[cnczeck]

hi guys,
i owne a 7*12 mini lathe with the sieg spindle board but just cant get a fine working spindle control

i do have:
bob with buffered I/O
seperate power supply units to keep optoisolation
5,09V >2A for the bob
12,01V 1A for the cnc4pc C6
fine working index pulse sensor (also cnc4pc)

i run the C6 with 1000steps/unit, 500units/min, 5us
i get a clear output signal of ~5,8V at mach3 max spindlespeed and drawned it down to 5,59V to exactly match the max poti wiper of the sieg spindle control board.
i connected the C6 output to P1 (poti GND) and P2 (poti Wiper) of my Sieg spindle card and pulled all Poti cables off (P1,P2,P3)
So when i give S1100 for max. spindlespeed of ~1100 i do get my max. spindlespeed of 1100 - properly set Pulley at mach3.

The problem is when i want to thread sumthin with S200 - it gives only real ~120rpm.
The C6 OUT gives 0,92V in that case, which i think is also "nearly" fine - 5,59V /1100 *200 = 1,016V - so im not that far away

My spindle doesnt turn that linear as mach3 wants it to turn, max. speed fits, but nothing else

I tried every ****ing combination up to 25khz, 0us<->15us, replacement bob, high/low signals but i never got fitting speeds

After AutoCalc Spindle at Mach3 i get the same results in the other way - s200 results in rpm 260 / s500 results in rpm 540 / s1100 results in rpm 1100


Can someone tell me what im doin wrong?

[neilw20]

You will find it best using the lowest PWM frequency practical.
You probably have PWM distortion, where the rise time and fall times are not the same somewhere in the PWM circuitry between Mach3 and where it is decoded to speed.
Ordinary 'standard' optos are not up to the task.
I use a 10 Mbaud device to overcome PWM distortion.
It is a device used in communications, and has equal rise and fall times, and exact rail to rail output.
A simple open collector trying to integrate with a resistor and capacitor just won't work properly. Charge impedance to capacitor must be the same as the discharge impedance, for starters, and it needs to be CMOS rail to rail drive.
Or simply use a microprocessor, like a PIC to decode the PWM accurately.

See my PM.

[phomann]

Hi cnczeck,

There are a couple of things that are going on here.

Fist is, forget using Mach3 auto calibrate function as it doesn't work properly and causes more problems than it solves.

Delete the linearity.dat file from the C:\mach3 directory. This will reset the linearity profile.

Then, don't play with the auto spindle calibration again.

These are a few notes on setting up a Mach2 PWM controlled spindle for my DC-03 Digispeed, but they should be relevent to the step/dir controlled board you have.



Controlling a spindle via a 0-10V (or 12V) signal from Mach3 is an Open Loop control. Putting aside Mach3 closed loop function that has some problems, there is no feedback loop to to ensure that the speed you are asking for is actually being obtained by the motor.

The control voltage is generated as a ratio of the speed set by the S over the maximum speed set for the Mach3 pulley being used.

So, if you are using Pulley 1 and have set its maximum speed to 5000 rpm, then when you set the speed in Mach3 to 1000 rpm , 2 volts is generated as
1000rpm/5000rpm * 10V = 2V

or a 1/5 of the maximum speed.

Now,the speed of most spindles is fairly linear with respect to the control voltage. More so for VFD controlled spindles as they have their own feedback loop.

A DC spindle is very linear in the 10% to 90% speed range. Below 10% the spindle needs to overcome the drive chain friction and so the actual speed will usually be lower than asked for.

Above 90%, the spindle speed saturates and again is usually lower than asked for. So, the response is 'S' shaped. The important thing to note is that it is linear in the spindle working range. After all, if you want the spindle to go flat out it doesn't matter that it is off by 5%. But, if you want the spindle speed to be 1000 rpm it is important to be as close to that as possible.

You use the Max Pulley speed setting to calibrate the spindle. This is how I do it;

1. Initially let the spindle warm up for 10 minutes running at around 50%
2. Initially set the Max pulley speed to 1000rpm
3. In Mach3 set the speed to 1000rpm and measure the actual speed. (say 3145rpm)
4. Enter 3145 into the Max speed pulley setting
5. Set the speed to around 50%, say 1500rpm and measure the actual speed. It will probably be low.
6. If the actual speed is low, increase the Max speed pulley setting and repeat steps 5 & 6 until the actual speed matches.

Basically, you want to adjust the Max pulley speed to that the actual speed matches the set speed in the area that you do most of the work on you machine. I can usually get the actual speed within a few rpm of what I set.

Hope this helps.

Cheers,

Peter.

[hoss2006]

cnczeck,
If you are trying to thread on your lathe do you have an index pulse feeding into mach via say a C3 board and a pickup on your spindle?
Hoss

[cnczeck]

neilw20,
thanks for pm

hoss,
yes i do have an working index pulse card (cnc4pc C3) for (theoretic) threading
practically it wont work cause the set Spindle command results in way too low real spindle rpm - S200=120rpm
The pid closed loop spindle function doesnt work for me also. it needs ages to claim the set speed and when reached S200=rpm200 its unstable as hell

phomann,
higher pulley settings should do even lesser real rpm?
but ill give it a try in both ways

between p1 and p3 i got 5,59V out. do i may have to raise a little bit to compensate the lower speed range voltage? with 5,59V i allready reach the spindle max 1100rpm btw

[phomann]

phomann,
higher pulley settings should do even lesser real rpm?
but ill give it a try in both ways

between p1 and p3 i got 5,59V out. do i may have to raise a little bit to compensate the lower speed range voltage? with 5,59V i allready reach the spindle max 1100rpm btw

Don't use the closed loop control.

If the actual speed is too low then decrease the max pulley speed . If the actual speed is too hi, then increase the max pulley speed.

There is another issue that may be affecting your linearity.

The C6 uses step/dir control so you also need to insure that you have tuned the steps/unit in the spindle axis tuning tab.

The manual states that it needs a 25KHz signal to generate 10V out.

This also need to be tuned first too ensure that the C6 board is producing a linear voltage out. You need to do this prior to connecting it to the Spindle speed controller.

The thing to watch out with tuning the steps/dir value is that if you give the C6 a too high a value, it will saturate the output and reach the 10V too early. IIRC the step pulse width that you set in Mach3 also affects the gradient of the voltage rise in the C6.

The best thing to do is;
1. The the C3 disconnected from the Motor controller, Turn the attenuation trimpot on the C6 so you get the max voltage out.
1a. measure the max voltage out of the C6, say 11.8V, then
2. enter 1180 as the max pulley speed
3. Set the speed to 50, you should see 0.5V
4. Now graph it out all the way to 1180 (or what your max voltage was)
5. If the graph tapers off at the top, you need to reduce the steps/unit as you are overdriving the C6
6. If it is linear, then increase the steps/unit until you are just at the point where is starts to flatten out and back off slightly

This tuning will ensure that the C6 is producing a linear output. You can then use the trimpot on the C6 to reduce the max voltage to what you need, say 10.0V or whatever.

I used to sell a step/dir speed controller board using the same freq/voltage converter chip, but I pulled it as too many people had problems setting it up as you need to do the above tuning to get a linear voltage output, then tune the motor with the max pulley speed setting. The PWM speed controller method I use in the DC-03 inherently produces a linear voltage output.

Anyway tune the C6 to have a linear voltage output first, then do the motor tuning.

Cheers,

Peter.

[cnczeck]

phomann,
thanks for your time.

As mentioned the C6 allready gives "linear" DC out

The problem is when i want to thread sumthin with S200 - it gives only real ~120rpm.
The C6 OUT gives 0,92V in that case, which i think is also "nearly" fine - 5,59V /1100 *200 = 1,016V - so im not that far away

but those missing ~0,1V only give me about 18 rpm more


i reach the output cap (10,5V) much earlier, way befor 25khz. guess it was 9,5khz iirc at us3 (and youre right pulse width affects the C6 output dramatically)

I'll try the step reducement!

[phomann]

OK, it may be worth measuring the voltage off the manual pot setup to see what voltage is required to set the rpm at 200rpm?

It maybe that the response of the sieg controller is not linear.

The other thing is that at low rpms a greater percentage of the the power being developed is being used to overcome the drive train friction.

Does the lathe have a hi/lo gearbox that could be used?


Cheers,

Peter.

[cnczeck]

Yes, it's a C2
1100 / 2500

[cnczeck]

I spent the whole day fine tuning the C6 board and i wasn't able to get a linear output...

Steps per : 500-1000
Velocity : 100-1500
pulse : 0-15

i fine tuned the C6 output after every new setup at 10V and checked linearity then

i got the best "ration" with 1000steps, 1300 Velocity and pulse 11 resulting in about 15% off at range 10-75%
very weird but the same configuration with pulse 12 hardly overscaled the output range 10-50% by about +50% V

i need 1,34V for 200 rpm, which isnt linear to the maximum speed (5,59V /1100 *200 = 1,016V)

at this point im allready to kick myself for not picking a pwm controller instead of the step/dir one. And shipping charges are too high to get just a pwm controller -.-

i'll give it tomorrow another try before i replace the C6 with the stock poti (and some punches ofc)

[phomann]

Hi,

Try this. Increase the Max pulley setting so that you get 1.34V when you set the spindle speed to 200rpm.

Then see how accurate it is at higher speeds.

Also did you check if the Seig controller gives a linear response when using the manual speed pot? That is plot the voltage off the manual speed pot against the actual rpm. If it doesn't, no speed controller will solve your problem

Cheers,

Peter

[SCzEngrgGroup]

I spent the whole day fine tuning the C6 board and i wasn't able to get a linear output...

Steps per : 500-1000
Velocity : 100-1500
pulse : 0-15

i fine tuned the C6 output after every new setup at 10V and checked linearity then

i got the best "ration" with 1000steps, 1300 Velocity and pulse 11 resulting in about 15% off at range 10-75%
very weird but the same configuration with pulse 12 hardly overscaled the output range 10-50% by about +50% V

i need 1,34V for 200 rpm, which isnt linear to the maximum speed (5,59V /1100 *200 = 1,016V)

at this point im allready to kick myself for not picking a pwm controller instead of the step/dir one. And shipping charges are too high to get just a pwm controller -.-

i'll give it tomorrow another try before i replace the C6 with the stock poti (and some punches ofc)

Just my two cents worth: Buy one of Peter Homanns DigiSpeed spindle control boards - they just work, and work beautifully, and they're cheap (about $35, IIRC). I've been using a DC-05 on my knee mill for years. It took just a few minutes to setup and it has worked flawlessly since day one.

Regards,
Ray L.

[neilw20]

And I second that, for the DC06. The speed error is not worth measuring.

[cnczeck]

phomann,
Today i tried some setups of other step/dir controller with up to 2000steps/per - but no success with my C6

Installed the manual poti again, wharmed spindle up for 30 minutes at 50% voltage
heres what the manual pot brings, measured between GND and poti wiper ofc

RPM - Volt
100 - 0.84
200 - 1.43
300 - 1.82
400 - 2.33
500 - 2.80
550 - 3.04
600 - 3.30
700 - 3.77
800 - 4.27
900 - 4.73
1000 - 5.22
1075 - 5.57

i also attached a diagram

im driving mad, i wanted the spindle control so hard for radius compensation because my small lathe has still problems with cutting off pieces

[neilw20]

The graph is quite linear, but has 0.5 or 0.6v offset. Hmmm.. Just 1 diode drop, almost exactly.
Can you take a photo of the control card so I know which version it is.
The offset is intended to ensure that when the speed control is turned to zero, it is definitely stopped.
It means that your current indicated speed will be offset by a constant amount.
We are getting somewhere now.

[phomann]

The graph is quite linear, but has 0.5 or 0.6v offset. Hmmm.. Just 1 diode drop, almost exactly.
Can you take a photo of the control card so I know which version it is.
The offset is intended to ensure that when the speed control is turned to zero, it is definitely stopped.
It means that your current indicated speed will be offset by a constant amount.
We are getting somewhere now.

My guess is that the offset i due to the mechanical drag/friction in the system that needs to be overcome before the spindle will turn.

Cheers,

Peter.

[cnczeck]

neilw20,
this is my board

[neilw20]

You say you are using the C3 index pulse board. That is to read shaft speed back to Mach3.
What are you using to output the signal to the C6 speed control board?
You must have a breakout board to do that.
How have you wired it. I don't understand.

[cnczeck]

i connected:
GND -> C6 Input GND
DIR -> C6 Input DIR

the C3 gives spindle feeback
bob gives buffered I/O 5.09V of my Computers PSU

added a photo of current montage

I also tested the "mechanical drag/friction in the system that needs to be overcome before the spindle will turn"
declutched the Gears for Pulley 1/2 and slowly increased Poti until the Lathe motor turned slowly. then shutdown the spindle board and clutched in Pulley #1 - it turned.
so the speed where the spindle stops turning is indeed the same speed the motor stops turning without resistance through the gearbox

[neilw20]

As Peter said. Have you deleted the file as per 4th line of post #3?
Ignore the spindle pulse for the speed control, at least for the time being.
The pulse is for synchronizing during threading operations.
You might save the file and examine the contents.
It might be possible to do some manual entry to file to fix up the 0.6v offset.
You can also fix it electronically but you need to add 0.6v from your output signal which is more difficult than subtracting. (just put a diode in series with it)