits\ and see what speed% is set in the RH column.  The default in Mach3 is 20%, IIRC on my machines I have set it to 5%.  I think this multiplier works on both the homing speed and acceleration.

Again, how on earth can the machine anticipate when home will be reached when the object of homing is to find that point!  Usually there should be a slight overrun possible on the home switch so the overrun doesn't cause lost steps.   

Title: Re: Homing acceleration in mach3
Post by: mjzrpr on April 23, 2022, 08:12:02 AM

Quote

I think this multiplier works on both the homing speed and acceleration.

I do not think homing acceleration is a percentage of acceleration axis. Based on what happens and is seen with the eye!

Quote

Usually there should be a slight overrun possible on the home switch so the overrun doesn't cause lost steps.   

It can set zero the machin cordinate as soon as the microswitch is activated then slow down at the deceleration. it cause a difference between home switch point  and stopping point. This is not a problem. This will not cause the microswitch to break. This could be selectable.
thanks

Title: Re: Homing acceleration in mach3
Post by: JohnHaine on April 23, 2022, 09:54:00 AM

Have you tried changing the homing speed setting?

Title: Re: Homing acceleration in mach3
Post by: mjzrpr on April 24, 2022, 12:09:13 AM

Quote from: JohnHaine on April 23, 2022, 09:54:00 AM

Have you tried changing the homing speed setting?

Yes sure

Title: Re: Homing acceleration in mach3
Post by: mjzrpr on April 24, 2022, 12:36:01 AM

Hi JohnHaine
I repeat test on another mach3 machine with lpt board (mach3 parallel). After the switch is activated, the axis acceleration is very smooth to stop.
first test on china mach3 board that have plugin for connect to board (mkx-et). its not standard mach board.
sorry for incorrect information in first.
thanks

Title: Re: Homing acceleration in mach3
Post by: smartwin on June 03, 2022, 03:05:25 AM

I think you should change homing speed .