Homing Enhancements

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Homing Enhancements

Postby Gary Campbell » Fri Sep 08, 2017 2:00 am

With the high percentage of router tables that have dual drive axes, I would suggest some enhancements to the homing routine as it applies to these slaved axis machines. Here would be my wishlist for parameters: (assumes existing parameters remain in place)

Approach speed (1st hit)
Roll back distance
Approach speed 2nd hit (optional)
Slaved axis adjustment

Thanks, GC
Gary Campbell
 
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Re: Homing Enhancements

Postby cncdrive » Fri Sep 08, 2017 4:55 am

Gary,

There is no need for these because:

1.) Slave axes homing is already implemented. As soon as you set different home pins for the master and the slave then the gantry squaring will automatically happen. The UCCNC will move the master and the slave to the home switches with moving them together and once one of the home switches are found then the motion stops and the master and slave connection is removed and both axis will home on it's own squaring the gantry.
Maybe what would be useful is to add separate backoff distances for the master and the slave, so then the home switches do not have to be aligned to be in square.
However it can be already done in macro, there is a Slaveaxis function which you could use to temporarily Slave/Unslave axes, so you could for example unslave them, command them to move separately different distances and then slave them back together.
The function prototype from the documentation:

Code: Select all
Function: void Slaveaxis(int masteraxis, int slaveaxis)
Description: This function slaves an axis to an axis. The masteraxis can be axis X, Y and Z axis (numbers 0, 1, 2 respectively) and the slave axis can be A, B and C axis (3, 4, 5 respectively). To remove the slave from the master axis use value 0 on the slaveaxis parameter.
Be careful with saving the axis settings when the slaveaxis function is in use. If the settings are saved without pressing the Apply settings button first then the slave parameter will be saved for the master axis!
Example: exec.Slaveaxis(0,3); //Makes A-axis slaving the X-axis.


2.) There is no need for 2 approach speeds for homing. I understand that you want this to be able to quickly reach the home position and to get a precise home position the same time.
There are 2 homing speed parameters in the UCCNC, one is the home up and the other is the home down speed. The up means when the axis is running towards the switch and the down is when the axis is running downwards the switch. So, you can set the up speed high and so the home position will be reached fast and the down speed you can set low, so the registered position will be precise.
The UCCNC registers the home position when the downwards process, at the position point of when the axis leaves the home switch when running off the switch, so the position is registered when the axis is running down with the down speed slowly off the switch.
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Re: Homing Enhancements

Postby ger21 » Fri Sep 08, 2017 12:28 pm

Slaved axis adjustment


I plan on implementing this in the next version of my screenset. It'll be a few months, though.
Gerry
UCCNC 2017 Screenset - http://www.thecncwoodworker.com/2017.html
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Re: Homing Enhancements

Postby Gary Campbell » Sat Sep 09, 2017 3:48 am

"There is no need for these because:"....

This, of course, would be a matter of perspective. Without a setting for the differential, the dual drive axis can only be as square as the switches happen to be mounted. Which cannot be verified until the machine is run. As a service tech on numerous brands of machines, I can say with some certainty that different types of switches can benefit from both different approach speeds and different roll back distances. I also believe that most of the mechanical and some of the inductance sensors have an increased hysteresis when moving off, or release than they do on move on.

It appears, and Gerry has verified that this can be done with a macro, but I am not interested in being in the learn to write macro business. Which of course will be my loss.
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Re: Homing Enhancements

Postby cncdrive » Sat Sep 09, 2017 6:17 am

Higher hysteresis should not be a problem, because it will always be at the same point and same distance, so it will not influance the precision of the reference point.
A problem could be if the hysteresis varies, because that would cause a position difference, but I did not see this with proximity sensors, I mean I did not see a difference if going on or off the sensor.

Yes, I mentioned the same, that the gantry will be only as square as how square the switches are placed, because currently there is no built in backoff distance in the UCCNC.
As said now you can only add a macro to make the separate back-offs or physically adjust the sensors to square.
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