Help determining proper power supply for my G540

[telah]

Hi,

I have been using my G540 4 axis drive for a couple week, I have since some issue with my Z axis, I was looking at mechanical issue and changed my Z from direct shaft drive to a 1-2 pulley with a gantry belt to help with the torque but it even worse, at low speed the axis move but at faster speed (Fast jog) the motor jam like there is not enough torque ( I can turn the lead screw by hand)

If i connect all motor and operate them without any load they all work perfectly impossible to turn by hand with holding torque and when they spin, I tried apply tension with my hand and they seem to have a lot of torque

The Setup I have is

1x 4 axis Gecko Drive G540

1x 24V 10A power supply

1x NEMA 23 BIPOLAR STEPPER MOTOR 425 oz-in KL23H286-20-8B

( Spec http://www.kelinginc.net/KL23H286-20-8B.pdf )
the motor is wired Bipolar ( Parallel ) with a current set resistor of 2.8k

3x NEMA 23 Unipollar Miniangle Stepper 3.5V / Phase 1.4 A / Phase Astrosyn Minebea 23LM-C343-02
The motors are unipollar with a current set resistor of 1.4k

Do you think the power supply is not enough to drive those at optimal performance?

What power supply should I be using ?

I have heard about a filter capacitor, is it needed with the G540 and how do I determine what capacitor is needed?

other then that I have an E-stop and limit switch connected in series, I also have a probing tool as an input but nothing more then that.

I will eventually connect a relay to control my spindle on/off and the speed with a 10amp dimmer but I don't have that installed right now.

Is there anything I am doing wrong with the electronic ?
OR is there anything I am missing or don't understand?

many thanks for the help.

[Jeff-Birt]

There could be several things going on here. First I would suggest going back through all the mechanical bits, everything should move smoothly by hand. The next thing to look at is how you have the motors tuned. Are your acceleration and max velocity values Reasonable. The Z-axis is typically set to lower accel and velocity because your fighting gravity with a heavy load.

Your motors have a relatively high inductance for the power supply voltage you are using. This means you won't be able to accelerate as quickly. It's human nature to want to use the biggest rated motor that fits your driver but this seldom leads to good performance. The motor needs to be matched to the load, the driver matched to the motors and then the right power supply chosen.

In this case you have the motors already so I would suggest a 48V power supply if you want to upgrade it. As to current capacity of the supply, the G540 has an internal fast blow 7A fuse. You will never draw more than 7A. What does all of this mean? If you are using a linear, unregulated supply it is common to 'upsize' them about 30%. This help to keep the output voltage in a reasonable range given the range of output current expected. A good quality switch type supply will be able to output its full current/voltage rating with no issues. Depending on how the switcher is constructed you might need a bit of capacitance added to the output. On my G540 system I use 320W 48V MeanWell power supplies.

[rowbare]

Ideally you want a 3.5A motor with about 2.4mh inductance for maximum performance with a G540. That isn't to say that you can't get decent performance from other motors but a motor with those specs will wring the most out of the drive.

Your 425 oz/in motor has an inductance of 6.8mh. Using the formula 32*sqrt(inductance) to calculate the optimum voltage for your motor, you get 83v. So your 24V power supply falls short.

I can't find specs for your other motors but from what I can find they are the old round can type and they are only 1.4 amp motors to begin with. Without an inductance specification one you can use 20x the motor voltage as a guide line. That gives you 70v for those motors.

You will certainly get better performance with a higher voltage power supply. To calculate the current requirements figure on 2/3 of the sum of the amperages of all of the motors in the system. In your case that would be 2/3 * 7 = ~5A. Keling has a 48V 7.3A supply that works quite well for an optimal 3 axis setup. An optimal 4 axis setup wants about 10.5 amps minimum so the Keling 48v 12A supply fits the bill nicely.

You haven't said anything about your machine so it is hard to say whether or not a power supply upgrade would suffice to give you the performance you need. It would be a good first step though and if you find that you still fall short then you can get motors that are better matched to the G540.

This is a very informative post: http://www.cnczone.com/forums/530370-post11.html

good luck
bob

[telah]

thank you very much both this is a lot of quality information !

[tumutbound]

Originally Posted by rowbare Your 425 oz/in motor has an inductance of 6.8mh. Using the formula 32*sqrt(inductance) to calculate the optimum voltage for your motor, you get 83v. So your 24V power supply falls short.

Don't forget the maximum voltage for a G540 is 50V.

[Jeff-Birt]

Ideally you want a 3.5A motor with about 2.4mh inductance for maximum performance with a G540. That isn't to say that you can't get decent performance from other motors but a motor with those specs will wring the most out of the drive.

Respectfully, this kind of thinking is ass-backwards. You need to match the motors specs to the job at hand and match the power supply/driver to the motor. So many people want to think that by bolting on the biggest motor they can find that falls within a drives specs that they are getting the best set up, nothing could be further from the truth.

Case in point. I use 'little' 166 oz-in, single stack nema 23 motors for Taigs and Sherline machines with the stock screws. Why? The stock lead screws are 20 TPI, that is a LOT of reduction so the acceleration and top velocity of the motor is far more important that its peak torque. My 'tiny' motors can really make these machines go.

YouTube - 250 IPM SS
If you have say a A2Z monster mill with the 4 TPI screws than a larger, double stack motor is a better option. Why? It has the torque down in the speed range where the motor will be operating most.

You have to match the the motor to the job.

An automotive analogy would be that placing a large V8 from a truck into your sports car would make the car faster. You would be unimpressed with the results I think. Truck engines are design to produce a lot ot torque at low RPMs (where trucks need it.) Sports cars are designed to take advantage of high-reving engines that move the powerband up the RPM range (so they can go faster.) Even the transmission and rear end gearing is drastically different between the two vehicles.

Sorry to harp on this so much but it really bothers me to see folks misunderstand these fundamental concepts and spend their hard earned money on the wrongs parts.

[rowbare]

Originally Posted by Jeff-Birt Ideally you want a 3.5A motor with about 2.4mh inductance for maximum performance with a G540. That isn't to say that you can't get decent performance from other motors but a motor with those specs will wring the most out of the drive. Respectfully, this kind of thinking is ass-backwards. You need to match the motors specs to the job at hand and match the power supply/driver to the motor. So many people want to think that by bolting on the biggest motor they can find that falls within a drives specs that they are getting the best set up, nothing could be further from the truth. Case in point. I use 'little' 166 oz-in, single stack nema 23 motors for Taigs and Sherline machines with the stock screws. Why? The stock lead screws are 20 TPI, that is a LOT of reduction so the acceleration and top velocity of the motor is far more important that its peak torque. My 'tiny' motors can really make these machines go.

You are right, I should have said something about matching the motors to the task at hand. That is something you have done very well with your 2.8A 2.4mh 166 oz/in motors on the Taig .

That reminds me, that I should get around to making cables for my 185s so I can try them out...

bob