Messages

6801

General Mach Discussion / Re: Loosing steps on the Z?

« on: August 26, 2017, 12:27:17 PM »

Hi,
try reducing speed and acceleration to half of current settings and try again. If it solves the problem you'll know that the problem is lack of torque
on Z axis motor. If it doesn't solve it then I would be looking at an electrical/mechanical issue.

Craig

6802

General Mach Discussion / Re: Control A131 ASKPOWER with MACH3

« on: August 26, 2017, 12:22:14 PM »

Hi,
the G540 is setup for one analogue output. One of the digital outputs could be used as a relay signal. May I suggest using this scheme while you
consider the coding required to implement Modbus control.

On the ESS assign pin 14 port 1 as PWM output, pin 17 port 1 as relay. Once the G540 is plugged in screw terminal 8 should be analogue voltage out
with screw terminal VFD ground and screw terminal 9 as VFD 10V. Screw terminal 5 is on/off signal for VFD, a relay maybe.

Craig

6803

General Mach Discussion / Re: C11G PWM control voltages go down when increasing speed in Mach3

« on: August 26, 2017, 01:29:37 AM »

Hi,
it is certainly possible to use an opamp to invert the signal but it shouldn't be necessary. Finding out what the problem is will probably
stand you in good stead down the road.

If you probe the input to the BoB, that is pin 14 of the DB25 connector. If you flip the board upside down you should be able to probe it without
shorting to any adjacent terminal. Be sure to read up on the pin numbering scheme for a DB25, it is different to most connectors.

I would expect to see a normal PWM, that is to say a short logic high followed by a longer logic low for low rpm. MDI a high rpm, s=20000 say,
and I would expect a long logic high followed by a shorter logic low. Given the description of your problem I think you will find that what you
see will not be what is expected indicating a fault or incorrect setting in the ETH400 which drives the BoB.

I use an ESS and so can't comment on the plugin of any of the CNCDrive products. I would have thought there must be some sort of plugin and settings
that can be made.

One reason I suggested that you disconnect the VFD is so that should the internal impedance of the VFD somehow feed back into the BoB its contribution
can be eliminated. If you experiment and can be 100% sure that there is no conflict between the VFD and the Bob then hook it back up. I don't know
how many times when diagnosing electronic faults I have overlooked or assumed a certain thing only to find later, usually much later, that the fault was in
fact very simple but I precluded myself from finding by virtue of my mindset. I try to eliminate faults like that but realise that as long as my anus points
downwards its not likely to happen!

What are you using for a power supply for the analogue control signal? The BoB itself is 5V so how is it supposed to produce 0-10V? I would have expected the
output buffer to be between 0 and 5V. Here again if the VFD is disconnected it would preclude any confusion as to which device is sourcing voltage.

Craig

6804

General Mach Discussion / Re: movement on curve manually in oxy cutting machine by Mach3

« on: August 26, 2017, 12:09:23 AM »

Hi,
have you experimented with G3 and G3? I've found that the centre format command style to be useful assuming you know where the centre of the
arc is supposed to be.

Craig

6805

General Mach Discussion / Re: C11G PWM control voltages go down when increasing speed in Mach3

« on: August 25, 2017, 11:46:54 PM »

Hi,
I think that maybe you should disconnect the VFD for the moment. Until you get the voltage from the BoB sorted it will only confuse you.

Double check that the pin you are measuring is pin 14 and that you have identified the LED that reflects its current output state.

You say you are using an ETH400, then you have another whole board in the system that we did not know about. Do you have an oscilloscope?
I think your going to have to probe the input to the BoB, I now suspect the ETH400 is producing a signal of inverse polarity. I'm guessing
or perhaps hoping that the ETH400 has a setting in its plugin which determines the polarity of the PWM signal.

Craig

6806

General Mach Discussion / Re: C11G PWM control voltages go down when increasing speed in Mach3

« on: August 25, 2017, 09:10:47 PM »

Hi,
I'm looking at the C11 manual. On page 7 it shows that pin 14 should be PWM output pin.

Section 7.2 page 10 shows an LED installed across the output. With the recommended IEEE 1284 pull-up at the input then the output buffer should be
low in absence of PWM, ie the LED should be off.

The LED should increase in brightness as the PWM duty cycle increases, ie Mach demands increasing spindle speed. Is This what you see on the board?

Craig

6807

General Mach Discussion / Re: C11G PWM control voltages go down when increasing speed in Mach3

« on: August 25, 2017, 08:49:34 PM »

Hi,
do you have a multimeter? If so measure the voltage at the pin.

It should change if you reverse the polarity of the PWM signal.

What pin are you using for the output? Could it be a pull-up or pull-down signal which is confusing the issue?

Craig

6808

General Mach Discussion / Re: C11G PWM control voltages go down when increasing speed in Mach3

« on: August 25, 2017, 08:12:38 PM »

Hi,
tweakie has already told you

Config/Ports and Pins/Motor Outputs---reverse the Spindle Step Low Active setting.

Craig

6809

Mach4 General Discussion / Re: New people welcome !! Come in here and introduce your self!

« on: August 25, 2017, 06:25:41 PM »

Hi racewayron,
welcome aboard. Mach4 doesn't drive your servos directly, Mach4 lives on a PC which in turn talks to a motion controller (an electronic board worth
a couple of hundred dollars or so) and that tells your 110V servo drives what to do.

The trick for you is to determine 'what instructions/voltages/signals' do your drives require which will in turn determine the sort of motion controller you
will require. I suspect you will find that the 'Mach' part of a Mach4 conversion will be easy....the motion controller to servo drive link will probably
have you scratching your head for a bit.

Do you have any manuals, particularly circuit diagrams, of your mill? They would help enormously.

Craig

6810

General Mach Discussion / Re: Loosing steps on the Z?

« on: August 25, 2017, 05:52:08 PM »

Hi,
steppers lose torque the faster they go. You can try to counteract that by using high voltages to drive them but it seems that 80V is about the limit
for readily available drivers.

The graph attached shows a fairly typical two phase 23 size stepper rated at 198 oz.in. You can see by 500 rpm the pullout torque is reduced to about
half and by 1000 rpm down to about a quarter of rated torque.

On the Tormach website there is a clip where they assign the max speed to any stepper of 375 rpm to ensure that the torque remains high enuf for reliable
motion, ie without losing steps. Tormach are quite conservative. I regularly think that 500 rpm is a reasonable compromise.

If your machine has a 5mm pitch screw then at 500 rpm that works out to 2500 mm/min or about 100 in/min. With a 10mm pitch screw that would be
about 200 in/min but remember a 10mm pitch screw is going to need twice the torque to drive it...you may be in danger of exceeding the pullout torque
of the stepper and create a stall.

Stepper motors are great at slow speeds, in terms of 'torque density' they are better than a servo of the same size. As the speed gets up that's where servos are
come into there own. Downside is that servos, even cheap ones are much more than a stepper. Don't lose hope though...many CNCers use steppers with great
results.....just be aware that there is a speed limitation.

Craig