Very mysterious dropping steps on one Y axis motor...I'm starting to lose it!!

[JAZZCNC]

Thanks so much for helping me with this.
Here's where I'm at.
Like you said I made a test toolpath that jogs the Y axis up and down 100 times.
First I ran it with motor A polarity reversed and sharing motor Ys signal from the control board. it worked fine.
Next I ran it with motor A slaved off motor Y with motor A step low activated and it lost steps.
Then I ran as above with motor Y step low activated and it lost slightly more steps.

What controller are you using and what frequency is it running at.? If the frequency is too fast then the drive opto's might not be able to keep up so steps are getting lost.

[Hatchett Job]

This is the board I have.
Is the frequency the Kernal speed in ports and pins configuration?...if so it's 25,000hz

[JAZZCNC]

This is the board I have.
Is the frequency the Kernal speed in ports and pins configuration?...if so it's 25,000hz

Ok so you are using the parallel port now I'm not saying that is your problem, thou it's highly possible, but what I am suggesting is you do yourself a favor and buy an external motion controller like the AXBB-E which uses an Ethernet connection. Combine this with more volts for the steppers and you'll transform the machine into a different animal.

It will be more reliable and faster, you'll also be able to dump Mach3 and go with UCCNC software which is much better.

Now back to your issue.!

Because you are using the parallel port some of this could be because you have the machine overturned, So give us the settings you have for the motor tuning and the micro-steps set on the drives for each axis.

Also, have you checked the STEPS PER is correct by measuring it moves the correct distance told.?

[Hatchett Job]

Yeah that Ethernet board does look like a better job alright.
Here's pics of my my motor tuning and the motor controller jumpers.
Yup I have the steps per distance set correctly.
That in itself has been an issue, when I use the feature in Mach 3 settings to do this the actual cut dimension is different so I have to make a cut and measure that.

[Cube3]

Many moons ago I used that board and had missing step issues. I put it down to the speed of the opto isolators, but couldn't say for certain.I then used a board from CNC4YOU which was a lot better and worked ok in Mach3 and had 10v PWM for the VFD.

I finally got fed up with Mach3 and bought the AXBB and wouldn't go back. I can now run my toolpaths without babysitting the machine and hovering over the emergency stop button. Very confident with UCCNC.

Sent from my SM-A715F using Tapatalk

[dazp1976]

Many moons ago I used that board and had missing step issues. I put it down to the speed of the opto isolators, but couldn't say for certain.I then used a board from CNC4YOU which was a lot better and worked ok in Mach3 and had 10v PWM for the VFD.
I finally got fed up with Mach3 and bought the AXBB and wouldn't go back. I can now run my toolpaths without babysitting the machine and hovering over the emergency stop button. Very confident with UCCNC.
Sent from my SM-A715F using Tapatalk

Same.
Although went the UC300eth and UCBB route.

I did however have zero issues with the 5 axis parallel board and mach3 at 35,000 khz.
Will be re-using it on uc300eth port#3 for switching some relays.

[Doddy]

Just a point of sanity - that board has no opto-isolated outputs to drive the stepper driver (which will have) - the buffer devices - 74HC series has a rise/fall time measured in 10's of nano-seconds and current source/sink in the order of 35mA - that's NOT the problem here.

[dazp1976]

Just a point of sanity - that board has no opto-isolated outputs to drive the stepper driver (which will have) - the buffer devices - 74HC series has a rise/fall time measured in 10's of nano-seconds and current source/sink in the order of 35mA - that's NOT the problem here.

That's a good point.
Only optos on the inputs.
I'm pointing to the 48v psu.
Might turn out he's trying to run 2* 86's on a single 350w.
Not happening.

Prev user prob had same problem.

[Hatchett Job]

You guys have started to lose me with the Opto isolators chat, can you put it in layman's terms?
Also the relevance of the frequency?
I'm good at making stuff but electrical engineering and computers are not my strong point.

[Doddy]

Apologies. This particular thread of conversation started with questions around signal integrity (pulse widths, and the like). That lead into a general concern if the breakout board (bob) might suffer in its design with the use of slow opto-isolators - devices that act like electronic switches, that would couple the stepper pulse from the computer to the stepper drivers. It’s a weakness in design that crops up from time to time and exhibits the problems you have witnessed. My post was simply to identify that these devices are not present on your bob, for the stepper driver signals, and that we shouldn’t get distracted with talks of changing bobs on the basis of an invalid assumption.