Messages

261

General Mach Discussion / Re: just bought a little baby cnc 280mm square davinci style thing

« on: February 12, 2023, 03:37:21 PM »

Hi,
You have yet to identify the motor design. Its impossible to say whether its suitable for Mach3 until that question is answered.

Do some testing with a multimeter and determine what the motor is. The answer to other questions may then be apparent.

Craig

262

General Mach Discussion / Re: just bought a little baby cnc 280mm square davinci style thing

« on: February 12, 2023, 02:21:46 PM »

Hi,
Yes, I agree with your Brown and White assignments, Those I would expect to be Motor+ and Motor-.

The two wires for the Hall sensor I dis agree with. Firstly Hall sensors require three wires, a positive and negative supply, and a signal output wire.
Secondly the motor looks to have two wires for DC input, if this were a brushless motor there would be three, so my estimation is that this is
a brushed DC motor.

If that assumption is correct then I would guess the two remaining wires are actually a tacho-generator not Hall senors at all.

Take a multimeter, or better a Kelvin Bridge and measure the resistance between the Brown and White wires. I'd expect to see armature resistance
say 1 Ohm. Then measure between Yellow and Green, if its a tacho generator I would expect to see several hundred Ohms at least.

Craig

263

General Mach Discussion / Re: hello there - help please, how do you do the light sensor limit switch - 3 wires

« on: February 08, 2023, 04:37:59 PM »

Hi,
check on the specs, what I can find of them is that they are 5V devices, you wire them to 12VDC and you'll blow them up.

They can be used as either, or both, Homing and Limit switches, although my preference is for other than Homing switches, not withstanding that they work.

Craig

264

Mach4 General Discussion / Re: Z home tripped

« on: February 07, 2023, 07:44:33 PM »

Hi,

Doesn't one of the ends of contact need to be isolated from each other as there is continuity between the work piece and the tool through the mill itself?

Yes, that is correct. Therefore probing metallic parts clamped in a vice which is electrically connected to earth requires that the probe tip be insulated from the body of the spindle.
You have selected a good way of doing that. I have used 3.128 mm diameter cylinder, which fits my commonly used collet with a layer of heatshrink insulation around and inside a snug fit
brass tube. the tube is very close to concentric, say within 0.05mm, and yet isolated from the spindle/machine earth.

Craig

265

Mach4 General Discussion / Re: What is Out-Of-Band Motor?

« on: February 07, 2023, 03:46:52 PM »

Hi,
another really good use of an out of band motor is for a variable speed pump. In effect you can only jog an OOB, it does not stay coordinated with other axes. But it can of course
be jogged at a certain speed (velocity mode) or a certain 'distance' (incremental mode).

I find this later mode just the ticket to have a pump fill up my beer glass....it pumps 500ml at a time, every time, after all one would hate to over-fill the glass and waste it!

Craig

266

General Mach Discussion / Re: Hi new guy here would like someone to check my math on motor tuning.

« on: February 07, 2023, 03:38:04 PM »

Hi,

I got the same as you. That will get you in the ball park. You will then have to calibrate or fine tune each axis using the axis calibration in mach3

No, the calculation should be perfect. There should be no need to tweak it, if you do then that means that you are doing something wrong or the stepper is missing steps.

It is nice to think that microsteppeing improves resolution, but it does not work out that way in practice. There is a rather long a tedious explanation as to why that is case,
it all comes down to diminishing torque between microsteps. In truth most steppers can do no better than half-stepping, ie 400 step/rev.

The principle gain with micro stepping is not resolution but motion smoothness. Astronomers first invented microstepping with steppers mainly to smooth the movement
of their telescopes. At around 8 microstepps per full step is a good compromise. You get the majority of the smoothing that is available, whatever resolution gain you can get
without overly increasing the signalling rate. I would suggest changing your driver switches to either 8, or 10, or 16 microsteps per full step.

The manner of the calculation remains the same.

Craig

267

Mach4 General Discussion / Re: Z home tripped

« on: February 06, 2023, 08:23:24 PM »

Hi,
if its not causing a fault I wouldn't get to hung up about it. You may well come to some conclusion or even a solution at a later date. In the mean time
you need to start making chips. Nothing but nothing teaches you faster about your machine, Gcode, Mach4....the meaning of life etc than making chips.

Craig

268

Mach4 General Discussion / Re: Z home tripped

« on: February 06, 2023, 08:19:05 PM »

Hi,
the ESS and the BoB will power-up prior to Mach taking control. It is not clear to me whether the ESS starts running before Mach4 runs or vice-versa.

Craig

269

General Mach Discussion / Re: tips for getting started with 2 axis plasma cutter

« on: February 06, 2023, 08:13:51 PM »

Hi,
the issue is lets say you want to cut from 0,0 the current location to 150,150 (in mm) through 6mm steel.

Lets ay you also know that you can cut at 1000m/min with 6mm steel. You could cause this to happen by coding:
G1 X150 Y150 F 1000.

The machine cannot go from zero speed to 1000mm/min instantly, it will have to accelerate up to speed. Likewise at the end of the cut the machine
will have to decelerate to a stop. During the acceleration and deceleration the plasma arc voltage will vary. It might be stable at 100V during the majority of the cut
but the 10mm at each end the voltage will increase, and that is where you expect the tip of the torch to go down a little bit to maintain the right, or optimum cutting voltage.
But what happens when it actually stops, the voltage will increase and the THC will try to drive the tip into the material. This is called 'tip dive'. A good THC system
will have strategies to overcome this called 'anti dive'. It will include at look ahead through the Gcode to find places where it might expect the tip to dive and counter it.

I suspect this is where your notion to use an Arduino will fall short. Very simple THC systems often have the problem of tip dive, and they don't accommodate it well.

Another sure-fire test for a THC system is if you go and do a cross cut over the top of a previous cut. Right at the moment that the arc is in the other cut the voltage will spike high
and the tip of the torch will dive into the plate. For this reason its considered poor practice to cut over the top of an existing cut with simple THC. A good THC with good anti-dive
strategies can do it whereas simple ones fail.

Craig

270

Mach4 General Discussion / Re: Z home tripped

« on: February 06, 2023, 07:23:41 PM »

Hi,
I wonder if as the machine is powering up there is a logic error.

As an example of what I mean, the MB02 breakout boards I used to use from Homann Designs in Australia, the outputs 1,14,16 and 17
all go high when the BoB is powered but the ESS is not yet in control and running. If I'd had a coolant pump or something controlled by one of those
outputs the pump would run as soon as the machine was powered.

In the event I made my own breakout board because I was running servos and wanted differential Step/Dir outputs and I want 24V tolerant Enable, Reset
and Alarm signals. I was able to ensure as part of my design that no inputs or outputs clashed while the machine is powering-up but before Mach/ESS was in control.

Maybe your limits are changing state part way through the power-up phase.

Craig