Newbie- Easy Mach question

[Scottluther]

I'm trying to setup Mach3 for the first time and have a couple of questions:

1) easiest one first. The active low check box, is it suppose to be a check or an X? Does X mean active high? And a check active low? So if I'm wiring an NC limit switch, i think of it as triggered when open, so active low, that would mean a Check in the box? Or does it mean under operating conditions it is active high and should have a X in box. Same question with step and direction pins.

2) other question is about motor tuning and setup. I will be working in metric, do I still set up the motor tuning in in or should in convert my TPI to meteric and use those numbers for that screen. I ask because there was a warning screen about this not being we're you setup units.


Thanks

Scott


Ps. Does anyone have/know of a 5 axis screen with a larger resolution like 1280x768

[Eurisko]

Mach's setup screens can be very confusing. The green check mark = active low, the red X = active high. This is true for the input pins and the step and direction pins. For example, if your limit switch goes from high to low when triggered, it is "active low".


And now for the "native units" setting.
I use 5mm pitch ball screws on all axes, so I use mm as the "native units" setting in Mach. Note that the "steps per" setting under "motor tuning" is how many steps Mach must output to advance the axis one native unit. In my case, the motor shaft is directly coupled to the screw. One revolution will move the axis 5 mm, 1/5 revolution will move the axis 1 mm. There are 2000 steps per revolution, and 400 steps in 1/5 revolution. So, my "steps per" mm = 400.

Also note that the "native units" setting is strictly used for motor tuning, and all motors have to use the same "native units". I could just have easily used inches as the native units, and the "steps per" inch would be set to 10160.

To borrow a catchphrase from a popular infomercial, "Set it and forget it".
Set your "native units" whichever way you want, inch or mm, and forget about it.

Even though I use mm for the "native units", I'm not forced to use mm in the actual gcode. I program in inches. Use G20 to set inch programming. Use G21 for metric.

[ger21]

It's recommended to set the native units to whatever units you'll be using in your g-code. So if you're g-code will be in inches, set you're native units to inches.

It's also recommended that if you'll be using both metric and imperial g-code, that it's best to setup two profiles, one with inches as the native units, and one with mm's as the native units.

While in most cases you can run either by using G20/G21, there's a greater chance for problems to occur.

(These recommendations are from the original author of Mach3)

[Eurisko]

Originally Posted by ger21 ...While in most cases you can run either by using G20/G21, there's a greater chance for problems to occur. (These recommendations are from the original author of Mach3)

Gerry,

Mach3 is a great program, but the "native units" concept seems to be poorly thought out. I use G20 in Mach's initialization string and have never had a problem, but I'm not taking any chances. If Mach's programmer doesn't trust the program to do the right thing, who am I to argue ???

[ger21]

Mach3 is a great program, but the "native units" concept seems to be poorly thought out.

I believe the issue is that as more and more features were added, the internals became more and more complex, with many thinks interacting with many others. When running code using different units then the native units, unit conversions may be required in many different places internally. While in most cases you won't see any problems at all, the chance for a bug to rear it's head is greater than when staying with the native units.
Now, Mach3 has been in what appears to be a constant state of bug repair for the last few years, so this may not be an issue at all at this point in time.