Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: glbaird on June 20, 2008, 12:10:35 PM

Title: Understanding Driver Test
Post by: glbaird on June 20, 2008, 12:10:35 PM
I have Mach3 running fine no problems but cannot find any info on setting the configuration up for
the 25000 mhz or can I use 45000mhz I have done the driver test and it looks like all is fine up to the 65000mhz
test but again don't know the advantage to change from the 25000mhz setting

Anyone have more info on this why change to higher mhz setting if it works at 25000 Why is this option even in Mach3
if we don't know how to use it I have read the complete manual and find nothing that covers it

thanks Greg
Title: Re: Understanding Driver Test
Post by: Hood on June 20, 2008, 02:14:08 PM
If you can get the speed you require by having a 25KHz kernel speed then use it however some people need a faster kernel speed to get their motors running at their max speed. This is all down to the resolution, servo motors use encoders and as an example mine on the Lathe have 8000 pulses per revolution. I have it geared 1:1 and the ballscew has a 5mm pitch. If I set the kernel at 25KHz the max speed I could get is as follows 8000to move 5mm = 1600 to move 1mm  25,000Hz kernel / 1600 = 15.625mm/sec x 60 = 937.5mm/min.
 If I use a 45KHz kernel then its 1687.5mm/min
 If  100KHz kernel then = 3750mm/min
In reality to get the full potential out of my AC servos I need a pulse rate of 2.4MHz and that is why the SmoothStepper is such a benefit to people with high resolution servo systems as it can give a clean pulse of 4Mhz.

Title: Re: Understanding Driver Test
Post by: glbaird on June 20, 2008, 05:53:15 PM
Thanks Hood

I have dc steppers with gecko 203V drivers and all seems to work fine I was unsure of the reason for the mhz changing need

I have tested at 100000 mhz and during the complete test only 2 small jogs in the test line

thanks again Greg
Title: Re: Understanding Driver Test
Post by: Hood on June 22, 2008, 01:54:15 PM
A few questions for general understanding.

When you select a kernal speed, should it be such that it takes into account a worst case of all the axis's running
at some total pulse rate for a desired feed rate of each?
The Kernel chosen will dictate the max speed you can get. If you have a Step (pulse) per unit of 5000 @ 25KHz the max you will get is 5 revs per second(300RPM) at your motor. This is for each axis so no worries about it being shared :)

Is it correct, that with the SS generating the steps and not MACH that the kernel speed of MACH is not so important?
When using the SmoothStepper the kernel in Mach should be set to 25KHz, this is for no other reason other than if set to anything else the plugin shows wrong feedrates in Mach. The feedrate is correct but just shows wrong, set to 25KHz and it displays fine. Other than that the kernel speed has no effect on the SS as all of the pulses are produced externally from the computer.

When talking of "kernal speed" is this the rate that Mach can function / take priority in the Windows enviroment with out something interfering with it's ability to generate pulses?  Maybe I'm just asking for a definition of kernal speed.

 Its simply the max  frequency that the pulse engine in Mach will work at.


Title: Re: Understanding Driver Test
Post by: Hood on June 25, 2008, 07:51:34 PM
I have never seen anything like that on any of my computers, would say it certainly could be a problem. If moving the mouse does that then I would think its going to be putting out a bad pulse to the drives every time you move the mouse. What gets reported in the panel below the graph when its like that?