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mach 4 learning the machine drive ratios
« on: December 11, 2020, 02:52:30 PM »
Good day everyone. Welp, I have just purchased a bridgeport cnc series 1 from an auction. I have to upgrade all the motors, drivers, breakout board, and have to  find drive pulleys for the motors, as all this stuff has been removed before the auction. My questions are
1. Can mach 4 learn from the ratios between the motor drive and driven pulleys, as I have two pulleys that I cannot source with what tooth count I think I need. I believe these were originally a 2 to 1 drive system for the x and y. Can I compensate in the software for a close, but different ratio
2. I have to find out what stepper drivers, and breakout board mach 4 needs. Is there any resource for this?
The system will be windows 10, 64bit
Thanks in advance. 
Re: mach 4 learning the machine drive ratios
« Reply #1 on: December 12, 2020, 03:46:51 PM »
Hi,

Quote
1. Can mach 4 learn from the ratios between the motor drive and driven pulleys, as I have two pulleys that I cannot source with what tooth count I think I need. I believe these were originally a 2 to 1 drive system for the x and y. Can I compensate in the software for a close, but different ratio

Fit what pulleys you can find, then do the calculation and install those numbers into Mach4. Mach4 does not 'learn' what you have done, you tell it
what it needs to know. Mach can quite handily accommodate non-integer ratios etc, and there is plenty of help to do the calculation and even
a 'suck it and see' type tuning aid available.

Quote
I have to find out what stepper drivers, and breakout board mach 4 needs. Is there any resource for this?

While Mach4 has a parallel port version called Darwin ($25 license fee applies) it is limited to 32 bit Windows 7 and earlier just like Mach3's parallel port.
In short Mach4 really requires an external motion controller, of which there are half a dozen manufacturers , some more expensive than others,
some more capable than others. There are a number of threads on the Mach4 board that cover the options.

I use and recommend an Ethernet SmoothStepper ($180) by Warp9TD, and many users pair that with an MB3 breakout board from
CNCRoom ($180). Thereafter you fit whatever stepper or servo drives you like.

There are cheaper breakout boards but few match the quality and well thought out design and balance of IOs of an MB3. If you are handy at
electronics and can add a handful of components to a cheaper and simpler (eg C10 for $23, single parallel port equiv) board you can have all the
flexibility AND save some dollars.....but you'll have to design and build a few extra circuits probably. There is help with those circuits if you need
it, electronics is my thing and they are all simple enough.

A somewhat cheaper alternative, albeit limited, is a PMDX411 and a Gecko G540. The PMDX411 is a single (parallel port equivalent) port
USB connected external motion controller with Mach4 plugin and the G540 is a 50V four channel stepper driver/breakout board combination.

I suspect you will become rather frustrated that much of Mach4's abilities are beyond reach because your controller (PMDX411=UC100=57CNCdb25)
only has 17 IOs, ie one parallel port equivalent, whereas a PMDX424 has 34 IOs, an Ethernet SmoothStepper has 51 IOs, a 57CNC has 57 IOs and a UC300
has 85 IOs. I highly recommend an external controller with 30 or more IOs.....you'll benefit in the end.

The Gecko G540 is an age old gem, many people use it. Note that it is a one parallel port equivalent input breakout board and four 50V stepper drivers for
about $350. 50V is not bad.....but 80V is better. Having separate breakout board and drivers is more flexible......but usually more expensive too.
Pay your money and take your pick.

When it comes to steppers, do not go for the highest torque units, they look attractive but they have high inductance and lose torque badly at speed
and will stutter and stall at only modest speeds. Lower torque units with comensurately lower inductance will run much MUCH faster without stuttering or stalling.
Manufacturers make high torque units to attract first time buyers who don't know about inductance. Don't waste your money.

With 23/24 size steppers look for inductance of 1mH to 2mH, 1mH preferred and reject anything over 2mH.
With 34 size steppers look for 2mH to 4mH, 2mH preferred and reject anything over 4mH.

Craig
My wife left with my best friend...
     and I miss him!
Re: mach 4 learning the machine drive ratios
« Reply #2 on: December 13, 2020, 11:53:45 AM »
Thanks Craig. I'm not that proficient with electronics. I'm a retired automatic transmission builder. I will follow your guidance. I am a firm believer that once right beats twice cheap every time. My needs will be for moving weight on the x/y axis, and I thing I would like nema 34 1800oz motors. Every time I try to save a buck, I end up sending 2$ after a dime.
This machine is in nearly new condition, and it is pristine. I bought it from a research university that did medical prototypes, and was quickly shoved in the corner when they upgraded to new machines. Again, I appreciate your knowledge, and willingness to share such knowledge.
Re: mach 4 learning the machine drive ratios
« Reply #3 on: December 13, 2020, 01:06:02 PM »
Hi,

Quote
and I thing I would like nema 34 1800oz motors.

Watch out for those high torque motors, many have bought them but found they are useless. They stutter, stall and vibrate like hell
above a few hundred rpm.

Quote
With 34 size steppers look for 2mH to 4mH, 2mH preferred and reject anything over 4mH.

A 34 size motor of 3mH inductance but only 750 oz.in will still be better than 1800 oz.in at 8mH. You must get low inductance motors
or your machine will b as slow as a wet week.

Craig
My wife left with my best friend...
     and I miss him!
Re: mach 4 learning the machine drive ratios
« Reply #4 on: December 13, 2020, 02:02:22 PM »
Perhaps a nema 23?. Again, I appreciate your assistance
Re: mach 4 learning the machine drive ratios
« Reply #5 on: December 13, 2020, 02:24:50 PM »
I guess if you had a 2hp machine, that you wanted to do heavy metal on, which motors would you use?
Re: mach 4 learning the machine drive ratios
« Reply #6 on: December 13, 2020, 02:54:50 PM »
Hi,
for my current build mill I have selected 750W Delta B2 series servos.

If your budget permits servos are preferred, if not you need low inductance steppers.

Don't be taken in by the hype around closed loop steppers, the manufacturers claim they are like servos.....they are not......
they are still steppers and suffer from rapidly degrading torque capability as speed increases. If you want closed loop performance
get servos.....don't mess around with Mr In-Between, aka closed loop steppers.

Low inductance 34 size steppers are probably right for your application.

It may surprise you but the dominating component of the inertia of your machine is not in fact the axis beds but is in fact the ballscrew.
I'm using rather large ballscrews, 32mm diameter, and they represent  85% of the inertia, the servo armature another 10% with the axis bed, 115kg,
representing the last 5%.

Because the ballscrew spins so fast, and by comparison the axis moves so slowly, it is the ballscrew that dominates the inertia equation.

If you can provide details of the ballscrews we can do some calculations that will at least put you in the right ballpark.
For these calculation we need an accurate measurement of ballscrew diameter, mucho important!. Next we need the length and the pitch,
important but not nearly as critical as diameter. An estimate of axis mass.

Craig
« Last Edit: December 13, 2020, 02:59:23 PM by joeaverage »
My wife left with my best friend...
     and I miss him!
Re: mach 4 learning the machine drive ratios
« Reply #7 on: December 13, 2020, 03:13:06 PM »
Hi,
not sure why the other pics did not attach...

Craig
My wife left with my best friend...
     and I miss him!
Re: mach 4 learning the machine drive ratios
« Reply #8 on: December 13, 2020, 07:49:50 PM »
Super thanks, I will get all the data I can. My email is coloradochris20002gmail.com if this is more convenient to communicate. I'm really excited about this project. This looks like amazing fun.
Re: mach 4 learning the machine drive ratios
« Reply #9 on: December 13, 2020, 07:50:34 PM »
correction, coloradochris2000@gmail.com