Spindle speed, vfd and Mach4

I’ve failed to get to the bottom of this so far. The setup is a 2.2kW water cooled spindle with a HuanYang vfd, and Mach4 with an Ethernet Smoothstepper and an MB3 breakout board.

Using MBI, if I run M3 Sxxxx I don’t get the commanded spindle speed. At lower speeds, the spindle runs slightly faster than it should, and at the higher speeds it is slower, eg

6000rpm, 121Hz, gives me 7400

9000rpm, 152Hz, 9000

12,000rpm, 181Hz, 10800

15,000, 214, 12750

18,000, 250, 14,900

21,000, 283Hz, 16,800

24,000, 318 Hz, 19,200

The actual frequency delivered clearly corresponds to the resulting rpm of the spindle, and this is borne out with checks I’ve done so far. I disconnected the analogue output (two wires) from the breakout board and meter to check the analogue output, which shows a perfect proportional output from 0 to 10volts at all speeds ie m3 s6000 gives 2.5v, s12000 gives 5v, etc.

I also connected a benchtop power supply to the vfd analogue input, and again checking with various voltages from 0 to 10v gives the correct frequency and spindle speed, right up to the 400Hz maximum which should be 24,000rpm.

So, the ESS/MB3 is working correctly when tested, and so is the VFD. Mach4 also seems to be delivering the correct information to the ESS. But when it is connected up it doesn’t.

i have the vfd set to 400Hz Max, and 120Hz minimum. I have trawled the Internet for the correct parameters and I’m pretty confident that I have them correct. There are some settings in Mach4 which I’m not altogether sure about - the spindle is set up in the ESS confit as PWM, frequency 50Hz. There is no sensor fitted to it so PID is not relevant. The min and max speeds in the Mach4 config dialog is set to zero and 24,000.

Two possibles that occur to me - first there is a setting somewhere in Mach4 or in the vfd parameters that I’ve missed, or secondly there is some sort of electrical noise that is disrupting the analogue output of the ESS.

Just in case this helps someone else (which is unlikely given the response!!) I have managed, with help, to diagnose the problem. It seems that the analogue inputs of the Huan Yang vfd are prone to generating noise which affects the applied signal. The cure was cheap, simple and 100% effective - a 0.1 uF polyester capacitor across the analog input terminals (marked AO and ACM). As well as restoring the Hz output of the vfd to what Mach4 tells it to be, it also eradicates the hunting that was occurring, with the frequency floating approx +/- 12hz.

Thanks Steve. I will be setting my vfd up on my cnc lathe soon, and this is most helpful.

John

Steve

Thanks for the update , its useful to know a solution to a problem that I may have soon !!! Just received a Huan Yang unit !

Regards

The PWM output is a pulse train and has to be smoothed to generate the steady voltage that the VFD expects to see. Normally one would have a series resistor and shunt capacitor with a time constant (R x C) 5 to 10 times the pulse length (20 ms for 50 Hz, so 100 - 200 ms.).

Steve, I hope that you are still around. I have a very similar setup with the Huanyang VFD, MACH4 and the ESS. I'm having trouble configuring my spindle to get the correct RPM's when commanded. Basically up to 12000 I'm ok but after that Up to 24000 the spindle doesn't change for me. Can you share your VFD SP settings that you use?

Thanks,

Rick

Yes, I’m still around!

I have a file in the workshop with all the paperwork and I’m sure I noted all the vfd parameters - I’ll have a look tomorrow and let you know.

Sorry, it has taken far too long to find the necessary piece of paper.

My parameter settings are:

PD No - setting

1 - 1

2 - 1

3, 4 and 5 - 400 Hz

6 - 2.5 for 50 Hz

7 - 1.2

8 - 220v

9 - 15

10 - 8

11 - set to 133 Hz for air cooled spindle to give min 8000 rpm, for water cooled any figure but below about 6000 rpm gives reduced torque

14 - 5 secs

15 - 7 secs

44 - 2

45 - 3

72 - 400 Hz

73 - 120 Hz

142 - 8.5 amps

143 - 2 pole

You’ll need to check in your manual what each of the parameter settings does, and if in doubt possibly leave some of them at the default, but having said that the important ones to check in your case will be the frequency and no of poles, ie PDOO3,4,5, 72, 143 and 144.

Thanks Steve, I found my main issue with PD 11 not set correctly for 50 Hz.