[tangeray]

Hello all,

Did my searching beforehand and been jobbing on this all day...here it goes..

First off, I built and have been operating a CRP4848 for the past 5 years with a Hitachi M12VC with no issues running Mach 3. Recently upgraded to the Chinesium 2.2kw watercooled spindle VFD and built a new computer so trying to square away settings...here is what im up against.



MACH 3 Commanded Feedrates dont match Actual gantry drive speeds:

My motors are set to max speeds of 860ish in the motor tuning pages. I have the standard A axis slaved to X on NEMA 23s. Mach 3 will NOT let me set my motor speeds higher than this 860 number for whatever reason. When I hold shift and do a rapid move, My "Units/min" box shows approx 197. I measured the actual gantry movement, and it is showing the actual movement travelled.

When I issue a G1 X25 F60, my "units/min" box shows something like 8.5, and its actually moving at 8.5 inches in that minute. I dont understand where the disconnect is, all units are set to inches and either way, the numbers dont make sense that it is a simple units mistake (IE. 860mm is not 197 inches)

Im stumped. I know this isnt normal because I normally try and run at 60 IPM for hardwoods and its running right now at 8-9, something is wrong.


Any help is appreciated!! go nuts....

[dazp1976]

First off I'd check your jog settings in the dialogue box (pressing tab on keyboard) and see if it's all at 100%.

If I'm doing say a manually fed face skim I drop the speeds via the jog box. Sometimes forget to put it back before next use.
Easier than changing all the motor velocities.

My Mach 3 is also off slightly but nothing like yours (only about a 20-30mm/min difference) never figured it out.

[tangeray]

checked the jog settings. All sitting at 100 percent. Anyone ever experience this or have a work around?

Thanks,

[tangeray]

***UPDATE***

Been messing around with a mach 3 on my side computer messing with settings to try and figure this out. I made some progress in the fact that if i up my Kernel speed from 25khz to 45khz, then i am within 30% of the commanded feedrate as actual feedrate. So when I command a G1 X20 F100, I get an actual feedrate of 70IPM. Small workaround is I set the Feedrate overide to +30% to compensate and now the numbers are accurate. My question now is, am i jerry rigging this thing just to make it work? or is there a proper fix to this issue rather than speeding up the kernel and offesetting the Feedrate overide, OR...is this how you have to do it?

Thanks,

[ger21]

If you're using the parallel port, make sure the actual kernel speed matches what you have set. Run Drivertest.exe in the Mach3 folder.

[tangeray]

If you're using the parallel port, make sure the actual kernel speed matches what you have set. Run Drivertest.exe in the Mach3 folder.

Do you mean run the drivertest to ensure that my 45k kernel setting in Mach 3 is actually giving out 45khz? Or are you saying that there is a place within the parallel port setup in the bios to select which kernel speed you would like?

Thanks ger...

[ger21]

Yes, the driver test will show the actual frequency you are getting.
Either the frequency is way off, or you have some settings wrong somewhere.

Mach 3 will NOT let me set my motor speeds higher than this 860 number for whatever reason.

Most likely because you are trying to exceed the kernel frequency.

[joeavaerage]

Hi,
there is a simple calculation that determines the maximum frequency pulse stream required of Machs parallel port in order for
your machine to achieve the max velocity you have programmed it for.

Max Frequecy= (steps per unit) x (max velocity in units per min) / 60

For example (in mm units):
Steps per unit = 500
Max velocity = 1500 mm/min
MaxFrequency= 500 X 1500 /60
=12500
=12.5kHz

So with these settings if you just leave Mach's kernel at its default of 25kHz then it will be adequate to drive your machine to its maximum.
If however you set a whole bunch of micro-stepping:
Steps per unit =5000
Max Velocity =1500mm/min
MaxFrequency= 5000 x 1500 / 60
=125000
=125kHz

So in this setup Mach's kernel would need to be 125kHz minimum, but that's a problem, Mach's parallel port can only go to 100kHz
and most PCs don't much like going faster than 35-45kHz. The rule with Mach is 'use the lowest kernel frequency you can and still meet your
resolution and max speed requirements.'

With Mach's parallel port there is a distinct limit to the resolution and max traverse speed.

External motion controllers tend to be much MUCH faster, for example the max frequency from an Ethernet SmoothStepper is 4MHz,
160 times faster than Mach's default parallel port kernel speed. External motion controllers are good for high resolution servos and fast
traverse speeds.

Craig