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Author Topic: Screwcutting issue under Mach4  (Read 1460 times)

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Re: Screwcutting issue under Mach4
« Reply #10 on: March 28, 2020, 08:02:45 AM »
Can you please change your configuration to PWM for the analog output? That may fix you up. I am on my phone now and if it works I will tell you why it is doing it .
Fixing problems one post at a time ;)

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Re: Screwcutting issue under Mach4
« Reply #11 on: March 28, 2020, 09:24:13 PM »
Brian - thank you for your help.
My speed control board (Built in to C11 Bob) only allows for Step pulses. Having said that, I did try resetting to PWM. The result was as expected, I got 3 speeds (dead slow, Mid range and flat out), so no change from parallel port operation. I did try screwcutting, and got a stable mid range speed, but not very useful.
On the same unit tried Mach3/ESS. Worked perfectly. Good speed control, and perfect Screwcutting.

Unless this can be fixed (I hope so, as I like Mach4 / ESS) I do have a couple of options.
Bearing in mind there are 4 machines (2 on USS), and all using the same spindle control.
1) Use a separate Speed control board.
2) Stay with Mach3. (At least I can use up my Current USS boards). Buying ESS as Parallel ports fall over.

Option 1 could be attractive if I can find one that doesn't want to take over everything. (Just PMW in - Voltage out)

Still hoping for a fix however.
Re: Screwcutting issue under Mach4
« Reply #12 on: March 28, 2020, 09:32:17 PM »
Hi,

Quote
My speed control board (Built in to C11 Bob) only allows for Step pulses.

I didn't think the C11 had a PWM to analogue circuit built in.

If I'm correct then a low duty cycle PWM signal would result in an effective low output, ie dead slow
and a high duty cycle PWM signal would result in a high level output, ie flat out and any
intermediate duty cycle would result in an intermediate speed but could not be called controlled.

Can you control spindle speed from MDI? From what you've described I would guess not.

Craig
My wife left with my best friend...
     and I miss him!
Re: Screwcutting issue under Mach4
« Reply #13 on: March 28, 2020, 09:35:34 PM »
Hi,
my apologies I was confusing BoBs, the C11 manual clearly shows a PWM to analogue output.
Please disregard my previous post.

Although I'm still interested can you control the speed from MDI?

Craig
My wife left with my best friend...
     and I miss him!
Re: Screwcutting issue under Mach4
« Reply #14 on: March 28, 2020, 09:55:10 PM »
Craig Thank you for your comments. Yes, the C11 board manual does say PWM - Voltage, but further down, describes how to setup as Step/Dir. I have never got PWM to work with this board's 0 - 10 volt output (Wish I could).
No speed control at all Direct on screen, MDI, or in program. Only Slow, Mid, Fast not speed control at all.

Just found a PWM to Voltage control board on Ebay - Simple, small, Cheap (AUD15.40). Will give this a try, cannot loose.
Re: Screwcutting issue under Mach4
« Reply #15 on: March 28, 2020, 11:49:08 PM »
Hi,
threading requires a stable spindle speed, the more stable the more accurate the pitch of the result.

The key word here is 'stable', is does not have to be accurate. For instance you might dial up 500 rpm
or so, but whatever non-linearaities results in a speed of 400rpm. Mach will read the actual speed, whatever it is
and then calculate the Z axis progression rate to make the thread. It does not matter to Mach particularly that
the speed is 500 OR 400, so long as it stays the same throughout the operation.

In truth Mach does try to recalculate the Z axis progression on the fly in order to get the right pitch despite spindle
speed variation, however the best result is till had when the spindle speed is constant.

You may be interested to know that Warp9's ESS has a fairly new (six months or so) feature of PID spindle control.
The spindle is fitted with an encoder of some kind, including an index signal, and the PWM output of the ESS is
adjusted under PID control to vary the analogue output with a view to control spindle speed in closed loop fashion.
This is a boon if your spindle is marginally powered or has very little inertia. It must be said that the closed loop
bandwidth is not high, certainly not as high as a position loop servo, but sufficent for an improved spindle speed control
for threading.

If you cannot control the spindle speed in a program or an MDI then threading is a joke. You must solve this lack of
spindle speed control. A PWM to analogue circuit can be made with a resistor and a capacitor (5 cents each) at the simplest,
and with an op amp and a handful of resistors an capacitors (less than $5.00) if you want something a bit flash.

Do you have or have access to an oscilloscope? If you do probe the PWM output of the ESS and see whats happening.
I'm suspicious that the BoB is not set up quite correctly.....everyone else has got PWM to work....why not you?

Craig
My wife left with my best friend...
     and I miss him!
Re: Screwcutting issue under Mach4
« Reply #16 on: March 29, 2020, 12:11:21 AM »
Craig
My spindle control works perfectly in Mach3 and Mach4 for everything except Threading under Mach4.
My spindle motor has plenty of power, and in normal turning, spindle speed does not vary at all from no cut to heavy cut.

The issue here is that I need Step/direction control to operate the C11's voltage output, and there is seemingly an issue with ESS/Mach4 when spindle control is not based on PWM. If you do know how to set a C11 board to Control the output voltage based on a PWM signal, Please let me know.

I cannot think why it is an issue, all I expect of the spindle speed control is to stay where I set it, without the ESS/Mach4 virtually shutting off the spindle at the start of the cut. It just needs to match the feed to the indicated speed. Further up this post is a link to a YouTube Video that shows what is happening very well.
Re: Screwcutting issue under Mach4
« Reply #17 on: March 29, 2020, 02:45:26 AM »
Hi,

Quote
The issue here is that I need Step/direction control to operate the C11's voltage output, and there is seemingly an issue with ESS/Mach4 when spindle control is not based on PWM.

Natively Mach4 and the ESS are for PWM. But it sounds like your C11 has a frequency to voltage conveter in it rather
than a PWM to analogue.

One alternative is to get a BoB that has a normal PWM to analogue circuit in it, the C25 ($29.55) for instance.

The other alternative is to use step/direction control....Mach4 can certainly produce a step/dir signal pair for a spindle.
See attached.All that would be required would be to ensure that the step output of the ESS be assigned to the
(spindle) step input of the C11.

Craig
My wife left with my best friend...
     and I miss him!
Re: Screwcutting issue under Mach4
« Reply #18 on: March 29, 2020, 04:15:59 AM »
Craig. yes back where this post started.
I have a problem with Mach4/ESS/Step/Dir Spindle Control ONLY when screwcutting.
All Other functions good. Mach3, same hardware good.
Re: Screwcutting issue under Mach4
« Reply #19 on: March 29, 2020, 04:52:40 AM »
Hi,
have you tried the setting I posted?

Have you considered an regular PWM to analogue board?

Craig
My wife left with my best friend...
     and I miss him!