KFLOP to Spindle VFD Controller (cnc4pc C6 board) struggles

[mckoz]

Background: I've just converted from a parallel port solution to the kflop, as I was unable to get deterministic performance, regardless of the PC chosen and optimization performed. The KFLOP has been a bit daunting, as I haven't been able to connect the dots in all cases. I am attempting to interface from the KFLOP to a VFD controller board from CNC4PC, the C6 board, for spindle control. My CNC has a 2HP 3450 RPM AC motor driven by a T-Verter N2-Series VFD that uses a 0-10V analog input to control speed.

Prior to changing to the KFLOP, I had all axis' and spindle working, just not working to my satisfaction.

On the kflop, I am doing the following:

Axis 0 = x-axis (gecko 320) (working)
Axis 1 = y-axis (gecko 320) (working)
Axis 2 = z-axis (gecko 320X) (working)
Axis 3 = spindle (step and direction to C6 Board) (not working)

I am struggling understanding the following:
1. Can I use Axis 3 to drive the spindle?
2. What configuration settings do I use in kmotion?
3. How do I produce a step signal in kmotion?

What I have tried (and failed at):
The KFLOP documentation says: "it is possible to configure an Axis Channel to output current Speed directly to a DAC." This is located HERE. It references channel 7 and I am unsure if I simply change the 7 to 3 across the board and it should work or if there is some other method. I have tried changing them from 7 to 3 and have had no luck.

Help is GREATLY appreciated.

David



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[TomKerekes]

Hi mckoz,

Yes you should be able to use KFLOP Axis 3 to output Step/Dir Pulses to the C6 board drive your Spindle. You don't have Kanalog with DACs so that reference does not apply to you.

I believe the C6 requires Sourcing Outputs (which is different from the G320s). So you will need to use KFLOP's TTL output mode (by adding 8 to the output channel number). Set KFLOP Axis 3 up as a Step/Dir Output mode and set OutputChan0 = 3+8=11. You will also need a GND connection to the C6 board. Then test by commanding Jog commands on the KMotion Console Screen such as Jog3=2000

HTH
Regards

[mckoz]

Tom, I did what you recommended, and by using a multimeter across Pin 21 and pin 25, I showed the following:

jog3=1000 turned 999.9 hz
jog3=2000 turned 1999.8 hz

That looks good, however I'm getting nothing from the C6 board 0-10V output, regardless of whether I use output #3 or #11. I can think of three options and would like your guidance:

1. The C6 board is defective (it is new).
2. The input frequency is somehow wrong?

Here is the input spec page:



and here is the manual: http://cnc4pc.com/Tech_Docs/C6R6_2_USER_MANUAL.pdf

[TomKerekes]

Hi Mckoz,

Did you connect a KFLOP GND to the C23 (GND near the Step Input) ?

Are you providing the +12V to the 23?

Regards

[mckoz]

I think you mean C6 instead of C23?

1. KFLOP JP7 PIN 25 is connected to the GND next to the step on the C6.
2. I am supplying 12VDC to the C6.

The full wiring diagram I prepared for you is attached in the first post for reference.

[TomKerekes]

Hi mckoz,

Yes I meant C6.

Your original wiring diagram does not show a GND connection that I can see. Are you saying you added one?

I don't know. The only other possibility I can think of is that the Step Pulses are not large enough. By default KFLOP has 2us pulses. I think the C6 specs 3us minimum. KFLOP can output a maximum of 3.78us by executing C code of:

FPGA(STEP_PULSE_LENGTH_ADD) = 63 + 0x80; // set polarity and pulse length to 3.78us

Also I believe 25KHz is required to get the full 10V out so 2KHz would only be 0.8V so you might try 10KHz or more - but you observed "nothing" ?

Otherwise if the step pulses are verified to be present from KFLOP then the problem should be further downstream.

Regards

[mckoz]

I looked back and the PNG file I uploaded was missing the ground circuit. Here is the updated diagram that reflects current wiring (and has the ground - it's been there all along, my apologies). I changed the console code to jog3=20000, and my fluke picked up the frequency change to 19,998hz, so that appears to work; however no change in output voltage.



This leaves me to try the larger pulses. I greatly appreciate the command, however I am unsure how / when to run the command. If I open the program screen, I have a sample program that says:

#include "KMotionDef.h"

main()
{
printf("Hello World!\n"); // send message to console
}

Would you mind directing me to the documentation or directly to the method to execute the FPGA command you listed?

Thanks, David McKay

[mckoz]

Just edited post, wrong image again.

[mckoz]

Ok, I thought I would try something and it appears to have worked. I put this in the program screen and then hit the button that says, compile, download and run:



Then using the console I typed: jog3=20000 and now the output of the 0-10V is 6.40 volts! So, if this is the case, it would also explain why the C11T would never work for transmitting step signals from the KFLOP for the x, y and z axis geckos - the pulses weren't wide enough!

I currently have removed the C11T, this makes me want to put it back in the system;

Two questions, Tom:

1. Does the FPGA command you gave me apply to all of the step signals processed by the KFLOP?
2. Is there any advantage to shortening the pulse length slightly since we went all the way to the maximum?

Cheers, David

[mckoz]

Good morning Tom, one test completed and three questions remain.

I swapped the C11T board back in place of the C6 and it works on the wider pulse length as well. I haven't had time to test the wider pulse length with the geckos on x-y-z, will do later today.

Questions:

1. Does the FPGA command you gave me apply to all of the step signals processed by the KFLOP?
2. Is there any operational disadvantage to keeping the width of the pulse at max?
3. I have the spindle moving both directions in the console and kmotioncnc, however I am only able to change speed in the console. I assume I need to tell kmotioncnc that axis three is my spindle, but can't find the link in the documentation. Would you point me towards it?

Thanks for your support, David.

[TomKerekes]

Hi David,

1. Does the FPGA command you gave me apply to all of the step signals processed by the KFLOP?

Yes it is global and applies to all 8 of KFLOP's Step/Dir Generators

2. Is there any operational disadvantage to keeping the width of the pulse at max?

It limits the max step frequency to about 1/(4us x 2) = 125KHz.

If you require higher frequencies for your other axes then an alternate approach might be to use KFLOP's Quadrature Output Mode for the spindle. This would generate a square wave type of output instead. I believe the C6 would be ok with that. However the "Direction" would then be another square wave (the B phase) and wouldn't work as a direction signal. But another manually driven Output could be used for the direction control.

3. I have the spindle moving both directions in the console and kmotioncnc, however I am only able to change speed in the console. I assume I need to tell kmotioncnc that axis three is my spindle, but can't find the link in the documentation. Would you point me towards it?

Basically a SpindleJog.c program needs to be created and configured to KMotionCNC's "S" code to receive the desired RPM setting and command the appropriate Jog Speed. See:

KMotionCNC Spindle Control


HTH
Regards

[mckoz]

Ok Tom, I believe I have connected the dots. I modified one of your user programs, but I am not understanding what variable kmotioncnc uses to pass the requested speed to my C program, nor if there is a way to define it in kmotioncnc.

Here is my clockwise jog program currently:

#include "KMotionDef.h"

#define SPINDLEAXIS 3
#define FACTOR 20.5 // custom factor using Hellcat CNC L1=H, L2=3 60000=60.00hz
#define SPINDLE_ENABLE_BIT 0
#define SPINDLE_DIR_BIT 1
#define SPEEDVAR 99
#define STATEVAR 98
#define KMVAR 1

// Old Code:
// #define SPINDLECW_BIT 1
// #define SPINDLECCW_BIT 155
// End Old Code
// desired speed is passed from KMotionCNC in variable KMVAR
// save in user variable STATEVAR whether it was off, CW, or CCW (0,1,-1)
// save in user variable SPEEDVAR the last desired speed

main()
{
	float speed = *(float *)&persist.UserData[SPEEDVAR];  // value stored is actually a float
	float LastState = persist.UserData[STATEVAR];  // get last state

	if (LastState==-1)
	{
		// if spindle was CCW now we want CW
		// spin down

		ClearBit(SPINDLE_ENABLE_BIT);
		Jog(SPINDLEAXIS,0);
		while (!CheckDone(SPINDLEAXIS)) ;
	}

	// turn spindle on CW
    ClearBit (SPINDLE_DIR_BIT);
    // Start and ramp to new speed
    SetBit (SPINDLE_ENABLE_BIT);

	// spindle is already on, so ramp to new speed
	//Jog(SPINDLEAXIS,speed * FACTOR);
	Jog(SPINDLEAXIS,speed * FACTOR);
	printf("Jogging Spindle %f counts/sec\n",speed * FACTOR);

	persist.UserData[STATEVAR] = 1;  // remember we are CW
}

[TomKerekes]

Hi David,

I left out some of the details. There are actually four C programs involved in Spindle Control:

1 - OnCWJog.c (M3)
2 - OnCWJog.c (M4)
3 - OffJog.c (M5)
4 - SpindleJog.c (S)

These are a bit complicated because of the way GCode works. Sometimes when the GCode encounters an "S" command the speed should change right away and sometimes the spindle should remain off and just remember the new speed until the spindle is turned on. However you shouldn't need to worry about this and just use these example programs from the

<>\C Programs\SpindleUsingJogs\CSS

directory and get all the required functionality.

All 4 of these C programs include a file called MySpindleDefs.h. This allows you to change only one file and have all 4 of the programs use the changes automatically. It is sort of like the compiler cuts/pastes that file into each of the 4 files when it encounters the #include statement.

It looks like you modified a program related to OnCW.

When you configure in KMotionCNC which C program to use for the "S" command you can also specify which "Var" the speed should be placed into. This must match the corresponding setting in MySpindleDefs as defined by the KMVAR. I don't think you are needing CSS so you might just use Var=1 (on both sides). But if you need CSS then a special var must be used defined as PC_COMM_CSS_S which is internally defined as 133.

Let me know how much of this you understand.
HTH
Regards

[mckoz]

Hi Tom, ok, I have the spindle working, in fact have added some modifiers to the spindledefs to "curve" match the non-linear nature of the VFD to output. Not happy with the tolerance, will definately be changing to closed loop spindle control. At the bottom of this post is what I have done to get the speeds closer to the reality.

In the meantime, I can't figure out how to tell kmotioncnc which axis=x and y and z. Can you help me with this?

#define SPINDLEAXIS 3		// Axis Channel to Jog to rotate Spindle
#define FACTORBHK3R270 37 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=270-400
#define FACTORBHK3R401 23 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=401-874
#define FACTORBHK3R875 22.8 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=875-950
#define FACTORBHK3R951 21.9 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=951-1250
#define FACTORBHK3R1251 21.4 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=1251-1500
#define FACTORBHK3R1501 20.9 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=1501-1850
#define FACTORBHK3R1851 20.5 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=1851-2650
#define FACTORBHK3R2651 20.3 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=2651-2850
#define FACTORBHK3R2851 20.1 // custom factor using Hellcat CNC BOB=H, Kaboom=3 60000=60.00hz RPM=2851-3200
#define SPINDLE_ENABLE_BIT 0   // bit to enable spindle
#define SPINDLE_DIR_BIT 1	// bit to activate direction 0=CW, 1=CCW
#define SPEEDVAR 99			// global persistant variable to store latest speed
#define STATEVAR 98			// global persistant variable to store latest state (-1=CCW,0=off,1=CW)
#define KMVAR 1 // variable KMotionCNC will pass speed parameter (1)

and

	// spindle is already on, so ramp to new speed
  /* check the speed factor to use */
   if( speed > 269 && speed <=400 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R270);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R270);
   }
   else if( speed > 400 && speed <=874 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R401);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R401);
   }
    else if( speed > 874 && speed <=950 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R875);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R875);
   }
    else if( speed > 950 && speed <1250 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R951);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R951);
   }
    else if( speed > 1250 && speed <=1500 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R1251);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R1251);
   }
    else if( speed > 1500 && speed <=1850 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R1501);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R1501);
    }
    else if( speed > 1850 && speed <=2650 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R1851);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R1851);
   }
    else if( speed > 2650 && speed <=2850 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R2651);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R2651);
   }
else if( speed > 2850 && speed <=3200 )
   {
       /* if condition is true then modify speed factor*/
        Jog(SPINDLEAXIS,speed * FACTORBHK3R2851);
        printf("Jogging Spindle %f counts/sec\n",speed * FACTORBHK3R2851);
   }

[TomKerekes]

Hi David,

Use the C Function DefineCoordSystem() to define which KFLOP Axis Channels correspond to which GCode XYZA axes. So for a normal XYZ system code:

DefineCoordSysyem(0,1,2,-1);

-1 indicates that the A Axis is not used.

I think there is a flaw in your linearization scheme. If you plot the result the piecewise linear correction "curve" will have discontinuities. For example as the RPM reaches 400 the speed will approach 14,800 but at RPM of 400.01 the speed will drop back to 9200. So you might add in (14800-9200) to the second segment to keep things continuous.

Regards

[mckoz]

Thanks Tom, I do see the discontinuity and will do some checking. Two questions on using the C function:

1. Is that included in a setup or initialization program you would recommend creating and running on startup (in the kflop)? I have the earlier FPGA command as well, wondering if I should create something.
2. If no, is that included in spindledefs? (or better yet, where do I use the command?)

Another independent question: can you give me an example of how code different gear ratios so they are selectable in kmotioncnc? I have two gear sets, one high-low, then a "following" gear set that has 1, 2 and 3. The example I'm asking for would include a way of selecting the gear, then using custom factors, likely in spindledefs) based on the gear selection to input the correct speed.

[TomKerekes]

Hi David,

I can't really follow what you are doing. But as I described earlier these are 4 separate C programs that are assigned to M3, M4, M5, and S. The code would not be included into the initialization program.

The FPGA command to set the maximum pulse width should be added to the Initialization Program. It only needs to be executed at least once after power up.

Regarding gearing: KMotionCNC doesn't provide any direct support for that. You might do somethng like create two custom User Buttons called "High Gear" and "Low Gear" where one sets a Virtual IO Bit (ie 48) and the other clears it. Your M3,M4,S programs can then test this bit (ie. if (ReadBit(48)) ) and select a different factor. You could also define MCodes (ie M100 and M101) to select the Gear also.

Regards

[mckoz]

Hi Tom, Figured out the initialization program by looking at some of your other posts.

I just put a photologik OPB940 slotted photoeye that is tripped every time around by the spindle. I'd like to investigate using it close the loop on the spindle VFD control and getting rid of the curve fitting entirely. Do you have any application and code examples for this use case?

Edited: I also have the option to mount another identical sensor, and based on reading this post:

Dynomotion/Kflop/Kanalog > Kflop. Spindle VFD digital control by pulse train

It sounds like the two sensors could then act like an A/B encoder pulse? If that is the case, I would be interested in your thoughts on where to mount the sensors in relation to each other: side by side, 90 degrees, 180...?

[TomKerekes]

Hi David,

Yes if you add 2 sensors placed 90 degrees apart on a disk that triggers the sensors for 1/2 of a rev then the AB signals could be connected to a hardware encoder input and it should behave exactly like an encoder with 4 counts/rev.

With just a single pulse you would need to count the transitions in software. Below and attached is an example program. The "pulse" must always be at least 180us long at your highest RPM (probably not an issue). You will need to determine the COUNTS_PER_REV2 value such that the measured speed matches the commanded Jog Speed.

Regards

#include "KMotionDef.h"

main()
{
    for(;;)
    {
        WaitNextTimeSlice();
        ServiceSpindleCount();
    }
}



#define SPINDLE_PULSE_BIT 46
#define SPINDLE_AXIS 5
#define COUNTS_PER_REV2 1000

void ServiceSpindleCount(void)
{
    static int LastState=0;
    int NewState;
    
    NewState=ReadBit(SPINDLE_PULSE_BIT);
    
    if (NewState != LastState)
    {
        chan[SPINDLE_AXIS].Position+=COUNTS_PER_REV2;
	LastState=NewState;
    }
}

[mckoz]

I will give it a shot! Thanks Tom.